Phonological Disruption in
Progressive Aphasia and
Alzheimer's Disease
Karen Philippa C r o o t
Corpus Christi College
Dissertation submitted for the degree of Doctor of Philosophy
University
of
May
Cambridge
1997
Declaration
This dissertation is result of my own work and includes nothing which is
the outcome of work done in collaboration.
No part of it has been submitted for
any other degree or qualification.
Chapter 3 is based on the paper by Croot, K., Patterson, K. & Hodges, J. R. (in
press). Single word production in non-fluent progressive aphasia. Brain and
Language.
Chapter 4 is based on a manuscript submitted for publication by Croot, K.,
Patterson, K. and Hodges, J. R. Familial progressive aphasia: Insights into the
nature and deterioration of single word processing.
The results from M.T., V.B. and K.M. in the naming, repetition and picturename judgement experiments described in Chapter 6 are reported in Croot, K.,
Patterson, K. & Hodges, J. R. (1996) Phonological disruption in atypical Dementia
of the Alzheimer's Type. Brain and Cognition, 32, 186-190.
Acknowledgements
I would like to acknowledge the contribution of my supervisors, Karalyn
Patterson and John R. Hodges, to the development of this thesis: in planning the
experimental work, clarifying theoretical ideas, and providing detailed feedback
on my writing.
Thank you: I could not have hoped for better supervision.
I would also like to express my deep appreciation for the involvement of all
the people with progressive aphasia or DAT who have taken part in this research
over the past three and a half years: A.S., F.M., L.M., P.G., D.B., R.S., V.B., N.K., P.B.,
J.G., J.M., K.M., M.T., S.W., R.G., R.B., C.B., G.D., C.M., Y.B., R.Sp., and H.K., and my
appreciation too for the support and assistance of their spouses and families.
This research was supported financially by a three year Cambridge
Commonwealth Trust Scholarship, a three month maintenance award from Corpus
Christi College, a three month award from the Lundgren Fund managed by the
Board of Graduate Studies, Cambridge University, and by generous supplements
from my parents, Maureen and Raymond Croot.
I thank the scientific and support staff at the Medical Research Council
Applied Psychology Unit for their commitment to training research students.
In
particular, thanks to Andrew W. Young for suggesting the idea for Chapter 3:
Experiment 2, and to Ian Nimmo-Smith and Peter Watson for statistical advice
I
would also like to thank Kim Graham, Paul Atkins and Elisabeth Hill for staunch
moral support and frequent practical assistance, and Sophie Scott and Sarah Ward
for useful discussion and practical help.
Further thanks are due to Naida Graham, Lindsay Stuart-Green, and Elaine
Giles for my training in neuropsychological testing, and, together with Sarah
Ross and Cheryl James, for carrying out most of the standardised general
neuropsychological testing which is reported in this thesis.
Kristin Breen also
carried out some of the neuropsychological testing reported for R.B and C.B.
Thanks also to Karalyn Patterson, Kim Graham and Richard Perry for the use of
unpublished test materials, and to Catherine and David Rush for the gift of their
car.
Finally, thanks to my parents, family, and friends, in Australia, England,
and elsewhere, for their love and encouragement all the way.
It was worth it!
Now to him who is able to do immeasurably more than all we ask or imagine,
according to his power that is at work within us, to him be glory in the church and in
Christ Jesus throughout all generations! Amen.
Ephesians 3: 20-21.
Abstract
This thesis presents a cognitive neuropsychological investigation of
phonological disruption in a series of patients with neurodegenerative disease.
The first aim was to give a principled account of the patients' phonological
impairments with reference to models of speech production derived from the
study of normal populations and patients with non-progressive aetiology.
The
second aim was to consider how data from the studies reported here may constrain
theories of normal phonological processing.
There are three experimental
chapters in the thesis.
The first experimental chapter describes an investigation of the spoken
single word production of two patients with non-fluent progressive aphasia, P.G.
and L.M.
Speech production was facilitated by phonological information available
from task stimuli and by a correspondence between input and output modality.
Access to phonology in reading was positively related to the degree of correlation
between orthographic and phonological forms.
These results are consistent with
an account of pathologically weakened connections between nodes in an
interactive spreading activation model of speech production of the type described
by Dell (1986).
A longitudinal investigation of the language deficits of R.B. and C.B., two
brothers with primary progressive aphasia, is presented in the second
experimental chapter.
Six experiments assessed word production and another
investigated receptive word processing.
R.B. was less successful in naming than
C.B., and made more errors to semantically related distractors in the input task,
whereas C.B. was more impaired than R.B. in repetition tasks and in detecting
phonological distractors at input.
Like the patients reported in the previous
chapter, both R.B. and C.B. had characteristics of weakened connections in the
Dell network, however, R.B. showed additional semantic-level deficits, and, over
time, C.B. developed pathologically rapid decay of activation within the network.
The final experimental chapter presents data from a group of patients with
either probable or autopsy-confirmed Alzheimer's Disease who, atypically,
showed striking phonological disruption.
This disruption was evident in
spontaneous speech and single word production and reception, demonstrating
that phonological processing is not always preserved in DAT.
these DAT patients have impaired activation of
It is concluded that
phonological representations
from semantic specifications, as well as specific phonological processing deficits.
Table of Contents
Chapter
1
Review of Phonological Processing in Normal and Aphasic Speech Production
1
A Brief Note on Some Terminology
1
MODELS OF NORMAL SPEECH PRODUCTION
3
Data from Normal Speech Errors
3
Levelt's Model of Speech Production
5
Dell's Interactive Activation Model of Production
9
Discrete Stages or Interactive Activation?
11
PHONOLOGICAL DISRUPTION IN APHASIC SYNDROMES
12
The Historical Development of Aphasic Syndrome Classifications
13
Syndrome-Based Investigations of Phonological Breakdown
17
The Neuroanatomy of Phonological Processing in Aphasic Syndromes
21
COGNITIVE NEUROPSYCHOLOGICAL STUDIES OF PHONOLOGICAL
DISRUPTION IN SPEECH PRODUCTION
Descriptive
Accounts
Accounts Using Dell's Interactive Activation Model
24
25
27
INVESTIGATING PHONOLOGICAL DISRUPTION IN NEURODEGENERATIVE
DISEASE
Chapter
28
2
Review of Non-fluent Progressive Aphasia
30
PROGRESSIVE APHASIC SYNDROMES
30
Historical Overview
30
Subtypes of Primary Progressive Aphasia
31
Nosological Issues in the Study of Fluent and Non-fluent Progressive
Aphasia
34
NON-FLUENT PROGRESSIVE APHASIA
37
Summary of Reported Cases
37
Age, Sex and Neuropathological Data
40
Associated Deficits
43
Profile on Neuropsychological Testing
45
Experimental Investigations of Non-fluent Progressive Aphasia
46
MIXED PROGRESSIVE APHASIA
47
CONCLUDING REMARKS
49
Chapter
3
Single Word Production in Non-fluent Progressive Aphasia
CASE DESCRIPTIONS
50
51
EXPERIMENT 1: SINGLE WORD PRODUCTION IN NAMING, REPETITION AND
READING
Method
57
58
Materials
58
Procedure
59
Scoring
59
Results
60
Production of Correct Responses
62
Production of Phonologically Related Responses
64
Increased Error Rate in Long Words: A Linear Function of
Opportunity?
68
Formal Paraphasias: Lexically Mediated?
70
The Severity of the Disruption to Phonological Production
72
Is the Disruption Phonological or Articulatory?
76
Discussion
78
EXPERIMENT 2: SINGLE WORD PRODUCTION IN WRITTEN VERSUS SPOKEN
MODALITIES
80
Materials, Procedure and Scoring
81
Results
82
Discussion
85
EXPERIMENT 3: READING ALOUD WORDS VARYING IN THE
PREDICTABILITY OF CORRESPONDENCE BETWEEN ORTHOGRAPHY
AND PHONOLOGY
87
Materials, Procedure and Scoring
88
Results
91
Discussion
93
GENERAL DISCUSSION
95
Chapter
4
Familial Progressive Aphasia: Insights into the Nature and Deterioration of
Single Word Processing
102
CASE DESCRIPTIONS
103
INVESTIGATION OF SINGLE WORD PRODUCTION
109
EXPERIMENT 1: NAMING, REPETITION AND READING
109
Materials and Procedure
110
Results
111
Production of Correct Responses
114
Production of Phonologically Related Responses
115
Rate of Word versus Nonword Errors
116
Discussion
117
EXPERIMENT 2: NAMING ITEMS WITH PHONOLOGICALLY SIMPLE NAMES
118
Materials and Procedure
119
Results
119
Discussion
121
EXPERIMENT 3: NAMING WITH PROGRESSIVE PHONEMIC CUEING
121
Materials and Procedure
122
Results
122
Discussion
124
EXPERIMENT 4: IMMEDIATE WORD REPETITION
125
Materials and Procedure
126
Results
126
Discussion
128
EXPERIMENT 5: DELAYED WORD REPETITION
129
Method and Hypotheses
129
Results and Discussion
130
EXPERIMENT 6: IMMEDIATE REPETITION OF TWO-WORD STRINGS
131
Method
132
Results
133
Discussion
135
DISCUSSION OF WORD PRODUCTION
136
INVESTIGATION OF RECEPTIVE WORD PROCESSING
138
EXPERIMENT 7: PICTURE-NAME JUDGEMENT
138
Procedure
138
Materials
140
Results
142
DISCUSSION OF RECEPTIVE WORD PROCESSING
144
GENERAL DISCUSSION
145
Chapter
5
Review of Phonological Processing Abilities in Dementia of the Alzheimer
Type
149
THE SOURCE OF THE "DOGMA": EVIDENCE SUGGESTING THAT PHONOLOGY
IS UNIMPAIRED IN DAT
Connected
Speech
151
151
Naming
152
Articulation
152
Receptive Word Processing
153
Reviews
153
CHALLENGING THE "DOGMA": HINTS THAT PHONOLOGICAL PROCESSING
MAY BREAK DOWN IN DAT
154
Early Reports
154
Connected
155
Speech
Word and Sentence Production Tasks
156
PHONOLOGICAL DISRUPTION IN HISTOLOGICALLY-CONFIRMED
ALZHEIMER'S DISEASE
158
Familial Alzheimer's Disease
158
Sporadic Alzheimer's Disease
158
Distribution of Pathology
160
SUMMARY
161
Chapter
6
An Investigation of Phonological Disruption in Atypical Dementia of the
Alzheimer Type
163
Two Accounts of Phonological Errors in DAT
163
Word-finding Deficits in DAT
166
The Present Study
166
CASE DESCRIPTIONS
167
ANALYSIS OF SPONTANEOUS SPEECH
175
Method
176
Samples of Conversational Speech
176
Error Categories
178
Results
180
Discussion
182
ANALYSIS OF SERIES SPEECH
183
Method and Results
184
Discussion
187
SINGLE WORD PRODUCTION
188
Method
189
Naming, Repetition and Reading: 9 Patients
189
Picture Naming: DAT Patients Compared with Elderly Controls
190
Results
192
Picture Naming: DAT Patients Compared with Elderly Controls
192
Naming, Repetition and Reading: 9 Patients
193
Longitudinal Testing on Naming, Repetition and Reading:
5 Patients
197
Naming and Reading Data from Previous Testing: 4 Patients
200
Discussion
204
RECEPTIVE WORD PROCESSING
206
Method
207
Results
208
Discussion
210
GENERAL DISCUSSION
211
Chapter
7
Conclusions and Implications for Future Research
215
ACCOUNTS OF PHONOLOGICAL DISRUPTION IN NEURODEGENERATIVE
DISEASE
Non-fluent
216
Progressive
Aphasia
216
Other Primary Progressive Aphasic Syndromes
217
Dementia of the Alzheimer Type
218
THEORIES OF NORMAL PHONOLOGICAL PROCESSING
220
Dell's Interactive Activation Model of Production
220
Generalisability of the Model
220
Some Limitations of the Model
220
Global versus Local Processing Deficits
221
Advantages of Processing Accounts
222
Applications of the Continuity Assumption
222
Models of Phonological and Articulatory Processing
223
Neuroanatomical Localisation of Phonological Processing
225
CONCLUDING REMARKS
References
226
Appendices
250
Appendix I
250
Appendix II
258
Appendix III
259
Appendix IV
260
Chapter 1
Review of Phonological Processing in
Normal and Aphasic Speech Production
This thesis presents a cognitive neuropsychological investigation of
phonological disruption in a series of patients with neurodegenerative disease.
The first aim of the thesis is to give a principled account of the patients'
phonological impairments with reference to models of normal speech production,
while the second, and complementary, aim is to consider how data from the studies
reported here may constrain theories of normal phonological processing.
As a
background to the experimental work in the thesis, this first chapter reviews a
number of influential models of normal speech production, focusing on the
phonological and articulatory processes these models describe.
The chapter also
reviews some of the models of speech production which have been developed to
account for the phonological and articulatory disruption occurring in aphasic
syndromes.
Finally, the chapter discusses the rationale for studying phonological
breakdown in patients with progressive disease.
A Brief Note on Some Terminology
It is important to clarify the use of the term p h o n o l o g i c a l
in this thesis, as
it has both general and specialised usage (Oxford English Dictionary).
In its more
general sense, the term refers to the sound properties of a language, with little
theoretical specificity about the nature of those sounds, except that they are a
distinct level of organisation compared with, for example, the syntactic or
semantic levels of language.
In the clinical literature, the term is usually used in
this general sense, for example, to describe patients with "phonological
breakdown" or the quality of their speech, which contains "phonological errors".
The term phonological may also refer to systematically occurring
properties of language sounds which are used within a language to encode
linguistically contrastive information (Clark & Yallop, 1990) . For example, in the
minimal pair [kQt ] — [k Q d], the difference between the length of the vowel and
the voicing of the final consonant in the two members of the pair flags a
systematic difference in meaning in English.
The differing sounds could thus be
described as functioning in a phonologically contrastive manner in that
1
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 2
language.
Current linguistic-phonological theories (e.g. autosegmental theories)
suggest that representations of phonological information are complex and
multidimensional, with different phonological features ascribed to separate,
independently functioning tiers in the representation (Harris, 1994; Kaye, 1989) .
Most neuropsychological theories of language breakdown, however, incorporate
abstract units of phonological contrast called p h o n e m e s as the units within which
linguistic-phonological information is encoded at the phonological level.
In the title of this thesis, Phonological Disruption in Non-fluent
Progressive Aphasia and Alzheimer's Disease, and the titles of several of its
chapters, the term p h o n o l o g i c a l is used in the more general sense, to refer to
properties of the normal sound structure of spoken language.
From the models of
speech production to be reviewed below, it is clear that there are at least two
broad levels of processing related to the production of speech sounds at which
errors may arise.
The first is of these levels involves the retrieval of information
stored in long term memory about the sound structure of a target word, most
commonly described as phonological retrieval and/or encoding.
The second
involves a r t i c u l a t o r y processing, where the linguistic target is produced by the
speech neuromusculature as an acoustic signal.
The investigation of phonological disruption in this thesis is deliberately
inclusive of both linguistic-phonological and articulatory level impairments for
several reasons.
Firstly, for patients with cortical lesions affecting speech
production, it is sometimes difficult to determine in practice which level is
impaired, as errors arising at the two levels may be acoustically
indistinguishable.
Secondly, as will be shown below, authorities in the field
remain undecided about where linguistic-phonological processing ends and
motor-articulatory processing in speech production begins.
Thirdly, in many
studies which report phonological disruption in clinical populations or single
patients, there is no guarantee that a principled distinction between linguisticphonological and articulatory error has been made by the researchers.
Where the term p h o n o l o g i c a l is used in the description of processes or
representations in specific models, however, it is used in the specific theoretical
sense intended by the proponents of those models, rather than as an inclusive,
descriptive term as outlined above.
Thus, for example, the level of phonological
encoding in the model proposed by Levelt and Wheeldon (1994)
does manipulate
representations with linguistic status; the phonological nodes in the model of Dell
and colleagues (after Dell, 1986) currently represent phonemes (Dell, Schwartz,
Martin, Saffran, & Gagnon, in press) .
Along similar lines, the term p h o n e m i c is
used in this thesis only when referring to phonemes as units of linguistic
contrast.
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 3
MODELS OF NORMAL SPEECH PRODUCTION
Data from Normal Speech Errors
Models of normal speech production have, until recently, been derived
primarily from the study of "slips of the tongue", speech errors produced by
normal speakers in everyday conversation.
Under this approach, errors are
categorised according to the linguistic unit(s) and type of error process involved,
and the assumption is invoked that if a particular type of unit is able to be
involved in an error process, it is a psychologically real element in the
production process (Fromkin, 1973) .
The analysis of speech errors has enabled
researchers to postulate different levels of processing in speech production,
related to semantic, syntactic, phonological and articulatory aspects of language
(e.g. Fay & Cutler, 1977; Garrett, 1976) , because linguistic units such as content
(open class) and function (closed-class) words, grammatical morphemes,
phonemes, and articulatory features have all been found to be independently
involved in different slips of the tongue.
Some examples of normal speech errors,
and the theoretical inferences drawn from them about normal speech processing
are shown in Table 1:1.
This table is meant to be illustrative, rather than
exhaustive: there are additional types of speech errors which constrain theories
of speech production (see Shattuck-Hufnagel, 1979) , and not all are unambiguous
in their interpretation (Cutler, 1988) .
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 4
Table 1:1.
Examples of speech errors/slips of the tongue from which models of
normal speech have been developed.
In the examples, the correct form is shown
first, followed by the erroneous production.
Type of Error
sentence
stress
Example of Theoretical Interpretation
unchanged despite word
location of stress determined
exchanges e.g. a weekend for maniacs → a
independently of the particular content
maniac for w e e k e n d s
word it falls on
(Garrett, 1976)
word
exchanges tend to be within
grammatical class acts as a constraint on
grammatical class e.g. Guess whose name came
lexical selection procedures
to mind → Guess whose mind came to name?
(Garrett, 1976)
word
lexical retrieval occurs at two stages
substitutions can be
semantically related or phonologically related
(Garrett, 1976)
e.g. at low temperature → at low speed;
corrected →
mixed
constructed
word
substitutions
(blends)
e.g. a ton/load of bricks → a toad of bricks
both semantic and phonological processes
involved in selection of word (Cutler, 1988;
Dell & Reich, 1981)
morpheme
stranding
content word roots (maniac) behave inde-
e.g. a weekend for maniacs → a maniac for
pendently of grammatical elements (-s)
weekends
suggesting they are involved in different
processing stages (Garrett, 1976)
morpheme
accommodation
phonetic specification of grammatical
phonetic form of morphemes is appropriate to
elements occurs after phonological form of
context despite exchanges e.g. in above
content words has been retrieved
example, -[s] in maniacs → -[z] in weekends
(Garrett, 1976)
syllable
syllables have internal structure whereby
onset
or
rime
exchanges are
more common than vowel or coda exchanges
the vowel and coda are structured into a
e.g. a wilting lilly → a lilting willy (onset)
rime (Fudge, 1987)
give your ma a hug → give your mug a ha (rime)
the roof is leaking → the leaf is [rukIN ] (onset +
vowel)
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 5
Levelt's
Model of Speech Production
The most influential and comprehensive review to date of the
representations and processes involved in speech production has been provided
by Levelt (1989) .
While Levelt's review is much indebted to the data provided by
speech error studies, it also incorporates considerable evidence from
experimental psycholinguistics, and from fields as diverse as artificial
intelligence, theoretical linguistics and phonetics.
The review surveys the
production process from the pre-verbal cognitive structures from which
intended communications are derived, through multiple subsequent processes to
the physiological factors in the vocal tract which influence speech production.
The processing involved in the spoken production of communicative messages is
summarised by a descriptive model in which there are three main stages:
conceptualising, formulating, and articulating (Figure 1:1).
Figure 1:1.
Levelt's model of components involved in the production of speech
(adapted from Levelt, 1989, p.9).
Audition and speech comprehension are shown
because they are involved in the monitoring of speech output.
Boxes represent
processing components; circle and ellipse represent knowledge stores.
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 6
In Levelt's model, the message to be communicated originates in the
Conceptualiser; the Conceptualiser selects which information is to be included
according to both the register and topic of a current discourse, and structures the
information in the message according to inferences about the listener's current
knowledge of the topic and mental model of the discussion.
The Conceptualiser
also monitors the generation of speech at all levels (content, syntax, phonology,
articulation and overt speech) via internal feedback loops and normal speech
comprehension processes, and implements repair strategies where necessary.
Conceptualising processes require conscious attention, and draw on information
in both long and short-term memory: the former memory system contributes to
the content and form of the intended message and the latter is involved in
monitoring
the
conversation.
The output from the Conceptualiser is a message in preverbal form, which
is given its grammatical shape and phonological specification by the Formulator.
The Formulator then produces an articulatory plan which is implemented by the
Articulator using the neuromusculature of the vocal tract to produce overt
speech.
Disruption to the normal production of speech sounds may arise from
abnormal processing in these latter two components.
The processes of particular
interest are the retrieval and encoding of the phonological form, and the
implementation by the Articulator of the phonetic plan produced by the
Formulator.
Word retrieval within the Formulator occurs in two stages, grammatical
encoding and phonological encoding (Levelt, 1992) .
When the Formulator
receives the preverbal plan from the Conceptualiser, semantically specified
lexical items (called lemmas, following Kempen & Huijbers, 1983)
are retrieved
according to how well they meet the conceptual constraints of the non-verbal
message.
These lemmas also have syntactic specification (information such as
grammatical class and permissible thematic roles), and thus, upon retrieval,
trigger syntactic operations such as the formulation of noun phrases and verb
phrases and the retrieval of appropriate closed class function words as necessary.
Lemmas are, however, unspecified for phonological form, thus the hierarchical
organisation of syntactic phrases generated in grammatical encoding must
subsequently
undergo
phonological
encoding.
The processes involved in phonological encoding (and in the early stages
of articulation) in English are described in detail by Levelt and Wheeldon (1994).
Their model is shown in Figure 1:2.
Phonological encoding, as well as
grammatical encoding, is triggered by lemma retrieval.
Phonological encoding
involves retrieval of stored information about the phonological form (called a
lexeme in the terminology of Kempen & Huijbers, 1983 or a phonological lexical
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 7
representation or PLR by Butterworth, 1992) .
Evidence from speech error data
showing that a number of different types of phonological segments (phonemes,
syllable onsets and rhymes, phonological features) may be omitted, exchanged,
added and so on, suggests that the sound structures of words are not stored as
wholes, but are constructed over and over again as required.
As shown in Figure
1:2, the retrieved phonological word form "spells out" two types of information: a
metrical frame containing information about a word's syllable structure and
stress pattern, and, separately, the segmental phonological content of the word.
The nature of the retrieved segmental content is still controversial, but accounts
favouring representations in the form of a string of "classical" phonemes (e.g.
Crompton, 1982; Kohn & Smith, 1995; Shattuck-Hufnagel, 1979)
are probably
losing ground to autosegmental accounts (Kaye, 1989; Romani, 1996; Romani &
Calabrese, 1996)
and underspecification theory accounts (Kohn, Melvold, & Smith,
1995; Stemberger, 1983)
Figure 1:2.
of phonological structure.
Processes involved in phonological encoding (adapted from Levelt &
Wheeldon, 1994, p. 242).
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 8
Spelling out the frame and segmental content of a word separately (as first
proposed by Shattuck-Huffnagel, 1979) allows the formation of a single
phonological word from several types of item retrieved during grammatical
encoding.
In English, phonological words are composed of a head word (or two
head words, in the case of some compounds) and its affixes and clitics (i.e.
unstressed closed-class words which are joined to the adjacent open-class words,
e.g. want to → [wÅnt´]). A frame for the phonological word is created by blending
the frames of its constituent words in order to make strings of individually
retrieved items into phonologically continuous rhythmic structures which are no
longer segregated by word boundaries.
The phonological segmental content
which is spelled out to the new phonological word frame (in segment-to-frame
association) is therefore not equivalent to the full citation forms of all the items
in the phonological word, but rather contains the reduced forms which
systematically arise in continuous speech.
The example in Figure 1:2 shows that
as a result of phonological word formation, the final /d/ in the word "demand"
comes to be the first segment of a newly-formed segment, / dIt / in combination
with the cliticised word, "it".
A further example given by Levelt (1992) is the
utterance, "Black Bear gave it him", in which the final three words would be
merged into one phonological word with three syllables, / g e I v I t I m/; the /h/
which is part of the citation form of the word "him" has disappeared.
Phonological words are the domain of syllabification in speech production.
Thus, following the process of segment-to-frame association, the syllables of the
phonological word serve as search instructions for sets of articulatory commands
or "gestural scores" stored in a library (Crompton, 1982) or syllabary (Levelt &
Wheeldon, 1994) which contain articulatory instructions for all the permissible
syllables in the language.
Thus, while phonological word forms are created "on
the fly" each time, the instructions for articulating individual syllables are
retrieved as wholes.
This mechanism explains why speech errors almost never
violate the phonotactic constraints of a language, and why phoneme and
morpheme exchange errors always result in the production of the correct
allophone for the new environment (see example of morpheme stranding, Table
1:1).
Although some of the basic groundwork for these models has been
contributed by speech error analyses, Levelt (1992) argues that speech error data
do not permit fine-grained distinctions between competing models, and suggests
that other techniques are required to provide testable hypotheses about the
processes involved at the various levels of speech production.
The first approach
to appear with this potential was the connectionist modelling of speech
production, especially of lemma and lexeme retrieval; the second has been
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 9
experimental studies of the time course of different types of processing in normal
speech
production.
Dell's Interactive Activation Model of Production
Connectionist models represent a theoretical advance over descriptive
accounts of speech production in their attempt to specify the p r o c e s s i n g
mechanisms involved in speech production, rather than simply delineating the
stages.
Interactive activation mechanisms in connectionist networks have
proven particularly appropriate for models of speech production, given the
notion already common in descriptive models that representations must reach
sufficient activation thresholds for production (Harley, 1995; Kay & Ellis, 1987;
Morton, 1979) .
Connectionist models thus allow a formal expression of such
activation theories, and so provide an alternative to naturalistic or experimental
speech data as a means of formally testing the hypotheses they generate.
A range
of such models has been proposed (e.g. Harley, 1995; MacKay, 1987; Stemberger,
1985) , but perhaps the most productive of these has been the model of Dell (1986),
developed with the help of various colleagues in subsequent years (Dell, 1990; Dell
& O'Seaghdha, 1991; Dell et al., in press; Gagnon, Schwartz, Martin, Dell, & Saffran,
in press; Martin, Dell, Saffran, & Schwartz, 1994; Martin & Saffran, 1990; Martin &
Saffran, 1992; Martin & Saffran, submitted; Martin, Saffran, & Dell, 1996; Schwartz,
Saffran, Bloch, & Dell, 1994) .
The model proposed by Dell and colleagues is of particular relevance to this
thesis because it has been used to guide the investigation of disorders of language
production (Dell et al., in press; Gagnon et al., in press; Martin et al., 1994; Martin
& Saffran, 1990; Martin & Saffran, 1992; Martin et al., 1996; Schwartz et al., 1994)
as well as the production of speech in normal speakers (Dell, 1990; Dell &
O'Seaghdha, 1992) .
The model's application to the investigation of aphasic speech
disorders is discussed below, and is examined in some detail in Chapters 3 and 4.
present, however, only the model's account of normal speech production is
presented.
An unelaborated version of this model (Dell & O'Seaghdha, 1992) is
shown in Figure 1:3; (although see Dell, 1986, for a version which also
incorporates morphemes, syllables, syllable constituents and articulatory
features).
At
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 10
Figure 1:3.
The interactive activation model of lexical access in language
production proposed by Dell and colleagues (from Dell and O'Seaghdha, 1991, p.
605)
In this model, activation is transmitted bidirectionally within a network of
semantic, lexical and phonological nodes.
In spontaneous speech, activation
begins at a level of semantic feature nodes according to the semantic
specifications of the intended utterance, and feeds forward through a layer of
nodes representing lexical items to activate nodes at a phonological level.
When
the network is operating normally, there is time for backward spreading
activation from the phonological level to reach the lexical level and increase the
activation levels of all words connected to the activated phonological segments.
The target lexical node, receiving feedforward activation from the semantic level
and
feedback activation from the phonological level, will typically receive the
most activation and be selected.
In an efficiently functioning network, feedback
loops between all levels tend to stabilise activation patterns upon the target;
interactive activation between the phonological and lexical levels in particular
will yield stable, noise-free phonological activation patterns for existing words.
In different single word production tasks, the information provided by task
stimuli enters the model at different levels.
In the task of naming a picture, as in
spontaneous speech, activation begins at the semantic level and spreads from
semantic to lexical to phonological nodes.
In word repetition, in the version of
the model implemented by Martin et al. (1994), activation stimulated by an
auditory-phonological input begins at the phonological level and feeds upwards
to effect selection of the lexical node to be replicated in production (but see Dell et
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 11
al., in press, for an alternative account of word repetition in which the first level
to be activated is the lexical level).
Reading aloud, by analogy with repetition
(Croot et al., in press; Dell, personal communication), presumably also activates
the phonological level first, rather than the semantic level (Coltheart, Curtis,
Atkins, & Haller, 1993; Plaut, McClelland, Seidenberg, & Patterson, 1996) .
According to this model, speech errors occur when a non-target node at
any of the three levels receives more activation than the target node and is
selected for production.
On some occasions in normal speech, noise in the
network may raise the activation level of a non-target node and a "slip of the
tongue" error will occur.
Two global processing parameters determine the efficiency of processing
in the network: the strength of connections between nodes and the rate of
activation decay at the nodes.
A systematic disruption in either or both of these
parameters leads to impaired functioning of the network as a whole.
As will be
described later in this chapter, such disruption may result in one or another of
several common aphasic syndromes.
The model of Dell and colleagues is obviously more circumscribed than that
of Levelt (Levelt, 1989; Levelt & Wheeldon, 1994), and focusses on detailed
investigation of only a few representational levels and processing parameters.
The two models nevertheless describe an essentially comparable series of
processing levels.
The semantic feature nodes of the Dell model correspond to
some of the information manipulated by the Conceptualiser in Levelt's (1989)
model; lexical selection approximately corresponds to the process of lemma
retrieval in Levelt's model, while activation of the phonological nodes
corresponds to phonological encoding.
One difference is that Dell's model has
been predominantly applied to single word production tasks (but see Martin &
Saffran, submitted, for an example of its application to two-word repetition); thus
a mechanism for combining grammatical head words and clitics, as described by
Levelt and Wheeldon (1994), has not been incorporated.
A second difference is
that the model of Dell and colleagues does not attempt to describe articulatory
levels of processing in speech production, so activities such as the retrieval of
syllabic gestural scores are beyond its scope.
Discrete Stages or Interactive Activation?
One major question on which the models of Levelt and Dell diverge is
whether processing within the speech production system occurs in discrete
stages, whereby processing at one level is independent of processing at the next
level (Levelt et al., 1991; Schriefers, Meyer, & Levelt, 1990) , or whether activation
from processing at one level may feed back or forward to influence processing at
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 12
neighbouring levels (Dell, 1986).
different sources.
The evidence for the two positions comes from
Levelt, Schriefers and colleagues have carried out dual-task
interference studies to see at what point in the time course of one task the
performance of the other will interfere.
For example, Schriefers et al. (1990)
showed that auditorily presented distractor words which were semantically
related to the picture name only affected response latency in picture naming
when presented before the picture was shown.
By contrast, phonologically
related distractors only affected response latency when presented with or after
the picture.
Schriefers and colleagues argued this was evidence that semantic
and phonological activation in picture naming were strictly successive stages.
Levelt and colleagues (1991) showed that semantic alternatives to a correct
picture name were not phonologically activated as would be predicted by an
interactive
activation
model.
Dell and colleagues have, instead, based their argument for interactive
activation between levels on statistical data from speech error corpora showing
that errors reveal a combination of semantic and phonological influence at a
much higher rate than would be predicted to arise by chance (Dell & Reich, 1981),
and have demonstrated that this effect is reproduced in simulations where
activation is interactive between levels (Dell, 1986).
In response to the dual-task
studies of Levelt and colleagues suggesting no interaction, Dell and O'Seaghdha
(1991) have argued that l o c a l interactivity (between adjacent levels) may in fact
appear like global modularity (discrete stages) throughout a model.
Harley (1995)
comments that from this impasse it is difficult to see how the two models may be
empirically
distinguished.
PHONOLOGICAL DISRUPTION IN APHASIC SYNDROMES
In addition to the various investigations of speech production based on data
from normal speakers, the study of phonological disruption in aphasia has
provided complementary insights and converging evidence on the nature of
normal speech production.
The early theories and the tradition they spawned in
the analysis of aphasic deficits have tended to emphasise the relationship
between lesion site and damaged function.
In recent years, however, the
cognitive neuropsychological approach to the study of aphasia has also argued
the value of theorising about functional processing components independently of
lesion site.
The first section of this overview of phonological disruption in
aphasia describes the development of a taxonomy of aphasic syndromes,
determined in part by the fluency or otherwise of spontaneous speech, and in
part by confirmed or probable lesion site.
Contributions from the study of these
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 13
syndromes to the understanding of phonological output processing are also
considered.
The second section reviews a number of cognitive
neuropsychological studies in which the processing components or mechanisms
are themselves the focus of the investigation, and in which the neuroanatomical
location of the lesion does not have explanatory status (Ellis & Young, 1988) .
The Historical Development of Aphasic Syndrome Classifications
In 1861, Paul Broca described to the Société d'Anthropologie de Paris the
case of a 51 year old man who had lost "the faculty of articulate language" (Johns
& LaPointe, 1976, p. 163), being unable to utter more than the syllable "tan" in
most conversational situations, but able to swear fluently in phrases of up to six
syllables (Broca, 1861/1965) .
His speech had been progressively impaired for
over 20 years, in the context of apparently preserved comprehension and
communicative gesture.
The patient's impaired swallowing was attributed to
pharyngeal paralysis, and he showed weakness of the left-sided facial muscles;
movement of the tongue and chewing were, however, unimpaired.
Autopsy
revealed a softening of the posterior portion of the 2nd and 3rd frontal gyri, the
inferior marginal gyrus of the temporal lobe, part of the insula and the
underlying part of the striate body.
Broca concluded that the pathological process
had originated in the posterior part of the third frontal gyrus because this region
lay approximately at the centre of the pathological distribution and was most
severely affected by the pathological process.
Broca described this man's speech difficulty as "aphemia", by which he
meant loss of memory for words (Herrnstein & Boring, 1965) .
Contrary to the
predominant equipotentiality hypotheses of brain function at that time (Flourens,
cited by Wernicke, 1874/1969) , Broca argued that there were functions specific to
small brain regions, and that the faculty of speech could be localised to the 2nd
and 3rd convolutions of the frontal lobe.
In the same year, supporting this
conclusion, Broca reported a second patient with almost identical language
symptoms and lesion site, and another neurologist, Auburtin, reported a patient
who lost speech following a frontal haemorrhage, and another patient who
exhibited immediate loss of speech when a surgical spatula was placed on his
exposed frontal lobe during an operation (Johns & LaPointe, 1976) .
By 1874,
evidence had accumulated such that Wernicke could state, "cases of pure motor
aphasia are so frequently to be found in the literature that there can no longer be
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 14
any doubt of its existence, or of the presence in these cases of lesions of the first1
frontal convolution" (Wernicke, 1874/1969, p. 66).
By this time, however, the
disorder was known as aphasia , rather than aphemia (Trousseau, 1864; cited in
Johns and LaPointe, 1976).
While Wernicke was convinced that aphasia affecting the production of
speech could be localised to the frontal lobe, he contested the idea that the
particular frontal region which came to be known as Broca's area was the only
speech centre.
Wernicke (1874/1969) described two cases who presented with
intact hearing, but nevertheless severely impaired comprehension.
Their speech
differed from that of the patients described by Broca, in being fluent, but
containing nonsensical or distorted words; their lesion site also differed from that
reported by Broca.
For example, the post-mortem examination of one patient,
Susanne Rother, showed posterior, rather than anterior, pathology, focused
around the superior temporal gyrus (Wernicke, 1874/1969).
Wernicke therefore
proposed that there were t w o general brain areas with primary functional
significance, the frontal lobe, and the temporal and occipital lobes together.
He
wrote,
The first is a motor area and contains representations of movement;
the second is sensory, containing memory images of past sense
impressions.
The parietal lobe proper, which lies between them, is a
transitional area (Wernicke, 1874/1969, p. 36),
and this account has been foundational to a system of classifying aphasic
syndromes which is still very much in use today (e.g. Geschwind, 1972) .
Wernicke's schema allowed the description of three possible types of
aphasia: one occurring when the frontal motor centres are impaired, one
occurring with impairment to the posterior sensory centres, and one in which
the two centres are disconnected by a lesion to some part of the connecting fibres
between them (e.g. the arcuate fasciculus traversing the parietal lobe).
In the
first, the production of speech is impaired in the context of spared
comprehension, while in the second, the reverse pattern occurs.
In the third
type, unimpaired "vocabulary" is available for both production and
comprehension, but because the transmission of information is impaired in both
directions between the motor and sensory centres, a fully comprehended spoken
word cannot be repeated without difficulty, and sound errors may be produced by
1 Wernicke (1874/1908) called the first gyrus anterior to the central fissure the first frontal
gyrus ; Broca (1861) referred to it as the third frontal gyrus.
known as Broca's area or Brodmann area 44 (Duss, 1976) .
Today it is most commonly
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 15
the frontal production mechanisms because these are no longer under adequate
control from the posterior sensory images (Wernicke, 1874/1969).
Lichtheim in 1885 added a third functional centre to Wernicke's schema, a
"concept centre".
He described a further two aphasic syndromes (transcortical
motor aphasia and transcortical sensory aphasia) which would arise when the
concept centre was disconnected by lesion from either the motor centre or the
sensory centre, respectively.
Lichtheim, 1885, p. 436).
This model is shown in Figure 1:4 (adapted from
Lichtheim's model was more successful as an account of
the relationship between cognitive functions than of the neuroanatomical sites
underlying those functions; however the five subtypes of aphasia that he
described form the basis for the classification schemata of aphasic syndromes in
several contemporary aphasia batteries, including the Boston Diagnostic Aphasia
Examination (Goodglass & Kaplan, 1983)
and the Western Aphasia Battery
(Kertesz, 1979) .
KEY:
T.M.A. = transcortical motor aphasia, T.S.A. = transcortical sensory aphasia,
B.A. = Broca's aphasia, C.A. = conduction aphasia, W.A. = Wernicke's aphasia
Figure 1:4.
Lichtheim's schematic representation of the origins of different
aphasic subtypes (adapted from Lichtheim, 1885, p. 436, and McCarthy &
Warrington, 1990, p. 13).
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 16
In the Boston classification system, the major aphasic syndromes which are
characterised by phonological disruption are Broca's aphasia, conduction aphasia,
Wernicke's aphasia, transcortical motor aphasia, mixed non-fluent aphasia and
aphemia.
Table 1:2 lists the clinical features and lesion site(s) associated with
these syndromes according to the Boston descriptions.
Table 1:2.
The Boston Diagnostic Aphasia Examination's classification of the major
aphasic syndromes in which there is phonological disruption (Goodglass &
Kaplan, 1983, pp. 75-98).
Syndrome
Characteristics
Lesion
Broca's
-awkward
left 3rd frontal
Aphasia
articulation
Site
-restricted
vocabulary
convolution,
-simplified
grammar
white matter extending to
-relatively
preserved
comprehension
inferior motor strip
(precentral
Conduction
Aphasia
-repetition
disproportionately
subcortical
gyrus)
any of the following:
impaired compared with fluency of
arcuate
spontaneous speech
supramarginal
-relatively
preserved
comprehension
-phoneme selection and sequencing
fasiculus,
gyrus,
superior temporal gyrus,
insula
errors, but production is wellarticulated
Wernicke's
Aphasia
- impaired auditory comprehension
posterior portion of 1st
- fluent spech with phonological and
temporal gyrus of left
semantic errors and sometimes
hemisphere
neologistic jargon
- word-finding difficulties
Transcortical
Motor
Aphasia
-repetition
relatively
intact
-spontaneous speech a mixture of
anterior, superior, or
deep to Broca's area
fluent & non-fluent
Mixed
Nonfluent
-as for Broca's aphasia, but with
large left hemisphere
Aphasia
impaired
comprehension
lesion
Aphemia
-isolated
articulatory
subcortical
disorder
-grammatically intact speech
-no facilitation of speech by
imitation or overlearning
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 17
Syndrome-Based Investigations of Phonological Breakdown
The syndrome-classification approach to the study of aphasia
approximately attributes non-fluent versus fluent aphasias to anterior versus
posterior lesion sites respectively (Goodglass & Kaplan, 1983).
Further, the
deficits of anterior aphasics are usually attributed to motor or articulatory
impairments, in which the correct phonological form has been retrieved and/or
encoded, but the articulatory implementation of this form is disrupted.
By
contrast, the difficulties of posterior patients are frequently attributed to a
higher-level
breakdown
in
symbolic/linguistic
processing,
whereby
the
correct
elements specified by the phonological representation of a word (lexeme) fail to
be selected, resulting in the substitution, addition and deletion of components
usually described as phonemes.
For an example of this motoric/linguistic
distinction, compare the descriptions of Broca's versus conduction aphasia
according to the Boston aphasia classification (Table 1:2).
As will be argued below,
however, the nature of the phonological disruption in the anterior versus
posterior aphasias requires more rigorous theoretical differentiation than is
presently
available.
Investigations of the phonological disruption in Broca's aphasia have
consequently focused on motor aspects of the production breakdown.
In one
early study, Alajouanine, Ombredane & Durand (1939; cited in Lecours &
Lhermitte, 1976) measured the oral and nasal airflow of anterior aphasic patients
during speech.
They concluded that the patients made errors on the duration and
timing of individual sounds, and became more impaired when the required
movements for a sound were more complicated.
They described these patients as
having "phonetic disintegration", attributed to the poor articulatory
implementation of an adequately retrieved phonological form.
(The term
"phonetic disintegration" refers to the abnormal acoustic end-product of the
speech disruption, rather than the production process which is putatively
impaired.)
A second early study of articulatory deficits by Shankweiler and
Harris (1966)
analysed the errors of five patients with anterior left frontal
lesions in the repetition of monosyllabic words.
This study found that beginnings
were more subject to error than the ends of words, and that consonants
(especially fricatives and affricates) were more difficult than vowels.
In recent years, the development of sophisticated instrumentation has
allowed precise measurement of the range and variability of the acoustic
properties of speech (McNeil, Liss, Tseng, & Kent, 1990; Tuller & Story, 1988) ,
and/or the movement dynamics of the lips, tongue and jaw during speech using
magnetic transducers attached to these articulators (Katz, Machetanz, Orth, &
Schonle, 1990; Shankweiler, 1996) .
These instrumental studies have confirmed
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 18
that anterior aphasics are able to produce the linguistic contrast between
different phonemes, despite a primary difficulty in the space-time co-ordination
of two independent articulators.
For example, anterior patients have been shown
to maintain the linguistic contrast between voiced and voiceless stops on the basis
of vowel duration (the same vowel is longer preceding a voiced stop than a
voiceless stop) even though voice onset time (which depends on correctly coordinating the release of the oral stop and the onset of phonation at the larynx)
may not provide a reliable cue to the linguistic identity of the sound (Baum,
Blumstein, Naeser, & Palumbo, 1990; Duffy & Gawle, 1984) .
Lecours and Lhermitte
(1976) attribute the same phenomenon to the inappropriate selection of buccophonatory
muscular
movements.
By contrast with the accounts of phonological disruption in Broca's
aphasia, accounts of the disrupted production of speech sounds
in conduction
aphasia usually describe a deficit in linguistic/phonological output processing.
Several studies have focused on the frequently described phenomenon whereby
conduction aphasic patients frequently make successive attempts at a
phonological target in speech, a phenomenon also referred to as "conduit
d'approche". For example, this is a conduction aphasic's attempt to produce the
target asparagus: [InspQr´d´ InspQs InsprQ InsprQt√k´ InspQ] etc. (Kohn, 1984,
p. 108) .
Kohn attributed the production of these successive approximations to a
failure in the process of what she called "prearticulatory planning", which
corresponds approximately to phonological encoding in the model of Levelt and
Wheeldon (1994).
Kohn proposed that the patients were able to retrieve the
phonological lexical representation and hold it in working memory, but failed in
repeated attempts to set up the proper articulatory programme.
She also argued
that the retrieval of syllable frames in phonological encoding was particularly
compromised (compare the retrieval of syllable-based sets of articulatory
commands described by Crompton, 1982, and Levelt and Wheeldon, 1994,
summarised above).
This hypothesised processing deficit thus accounted for the
patients' frequent self-interruptions at syllable boundaries, for the slow, careful
production of all syllables on the rare occasions when a complete polysyllabic
word was articulated, and for the patients' production of CV syllables as a default
structure.
In the latter instance, CV syllables were assumed to be the unmarked
form of syllable structure for all phonological representations, thus marked
syllables, which require further elaboration in production, were argued to be
more vulnerable to damage.
Finally, Kohn suggested the conduction aphasics
were also impaired in the use of acoustic feedback to modify speech output, citing
as corroborative evidence the finding that these patients were less affected by
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 19
delayed auditory feedback during speech production than normal speakers
(Boller, 1978) .
A study by Valdois, Joanette, and Nespoulous (Valdois, Joanette, &
Nespoulous, 1989)
reached a similar conclusion to Kohn (1984) about the
successful retrieval of the stored phonological form in conduction aphasia, in the
context of subsequent difficulty organising an articulatory programme.
These
authors, however, disagreed with Kohn's claim that speech monitoring abilities
are impaired in conduction aphasia.
Valdois et al. (1989), described a conduction
aphasic patient whose spoken attempts grew successively closer to the target
phonological form, and this was claimed as evidence for the patient's good
retention of the phonological form to be produced, as well as good monitoring of
the output which enabled the subsequent attempt(s) to be closer.
The linguistic/motoric dichotomy in accounts of speech breakdown in
Broca's aphasia and conduction aphasia represents a theoretical obstacle in the
investigation of speech production as a whole.
(language) and motor-speech
Investigations of a p h a s i c
disorders have evolved into somewhat separate
fields, although frequently their object of study — the disrupted production of
speech sounds following both anterior and posterior brain damage — is the same.
To add to the confusion, a further syndrome known as apraxia of speech, itself
inconsistently defined in the literature, in its various manifestations completely
overlaps the clinical description of the phonological impairment and the
anatomical localisation described for both anterior and posterior aphasic
syndromes (Bay, 1962; Johns & LaPointe, 1976; Rosenbek, Kent, & LaPointe, 1984;
Trost & Canter, 1974) .
Apraxia of speech is defined — at its simplest — as "articulation problems
associated with cortical lesions" (Johns & LaPointe, 1976, p. 172).
This definition
identifies apraxia of speech as a motor, not a linguistic disruption, but
differentiates it from all types of dysarthria2 except cortical dysarthria (Bay,
1962), with which it is synonymous3 .
The problem with this definition of apraxia of speech is that, without
precise instrumental measurements, it may be impossible to distinguish by ear
2 Dysarthria is the reduced or faulty innervation of the speech musculature (Darley, 1964) .
3 Other definitions of apraxia of speech link it theoretically with the various types of limb
apraxia
— another disorder in which theoretical analyses have, for many years, struggled to
bridge "the mental—physical impasse" (Miller, 1991, p. 138).
These definitions frequently
invoke the will as an explanatory factor in the execution of action (De Renzi, 1987) ,
introducing a further theoretical entanglement given that the specific role of volition in
speech production has remained unclear since the time of Hughlings Jackson (1874).
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 20
whether linguistic contrasts (such as in vowel length before consonants varying
on the phonologically contrastive feature of voicing) are being maintained.
It is
thus unclear whether the disruption is in fact o n l y affecting motor rather than
linguistic levels of processing.
For example, Miller (1991)
notes that conduction
aphasia and apraxia of speech are not reliably distinguishable from each other,
even on the basis of narrow phonetic transcriptions.
Further, even when
instrumental measures a r e used, the presence or absence of articulatory
disruption does not necessarily distinguish between the output disruptions of
anterior versus posterior aphasics.
Blumstein (1990)
reported articulatory
mistiming/misco-ordination in patients clinically diagnosed with apraxia of
speech, conduction aphasia, and even Wernicke's aphasia.
To make matters yet more complicated, while the definition of apraxia of
speech is clinically problematic, as described above, it is also theoretically
problematic because by definition the disorder is indistinguishable from the
motor disruption described in Broca's aphasia.
This overlap between apraxia of
speech and both conduction aphasia and Broca's aphasia thus highlights the fact
that while the s y n d r o m e s of conduction aphasia and Broca's aphasia are
considered to be distinct, the nature and account of the phonological disruption in
the two syndromes is far from clearly differentiated.
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 21
The Neuroanatomy of Phonological Processing in Aphasic Syndromes
Surprisingly, despite the overlap and inconsistency of the clinical
descriptions and theoretical accounts of phonological breakdown in the
syndromes, damage to a relatively circumscribed area of the brain is associated
with phonological disruption in Broca's aphasia, apraxia of speech, conduction
aphasia, and Wernicke's aphasia.
Figure 1:5 illustrates the areas involved, all of
which border the sylvian fissure of the language-dominant hemisphere.
Figure 1:5.
Diagram of the lateral surface of the left hemisphere of the human
brain, showing the cortical areas associated with phonological disruption in a
range of aphasic syndromes (See also Tables 1: 2 and 1:3).
Table 1: 3 shows the (predominantly) cortical lesion sites associated with
phonological disruption in four aphasic syndromes, and reveals some interesting
features about the relationships between the symptom clusters described by
syndrome labels, and the associated phonological deficits.
The data in the table
are summarised from three sources:
i) studies reporting the localisation of lesion in Broca's aphasia (Mohr et al., 1978)
, aphemia (Lecours & Lhermitte, 1976; Schiff, Alexander, Naeser, & Galaburda,
1983; Tonkonogy & Goodglass, 1981)
and conduction aphasia (Green & Howes, 1977;
Palumbo, Alexander, & Naeser, 1992; Valdois, Joanette, Nespoulous, & Poncet, 1988),
ii) the guidelines in two widely used aphasia batteries as to the likely lesion site
associated with these syndromes (Goodglass and Kaplan, 1983; Kertesz, 1979), and
iii) reviews of apraxia of speech (Johns & LaPointe, 1976; Miller, 1991).
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 22
Table 1:3.
Neuroanatomical sites reported to be involved in four aphasic
syndromes. A tick
indicates that a lesion to a particular site has been sufficient
to result in the particular syndrome; a tick and a plus sign
(+)
indicates that the
area was only associated with the syndrome when there was additional damage.
Structure
(Numbers in brackets
show Brodmann's areas)
Broca's area (44)
(3rd frontal convolution/
frontal operculum)
Inferior motor cortex (4,6)
(foot of precentral gyrus)
Broca's
Aphemia
Aphasia
Apraxia
of
Conduction
Speech
Aphasia
(+)
(G&K, Mohr,
Kertesz)
(Mohr, Schiff)
(J&L, Miller)
(+)
(G&K, Mohr)
(L&L, Schiff)
(Kertesz)
(T&G)
(Valdois,
Kertesz)
Parietal operculum (43)
(+)
(G&H)
Supramarginal gyrus (40)
Angular gyrus (39)
(Miller)
(G&H, G&K,
Palumbo,
Kertesz)
(+)
(Miller)
(G&H,
Palumbo)
Superior temporal gyrus
(22)
(G&H, G&K)
(+)
Temporal operculum (41)
(primary auditory cortex)
Insula (42)
(G&H)
(+)
(Mohr)
(Miller)
(G&K)
(+)
(G&H, Kertesz
Palumbo)
Arcuate
fasciculus
(Miller)
(G&K)
(+)
(Kertesz)
KEY:
G&H = Green & Howes (1977); G&K = Goodglass & Kaplan (1983); J&L = Johns &
LaPointe (1976); Kertesz = Kertesz (1979); Lecours & Lhermitte (1976); Miller = Miller
(1991); Mohr = Mohr et al. (1978); Palumbo = Palumbo et al. (1992); Schiff = Schiff et al.
(1983); Valdois = Valdois et al. (1988); T&G = Tonkonogy & Goodglass (1981)
Table 1:3 shows that a lesion to Broca's area alone does not lead to the full
syndrome of Broca's aphasia.
It may, however, be sufficient to cause what
Goodglass and Kaplan (1983) term a p h e m i a , and Alajouanine, Ombredane and
Durand (1939; cited in Lecours & Lhermitte, 1976) term phonetic
articulatory disturbance without naming or grammatical deficits.
disintegration:
Thus, aphemia
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 23
is almost certainly equivalent to the articulatory component of Broca's aphasia.
Damage to the inferior part of the primary motor strip may also cause aphemia, as
may damage restricted to the immediately adjacent parietal operculum.
At this
point it is worth noting that a lesion to the latter two structures is also claimed to
be sufficient to cause conduction aphasia; although the structure most frequently
implicated in that syndrome — and often on its own — is the supramarginal gyrus.
While a lesion in the superior temporal gyrus may be associated with conduction
aphasia, it is unusual for lesions more anterior in the temporal lobe (e.g. in areas
41 and 42) to result in conduction aphasia without additional damage to one of the
other sites already mentioned.
Apraxia of speech is attributed to sites spanning
the entire anatomical area just described.
In summary, isolated articulatory deficits are associated with the posterior
frontal and anterior parietal lesion sites.
Phonological deficits associated with
repetition impairment in conduction aphasia are most frequently associated with
posterior
perisylvian
lesions.
It remains to be established whether some of the sound deficits reported in
conduction aphasia are actually aphemia, given their overlapping (anterior
parietal and posterior frontal) anatomical sites.
Even more interesting is the
question of how the sound deficits arising from damage around the
supramarginal gyrus differ from aphemic deficits.
In one study which begins to
address this question, Valdois et al. (1988), concluded that there are at least two
subtypes of conduction aphasia.
In one type, damage includes the parietal
operculum, and patients present with an associated bucco-lingual apraxia and
hypoesthesia of the right hand.
In the other, the patients have a lesion which
spares the parietal operculum, and have no bucco-lingual apraxia and
hypoesthesia.
Analysis of the sound-substitution errors produced by the two
groups showed that substitutions were more similar to the target sound for the
anterior group than the posterior group, an effect which was consistent for
individual patients as well as for groups.
Valdois and colleagues suggest that the
anterior parietal regions are concerned with premotor processing, while the
frontal regions carry out motor processing.
Gracco and Abbs (1987)
also argue
that there are two motor stages involved in the implementation of phonological
goals — stages of motor programming and motor execution.
One speculation is that
the anterior parietal and inferior frontal regions are involved in these two motor
stages, while the more posterior parietal areas are associated with the processes
described by Levelt (1989) as phonological encoding.
A further question concerns whether the phonological paraphasias
arising in conduction aphasia and Wernicke's aphasia have the same source,
given the anatomical overlap between syndromes (in the region of the superior
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 24
temporal gyrus), or whether there are different types of phonological disruption
which arise from lesions to the superior temporal area compared with the area
around
the
supramarginal
gyrus.
The localisation studies described above predate the sophisticated imaging
techniques currently available using structural and functional magnetic
resonance imaging (MRI), single photon emission computed tomography (SPECT)
and positron emission tomography (PET).
Despite the low resolution of the
computerised tomography (CT) scans used in the above studies, however, data
from more recent MRI and PET studies support the earlier conclusions.
In
Chapter 6, all the patients with Dementia of the Alzheimer Type who show atypical
phonological disruption are reported to have perisylvian lesions evident from
MRI and/or SPECT scans (and some confirmed post-mortem).
PET studies of
normal subjects also implicate the perisylvian areas of the left hemisphere in the
receptive processing of phonological stimuli (Poeppel, 1996a) , "inner speech"
(McGuire et al., 1996) , and in the articulatory loop and phonological store
components of working memory (Poeppel, 1996b) .
COGNITIVE NEUROPSYCHOLOGICAL STUDIES OF PHONOLOGICAL
DISRUPTION IN SPEECH PRODUCTION
While the use of syndrome-based investigations does allow generalisations
about groups of patients, and has diagnostic and prognostic value in predicting
the likely pattern of recovery or progression of the aphasia, the debate about the
characteristics of each syndrome has obscured the precise specification of the
phonological disruption(s) occurring in and/or across syndromes.
For example,
while only some of the "classical" aphasic syndromes have phonological
breakdown as a defining deficit, Blumstein (1994, p. 31) claimed that in fact,
"whatever the nature of the underlying deficit...virtually all aphasic patients
regardless of lesion site display phonological output deficits" (italics added).
The
interest for models of speech production therefore lies in the differences between
individual, well-studied patients' phonological deficits and general aphasic
profiles as well as in the common features of their disorders.
An approach particularly suited to the investigation of specific cognitive
functions on a patient-by-patient basis, to some extent independent of both lesion
site and syndrome classification, is cognitive neuropsychology.
This approach is
particularly attractive in the investigation of phonological disruption, because it
avoids the conflation of anatomical and psychological models described above.
Instead, individual lesions are interpreted like experiments in which certain
functions are suppressed while others remain (Ellis, 1987) .
The aim is to give a
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 25
precise account of the integrity of a specific function, which is exactly the
information most likely to be obscured in syndrome-based group studies.
Within
the cognitive neuropsychological framework, phonological deficits in speech
production have been less well investigated than other aspects of cognition (such
as reading or immediate memory), but the approach is promising.
Both
descriptive and computational models have been employed in the enterprise; some
examples of investigations using both types of account are described below.
Descriptive
Accounts
In one of the earliest cognitive neuropsychological studies of speech
production using this approach, McCarthy and Warrington (1984) reported that
two conduction aphasic patients were more likely to repeat three syllable target
words correctly in tasks requiring semantic processing compared with their
repetition of the same words in isolation, while the reverse pattern was observed
in the performance of a transcortical motor aphasic patient.
From this, McCarthy
and Warrington argued for a "two route" model of speech production in which
one route involves semantic processing and the other a direct (nonsemantic)
transcoding from auditory-phonological input to speech output.
They predicted
that selective lesioning of either of these routes would result in the two different
aphasic
syndromes.
In contrast to the patients reported by McCarthy and Warrington (1984),
Caplan, Vanier & Baker (1986) reported a patient under the rubric of
"reproduction conduction aphasia" who showed an equivalent phonological
impairment in picture naming, word repetition and reading aloud.
These authors
argued that this patient had an impairment at a level of speech output processing
common to the three tasks.
They proposed that his deficit must differ from the
disruption in the transcoding of auditory-phonological input to speech output
proposed to account for the repetition deficits observed by McCarthy &
Warrington (1984), because such a transcoding process is not required in naming
and reading tasks.
Caplan and colleagues attributed the deficit to an error in
processing which occurs "between underlying and surface phonological
representations" (1986, p. 122).
These "underlying phonological representations"
correspond approximately to the phonological lexical representations or lexemes
in other models of speech production (Butterworth, 1992; Levelt, 1989); and the
deficit proposed by Caplan et al. thus occurs in a process equivalent to the
"encoding" or "spelling out" of the phonological form for production.
A
conduction aphasic reported by Wilshire and McCarthy (1993) , while impaired on
all three tasks, was not e q u i v a l e n t l y impaired in naming, repeating and reading,
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 26
so not all conduction aphasics who are impaired on single word tasks necessarily
have a deficit restricted to a common output level.
Other patients have been argued to show a deficit in the retrieval of the
phonological lexical representation, a process which occurs immediately prior to
phonological encoding.
and Ellis (1987)
For example, a
severely anomic patient reported by Kay
showed good picture recognition and comprehension, but was not
assisted in naming by the provision of phonological cues.
Kay and Ellis attributed
this patient's deficit to weak or fluctuating levels of activation between
representations in the semantic system and the phonological output lexicon.
Finally, researchers have investigated the performance of patients with
phonological output versus input difficulties to ask whether the phonological
lexical representations used for receptive word processing are the same as those
used in speech production.
The case for separate input and output lexicons is
argued partly on the basis of a double dissociation between word comprehension
and production.
This double dissociation is evident in patients with pure word
deafness and word meaning deafness who can speak normally but cannot
understand speech, compared with conduction aphasic patients who show
apparently normal comprehension, but make phonological errors in speech
production (Ellis & Young, 1988).
Monsell, 1987; Morton, 1979)
Additionally, priming studies with normals (e.g.
demonstrate little interference between the tasks of
overtly or silently generating words and recognising words, suggesting that
different representations are used in the different tasks.
The issue is, however, far from resolved.
Arguments against the
neuropsychological dissociations include the asymmetry of difficulty between
word production versus comprehension tasks (comprehension tasks can be done
on the basis of partially activated or degraded representations, while production
integrity is immediately compromised by a degraded phonological
representation), and the finding that impaired phonological input processing as
well as output processing can be demonstrated in conduction aphasia if the input
task requires very precise phonological processing (Allport, 1983) .
Further,
there is evidence for sub-lexical influences of speech production on speech
perception (Gordon & Meyer, 1984) , so that even if there is some separation
between input and output processing, the underlying systems are far from
independent.
The question of which processes and/or pathways, if any, are
shared by phonological input versus output is still controversial.
Dell and colleagues' approach to this issue has been to perform simulations
of repetition using a version of the model in which the same phonological level is
used for input and output processing, the single
network version (e.g. Martin et
al., 1994), and another version in which the phonological level used for output is
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 27
assumed to be independent of that used for input, the perfect
(e.g. Dell et al., in press).
recognition version
The former version provides the best fit to the naming
and repetition performance of patients with impaired phonological input
processing, the latter to patients with no apparent receptive phonological
impairments.
As most of the patients described in this thesis have phonological
input deficits, the single network version is the one most frequently discussed
(but see Chapter 4 for a discussion of the most suitable model to represent input
versus output processing for the two patients reported in that chapter).
Accounts Using Dell's Interactive Activation Model
More recently, cognitive neuropsychological theories have been
formalised in connectionist models using spreading activation mechanisms.
In
particular, the interactive-activation model of Dell (1986), described earlier in
this chapter, has shown considerable predictive and explanatory power.
The
model has been used to account for the error profile of a patient with deep
dysphasia (Martin & Saffran, 1992; Martin et al., 1994), a disorder characterised by
naming deficits, semantic errors in repetition and a severe difficulty in the
repetition of nonwords (Martin et al., 1996).
It has also provided an account of the
jargon aphasic speech of a second patient (Schwartz et al., 1994).
The latter
syndrome is characterised by fluent speech containing many phonological
paraphasias, although syntactic and prosodic aspects of speech production are
unaffected (Butterworth, 1979) .
These accounts attributed the patients' aphasic
deficits to pathological changes in one of two global parameters which are
hypothesised to regulate the efficient operation of processing throughout the
network.
These parameters are the rate of activation decay at the nodes, and the
strength of connections between nodes.
The phonologically related errors in naming and semantically related
errors in repetition associated with deep dysphasia were explained with reference
to a pathologically rapid decay of activation in the Dell network (Martin &
Saffran, 1992; Martin et al., 1994).
It was argued that in a semantically-driven
task such as naming, if the activation feeding forward from semantic to lexical
nodes decays too fast, selection of the lexical node should occur under greater
than usual influence from activation feeding back from the phonological level,
resulting in a real word error which is phonologically related to the target.
contrast, in a repetition task, activation in the single
By
network version of the
model begins at the phonological rather than the semantic level.
Under
conditions of pathologically rapid decay, lexical selection in repetition occurs
under greater than usual influence from activation at the semantic level because
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 28
initial lexical activation from phonological input decays too rapidly; the
predominant error-type should therefore be a semantically related word.
The phonologically related neologisms and perseverative errors of a
patient with jargon aphasia were attributed to weakened connection strength
between nodes in the lexical network (Schwartz et al., 1994).
follows.
The account was as
In the network, the strength of connections between nodes determines
the amount of activation which can spread from one node to another per unit
time.
When connection strength is reduced, it takes more time for activation to
build up at the correct nodes relative to activation from the processing of prior
and upcoming targets.
When the build up of target-node activation is too slow,
nodes which have previously been activated and retain residual activation are the
most likely competitors, thus errors are frequently perseverations of earlier
responses.
The lexical bias in "normal" speech errors should also be missing
under these conditions.
This is because when connection strength is weak, there
is not sufficient time for activation to feed back from the phonological level to the
lexical level, and in turn to feed forward from the lexical level to raise the
activation of phonological node combinations which have connections to existing
words relative to those which do not form words.
The patient will therefore make
a high rate of nonword errors.
INVESTIGATING PHONOLOGICAL DISRUPTION
IN NEURODEGENERATIVE DISEASE
The above review of only a few cognitive neuropsychological studies of
patients with phonological output deficits is sufficient to show that their
impairments are both varied and informative with regard to models of the
production of single words in various tasks.
Until now, however, such analyses of
phonological output difficulties have only addressed patients with nonprogressive deficits.
The study of degenerative cases therefore provides both an
opportunity for testing existing theories, and a potential source of converging
evidence.
Further, it is clear that in some types of neurological disease the
impairments are progressive within functionally specific systems, as seen in the
selective semantic memory decline which occurs in semantic dementia (Hodges,
Patterson, Oxbury & Funnell, 1992; Snowden, Goulding & Neary, 1989).
Such a
functionally selective decline raises the possibility that pathology tends to spread,
at least initially, within functionally specific neural networks (Weintraub &
Mesulam, 1993).
The study of degenerative cases may therefore prove especially
appropriate for informing current theories of neurocognitive function.
Chapter 1:Review of Phonological Processing in Normal and Aphasic Speech Production 29
This thesis contains three experimental chapters which investigate the
phonological disruption present in two patients with a progressive non-fluent
aphasia (Chapter 3), in two patients with progressive aphasia characterised by
phonological errors but somewhat more fluent speech (Chapter 4), and in a series
of thirteen patients with either probable or autopsy-confirmed Alzheimer's
Disease (Chapter 6).
As a background to these investigations, Chapters 2 and 5,
respectively, provide reviews of non-fluent progressive aphasia, and of the
phonological disruption occurring in some atypical cases of Dementia of the
Alzheimer Type.
As is the case for patients with phonological output deficits associated with
non-progressive brain injury, the phonological deficits of patients with
progressive disease are likely to be highly varied.
Thus, an essential stage in the
investigation of such disruption is the careful description of the nature of
phonological breakdown under investigation.
Such a description, based on
acoustic-phonetic transcriptions of the patients' speech, contributes to the
investigation of the phonological disruption in non-fluent progressive aphasia in
Chapter 3.
Further, the occurrence of phonological output deficits in a number of
different aphasic syndromes indicates that associations and dissociations between
performances on different tasks may provide clues as to the origins of the
phonological disruption in individual patients.
Chapter 4 compares two patients
performance on a wide range of different speaking and receptive phonological
tasks, and suggests that, while the initial impression is of a similar phonological
impairment in the two patients, the mechanisms underlying the deficits in each
may be different.
Finally, the investigation of phonological disruption in
Dementia of the Alzheimer type is in the preliminary stages; Chapter 6 therefore
provides some basic empirical data on the range and nature of that disruption
when it occurs.
Chapter 2
Review of Non-fluent Progressive Aphasia
Non-fluent progressive aphasia is one of a group of aphasic syndromes
arising in the context of neurodegenerative disease.
The first part of this review
considers historical aspects of these syndromes, and some of the issues raised by
the clinical and neuropathological overlap between types of progressive aphasia.
The second part focuses on non-fluent progressive aphasia in particular, and a
final section presents a brief overview of "mixed" progressive aphasia, which
typically manifests with some of the features of non-fluent progressive aphasia.
PROGRESSIVE APHASIC SYNDROMES
Historical Overview
Slowly progressive aphasia in the context of degenerative brain disease
was first described by Pick in 1892; Pick subsequently described another four
cases in 1904 (Hodges, 1993)
Pick's original case was a 71 year-old man with a two-
year history of behavioural deterioration, memory loss, and later speech and
language disturbance.
Post-mortem examination showed diffuse atrophy of the
left hemisphere, with severe involvement of the temporal lobe (Pick, 1892/1994).
Following Pick's early reports, there was a brief period of interest in
progressive aphasic syndromes by European neurologists (for a review of several
cases, see Mingazzini, 1913-1914) .
For instance, Dejerine and Sérieux (1897; cited
in Mesulam & Weintraub, 1992) described a patient whose pure word deafness
began at age 47 and progressed to a Wernicke-type aphasia over 5 years; autopsy 8
years after presentation demonstrated severe bitemporal atrophy with loss of
intracortical fibres and pyramidal cells.
Luzzatti & Poeck, 1991)
Rosenfeld (1909, Patient 1; cited in
reported a man who presented at age 62 with a progressive
condition described as "verbal amnesia" for the names of objects, a progressive
comprehension deficit and mild obsessional behaviour in the context of preserved
activities of daily living.
Death occurred 4 years after presentation; post-mortem
examination revealed prominent cell loss with nuclei surrounded by "granular
material" which may have been Pick bodies, lipofuscin, polyglucosan or Lewy
bodies (Luzzatti & Poeck, 1991, p. 229).
Creutzfeld (1921; cited in Pantel, 1995)
Chapter 2: Review of Non-fluent Progressive Aphasia
reported a man whose fluent aphasia progressed over a
finding difficulties to global aphasia.
31
5-year period from word-
This patient died at 60 years and showed
Alzheimer-type pathology predominantly in the left perisylvian region (first
temporal gyrus and marginal gyrus).
After the early years of the century,
however, progressive aphasic syndromes were largely neglected until, in 1982,
Mesulam again drew attention to what is now generally called primary
progressive aphasia (PPA).
Mesulam's 1982 paper described the clinical characteristics of six patients
whose aphasic symptoms typically began in the presenium, and increased without
more widespread cognitive deterioration over a period of at least seven years
(Mesulam, 1982) .
Five of these patients showed a relentless decline in language
abilities beginning with an anomic aphasia and gradually compromising reading,
writing and comprehension skills, eventually progressing to generalised
dementia in 2 of these 5 patients.
The sixth patient (the youngest of the series by
far, aged 17 at onset), was atypical, presenting with a pure word deafness which
steadily deteriorated over four years then stabilised.
In the decade following Mesulam's description of "slowly progressive
aphasia without generalised dementia", more than 50 similar cases were reported
(see Mesulam & Weintraub, 1992) .
On the basis of these reports and their own
experience, Mesulam and Weintraub (1992) proposed that the diagnostic criteria
for primary progressive aphasia should comprise a progressive deterioration in
language, together with an absence of deficits in other domains, for at least two
years.
The aphasia should be the only factor imposing any limitations upon the
activities of daily living over this period (Weintraub & Mesulam, 1993) .
There
should be no other factor, such as disturbance of consciousness, systemic disorder,
or other brain disease, to which the aphasia could be attributed.
Subtypes of Primary Progressive Aphasia
The patterns of aphasic symptoms occurring in the context of primary
progressive aphasia are somewhat heterogeneous (Westbury & Bub, in press) , but
two main clinical syndromes have emerged (Hodges & Patterson, 1996; Snowden,
Neary & Mann, 1996).
In one syndrome, there is breakdown of the semantic
aspects of language, with severe anomia but generally preserved speech fluency,
well-formed syntax, and correct production of sounds.
The primary semantic
deficits present in this type of progressive aphasia are reflected in the term
"semantic dementia" (Hodges, Patterson, Oxbury, & Funnell, 1992; Snowden,
Goulding, & Neary, 1989) , by which the syndrome has become known.
The second
main syndrome presents a progressive non-fluent pattern of aphasia, with
telegraphic
and/or
dysprosodic
speech
containing
frequent
phonological
errors.
Finally, a smaller number of patients show features of both types of progressive
aphasia, and are considered to have "mixed" PPA (Mesulam & Weintraub, 1992;
Neary, Snowden, & Mann, 1993) .
Table 2:1 contains examples of connected speech from a patient with
semantic dementia, J.L. (Graham, 1995, p. 34) , and from a non-fluent progressive
aphasic patient (Case 1, Weintraub, Rubin, & Mesulam, 1990, p. 1333) .
Both
patients were describing the "Cookie Theft" picture from the Boston Diagnostic
Aphasia Examination (Goodglass & Kaplan, 1983) .
J.L.'s sample illustrates the
word-finding difficulties and empty speech typical of fluent progressive aphasia;
by contrast the sample from Weintraub et al. (1990) is characterised by
phonological and syntactic errors and the occasional omission of grammatical
items.
The summary of nouns and verbs used in each example shows the semantic
dementia patient's reduced use of nouns, and tendency to use general, rather than
specific terms (such as "food", rather than "cookie"), compared with the nonfluent progressive aphasic patient's somewhat more appropriate use of nouns
than verbs.
The latter trend is attributed to the patients' syntactic deficits, given
that much of the syntax of an utterance is constituted in the structure of the verb
(Beland & Ska, 1992).
Pauses are shown by "....", experimenter prompts are
indicated by (PROMPT), and phonological errors are given in the International
Phonetic
Alphabet.
Chapter 2: Review of Non-fluent Progressive Aphasia
Table 2:1.
33
Spoken descriptions of the Cookie Theft Picture from the Boston
Diagnostic Aphasia Examination (Goodglass & Kaplan, 1983) given by patients with
a) semantic dementia and b) non-fluent progressive aphasia.
a) Patient with Semantic Dementia:
The boy's just giving the girl some food and....the water's pouring out there....(PROMPT) well
it looks like it's falling over....looks like it's gonna collapse (PROMPT) I suppose she's
gotta....use that in the water, which is over....running over, but that's what she (PROMPT)
well it looks as though he's trying to get something out there for, for hand it down there, for
her to eat.
n o u n s : boy, girl, food, water
verbs: be, give, pour, look, fall over, collapse, suppose, have to, use, run, try, get, hand, eat
b) Patient with Non-fluent Progressive Aphasia:
This is a picture of a woman....uh....who's....uh....lookin' out the....uh....[ w i n ]....uh....[windSi]....
uh....[windInd] and....uh....in the kitchen.
And....uh....he's....uh....she's....uh....he's dry, she is
dryin' the....uh....plate while the water is comin' out from the [s]....uh....
The water goin' on
the floor....from the [k ] kitchen whatever it is. [bihaId ] her....There [‘ ] boy is....is trying to
[goUk] up on the the top of the....drawer for [koU koU koU koUk] oh....standing on a stool....
which [ wUks ] looks it will falls....[s]. This. The girl is there [w o U k I N] waiting for the cookie
[kUk√k ]
n o u n s : picture, woman, [window], kitchen, plate, water, floor, boy, top, drawer, stool, girl,
cookie
v e r b s : be, look, dry, come, go, try, stand, fall, wait
The fluent type of progressive aphasia has received considerable
theoretical attention since the first modern reports of the syndrome by
Warrington (1975)
and Schwartz, Marin & Saffran (1979) , and the
neuropsychological basis of the language breakdown in the syndrome is now
reasonably well understood (Hodges et al., 1992; Snowden et al., 1989) .
The
primary language deficits in semantic dementia are explained by the progressive
deterioration of the patients' semantic memory (long term memory for word and
object knowledge).
Spontaneous speech increasingly lacks the content words
which express that knowledge, and on formal testing the patients are anomic —
unable to generate the names of items, whether in picture-naming, naming to
description, or category fluency tasks which elicit exemplars of particular
semantic categories.
Comprehension of word meanings also deteriorates with the
breakdown of the semantic knowledge base.
Further research on semantic dementia has investigated both the nature of
semantic organisation per se (Breedin, Saffran, & Coslett, 1994; Hodges, Patterson,
& Tyler, 1994; McCarthy & Warrington, 1988) , and the interaction between
semantic processing and other aspects of cognition.
Interactions between
semantic processing and autobiographical and episodic memory and new
learning (Diesfeldt, 1992; Graham & Hodges, 1997; Snowden, Griffiths, & Neary,
1994; Snowden, Griffiths, & Neary, 1995; Snowden, Griffiths & Neary, 1996) , shortterm memory function (Knott, Patterson, & Hodges, submitted; Patterson, Graham,
& Hodges, 1994a) , reading (Graham, Hodges, & Patterson, 1994; Patterson & Hodges,
1992) , and syntactic processing (Breedin & Saffran, submitted)
investigated.
have all been
Finally, the detailed report of one case (Graham, Patterson, &
Hodges, 1995) , plus briefer descriptions of several others all showing a
progressive fluent aphasia without a corresponding semantic decline, have
suggested that the syndrome of progressive fluent aphasia may be fractionated
into semantic dementia and progressive anomia.
The breadth of experimental research on the neuropsychology of
progressive fluent aphasia presents a striking contrast with the paucity of
theoretical investigation of the non-fluent and mixed varieties of progressive
aphasia.
Although more than 60 patients with a non-fluent progressive aphasia
have been described in the literature (see Table 2:1, below), most reports have had
a clinical focus.
Only three experimental studies of non-fluent progressive
aphasia have been published (Beland & Ska, 1992; Polk & Kertesz, 1993; Watt, Jokel,
& Behrmann, 1997) , and none of these have attempted to provide a principled
account of the non-fluent production of language which tends to dominate the
clinical presentation of the syndrome.
Reports of mixed progressive aphasia
even clinical reports — are comparatively rare (Table 2:6).
—
The one experimental
study of a patient with this type of progressive aphasia (Patterson, Suzuki, Wydell,
& Sasanuma, 1995)
concerns the patient's surface alexic pattern of reading,
rather than her language production.
These few investigations of cognitive
processing in non-fluent and mixed progressive aphasia will be described in
more detail below.
Nosological Issues in the Study of Fluent and Non-fluent Progressive Aphasia
Early investigations of primary progressive aphasia in the modern era
focused on nosological issues, particularly on whether the syndrome was an
independent entity or a precursor to a more global dementia (Craenhals, RaisonVan-Ruymbeke, Rectem, Seron, & Laterre, 1990; Karbe, Kertesz, & Polk, 1993;
Poeck & Luzzatti, 1988; Yamamoto, Fukuyama, & Yamadori, 1989) , and on the
relationship between the various clinical subtypes of PPA (e.g. Mesulam &
Weintraub, 1992; Snowden et al., 1992; Tyrrell, Warrington, Frackowiak, & Rossor,
1990) .
Neuropsychological studies reported the length of time during which
Chapter 2: Review of Non-fluent Progressive Aphasia
35
aphasia occurred in isolation from other cognitive deficits, and/or the nature and
progress of additional cognitive impairments as and when they arose.
It became
clear that, while some patients remained exclusively aphasic for very long
periods of time, even 10 or more years (Mendez & Zander, 1991; Mesulam &
Weintraub, 1992) , the usual progression was ultimately towards a more global
dementia (Green, Morris, Sandson, McKeel, & Miller, 1990; Kertesz, Hudson,
Mackenzie, & Munoz, 1994) .
Neuropathological reports considered whether the different clinical
presentations were determined by the locus of the degenerative process or by the
specific nature of the histological changes (Caselli & Jack, 1992) .
In the
relatively small number of fluent and non-fluent progressive aphasic cases
which have come to autopsy, some had Alzheimer-type neuritic plaques and
neurofibrillary tangles (e.g. Green et al., 1990; Greene, Xuereb, Patterson, &
Hodges, 1996; Karbe et al., 1993; Pogacar & Williams, 1984) , others had Pick cells
and Pick inclusion bodies (e.g. Graff-Radford, 1990; Kertesz et al., 1994; Scully,
Mark, & McNeely, 1986) .
A third group of cases have shown neuronal loss with
pathology lacking the specific histological markers of either AD or Pick's Disease
(Scheltens, Ravid, & Kamphorst, 1994; Scholten, Kneebone, Denson, Fields, &
Blumbergs, 1995; Snowden, Neary, Mann, Goulding, & Testa, 1992; Turner, Kenyon,
Trojanowski, Gonatas, & Grossman, 1996) , variously described as non-specific
spongiform degeneration, microvacuolation and neuronal loss, or dementia
lacking distinctive histology (henceforward DLDH, following Knopman, 1993) .
Occasionally, cases of progressive aphasia have been reported in association with
Creutzfeld-Jakob Disease (Mandell, Alexander, & Carpenter, 1989; Yamanouchi,
Budka, & Voss, 1986)
or Motor Neuron Disease (Caselli et al., 1993; Doran, Xuereb, &
Hodges, 1995) , but these pathologies are unlikely to present with an isolated
progressive aphasia over two years because the disease process usually advances
too rapidly.
It has become apparent that lesion site is more important than the type of
underlying pathology in accounting for the cognitive deficits (Karbe et al., 1993;
Snowden et al., 1992).
Pathology in semantic dementia, the fluent type of PPA, is
usually focused on the left temporal lobe, especially in polar and infero-lateral
regions (Hodges et al., 1992; Hodges
& Patterson, 1996); pathology in the non-
fluent cases typically involves the left perisylvian area, including fronto-parietal
perisylvian regions (Karbe et al., 1993; Kertesz et al., 1994; Turner et al., 1996).
As
Pick's Disease and DLDH usually involve frontal and/or lateral temporal structures
(Snowden et al., 1996), these pathologies are more frequently associated with both
fluent and non-fluent types of progressive aphasia than AD, which typically
originates in medial temporal lobe structures.
However, AD may be associated
with progressive aphasia in cases with somewhat atypically distributed pathology
(see Chapters 5 and 6).
The existence of mixed cases, with clinical features of both fluent and nonfluent types of PPA, has raised the question of whether the relationship between
fluent and non-fluent types of progressive aphasia should best be considered as a
continuum.
Radiological and neuropathological evidence suggests that the
distribution of pathology in the mixed cases overlaps regions implicated in the
two more commonly reported syndromes (Kirshner, Tanridag, Thurman, &
Whetsell, 1987; McDaniel, Wagner, & Greenspan, 1991) .
Furthermore, in the two
main types of PPA, with the evolution of more global deficits, the distinctions
between types may become slightly blurred, suggesting there has been a spread
of pathology beyond the initial neuroanatomical focus.
Thus, late in the disease
process, non-fluent patients may develop single word comprehension deficits and
impaired performance on non-verbal semantic tests (e.g. patient P.G. reported by
Hodges & Patterson, 1996), and over time, phonological and syntactic disruption
may emerge in patients who showed an isolated fluent aphasia for a long period
(e.g. patient F.M. reported by Tyler, Moss, Patterson, & Hodges, 1997) .
The question has also been raised as to whether the actual pathology
involved lies on a spectrum of cortical neuronal degeneration, with the
characteristic pathology of Pick's Disease (Pick cells and Pick bodies)
representing one endpoint, and the neurofibrillary tangles and neuritic plaques
characterising Alzheimer-type pathology representing the other (Morris, Cole,
Banker, & Wright, 1984) .
The middle of this spectrum is hypothetically occupied
by the range of non-specific cortical neurodegenerative processes summarised as
DLDH.
The possibility of a continuous spectrum is suggested by cases which show
degrees of more than one type of pathology, rather than a pure histological
profile typical of any one of the three main types.
McBurney, Moossy and Reinmuth (1985)
Thus, the patient of Holland,
showed Pick cells, Pick bodies and the
neurofibrillary tangles of Alzheimer-type pathology; others have shown
Alzheimer-type pathology with the focal lobar atrophy typical of DLDH (Morris et
al., 1984). Other researchers favour the conflation of Pick and DLDH pathology
into a continuum referred to as "fronto-temporal lobar degeneration" (Snowden
et al., 1992) or "Pick complex" (Kertesz et al., 1994), but consider Alzheimer-type
pathology a separate entity .
Finally, there are several reports in which the
pathological features of Parkinson's Disease have also been found in cases with a
progressive non-fluent pattern of speech production with or without generalised
dementia (Broussolle, Tommasi, Mauguiere, & Chazot, 1992; Cohen, Benoit, Van
Eeckhout, Ducarne, & Brunet, 1993; Kempler et al., 1990; Morris et al., 1984) , and
the relationship of this pattern to the cortical dementias awaits clarification.
Chapter 2: Review of Non-fluent Progressive Aphasia
37
NON-FLUENT PROGRESSIVE APHASIA
Summary of Reported Cases
Table 2:2 summarises the cases of non-fluent progressive aphasia reported
since the modern resurgence of interest in the syndrome initiated by Mesulam
(1982).
The table includes all the cases reviewed by Mesulam & Weintraub (1992),
and those reported subsequently (until early 1997) which also fit the criteria for
diagnosis as PPA outlined in that paper.
One additional case predating the
Mesulam and Weintraub (1992) review is included (Craenhals et al., 1990), as this
patient also showed no change in non-linguistic cognition over a 28-month
follow-up period and otherwise fits the criteria for PPA.
The length of history of
the cases reported by Cappa, Perani, Messa, Miozzo and Fazio (1996)
is not
reported, so it is possible these did not show an isolated aphasia for at least the
first two years.
Two cases of progressive aphemia are not included (Broussolle,
Tommasi, Mauguière & Charzot, 1992; Cohen, Benoit, Van Eeckhout, Ducarne &
Brunet, 1993), as these cases show articulatory deficits only, and thus do not meet
the criteria for diagnosis as non-fluent progressive aphasia.
The table format is
adapted from Mesulam & Weintraub (1992) and Graham (1995).
Table 2:2.
Summary of non-fluent progressive aphasia cases reported since 1982.
Table continues overleaf.
Author(s),
Year
of
Case
Report
Sex,
Age at
pres'n
Mesulam, 1982
3
F, 48
Region
of
imaging
nature
abnormality
and/or
of
revealed
by
neuropathology;
pathology
where
known
CT: L wide sylvian fissure
biopsy: DLDH, lipofuscin-pyramidal neurons
Heath et al., 1983
Holland et al., 1985
Mr E.
F, 69
CT: normal; EEG: left temporal
M, 66
npath: Pick L > R superior temporal, frontal
& parietal; neurofibrillary tangles
Scully et al., 1986
Mehler et al. 1987
Yamamoto et al. 1989
F, 68
npath: Pick frontal, temporal
1
M, 54
npath: DLDH frontotemporoparietal
2
M, 53
CT: L general atrophy
2
F, 67
MRI: L frontotemporal; PET: also parietal
F, 57
MRI: L perisylvian
F, 52
CT: wide L sylvian fissure; PET: L anterior &
Berger & Porch, 1990
Craenhals et al., 1990
S.A.
perisylvian
hypometabolism
Table 2:2.
Author(s),
Continued from previous page.
Year
of
Case
Report
Sex,
Age at
pres'n
Green et al., 1990
Region
of
imaging
nature
of
abnormality
and/or
revealed
by
neuropathology;
pathology
where
known
4
M, 57
npath: DLDH frontal & sup. temporal L > R
8
F, 71
npath: AD L inferior parietal, med. temporal
1
M, 47
PET: L parietotemporal
2
M, 56
CT: normal
3
F, 40
MRI: bilateral frontal, L > R
4
M, 74
CT: normal
6
M, 60
CT: wide sylvian fissure
Delecluse et al., 1990
F, 66
MRI: subcortical; SPECT: frontotemporal
Kartsounis et al., 1991
M, 58
SPECT: dorsolateral frontal L > R
Weintraub et al., 1990
Tyrrell et al., 1990
Tyrrell et al., 1991
2
M, 59
PET: bilat inf & mid frontal, temporoparietal
Mendez & Zander, 1991
9
M, 61
CT: general L
12
F, 59
CT: left perisylvian
1
F, 62
SPECT: L frontotemporal & anterior parietal
M, 66
npath: DLDH L superior frontal
McDaniel et al., 1991
= Wagner et al., 1995, C1
Lippa et al., 1991
Snowden et al., 1992
1, L.E.
F, 65
CT: L > R
= Goulding et al., 1989 &
4, S.B.
M, 63
npath = DLDH severe atrophy L > R especially
med. & sup. frontal gyri
Northen et al. 1990
5, J.H.
M, 59
SPECT: L frontotemporoparietal
Béland & Ska, 1992
H.C.
F, 58
perfusion scan: L frontotemporal parietal
Caselli et al., 1992*
1
F, 68
MRI: L frontal operculum
2
F, 73
MRI: L frontal & temporal
3
F, 59
MRI: L frontal, temporal, parietal, R parietal
1
n/a
CT/MRI: L temporal
2
n/a
CT/MRI: L wide sylvian fissure
3
n/a
CT/MRI: L frontal operculum
4
n/a
CT/MRI: L frontal operculum, premotor
5
n/a
CT/MRI: L anterior temporal
6
n/a
CT/MRI: no focal atrophy
7
F, 64
CT/MRI: L frontotemporoparietal
J.H.
M, 52
MRI: L inferior frontal & L anterior temporal
Caselli & Jack, 1992*
Watt et al., 1996
SPECT: anterior, superior & middle temporal
Chapter 2: Review of Non-fluent Progressive Aphasia
Table 2:2.
Author(s),
39
Continued from previous page.
Year
of
Case
Report
Sex,
Age at
pres'n
Karbe et al., 1993
Polk & Kertesz, 1993
Cappa et al., 1996
Greene et al., 1996
Grossman et al., 1996
Hodges & Patterson, 1996
imaging
nature
of
abnormality
and/or
revealed
by
neuropathology;
pathology
where
known
M, 81
npath: Pick in L superior parietal
2
M, 55
npath: AD, widespread, L middle frontal
3
F, 71
scan: mild-moderate generalised atrophy
4
F, 62
scan: L > R
5
M, 75
MRI: L frontal & perisylvian
6
M, 77
scan: mild-moderate generalised atrophy
7
M, 76
scan: mild-moderate generalised atrophy
8
F, 80
scan: mild-moderate generalised atrophy
9
M, 65
scan: L > R
10
M, 61
scan: mild-moderate generalised atrophy
C.W.
M, 50
MRI: diffuse L atrophy
M, 67
MRI: L sylvian fissure, SPECT: L temporal
1
M, 81
npath: Pick, L inferior frontal, sup. parietal
3
F, < 55†
Kesler et al., 1995
Bianchetti et al., 1996
of
1
Fuh et al., 1994
Kertesz et al., 1994
Region
npath: Pick, bilateral frontal
F, 52
CT: L temporoparietal
1
M, 72
SPECT: frontotemporoparietal L > R
2
M, 61
CT: L temporal; SPECT: L frontotemporal
5
M, 58
CT: L temporal; SPECT: frontotemporal L > R
7
F, 61
SPECT: frontal L > R
1
F, < 55†
2
M, < 46† MRI: L temporoparietal; SPET frontotemporal
3
M, < 44† SPET: L dorsolateral frontal, R 2yrs later
4
M, < 66† SPET: frontal, L > R
PET: L prefrontal
A.S.
M, 61
npath: AD in L perisylvian language areas
2
F, 69
PET: L temporal, inferior frontal
3
F, 57
PET: L temporal, inferior frontal
P.G.
F, 74
npath: AD, parietal, frontal, medial temporal
& temporal pole
L.M.
M, 67
MRI: mild general atrophy especially L
perisylvian; SPECT: L parietotemporal
Table 2:2.
Author(s),
Continued from previous page.
Year
of
Case
Report
Sex,
Age at
pres'n
Turner et al., 1996
1
F, 73
of
imaging
nature
of
abnormality
and/or
revealed
by
neuropathology;
pathology
where
known
npath: DLDH, bilateral frontal, anterior
parietal, anterior temporal
=Grossman et al., 1996, C1
=Grossman et al., 1996, C4
Region
2
F, 42
npath: DLDH, bilateral frontal, parietal
3
F, 64
npath: DLDH bilateral frontal (poles)
KEY: npath = post-mortem neuropathological examination
L = left, R = right, ant = anterior, bilat. = bilateral, inf. = inferior, med. = medial, sup. =
superior
AD = Alzheimer's Disease, Pick = Pick's Disease, DLDH = Dementia Lacking Distinct Histology
(neuronal loss, gliosis, spongiform change; Knopman, 1993)
* = there is a possible overlap between patients reported in these papers, but
Caselli & Jack (1992) provide insufficient data to determine if this is so
† where age at onset is given as < X years, length of history is not reported, so age at
presentation is given
Age, Sex and Neuropathological Data
Data on the age at illness onset, sex, and, where available, pathologically
confirmed diagnosis of patients listed in Table 2:2 are summarised in Tables 2:3
and 2:4.
Average age of onset was in the presenium.
There was negligible
difference between males and females in age at onset, overall incidence of nonfluent progressive aphasia, or the type of pathology found for the 17 patients for
whom pathology was reported (16 examined post-mortem; 1 biopsy).
Not included
in Tables 2:3 and 2:4 are cases 1—6 reported by Caselli and Jack (1992), because sex
and age were not reported for these cases, and some may overlap with another
three cases reported by the same authors (Caselli et al., 1992).
Where only the age
at presentation is given in the case report (5 patients in Table 2:2), this is used as a
conservative estimate of age of onset for the calculations in Tables 2:3 and 2:4.
Chapter 2: Review of Non-fluent Progressive Aphasia
Table 2:3.
patients
Summary of age of onset and pathology data for male versus female
with
non-fluent
progressive
aphasia.
Males
Females
All
33
30
63
62.1
62.0
62.1
(9.7)
(9.4)
(9.5)
DLDH
4
4
8
Alzheimer
2
2
4
Pick
2
2
4
Pick + Neurofibrillary Tangles
1
-
1
TOTAL
9
8
17
All
41
Cases
Number of Cases
Age at Onset (years): Mean
(s.d.)
Pathologically
Confirmed
Cases
Approximately half the cases for which pathology was available had DLDH.
The other patients had either Alzheimer-type pathology or Pick pathology, or in
one case showed some features of both (Holland et al., 1985).
There was a trend for
the patients with non-specific pathology to be younger than the patients with AD
and Pick's Disease at onset (Table 2:4), but the groups are too small for these
differences to be reliable.
The data from these 17 patients do not indicate that any
one of the pathologies is associated with a shorter length of illness, although
there is a trend for the patients with DLDH and Pick's pathology to live longer
than those with AD, even though they were not necessarily younger at onset1 .
Table 2:4.
Summary of age of onset and duration of illness for non-fluent
progressive
aphasic
patients
with
pathologically-confirmed
Age at onset
diagnosis.
Length of History
Pathology
n
mean
s.d.
range
mean
s.d.
range
DLDH
8
58.4
10.2
42-73
6.8
2.0
3-9
Alzheimer's Disease
4
65.3
8.8
55-74
4.5
1.3
3-6
Pick's Disease
4
71.3
12.5
55-81
7.0
4.1
3-11
Pick + Tangles
1
—
—
66
—
—
12.5
1
Length of history was calculated to date of report for the patient of Mesulam (1982), whose
pathology was determined by biopsy.
Quality of Speech Production
The speech of patients with non-fluent progressive aphasia has been
described using a wide variety of impressionistic terms, which nevertheless
highlight consistent abnormalities in the ease and accuracy of spoken language
production.
Speech is described as effortful or laboured (Kartsounis, Crellin,
Crewes, & Toone, 1991; Mendez, Selwood, Mastri, & Frey, 1993; Mesulam, 1982) , with
the initiation of speech decreasing over time (Berger & Porch, 1990; Lippa, Cohen,
Smith, & Drachman, 1991; Mehler, Horoupian, Davies, & Dickson, 1987) .
Impaired
syntactic processing is evident in morphosyntactic errors and "telegraphic
speech" which lacks function words (Holland et al., 1985; Kertesz et al., 1994;
Turner et al., 1996).
The patients show word-finding difficulty and make
occasional semantic errors, but more frequent phonological errors (Caselli, Jack,
Petersen, Wahner & Yanagihara, 1992; Craenhals et al., 1990; McDaniel, 1991;
Snowden et al., 1992).
Other characteristics consistently reported are stuttering
and stammering speech with the repetition of the first sound or syllable (Kertesz
et al., 1994; Kesler, Artzy, Yaretzky, & Kott, 1995; Mendez & Zander, 1991; Northen,
Hopcutt, & Griffiths, 1990; Watt et al., 1997) , groping and reduced agility in speech
production (Green et al., 1990; Scully et al., 1986), and dysarthric characteristics
such as slurring (Holland et al., 1985), distorted articulation (Delecluse et al., 1990)
, hoarse voice (Mendez & Zander, 1991)
and reduced volume (Kertesz et al., 1994).
Finally, the patients are frequently hesitant in speaking (Grossman et al., 1996;
Karbe et al., 1993; Patterson & Hodges, 1996; Scully et al., 1986; Snowden et al.,
1992), speak more slowly (Green et al., 1990; Kartsounis et al., 1991), and show
abnormal prosody (Delecluse et al., 1990; Green et al., 1990).
Although there is a well-established tradition of interpreting speech
errors as transparent indications of breakdown at particular levels of processing
in models of speech production (see Chapter 1), it is not a straightforward exercise
to disentangle cause and effect in the range of speech deficits summarised for
non-fluent progressive aphasia.
For example, does the slowed speech of the
syndrome reflect a primary inability to produce speech at a normal rate, or is it a
consequence of word-retrieval deficit, or even a compensatory strategy in the
attempt to reduce phonological error or articulatory imprecision by speaking
more slowly?
Similarly, do the prosodic abnormalities of the syndrome result
from specific deficits in the prosodic organisation of language, or are they
secondary to difficulties in other processes which preclude the production of
normal rhythm and stress?
In summary, the speech of non-fluent progressive aphasic patients seems
to be characterised by syntactic problems, word-finding problems in which
particular lexical items are unavailable for production when required,
Chapter 2: Review of Non-fluent Progressive Aphasia
43
disruptions to the phonological forms of words ranging from frank phonological
errors to stuttering or articulatory-type errors, and, possibly, primary prosodic
deficits.
The experimental investigations of non-fluent progressive aphasia in
this thesis will focus on the phonological disruption in the syndrome, taking
account of the word-finding difficulties and articulatory difficulties where these
appear to overlap with phonological processing deficits in spoken word
production.
The organisation and breakdown of syntax and prosody in the
syndrome will not be addressed.
Associated Deficits
Non-fluent language production is rarely the only impairment present in
non-fluent progressive aphasia.
There are regularly deficits reported in other
linguistic domains including comprehension — of syntax, and less commonly, of
single words — and the production of written language.
Writing is most often
described as "mirroring" spoken output: it is telegraphic in the omission of
function words, and contains errors on individual letters or series of letters
which might correspond approximately to phonological errors in speech.
Conversely, while word-finding difficulties in spontaneous speech and anomia on
formal testing are frequently implicated in non-fluent progressive aphasia, they
are not always present.
Patients with progressive aphasia also frequently show co-occurring n o n linguistic impairments: apraxia, acalculia and/or constructional deficits.
Deficits
in these domains are not, however, considered exclusionary criteria for a
diagnosis of PPA, because these functions are thought to be subserved by
anatomical networks overlapping those for language (Weintraub & Mesulam,
1993) .
Finally, progressive articulatory problems and dysarthria associated with
cortical lesions, but occurring in the absence of any linguistic impairment (e.g.
Broussolle et al., 1992; Cohen et al., 1993) are excluded from a diagnosis of PPA
(Mesulam & Weintraub, 1992) .
Progressive articulatory deficits do, however,
frequently co-occur with linguistic deficits in non-fluent progressive aphasia, as
noted above under quality of speech production.
A survey of the rate with which these varied linguistic and non-linguistic
deficits were reported in association with a non-fluent pattern of PPA in the
literature is summarised in Table 2:5.
As in Table 2:3, the total number of patients
surveyed was 63: patients 1—6 reported by Caselli and Jack (1992) were excluded
because it was not possible to determine whether these patients overlap with
those in Caselli et al. (1992).
Percentages shown in Table 2:5 were obtained by
rating each patient as impaired or unimpaired on each of the linguistic and nonlinguistic functions shown, according to the case reports of the non-fluent
patients summarised in Table 2:2.
Information on these abilities is not provided
for all patients, so Table 2:5 also shows the percentage of patients for whom
information about a particular function was provided.
Data from the first
comprehensive assessment are used where the patients are reported
longitudinally.
Table 2:5 is intended to provide a rough guide only: in some
instances where appropriate control data were available (e.g. Patterson & Hodges,
1996), the judgement as to whether a patient was impaired or not could be
determined by their results on neuropsychological testing, while for other
patients the judgement was based on fairly sweeping general statements about the
patients' abilities in particular domains.
Table 2:5.
Analysis of associated linguistic and nonlinguistic deficits (where
reported) in 63 cases of non-fluent progressive aphasia.
% patients for
Domain
whom
reported
% such patients in
whom domain is
impaired
Linguistic
Auditory
Comprehension
Single Words
63.5
20
Syntax
54.0
47.1
Naming to Confrontation
66.7
76.2
Writing
65.1
82.9
Limb
47.6
33.3
Orofacial
39.7
68.0
Articulation
23.8
73.3
Calculation
44.4
39.3
52.4
15.2
Non-linguistic
Praxis
Constructional
Abilities
The table suggests that, across the range of patients assessed and reported
using different criteria, single word comprehension is relatively well-preserved,
in the presence of impaired syntactic comprehension, naming and writing.
Moreover, it is likely that the patients' ability to comprehend syntax is
overestimated in this analysis, because the clinical observation that
comprehension is intact is frequently based on a patient's comprehension of
conversation in everyday life.
This measure is insensitive, because such
comprehension is assisted by context and single word comprehension.
Chapter 2: Review of Non-fluent Progressive Aphasia
45
Deficits in the non-linguistic domains of calculation, limb praxis and
constructional abilities are less frequently associated with non-fluent
progressive aphasia.
Interestingly, articulatory precision and non-linguistic
orofacial praxis are more frequently reported to be impaired, suggesting that the
networks supporting speech-motor processes and orofacial movement have
greater neuroanatomical overlap with the language functions impaired in this
syndrome than do functions such as calculation, limb praxis and constructional
abilities.
Dysphagia (swallowing difficulty) is also noted for a number of cases
(Fuh, Liao, Wang & Lin, 1994; Kertesz et al., 1994; Mesulam & Weintraub, 1992).
The
analysis in Table 2:5 may underestimate the preservation of the patients' abilities
in non-linguistic domains, because their performance is more likely to be noted if
impaired, given that the focus of these reports is primarily language function,
and preserved non-linguistic function is frequently summarised in terms such as
"other
general
neuropsychological
testing
was
unremarkable".
Profile on Neuropsychological Testing
With the exception of the non-linguistic domains of praxis, calculation and
constructional abilities described above, patients with primary progressive
aphasia, by definition, show isolated language deficits in the context of preserved
function in other cognitive domains.
The judgement that particular cognitive
processes are preserved is sometimes made on the basis of clinical observation,
but a more stringent view would require the patient's performance in nonlinguistic domains such as visuoperceptual function or memory function falls
within two standard deviations of the normal mean (e.g. Greene et al., 1996;
Hodges et al., 1992; Patterson & Hodges, 1996).
Thus, on tests of visuo-perceptual
and spatial abilities, such as Judgement of Line Orientation (Benton, Des Hamsher,
Varney, & Spreen, 1983) , copying the Rey Complex Figure (Rey, 1941),
and
matching objects seen from canonical versus unusual views (Humphreys &
Riddoch, 1984),
1996).
scores should be within the normal range (Patterson & Hodges,
Memory function, as measured by Rey Figure recall, the Three Words-
Three Shapes Test or the Rey Auditory-Verbal Learning list should also be
unimpaired (Weintraub et al., 1990), although patients may show some
impairment on verbally-mediated tests of memory (e.g. the latter two tests cited by
Weintraub et al., above, or the word version of Warrington's (1984) Recognition
Memory Test), with better performance on non-verbal memory tasks such as the
face version of Warrington's (1984) Recognition Memory Test (Mesulam &
Weintraub, 1992) .
Semantic abilities have not been systematically investigated in non-fluent
progressive aphasic patients, but two cases reported by Hodges and Patterson
(1996) scored within the normal range on the Pyramids and Palm-Trees Test
(Howard & Patterson, 1992) .
These patients also performed well on tests of single
word comprehension, such as the word-picture matching subtests from the
PALPA (Kay, Lesser, & Coltheart, 1992) , and the Hodges and Patterson Semantic
Battery (Hodges & Patterson, 1995) , long after other aspects of language
processing had begun to decline.
Both the non-fluent and fluent progressive
aphasic patients reported in this study were impaired on naming tasks, but the
non-fluent patients were less severely impaired than the fluent patients, and
only the non-fluent patients made phonological errors.
Non-fluent progressive aphasic patients are also impaired relative to
normal on verbal digit span tasks, phoneme judgement tasks, and tasks which
require the comprehension of complex syntax (Grossman et al., 1996; Hodges &
Patterson, 1996; Watt et al., 1996).
Finally, these patients are more impaired on
letter-based (FAS) than semantic category-based word-fluency tasks (Greene et
al., 1996; Hodges & Patterson, 1996).
Experimental Investigations of
Non-fluent Progressive Aphasia
Studies reported by Béland and Ska (1992), Polk & Kertesz (1993) and Watt et
al. (1996), have investigated gesture, musical ability and reading in patients with
non-fluent
progressive
aphasia
respectively.
Béland and Ska (1992) analysed the production of gesture in a 58 year-old
woman, H.C., with non-fluent progressive aphasia.
On five occasions over three
years of testing, H.C. was videotaped explaining how to wrap a gift, replace a
broken window pane, cook an omelette, or make a sandwich.
As her verbal output
became more restricted, her use of gesture increased as a compensatory
communicative strategy.
The authors concluded that her progressive aphasia
specifically impaired verbal output, rather than a central language processor
which is dually responsible for verbal and non-verbal communication.
Polk and Kertesz (1993) reported a double dissociation between the fluency
of language production and musical performance in a non-fluent progressive
aphasic, C.W., and a non-aphasic patient, M.A., who had posterior (predominantly
right-sided) cortical degeneration.
The non-fluent aphasic showed spared
expressive musical functions but impaired reception of rhythm; the posterior
patient had severe expressive deficits in musical production but unimpaired
reception of rhythm.
Polk and Kertesz suggested the right hemisphere is
involved in processing the global contour of a melody; the left, with processing
the specific intervals between notes which allows the computation of rhythm.
The study by Watt et al. (1996) investigated the oral reading of J.H., a 59
year-old man with a 6-year history of progressive non-fluent aphasia.
J.H. had a
Chapter 2: Review of Non-fluent Progressive Aphasia
47
surface dyslexic reading disorder i.e. he was relatively unimpaired in reading
aloud regular words and nonwords, with his poorer performance on exception
words characterised by regularisation errors.
In contrast with semantic dementia
patients, many of whom are also surface dyslexic (Patterson & Hodges, 1992), and
whose success in reading aloud may be related to preserved knowledge of word
meanings (Graham et al., 1994), J.H. showed well-preserved comprehension of the
meanings of single words, and no association between his error pattern in
reading and his semantic knowledge.
Watt and colleagues therefore suggested
that J.H.'s surface dyslexia arose from an impairment in the connections between
semantics and phonology, an account similar to that given for F.M., the
progressive anomic patient reported by Graham et al. (1995).
MIXED PROGRESSIVE APHASIA
A small number of patients have been reported who show characteristics of
both fluent and non-fluent forms of primary progressive aphasia (Mesulam &
Weintraub, 1992).
These patients have a non-fluent type of speech production,
with reduced phrase length, grammatical abnormalities, and phonological errors
in spontaneous speech; however they also show lexical comprehension deficits
and the tendency to use non-specific nouns and verbs, which are features more
typical of patients with fluent progressive aphasia.
Nosological and pathological
issues arising over the relationship between mixed progressive aphasia and the
fluent and non-fluent types have been addressed above.
Table 2:6 summarises the mixed progressive aphasia cases in Mesulam and
Weintraub's (1992) review, together with two other cases (Patterson et al., 1995
Yamamoto et al., 1990) .
Although the patient reported by Yamamoto and
colleagues is not included in the Mesulam and Weintraub review, he showed no
generalised dementia four years after the onset of his language difficulties,
continuing to treat patients in his dental clinic, and to manage the financial
affairs of his family and the clinic.
His spontaneous speech was fluent,
containing phonological errors and paragrammatic errors, as well as empty
phrases and stereotypes; his auditory comprehension was also impaired.
Table 2:6.
Author(s),
Summary of mixed progressive aphasia cases reported since 1982.
Year
of
Case
Report
Sex,
Age at
pres'n
Assal et al., 1984
F, 60
Region
of
imaging
nature
of
abnormality
and/or
revealed
by
neuropathology;
pathology
where
known
CT: bilateral cortical & subcortical atrophy,
wide sylvian fissures
Kirshner et al., 1987
1
M, 61
=Kirshner et al., 1984, C2
Hamanaka & Yamagishi,
npath: DLDH, L focal atrophy inferior frontal
and superior temporal gyri, general atrophy
2
F, 60
not reported
De Oliveira et al., 1989
M, 63
CT: general atrophy, especially L perisylvian
Yamamoto et al., 1990
M, 57
CT: wide L sylvian fissure; PET L temporal
1986*
McDaniel et al., 1991
2
F, 73
SPECT: L posterior frontal lobe, L temporal
Patterson et al., 1995
N.K.
F, 68
MRI: L temporal; PET: L perisylvian
KEY: npath = post-mortem neuropathological examination, L = left
DLDH = Dementia Lacking Distinct Histology (neuronal loss, gliosis, spongiform change;
Knopmann, 1993)
* = cited in Mesulam & Weintraub (1992)
Five other cases with a mixed profile of progressive aphasia have been
reported by Snowden and colleagues (1992), presumably not included in the
Mesulam & Weintraub review because their aphasia appeared in conjunction with
behavioural changes typical of frontal-type dementia.
On SPECT scanning, these
five patients showed hypoperfusion in the frontal regions, more pronounced on
the left in three patients, on the right in one patient, and bilaterally in the other.
In addition to aphasic symptoms, these patients also displayed behaviour ranging
from obsessional, aggressive and gluttonous to inert and apathetic (Snowden et
al., 1992).
An experimental study of one Japanese patient with mixed progressive
aphasia (Patterson et al., 1995) revealed a surface dyslexic pattern of reading.
The
patient's flawless reading of kana script, in which the relationship between the
characters and their pronunciation is highly predictable, contrasted with her
impaired reading of words in kanji script, where the relationship between
characters and their pronunciations is unpredictable (in the same way that the
pronunciation of pint as [p a I n t ] not [pInt ] is unpredictable in English given the
existence of words like m i n t , p r i n t , h i n t , flint and so on).
By contrast, the
Japanese dentist reported by Yamamoto and colleagues (1990) had greater
difficulty reading and writing kana characters than kanji.
Furthermore, while
Chapter 2: Review of Non-fluent Progressive Aphasia
49
the patient with impaired kanji reading also showed semantic memory deficits
(Patterson et al., 1995), it would appear from the other patient's continued ability
to practice dentistry, and the absence of semantic errors in his naming, that this
patient with poorer reading of kana may have had well-preserved semantic
abilities (Yamamoto et al., 1990).
In these two cases, therefore, the degree of
difficulty in reading kanji versus kana seems to be related to the d e g r e e of
semantic versus phonological deficit in aphasic profiles which combine elements
of both.
These two cases illustrate that patterns of dissociating cognitive abilities
in cases of mixed progressive aphasia can inform cognitive neuropsychological
studies of cognition and its breakdown, even though the deficits occurring across
different patients with the syndrome are far from homogeneous.
CONCLUDING REMARKS
Because there have been so few experimental, analytic studies of nonfluent progressive aphasia, the mechanisms underlying the non-fluent pattern
of language breakdown in progressive aphasic syndromes remain poorly
understood.
Chapters 3 and 4 of this thesis present an experimental investigation
into the speech production deficits of four patients with phonological disruption
in the context of primary progressive aphasia.
Just as cases of fluent progressive
aphasia have allowed the investigation of semantic processing, so the focal
phonological deficits of these phonologically impaired patients are likely to
inform models of phonological processing and speech production.
Chapter 3
Single Word Production in
Non-fluent Progressive Aphasia
This chapter presents an empirical investigation of the speech production
deficits of two patients with non-fluent progressive aphasia1 .
The three
experiments in the chapter addressed the issues of which aspect(s) of their single
word output processing were impaired, and how their performance on different
single word production tasks might inform current models of speech production.
In attempting to characterise the phonological deficit(s) which occur in
the syndrome of non-fluent progressive aphasia, it seems clear from the review
of cognitive neuropsychological studies of phonological disruption in Chapter 1
that comparing the patients' performance across different single word
production tasks such as naming, repetition and reading, should provide one
important kind of information.
As suggested by Caplan et al. (1986), similar
patterns across tasks, both quantitatively and qualitatively, would imply a deficit
at a level common to all speech production tasks (for example, phonological
encoding, or the articulatory implementation of the phonological form).
A
differential performance across tasks would invoke a more complex account of
the production impairment: either a deficient process specific to one task (as in
McCarthy and Warrington's (1984) study suggesting semantic versus nonsemantic routes to speech production), or an account like that of Dell and
colleagues (Dell, 1986; Martin et al., 1994; Schwartz et al., 1994) whereby
processing at a level common to all tasks is nonetheless differentially activated
across tasks.
One variable likely to illuminate phonological output deficits in different
tasks is word length.
Patients with phonological output problems typically find
longer words more difficult than shorter words (Pate, Saffran & Martin, 1987;
Wilshire & McCarthy, 1993), presumably because words containing more sounds
allow greater possibility of error, whatever the nature of the error mechanism.
1 I would like to thank Gary Dell and two anonymous reviewers for helpful comments on an
earlier report of the experiments described in this chapter (Croot et al., in press).
50
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
51
According to Caplan et al. (1986), finding similar effects of word length on
different single word production tasks strengthens the argument for a single
locus of impairment in all tasks.
The first experiment with non-fluent progressive aphasic patients
compared their production of words of different lengths in three common single
word speech production tasks which differ in the processing required prior to
speech production: word repetition, reading aloud and picture naming.
The
results of this experiment suggested that successful performance was affected by
both length and task.
Two subsequent experiments sought to clarify which
aspect(s) of the difference between tasks might be influencing the patients'
speech production.
In the general discussion of the three experiments, it is
proposed that a stimulus which closely corresponds to the required phonological
output is more effective in activating target nodes in the processing of
phonological
output.
A description of the two non-fluent progressive aphasic patients whose
results are presented in this chapter appears below.
described in Hodges and Patterson (1996).
These patients are also
The neuropsychological data in Tables 1
and 2 were collected by Karalyn Patterson, John R. Hodges and their research
assistant at that time, Naida Graham.
Naida Graham was also the conversational
partner in the samples of spontaneous speech.
CASE DESCRIPTIONS
P . G . was an ex-secretary who presented in 1991, aged 76, concerned about a
progressive loss of speech fluency over the preceding two years.
On initial
neuropsychological testing her performance on single word comprehension,
reading, non-verbal memory and visuo-perceptual tests was in the normal range,
while her comprehension of syntactically complex sentences was severely
impaired, and her forward digit span and performance on letter fluency, naming
and non-word reading tasks were impaired relative to normal controls.
Her
spontaneous speech was characterised by hesitancy and frequent phonological
errors.
An MRI scan performed in 1991 showed minimal left-sided cerebral
atrophy with widening of the sylvian fissure; perfusion measured by 99m Tc-HMPAO SPECT was normal.
She wore a hearing aid in her right ear, but further
audiometric information was unavailable, and an attempt at audiometric
assessment in 1995 was unsuccessful because by that time she was unable to
understand
the
procedure.
Longitudinal neuropsychological data for P.G. are summarised in Table 3:1.
Table 3:1 shows that for the first three years, P.G.'s performance on linguistic
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
52
tasks progressively declined while her performance on most visuo-perceptual
tasks and some non-verbal memory and semantic tasks remained within two
standard deviations of normal performance.
Scores on some tasks in the latter
categories began to decline late in the third year and showed marked decline
subsequently, principally because she was no longer able to comprehend the
requirements of most tests.
By early 1995, she was producing almost no
spontaneous speech and only minimal gesture.
The data reported in this chapter
were collected between February and November 1994.
Table 3:1.
P.G. died in August 1995.
Summary of 6 rounds of neuropsychological testing for P.G.
Control
data are from Hodges and Patterson (1995). (KEY overleaf)
P.G.
Global
Rating
July
Jan
June
April
Feb
Aug
(n=25)
1991
1992
1992
1993
1994
1994
28
23
25
18
9
4
29.2
1.0
mean
s.d.
Scale
MMSE /30
Visuospatial
Controls
&
Perceptual
Tests
Object Match /40
n/a
37
37
39
34
26
37.3
3.1
Benton Line Orientation /30
29
23
27
25
0
0
27.4
4.0
Rey Figure 3:Copy /36
29
31
29
28
29
26
3 4
3.0
46
n/a
23
18
n/a
n/a
47.3
2.8
36
35
31
29
n/a
n/a
n/a
4,4
5,4
5,2
3,3
0,0
0,0
6.8
Memory
Tests
RMT: Words /50
Faces /50
Digit Span forward, backward
Nonverbal
(fwd)
Reasoning
Ravens Prog. Matrices /36
Language
&
Semantic
1.0
28
26
23
24
18
12
n/a
Tests
Fluencies: living things ¶
37
27
29
21
8
0
58.3
12.3
man-made¶
32
27
17
18
8
0
55.4
8.6
letters (FAS)¶
11
11
12
10
2
n/a
44.6
10.2
39
38
34
31
14
8
43.6
2.3
126
122
124
118
79
70
125.2
2.7
122
118
118
110
60
50
123.6
3.1
TROG /80
60
59
60
53
43
29
78.8
1.8
P&PT: words /52
n/a
n/a
50
49
44
41
> 48
-
n/a
50
47
47
41
46
> 48
-
Picture Naming ¶ /48
Reading: regular words /126
exception wds /126
pictures /52
KEY: MMSE = Mini Mental State Examination (Folstein et al., 1975); VOSP = The Visual Object
and Space Perception Battery (Warrington & James, 1991); RMT = Recognition Memory Test
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
53
(Warrington, 1984) ¶ = Semantic Battery (Hodges & Patterson, 1995); TROG = Test for the
Reception of Grammar (Bishop, 1989); P&PT = Pyramids and Palm Trees (Howard & Patterson,
1992).
A sample of P.G.'s conversational speech from February 1994 is given
below.
The names "Maybank" and "Sunnybank" have been substituted for the
names of two villages, which P.G. produced without phonological paraphasia.
Less
clear utterances are given in phonemic transcription, and subsequent words in
underlined italic brackets indicate the likely target, where known.
Where no
gloss is given, the word(s) were unintelligible.
NG
and what do you think of your new house?
PG
oh yes (waves hand to encompass surroundings) good
NG
do you like it better than the other one?
PG
yes
oh (emphasis
Maybank
gesture) mm
the these ah well the um Maybank
the um (gesturing a road between two places)
M* [eI ] um drive
mm ( n o d d i n g )
NG
and where did you go last week?
was it last week you were away?
PG
oh yes oh the um Maybank (screws up face)
er the um Sunnybank ( n o d d i n g )
NG
and who lives there?
oh yes the the the er [d´ daIvIn ] (driving) (gestures driving a car)
NG
so you drove there did you?
PG
yes (hand on chest)
mm
NG
do you like to drive?
PG
no (smiling, shaking head,
driving er the um [b Q v m ´ n]
NG
so was it your son you visited last week?
PG
yes the um Maybank (makes face, shakes head, closing eyes, holding up
pantomiming
driving)
hand to pause) Sunnybank ( n o d )
NG
then how long did you stay there?
PG
(holds up five fingers, then three, four, then five) three
NG
was it a nice visit?
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
PG
yes ( n o d ) no (smiling,
nodding,
NG
and when did you move to this county?
PG
(holding up five fingers) the um Maybank
NG
PG
mhm
the um [´ z ] the three three
NG
so it was three years ago, was it?
PG
yes (shaking
54
laughing)
head)
L . M . , right-handed, was formerly a clerk.
He presented in 1991, aged 75,
with an 18 month history of difficulties in producing speech, but no other
problems in the activities of everyday life.
His initial neuropsychological profile
(October 1991; see Table 3:2) showed poor phonological and syntactic processing,
impaired performance on naming, reading and word fluency tasks and reduced
digit span, but otherwise preserved visuospatial, perceptual, mnestic and semantic
abilities.
His spontaneous speech was characterised by evident word-finding
difficulties, poor articulation, and numerous phonological errors.
A 99m Tc-HM-
PAO SPECT scan performed at the time showed extensive reduction in the left
parietal and temporal regions and MRI indicated mild cerebral atrophy with
accentuation in the left peri-sylvian region .
On the battery of neuropsychological tests carried out at approximately sixmonthly intervals over the first two years after his initial assessment, L.M.'s
performance on the visuo-perceptual and non-verbal semantic tests remained
within two standard deviations of normal but performance in reading, writing,
sentence comprehension, fluency, and naming tasks declined, in some cases so
precipitously as to render him unable to perform the tests.
L.M.'s results from
longitudinal neuropsychological testing are also shown in Table 3:2.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
Table 3:2.
Summary of 4 rounds of neuropsychological testing for L.M.
55
Control
data are from Hodges and Patterson (1995).
L.M.
Global
Rating
Oct
Feb
Sept
July
(n=25)
1991
1992
1992
1993
mean
s.d.
25
23
22
20
29.2
1.0
Scale
MMSE /30
Visuospatial
Controls
&
Perceptual
Tests
Object Match /40
38
39
36
35
37.3
3.1
Benton Line Orientation /30
29
27
n/a
25
27.4
4.0
Rey Figure 3:Copy /36
34
36
36
35
3 4
3.0
RMT Words /50
43
42
n/a
n/a
47.3
2.8
RMT Faces /50
37
31
n/a
n/a
n/a
Digit Span forward, backward
3,2
4,2
3,2
2,2
6.8
Memory
Tests
Nonverbal
1.0
(fwd)
Reasoning
Ravens Prog. Matrices /36
24
n/a
22
19
n/a
15
16
17
10
58.3
12.3
25
18
20
8
55.4
8.6
9
7
7
10
44.6
10.2
27
27
15
9
43.6
2.3
118
110
98
80
125.2
2.7
87
88
58
50
123.6
3.1
TROG /80
55
64
53
41
78.8
1.8
P&PT: words /52
n/a
48
n/a
44
> 48
-
n/a
50
51
50
> 48
-
Language
&
Semantic
Tests
Fluencies: living things¶
man-made¶
letters (FAS)¶
Picture Naming¶ /48
Reading: regular words /126
exception wds /126
pictures /52
KEY:
MMSE = Mini Mental State Examination (Folstein et al., 1975); VOSP = The Visual Object
and Space Perception Battery (Warrington & James, 1991); RMT = Recognition Memory Test
(Warrington, 1984); ¶ = Semantic Battery (Hodges & Patterson, 1995); TROG = Test for the
Reception of Grammar (Bishop, 1989); P&PT = Pyramids and Palm Trees (Howard & Patterson,
1992).
An audiometric assessment carried out in early 1995 indicated that L.M.'s
hearing was unimpaired at and below 1000 Hz (10-20 dB loss), moderately impaired
at 1500 Hz (60 dB loss) and severely impaired at higher frequencies (more than 80
dB loss).
Data reported in this chapter were collected between January and
November, 1994.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
56
Twenty-seven months after presentation, at the beginning of the study
reported here, L.M. still showed high motivation to communicate despite being
frustrated and sometimes depressed by his language difficulties.
unintelligible because of phonological paraphasias.
He was at times
His spontaneous speech
lacked all but the simplest function (as opposed to content) words, although
stereotypic, high-frequency phrases (such as "it's alright") were preserved, and
his communication using gesture, body language and pointing was still very
clear.
An example of his conversational speech follows.
The symbol * is used in
place of LM's wife's name, produced without phonological paraphasia.
As for the
sample from P.G., less clear utterances are given in phonemic transcription, and
subsequent words in underlined italic brackets indicate the likely target, where
known.
Where no gloss is given, the word(s) were unintelligible.
NG
LM
could you tell me something about your holiday in Norway?
[unintelligible]( w e n t ) one way [´ t ] coach
NG
LM
mhm
and [ s´] (pointing out of the room towards where his wife is) er * and and
the [´ z] (covers forehead with hand, then pretends to be asleep)
yes
NG
did she sleep on the coach?
LM
two two two days (showing two fingers)
and [´ ] (heart) [´ deI]
it's
alright
well you know (pointing to NG)
(tapping his heart)
NG
LM
the pacemaker
[pQnts´ ] ( p a c e m a k e r )
and er [naIdz] (nine days) (holding up nine fingers)
and (points to the window)
an [EroUploUnd ] have flow and [´ mçnd bQnd´l´nz] and er the
[unintelligible](aeroplane)
when we came out (pointing down) [´ ] coach (pointing
down) and
took [ ´ d ] all round (gesturing "all round")
[´ ] ( y e s )
[hoUd´l ] (hotel)
three days and er (holds up three fingers)
we [´ ] coach [´ ] two days (holds up two fingers)
and [´ spIp oUt] and [´ o U t ] five days (holds up five fingers)
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
[´z ´] (mimes
57
sleeping) [´ z] like ( l a u g h s )
and two days (holds up two fingers) and went [tu kwçnd]
and when we back
aeroplanes
it was alright
yes
yeah
ah I think two days (holding up ten fingers) [´z wÅn] (pointing outside the
room in the direction of his wife and shaking his head)
no five days (holds up five fingers)
it's alright (gives "thumbs up" sign)
EXPERIMENT 1: SINGLE WORD PRODUCTION
IN NAMING, REPETITION AND READING
The first experiment sought to determine whether the patients' single word
production was equally or differentially impaired when the nature of the stimuli
differed across tasks with the same target responses.
The tasks of naming
pictures, repeating spoken words and reading written words were selected
because these allowed several comparisons of theoretical interest.
An outcome of
performance equivalently disrupted on all tasks would suggest a deficit at a level
common to all tasks, with two particular candidates being phonological encoding
or articulatory implementation.
The comparison between naming versus reading
and repeating would allow us to evaluate the patients' use of a "semantic'' versus a
"direct" route to speech production (according to McCarthy and Warrington's 1984
formulation, described in Chapter 1), and the comparison between naming and
repetition would (in the single network version of the Dell model, also described
in Chapter 1) reveal the effect of initial activation at the semantic level versus
the phonological level of speech output processing.
Both patients had presented with difficulties in spontaneous speech,
suggesting an impaired "semantic" route for speech production.
It was therefore
hypothesised that the patients would be more successful in both repeating and
reading tasks than naming, since naming, like spontaneous speech, must begin
with semantic activation.
By contrast, if the phonological information provided
in a repetition task directly activates the level of phonological processing used
for output (as occurs in the models described by both McCarthy and Warrington
(1984) and Dell, Martin and colleagues (Martin & Saffran, 1992; Martin et al.,
1994)), this information is likely to assist the production of the required response.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
58
Further, while the processes involved in reading aloud are not directly specified
in either McCarthy and Warrington's model nor Dell's model, it may be adduced
from other research on reading that non-semantic translation from orthography
to phonology directly activates a phonological level for output, although the
precise nature of this processing is still controversial (Coltheart, Curtis, Atkins &
Haller, 1993; Plaut, McClelland, Seidenberg & Patterson, 1996).
As hypothesised for
repetition, therefore, the activation of output levels by phonological information
might be expected to assist the patients' performance in reading.
It was also hypothesised that the patients would have more difficulty
producing longer words than shorter words.
Similar length effects across tasks
would be evidence for a deficit at a level common to all three tasks.
In addition to assessing the effects of speaking task and word length on
single word production, Experiment 1 provided a large corpus of error responses
that could be analyses in various ways to yield a detailed characterisation of the
word production impairment in these non-fluent progressive aphasic patients.
Method
Materials
The patients were asked to produce the same 180 words, of 1, 2 or 3 syllables
(N=60 each), in a naming task which had line drawings of familiar objects as
stimuli, a repetition task for which the stimuli were words spoken by the
experimenter, and a reading task in which printed words were the stimuli.
On the
basis of the Hofland & Johansson (1989) written word frequencies for British
English, the words were matched across length groups for frequency (1 syllable
mean frequency = 10.6 per million, s.d. = 17.9; 2 syllable mean frequency = 10.5 per
million, s.d. = 16.9; 3 syllable mean frequency = 10.4 per million, s.d. = 21.0).
All items were concrete nouns so that they could be illustrated for naming.
Sources for pictures used in the naming test included the Snodgrass and
Vanderwart (1980) picture set , the Graded Naming Test (McKenna & Warrington,
1983), the Boston Naming Test (Kaplan, Goodglass & Weintraub, 1983), the A.D.A.
Comprehension Battery (Franklin, Turner & Ellis, 1992), the Hundred Pictures
Naming Test (Fisher & Glenister, 1992), the Peabody Picture Vocabulary Test
(Dunn & Dunn, 1981) and the British Picture Vocabulary Scale (Dunn, Dunn &
Whetton, 1982).
All words had reasonably predictable, regular grapheme-to-
phoneme correspondences to make the reading task as straightforward as
possible.
Some of the three syllable items were either compound words (e.g.
handlebars, flowerpot, coathanger) or two-word items (e.g. rocking chair, safety
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
pin).
59
The words were divided into three blocks containing equal numbers of 1, 2
and 3 syllable items matched for frequency across blocks.
Procedure
The test was carried out in three sessions, one week apart.
the patient responded to one block of items in each condition.
On each occasion
The same random
order of items was used within each block, although order of block presentation
and order of task performance were counterbalanced across the sessions.
In the
naming task, the patients were presented with black and white line drawings of
the items on cards and asked "Can you tell me what this is?"
In the repetition task,
words were spoken by the tester and the patient was instructed to "repeat what I
say".
The spoken model was given more than once if the patient requested it, or
seemed unsure of the target in being slow to respond.
In the reading task, the
words were printed on individual cards and the patient read them at his or her
own rate.
The subjects' responses were partly transcribed by the experimenter at
the time of testing, and were also videoed so that the in situ transcriptions could
be supplemented with transcriptions from the video for greater accuracy.
Scoring
The classification of the patients' spoken responses followed fairly closely
the criteria for classifying naming and repetition errors described by Martin et
al. (1994).
These criteria applied equally well to the classification of reading
errors in the current study.
Martin and her colleagues offered the following
categories for responses:
1.
correct
2.
formal paraphasia (phonologically but not semantically related word)
3.
semantically related response, including semantically related words
(semantic paraphasias) and descriptions of the target containing semantic
information
4.
formal a n d semantic paraphasia
5.
phonologically related neologism
6.
abstruse neologism (no evident relationship to the target)
7.
formal paraphasia on a semantic paraphasia
8.
neologism on a semantic paraphasia
9.
unrelated lexical item
10. no response.
The Martin et al. criteria were modified in the following ways.
Firstly,
categories 3, 4, 7 and 8 were broadened to include errors which in the naming
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
60
task had a visual or a semantic relationship to the target (e.g. goat → "deer",
magnet → "horseshoe").
Secondly, even the modified category of formal lexical
paraphasias on semantic paraphasias (Martin et al.'s category 7) was not required,
because there were no instances in which the patients met the stringent
requirement that they indicate verbally or non-verbally that their intended
utterance was other than the target.
Thirdly, a category was added for
"perseverations", and these further classified with regard to their lexical status,
and their phonological and semantic relationship to the target.
On the (relatively
rare) occasions that the patients made multiple attempts at producing a particular
target word, the first response was usually analysed.
The exception was in the
naming task, where if the patient first gave another word related to the picture
but subsequently produced the target (e.g. hump → "camel; hump"), the attempt at
the correct target was scored.
The liberal criterion of at least one stressed vowel or one consonant in
common with the target was used to classify the patients' phonologically related
errors (whether formal paraphasias, formal and semantic paraphasias or
phonologically related neologisms).
This criterion followed the procedure
adopted by Martin et al. (1994), and was chosen in order not to exclude any
responses showing a possible influence of the target phonology.
In fact,
however, the great majority of the responses classified as phonologically related
showed much more substantial phonological overlap with their targets than one
consonant or one stressed vowel.
The patient's incorrect lexical responses were
classified as semantically related or unrelated on the basis of judgements by 10
postgraduate psychology students about which if any of the target-response pairs
were semantically related.
Another liberal criterion was adopted, this time to
capture any possible semantic influence in the patients' error responses, by
which a response was classified as semantically related if a n y of the students
judged it so; nonetheless, very few responses were semantically related.
Results
Table 3:3 shows the percentage of each type of response given by each
patient across all tasks combined, with some examples of each type.
The patients'
phonological difficulties are immediately apparent from the fact that the largest
category of error — and indeed, for L.M., the largest category of response — was
phonologically
related
neologisms.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
61
Table 3:3. Percentage of responses of each type given by P.G. and L.M. in each
task, and overall.
% Responses Given
Response Type
P.G.
L.M.
Name
Rpt
Read
Total
Name
Rpt
Read
Total
target correct
36.2
49.7
58.1
48
6.9
7.8
18.9
11.2
phonologically related neologism
21.1
29.9
31.3
27.4
46.9
59.4
60.5
55.4
5
13.6
6.1
8.2
9.7
16.1
13.9
13.2
4.4
2.8
3.3
3.5
4.5
1.6
5.6
3.9
perseveration of entire response
7.8
1.1
0.6
3.2
7.4
8.9
1.1
5.8
visually/semantically
6.1
0
0
2.1
3.4
0
0
1.1
4.4
0
0.6
1.7
2.9
0
0
0.9
2.2
0
0
0.7
4.5
0.6
0
1.7
2.2
0.6
0
0.9
10.9
5.6
0
5.4
10.6
2.3
0
4.3
2.9
0
0
0.9
100
100
100
100
100
100
100
100
(e.g. skunk → [ sk√nt ] )
formal paraphasia
(e.g. swing → wing)
phonologically and visually/
semantically related word
(e.g. safety pin →
pinned)
related
word (e.g. beaver → rat)
visually/semantically
related neologism
(e.g. computer → [ tEl´v ] )
unrelated word
(e.g. tiger →
carver)
abstruse neologism
(e.g. magnet → [ fUf ] )
no response
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
62
Production of Correct Responses
To test the hypotheses that the patients' success at single word production
would vary across tasks and word lengths, the numbers of correct targets
produced by each patient across the three tasks and lengths were compared,
illustrated in Figure 3:1.
The test statistic used for comparisons across tasks is
Cochran's Q, a nonparametric statistic for matched data with a sampling
distribution approximated by a chi-squared distribution (Winer, 1970); the length
effect was assessed with a simple chi-squared statistic.
Both patients showed a
significant main effect of task, demonstrating that the nature of processing
required prior to production did influence whether the target was produced
correctly (P.G.: Q(2) = 20.19, p < 0.01; L.M.: Q(2) = 17.08, p < 0.01). The hypothesis that
longer words would be harder to produce correctly was also supported by a
significant main effect of word length (P.G.: χ 2 (2) = 40.14, p < 0.01; L.M.: χ 2 (2) =
23.90, p < 0.01).
Each patient also showed an interaction between the effects of task and
word length on number of correct responses.
P.G. produced significantly more 1
syllable words correctly in reading than in naming and repeating (1 syllable:
naming vs. reading Q(1) = 7.00, p = 0.01; repetition vs. reading Q(1) = 4.48, p = 0.03)
and more 2 syllable words correctly in repeating and in reading than in naming
(2 syllable: naming vs. reading Q(1) = 12.46, p < 0.01; naming vs. repetition Q (1) =
8.17, p < 0.01).
There was no difference between tasks in the (small) number of
her correct responses to three syllable words.
L.M. produced significantly more
correct 1 syllable words in reading than in naming and repeating (1 syllable:
naming vs. reading Q(1) = 15.7, p < 0.01; repetition vs. reading Q(1) = 8.91, p < 0.01),
but showed no further task differences in the two or three syllable words, where
his performance was at floor level.
Overall, there was some support for the
hypothesis that the patients' performance would be poorest on naming, and that
their difficulties on all tasks would increase with word length.
The patients were
not much more successful in repetition than naming, however, contrary to
expectations.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
63
Correct
0.6
Proportion
a) PG
0.8
0.4
0.2
2
1
Read
Repeat
Name
Read
Repeat
Name
Read
Repeat
Name
0
3
Word Length (Syllables)
b) LM
Correct
0.6
Proportion
0.8
0.4
0.2
1
2
Read
Repeat
Name
Read
Repeat
Name
Read
Repeat
Name
0
3
Word Length (Syllables)
Figure 3:1.
Proportion of correct targets produced by P.G. and L.M. in the naming,
repeating and reading tasks for targets of 1, 2 and 3 syllables in Experiment 1.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
64
Production of Phonologically Related Responses
Although analysis of the number of targets produced correctly suggested
that the nature of processing prior to production did affect their successful
production of single words, this proved not to be the best measure of the effect of
speaking task on the patients' output.
As L.M. only produced a total of 11% of
responses correctly, effects within these responses are only informative about a
very small proportion of his speech production, and in terms of number of
completely correct responses he was at floor level on everything except reading
the one syllable words.
A better indication of the influence of speaking task may
therefore be observed in the extent to which the patients' responses in each task
were phonologically related to the target, especially as it was hypothesised that
phonological information available via a nonsemantic route would facilitate
production in repetition and reading.
Considering, however, that the lenient criterion of an overlap of one
stressed vowel or one consonant between response and target might have
captured many responses in which such a small overlap occurred purely by
chance, it was necessary to ensure that the responses classified as phonologically
related were in fact related at a greater than chance level.
Adopting the
procedure which Martin et al. (1994) devised for this purpose, the rate of
phonologically related target - response pairs in P.G. and L.M.'s error responses
(excluding no responses) were compared with the rates obtained from three
random pairings of all their error responses with the target items.
The random
pairings were scored for phonological relatedness to the targets in the same
manner as the patients' responses.
McNemar tests confirmed that in all tasks the
patients' real error responses were classified as phonologically related to their
targets significantly more often than were the random re-distributions of their
error responses (Table 3:4).
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
Table 3:4.
65
Numbers of phonologically related and unrelated pairs in P.G.'s and
L.M.'s responses in each of the three tasks compared with three random
assignments of their responses to the targets.
Patient
Task
P.G.
Name
Repeat
Read
Random
Distributions
Phonological
Patient
Relationship
Errors
1
2
3
Related
66
46
43
42
Unrelated
32
Related
83
Unrelated
2
Related
75
Unrelated
0
49
52
53
χ2(1) = 6.0
χ2(1) = 6.9
χ2(1) = 8.5
p = 0.02
p = 0.01
p < 0.01
48
52
51
37
33
χ2(1) = 31.2 χ2(1) = 27.3
p < 0.01
p < 0.01
p < 0.01
47
46
47
28
29
χ2(1) = 26.0 χ2(1) = 27.0
L.M.
Name
Repeat
Related
115
Unrelated
45
Related
150
Unrelated
16
Related
Unrelated
145
1
28
χ2(1) = 26.0
p < 0.01
p < 0.01
p < 0.01
83
87
92
77
73
χ2(1) = 15.5 χ2(1) = 10.4
68
χ2(1) = 8.2
p < 0.01
p < 0.01
p < 0.01
94
87
89
72
79
χ2(1) = 40.9 χ2(1) = 43.0
Read
34
χ2(1) = 26.7
77
χ2(1) = 52.2
p < 0.01
p < 0.01
p < 0.01
86
89
87
60
57
χ2(1) = 57.0 χ2(1) = 52.2
p < 0.01
p < 0.01
59
χ2(1) = 56.0
p < 0.01
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
66
Having established that the responses scored as phonologically related
were reliably related at greater than chance levels, the patients' rate of such
responses across the three tasks was compared.
Within each task, the
phonologically related responses (correct responses, formal paraphasias,
formally and visually/semantically related responses and formally related
neologisms) were combined, and the number of these was compared with the
number of phonologically unrelated responses (all other response categories).
Both patients showed a significant main effect of task in a direction
supporting the direct phonological input hypothesis.
As demonstrated in Figure
3:2, both P.G. and L.M. produced more phonologically related responses in the
repetition and reading tasks than in the naming task (P.G.: naming vs. repetition
Q (1) = 47.61, p < 0.01; naming vs. reading Q(1) = 53.26, p < 0.01; L.M.: naming vs.
repetition Q(1) = 14.22, p < 0.01; naming vs. reading Q(1) = 53.26, p < 0.01). L.M.,
however, also produced a higher proportion of phonologically related responses
in the reading task than in repetition ( Q(1) = 23.15, p < 0.01), which had not been
predicted. The main effect of length was not significant for either patient (P . G . :
χ 2 (2) = 2.55, p = 0.28; L.M.: χ 2 (2) = 1.56, p = 0.46), but L.M. showed a significant
interaction between task and length, which, again contrary to expectations,
indicated there was no significant difference between naming and repetition in
the number of phonologically related responses to 2 and 3 syllable words, and
fewer phonologically related responses in both these tasks compared to the
reading task (2 syllable words: naming vs. reading Q(1) = 10.89, p < 0.01, repetition
vs. reading Q(1) = 6.4, p = 0.01; 3 syllable words: naming vs. reading Q(1) = 16, p <
0.01, repetition vs. reading Q(1) = 10, p < 0.01).
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
67
Proportion Phonol. Related
a) PG
1
0.75
0.5
0.25
1
2
Word Length (Syllables)
Read
Repeat
Name
Read
Repeat
Name
Read
Repeat
Name
0
3
Proportion Phonol. Related
b) LM
1
0.75
0.5
0.25
1
Figure 3:2.
2
Word Length (Syllables)
Read
Repeat
Name
Read
Repeat
Name
Read
Repeat
Name
0
3
Proportion of phonologically related responses produced by P.G. and
L.M. in the naming, repeating and reading tasks for targets of 1, 2 and 3 syllables
in Experiment 1.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
68
Increased Error Rate in Long Words: A Linear Function of Opportunity?
It was hypothesised that longer words would be more susceptible to error in
these patients with impaired phonological skills, because words that require more
phonological processing provide more opportunity for error.
was confirmed.
This hypothesis
The next investigation considered whether the increased
probability of error on longer words depended directly on the number of
syllables or sounds in the target word in a linear fashion.
The percentages of
phonologically related errors made by both patients on words of each length
(across all tasks) are shown in Figure 3:3, with word length considered in terms of
the number of both syllables and phonemes in each word.
The linearity of increase was tested by fitting a binomial model in GLIM
(Aitkin, Anderson, Francis, & Hinde, 1989) to the proportions of phonologically
related errors observed at each length, and estimating the power which best
described the rate of change of the increase in errors.
In such a model, an
estimated power equal to one describes a perfectly linear increase.
P.G.'s rate of
errors as a function of length was not significantly different from linear for
either measure of word length (syllables: estimated power = 0.7, Ho : power = 1 not
rejected for χ 2 (1) = 2.96, p = 0.09; phonemes: estimated power = 0.8, χ 2 (1) = 1.22, p =
0.27). L.M.'s rate of phonologically related errors increased at a significantly
lower than linear rate (syllables: estimated power = 0.35, χ 2 (1) = 24.2, p < 0.01;
phonemes: estimated power = 0.32, χ 2 (1) = 27.03, p < 0.01).
Thus the likelihood of
P.G. making a phonological error in speaking single words increased roughly
linearly as a function of target word length.
The less-than-linear increase in
L.M.'s likelihood of error probably arose because he made so many phonological
errors on shorter words that there was little room for increase as the words
became
longer.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
0.25
Errors
0.5
1
0.75
Proportion
Errors
0.75
Proportion
1
0.5
0
0.25
0
1
2
3
Number of Syllables
PG
1
LM
0.25
0
Errors
1
0.75
Proportion
Errors
Proportion
0.5
3
Number of Syllables
1
0.75
2
0.5
0.25
0
2-3 4-5 6-7 8-9
Number of Phonemes
PG
Figure 3:3.
2-3
4-5
6-7
8-9
Number of Phonemes
LM
Proportion of phonologically related errors according to length, in
syllables and phonemes, produced by P.G. and L.M. in Experiment 1.
69
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
70
Formal Paraphasias: Lexically mediated?
Some of the patients' phonologically related errors were words (formal
paraphasias, phonologically and visually/semantically related words) while
others were neologisms; therefore an important question is whether the real
word errors arose from a misselection at the lexical level of speech processing or
from a disruption at the phonological level.
In the interactive spreading
activation model of Dell and colleagues, the former occurs when the node for a
competing item is selected instead of the target node at the lexical level:
phonologically related competitors may gain an advantage over the target
because of feedback activation from the phonological level (Dell, 1986; Martin &
Saffran, 1992).
By this account, errors attributable to a misselection of lexical
node should show less phonological similarity to their targets than
phonologically related neologisms, because the neologistic errors are
phonological corruptions of the correct target whereas the phonologically
related real word errors are driven by a different lexical node (Gagnon, Schwartz,
Martin, Dell, & Saffran, 1995; Martin et al., 1994).
Alternatively, however, a disruption at a phonological level of speech
output could also be expected to generate some phonologically related errors
which would happen to be real words simply because small phonological changes
to many words yield other words.
It might be predicted that, if the production of
phonologically related words is arising at this level, the likelihood of the response
being a word should show a significant negative relationship to word length,
because shorter words have a higher number of close phonological neighbours
(Forster & Davis, 1991).
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
71
The closeness of the phonological relationship between targets and
responses for real word responses versus neologistic responses was compared
using a measure of error complexity similar to that reported by Schwartz et al.
(1994).
"Simple errors" were defined as those differing from the target in one
phoneme only, and "complex errors" as those involving more than one altered
phoneme.
Simple errors are thus more closely related in phonological form to the
target than complex errors.
Figure 3:4 shows that P.G.'s proportions of simple and
complex errors did not differ between lexical and nonlexical responses,
demonstrating that her real word and neologistic responses were equally close to
the target items in phonological form. L.M. produced a significantly h i g h e r
proportion of lexical than neologistic responses containing simple errors ( χ 2 ( 1 ) =
34.27, p < 0.01), indicating that his real word responses were actually closer in
phonological form to the targets than his neologistic errors.
Thus, there was no
evidence to suggest different sources for the phonological paraphasias that had
real-word versus neologistic forms.
Further, although lexically mediated errors
are assumed to occur under the influence of both feedback phonological
activation a n d feedforward semantic activation associated with the target (Martin
et al., 1994), the patients produced few errors that were semantically related to
their
corresponding
targets.
Simple
1
Error
Complex
Error
Proportion
0.75
0.5
0.25
0
word neol.
PG
Figure 3:4.
word
neol.
LM
Proportion of simple versus complex errors produced by P.G. and L.M.
in responses constituting real words and neologisms in Experiment 1.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
72
To evaluate further the hypothesis that both real word and neologistic
errors arose at the phonological level, the rates of word versus neologistic errors
produced in response to targets of each length were compared.
Figure 3:5 shows
that both patients produced significantly more phonologically related neologisms
and fewer phonologically related words as the target items became longer (P . G . :
χ 2 (2) = 47.04, p < 0.01; L.M.: χ 2 (2) = 53.61, p < 0.01), suggesting that the lexicality of
the phonological paraphasias was more likely to be due to chance and to the
structure of the English language than to the patients' impairments.
Finally,
although the nature of the task affected so many other aspects of the patients'
speech production, there was no difference across tasks in the ratio of words to
nonwords among the phonologically related errors (P.G.: χ 2 (2) = 2.42, p = 0.30; L . M . :
χ 2 (2) = 1.83, p = 0.40).
1
1
Word
Neologism
0.75
Proportion
Proportion
0.75
0.5
0.25
0.5
0.25
0
0
1
2
3
Number of Syllables
PG
Figure 3:5.
1
2
3
Number of Syllables
LM
Proportion of phonologically related words versus neologisms
(excluding correct responses) produced by P.G. and L.M. in response to 1, 2 and 3
syllable targets in Experiment 1.
The Severity of the Disruption to Phonological Production
The next series of analyses aimed to characterise the patients' phonological
impairment in terms of the severity of disruption to the words attempted and the
robustness of different components of the target's phonological form under the
effects of this disruption.
The effects of speaking task and target word length
upon phonological processing at these more specific levels were also considered.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
73
Both patients produced more complex errors than simple errors overall
(P.G.: 61% : 39%; L.M.: 78% : 22%), and the distribution of these across tasks is
shown in Figure 3:6.
Although there was a trend for her errors in reading to be
less complex than in the other two tasks, P.G. showed no significant difference in
error complexity across tasks ( χ 2 (2) = 2.00, p = 0.37), while L.M. did produce a
significantly lower proportion of complex errors in the reading task than in the
other two tasks (naming vs. reading: χ 2 (1) = 9.84, p < 0.01; repeating vs. reading:
χ 2 (1) = 18.11, p < 0.01).
Regardless of whether success is measured by the number
of fully correct or phonologically related responses, or by the degree of
disruption to the spoken forms, it is clear that for these patients the orthographic
stimulus in reading elicited more successful spoken responses than either the
spoken-word stimulus in repetition or the pictures for naming.
Simple Error
1
Complex Error
Proportion
0.75
0.5
0.25
0
N a m e R p t Read
PG
Figure 3:6.
N a m e R p t Read
LM
Proportion of simple versus complex errors in error responses
produced by P.G. and L.M. in the naming, repeating and reading tasks in
Experiment 1.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
74
The relationship between word length and error complexity further
emphasised the patients' difficulty in producing longer words: more complex
errors were produced as the targets became longer (Figure 3:7).
P.G. only
produced significantly more complex than simple errors to 3 syllable targets (1
vs. 2 syllables: χ 2 (1) = 1.82, p = 0.18; 1 vs. 3 syllables: χ 2 (1) = 13.94, p < 0.01; 2 vs. 3
syllables: χ 2 (1) = 5.36, p = 0.02); L.M. showed a significant increase in complex
errors at each increment in number of syllables in the target word (1 vs. 2
syllables: χ 2 (1) = 20.12, p < 0.01; 2 vs. 3 syllables: χ 2 (1) = 26.35 p < 0.01).
Simple
Error
Complex Error
1
Proportion
0.75
0.5
0.25
0
1
Figure 3:7.
2
3
Syllables
PG
1
2
3
Syllables
LM
Proportion of simple versus complex errors in error responses
produced by P.G. and L.M. to words of 1, 2 and 3 syllables in Experiment 1.
Investigating which parts of the target word were best preserved in these
patients' phonologically related errors, it was found that P.G.'s responses
preserved the primary stressed vowel in 75% of responses, the initial phoneme
(produced in initial position) in 63% of responses, and the final phoneme (in
final position) in 45% of responses.
L.M.'s responses preserved the stressed vowel
in 63% of responses, the initial phoneme in the initial position in 71% of
responses, and the final phoneme in the final position in only 20% of responses.
Considered across tasks, both patients were more likely to preserve the initial
segment and the primary stressed vowel in reading than in naming or repetition,
and L.M. was as likely to preserve the vowel and final segment in repetition as in
reading, all significantly more often than in naming (Figure 3:8).
Thus, even
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
75
when the preservation of particular segments is considered, the tasks where
stimulus input provides information about the phonological output form showed
an
advantage.
Proportion Correct
1
Initial
Phoneme
0.75
0.5
0.25
0
PG
Proportion
Preserved
1
LM
Primary-stressed
Vowel
0.75
0.5
0.25
0
PG
Proportion Correct
1
LM
Final
Phoneme
Name
0.75
Repeat
Read
0.5
0.25
0
PG
Figure 3:8.
LM
Proportion of responses given by P.G and L.M. in each task in
Experiment 1, in which the initial phoneme of the target appeared as the initial
phoneme in the response, the primary-stressed vowel from the target word was
preserved in the response, and the final phoneme of the target appeared as the
final phoneme in the response.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
76
Is the Disruption Phonological or Articulatory?
The final question considered was whether any of the errors hitherto
classed as "p h o n o l o g i c a l l y related" could in fact be due to p h o n e t i c
similar to that reported in the speech of some Broca's aphasics.
disintegration,
Although an
investigation of the timing and coordination of the patients' neuromuscular
activity during articulation was beyond the scope of the present study, an attempt
was made to characterise in detail the types of errors produced by the patients in
the responses earlier categorised as formal paraphasias, phonologically and
visually/semantically related words, and phonologically related neologisms.
Responses which were ambiguous as to the nature of the disruption, and/or
appeared to be subject to more than one error process occurring to the same
segment(s) at once were excluded.
On these grounds, 24 of P.G.'s 219
phonologically related errors were excluded, as were 141 of L.M.'s 406
phonologically related errors.
In the remaining responses, the production of
only one segment was disrupted (the "simple errors" of earlier analyses), one or
more segments or syllables was deleted, or more than one segment in a word was
disrupted but neither disruption was ambiguous in source.
The errors in this
subset of responses could then, with reasonable confidence, be attributed to one of
the error processes listed in Table 3:5; this Table 3:also shows the number of
occurrences of each of these types.
Many of the error processes listed in Table 3:5 may be interpreted as
arising either from an inappropriate or inadequate activation of features at the
phonological level o r from inappropriate muscular movement(s) or the
miscoordination of two articulators. Thus, a stop may have been added after a
nasal (moon → [mund] ) because the phonological features of the stop were
activated at the phonological level or, because during the articulation of [n], the
oral occlusion at the alveolar ridge was erroneously released after the raising of
the velum (instead of simultaneously with this), creating an unintentional voiced
alveolar oral stop [d].
Competing phonological and articulatory level arguments
could similarly be offered to explain voicing and frication errors, the insertion of
[h] before an initial vowel, the insertion of nasals, glides, fricatives and schwas in
the contexts described, and some of the other error processes listed in Table 3:5.
Thus, while it is impossible to demonstrate conclusively the occurrence of
articulatory errors in the context of preserved phonological contrast without
instrumentally measuring the movements and timing of the articulators in
question (and not always unambiguously then), this survey does not rule out the
possibility that some of the errors that were categorised as "phonologically
related" may have been of the type(s) described as "phonetic disintegration"
errors in other investigations.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
77
Table 3:5. Error processes occurring in responses produced by P.G. and L.M. in
the phonologically related error categories, showing the number of occurrences
of each type.
Error
Process
Example
Tally
P.G.
L.M.
n=195 n=265
Target
Response
arch
hatS
8
2
palette
pQl´nt
2
7
hammer
hQm´l
5
2
add stop after nasal/stop nasal
banana
b´dan´
10
24
add word-final stop after vowel or
funnel
f√n´ld
1
4
add word-final fricative [s/z/v]
bee
biv
4
21
add word-final schwa
pipe
peIp´
1
2
insert schwa in cluster
tractor
trQk´t´
3
1
add other segment
Eskimo
EskwIn´
6
11
delete
Indian
Indi´
7
6
stool
sul
18
21
pineapple
paIn´l
11
8
witch
wIdZ
17
24
goat
goUs
4
7
typewriter
taIsraIt´
23
53
cigarette
()Ig´rEt
6
3
apple
eIp´l
14
33
tulip
tupIl
4
5
elephant
fEl´ft´nt´
20
3
lawnmower
lçnloU´
6
6
bucket
b√k
20
21
typewriter
taI taI taI taI
4
0
wheelbarrow
wilmaIbQroU
1
1
insert h before initial vowel
insert nasal before stop
add glide [l/w/r]
after vowel
dark [l]
segment
delete segment from cluster
delete segment: reduce syllables
voice
error
fricate stop
other
consonant
unclear
vowel
substitution
consonant
substitution
exchange two segments
anticipate
perseverate
segment
segment
delete syllable (s)
perseverate
syllable
add other syllable
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
78
Discussion
The results of this experiment establish that the nature of the stimulus in
three speech production tasks influenced the success of the non-fluent aphasics'
single word production.
Specifically, the patients were more likely to arrive at a
reasonable phonological approximation to the target, and in some cases to achieve
a fully correct pronunciation, in the tasks where the stimulus provided
information about the required phonological output.
Thus the patients had more
difficulty in reaching even an approximation of the phonological output form
required in naming compared with repetition and reading.
When the similarity
of these phonological approximations to their targets in each task was considered,
L.M.'s errors in the reading task were phonologically closer to the targets than
his errors in the other tasks, and P.G.'s errors showed the same trend.
The
distribution of completely correct responses across tasks also supports the direct
phonological input hypothesis to some extent, although P.G.'s advantage in
repetition and reading on this measure was only statistically reliable for the two
syllable words, and among the one syllable words her repetition was no more
likely to be successful than her naming.
In L.M.'s case, the task most likely to
elicit a correct response to one-syllable words was reading; he otherwise gave so
few correct responses that the number of these was not particularly informative
about the effects of the different tasks on his speech production.
The patients' impaired performance on all tasks clearly rules out a taskspecific deficit, and suggests that a processing level common to all three tasks —
phonological encoding and/or articulatory implementation — must be impaired.
The patients were not, however, equally impaired on all three tasks, so an account
of their deficit must also explain their differential performance across tasks.
It
appears that while the patients have difficulty with phonological encoding under
all conditions, when the task stimulus provides information about the required
output phonology this facilitates the production of the appropriate output form.
Thus in McCarthy and Warrington's terms (1984), the "direct" route is more
efficient for speech production in these patients than the semantic route; in the
formulation of Dell (1986), activation of the phonological level of the lexical
network guarantees a more successful production of the phonological target than
activation at the semantic level.
Considering, however, that the spoken word in repetition should provide
phonological information more directly than the written word in reading, the
patients might have been expected to show an advantage in repetition over
reading; but if anything, the reverse was true.
Both P.G. and L.M. read aloud more
targets correctly than they repeated in the one syllable words, and L.M. produced
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
79
more phonologically related responses overall in the reading task than in the
repetition
task.
The reason for the observed advantage of reading over repetition almost
certainly lies in the fact that the patients have better preserved processing of
orthographic input than of auditory-phonological input.
For example, both
patients showed essentially perfect performance on case-matching tasks which
require discrimination among orthographically similar distractors (P.G. scored
95% correct on words and 100% correct on letters; L.M. scored 100% on both), but
their auditory-phonological discrimination skills were severely impaired.
On the
Four Alternative Auditory Feature Test (Foster & Haggard, 1986), in which a
spoken word must be matched to one of four written words where the distractors
are phonologically very similar (a test on which normal subjects perform at
ceiling),
P.G. scored 66% and L.M. scored 44%.
As neither patient showed a bias
toward errors on the words discriminable by high frequency acoustic cues only
(as in pairs differing only on voiceless fricatives or stops), this severe deficit
cannot simply be attributed to hearing impairment, although there is no easy way
to determine the relative contributions of hearing loss and phonological
processing deficit to their difficulties in processing spoken input.
For these
patients, it thus appears that the phonological information potentially available
in spoken word stimuli is degraded, and consequently less able to assist in
activating the phonological form in the repetition task.
The length of the target item did not affect the patients' ability to achieve
some degree of phonological approximation to the correct response, but did affect
the likelihood of their attempts being correct, and did affect the severity of the
disruption to the forms which were not produced correctly.
The probability of
error as a function of increasing word length rose in a linear fashion in P.G.'s
case, reflecting simply the requirement to produce a greater number of sounds,
while L.M.'s extremely high error rate at all word lengths make his less-thanlinear increase difficult to interpret, but unsurprising.
One account of an increase in error rate to words of increased length
invokes a deficit in a "phonological" or "articulatory" output buffer, such that the
phonological/articulatory plan for the unit of speech to be produced exceeds the
capacity of the buffer (Cohen & Bachoud-Levi, 1995).
If the use of this buffer is
common to all speech production tasks, however, it is not clear why the patients
would show a differential performance across tasks, unless an additional
phonological deficit is also proposed.
For reasons to be considered in the General
Discussion, the better account is one in which the inefficient activation of the
phonological
representations
errors across all tasks.
themselves
results in the phonological/articulatory
These representations, however, may be more effectively
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
80
activated in some tasks — those for which the stimuli provide phonological
information — than others.
EXPERIMENT 2: SINGLE WORD PRODUCTION
IN WRITTEN VERSUS SPOKEN MODALITIES
The first experiment showed that the single word production of two
patients with non-fluent progressive aphasia was more successful in a reading
task than in a repetition or a naming task.
The patients' success in reading
relative to naming was attributed to the direct delivery of phonological
information available from the written word to the level of phonological output
processing.
It was argued that the advantage for reading compared with
repetition could be explained by the hypothesis that the patients' impaired
auditory-phonological processing resulted in a degraded form of the phonological
information potentially provided by the spoken word.
In the naming task, with
no phonological information available in the stimulus on which to model the
production of the required output, the patients were least successful.
The phonological information obtained from the stimuli in reading and
repetition tasks is thus hypothesised to facilitate the patients' performance in
these tasks.
While this information may be conveyed along putative "direct"
(non-semantic) routes from phonological and orthographic input processing to
phonological output processing, an alternative possibility is that the privileged
availability of this information at output in repetition and reading tasks arises
because the stimuli in these tasks have a principled correlation with the required
output forms (Patterson, Croot & Hodges, 1994).
In repetition, setting aside the
differences in accent between speaker and listener, there is a near-perfect
correlation between the auditorily presented stimulus and the phonological
structure for output (although there is reason to believe that, for these patients,
such a correlation is significantly reduced).
In reading — in an alphabetic
language such as English — there is a systematic, but not perfect, correlation
between a written word and its phonological form.
In naming, however, because
objects (and pictures of objects) are only arbitrarily related to the soundstructure of their labels, there is no correlation between the form of a picture and
the spoken name of the pictured object.
Experiment 2 was designed to test the hypothesis that, rather than — or in
addition to — the existence of a direct/nonsemantic route, the patients' success in
speech production would depend on the strength of the correlation between input
and output forms.
The tasks of reading, repetition, copying written words and
writing words to dictation were used — all tasks for which direct/non-semantic
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
routes are hypothetically available (Ellis & Young, 1988).
81
Although there is a
principled correlation between input and output forms in all of these tasks, the
degree of correlation should be higher when input and output are both in the
same modality (written or spoken) and lower when the output is required in the
alternative modality from the input.
It was hypothesised that the higher degree
of correlation should facilitate production.
This experiment was carried out 6
months after Experiment 1 and only P.G. took part, as L.M.'s correct pronunciation
rate was too low, especially in repetition.
An additional factor which has been shown to influence the correct
production of single words is word frequency (Dell, 1990; McCarthy & Warrington,
1984; Pate, Saffran & Martin, 1987); a frequency manipulation was also introduced
into this experiment.
Materials,
Procedure
and
Scoring
P.G. was asked to do four tasks in which the modality of input, output, and
their correspondence was varied: repetition, copying written words, reading
aloud and writing to dictation.
letters/3.7
phonemes)
with
The same 48 one-syllable words (mean length = 4.5
regular
spelling-sound
correspondences
were
produced in each task, with each task completed on a different occasion.
Half the
words were considered to be high frequency, with a written frequency of more
than 50 per million, and half low frequency (less than 30 per million) (Kucera
and Francis, 1967).
By contrast with Experiment 1, in this experiment the number of target
presentations in repetition was limited, as was the duration of target presentation
in reading.
This was to control the patient's "level of exposure" to the input across
tasks with same-modality stimuli.
In a pilot study investigating whether exposure
duration per se affected P.G.'s performance, it was found that there was no
difference in her rate of correct reading responses to written words presented at
250 versus 500 ms on a C.R.T. screen, or her rate of correct repetition responses
after one compared with two spoken presentations.
In the present experiment,
the longer exposure time and two repetitions of the target was used because these
were closer to the conditions the patient had experienced in Experiment 1.
In the
reading and written copying tasks, therefore, the words were presented in
lowercase print on a computer screen for a duration of 500 msecs each, and in the
repetition and writing to dictation tasks, P.G. was provided with two spoken
presentations of the target word before a response was required.
Responses were scored using the same categories and criteria used in
Experiment 1.
As an analogue of spoken responses classified as phonologically
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
82
related to the target when there was one stressed vowel or one consonant from
the target occurring in the response, the written responses were judged to be
related in form to the target when one letter from the target occurred in the
response, although in all cases there was more than a single letter from the target
occurring in the formally related written words.
Because every writing to
dictation response contained at least some perseverative material (see Table 3:6
for examples), any extraneous t h e , final - e d , or perseveration of a word or wordlike chunk from the previous few responses was disregarded and each response
was categorised on the basis of the "residue".
Thus, the results for the dictation
task are discussed with the proviso that all writing to dictation responses were
qualitatively different from responses given in the other tasks because of the
high rate of perseverative material they contained.
in all four tasks are given in Table 3:6.
Examples of P.G.'s responses
Her responses in the copying task were
produced in upper case print (despite the lower-case stimuli); her responses in
the writing to dictation task in a lower case, semi-cursive style; in both instances
by her own choice.
Table 3:6. Examples of P.G.'s responses in the copying, repetition, reading and
writing to dictation tasks; b o l d lettering indicates that part of the writing to
dictation response scored when extraneous perseverative material (shown in
italics) was ignored.
Task
Target
Word
Copying
Repeating
Reading
Writing to Dictation
chair
CHAIRH
tSE´ ( )
tSE´ ( )
The c h a i r ed ( )
stub
STUB ( )
stQb
s√b
The stepp e d
sense
SENSE ()
sINk
sEdz
Tension
grove
GROVE ()
no
groUv ( )
G r o w n ed the tension
claim
CLAR
kleIm ( )
bleIg
Clain
response
Results
The number of correct responses in the tasks with input and output in the
same modality (copying and repeating) was higher than that for the tasks with
differing input and output modalities (reading and writing to dictation) (Q (1) =
29.51, p < 0.01), as had been hypothesised.
There was also, however, a significant
interaction between correspondence of input-output modality and input modality,
such that P.G. was more likely to be correct in the tasks with written stimuli than
those with spoken stimuli (Q (1) = 26.76, p < 0.01). There was no interaction between
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
83
correspondence of modality and output modality (Q (1) = 1.15, p = 0.28), thus P.G.'s
likelihood of giving a completely correct response was not related to the response
modality per se.
Figure 3:9 illustrates the proportion of correct responses in each task.
Pairwise task comparisons confirm the obvious trend in the figure.
P.G. produced
more correct responses in copying than in repeating and reading, and more
correct responses in both of these latter tasks than in writing to dictation
(copying vs. repeating: Q(1) = 14.44, p < 0.01; copying vs. reading: Q(1) = 14.29, p <
0.01; repeating vs. writing: Q(1) = 10.89, p < 0.01; reading vs. writing: Q(1) = 11.27, p <
0.01); there was no significant difference between repetition and reading.
There
was also no significant effect of frequency and no interaction between the effects
of frequency and task on the number of correct responses.
Correct
0.6
Proportion
0.8
0.4
0.2
0
Copy
Figure 3:9.
Repeat
Read
Task
Write
Proportion of correct responses given by P.G. in the copying,
repetition, reading and writing to dictation tasks in Experiment 2.
The number of responses which were related to the targets in orthographic
or phonological form (henceforth simply "related") showed no significant main
effect of the correspondence between input and output modality (Q (1) = 2.05, p =
0.15), but there was both a significant interaction between correspondence of
modality and input modality (Q (1) = 23.12, p < 0.01), and an interaction between
correspondence of modality and output modality approaching significance (Q (1) =
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
3.53, p = 0.06).
Both interactions show that P.G. tended to produce a higher rate of
related responses when a
required.
84
written stimulus was given or a written response
Only in writing to dictation was there a higher rate of related responses
to the high frequency compared with the low frequency words, and there was no
significant main effect of frequency overall.
Figure 3:10 shows this small
interaction between frequency and task, and also illustrates the distribution of
related responses across tasks.
All responses in copying, and almost all in reading
were related to the target, and although slightly fewer related responses were
produced in the writing to dictation task, this decrease was not statistically
significant.
In the repetition task there was a notably lower rate of related
responses, but the difference between repetition and writing only approached
significance (copying vs. repeating: Q(1) = 15.00, p < 0.01; reading vs. repeating:
Q (1) = 12.25, p < 0.01; writing vs. repeating: Q(1) = 3.27, p = 0.07). The unrelated
responses in repetition were predominantly failures to give any response (29%)
while the unrelated responses in writing to dictation primarily consisted of
perseverations (10%) over and above the perseverative material which was
systematically excluded from scoring in the manner described above.
High
Frequency
Low Frequency
Related
0.75
Proportion
1
0.5
0.25
0
Copy
Figure 3:10.
Repeat
Read
Task
Write
Proportion of phonologically or orthographically related responses
given by P.G. in each task in Experiment 2.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
85
Discussion
The rate of correct responses P.G. produced across the various tasks
provides some support for the hypothesis that a correlation between input and
output modality facilitates performance.
The analysis of related responses,
however, provides no additional support, while the significant interaction terms
in the analyses of both correct and related responses highlight P.G.'s difficulties
in dealing with auditory-phonological input and speech output in general.
She
was more likely to produce a correct response given a written than a spoken
input, and more likely to produce a related response on occasions when either the
stimulus was in the written modality or a written response was required.
P.G.'s
best performance occurred in the copying task for which both input and output
were in the written modality, and her poorest performance as measured by
number of related responses was in repetition, the task requiring the processing
of phonological information in both the input and output aspects of the task.
It is
clear that for this non-fluent progressive aphasic patient, at least, congruent
input and output modality is not enough to predict successful performance, and
the difficulty of processing phonological information per se must also be taken
into account.
As noted earlier, P.G.'s difficulty in repetition must be partly due to
impaired processing of auditory-phonological input, whereby degraded
representations of the spoken stimulus reduce the high correlation between
input and output normally characteristic of repetition.
Nevertheless, an
auditory-phonological input deficit cannot completely account for P.G.'s impaired
performance in repetition, because she was able to produce a greater number of
related responses in writing to dictation than in repetition, even though both
tasks require the processing of spoken words.
It seems, therefore, that her
particular difficulty in repetition stems from the demand for phonological
processing at b o t h input and output stages of this task.
On nearly one third of
occasions the phonological processing demands in repetition exceeded P.G.'s
ability and she was unable to give any response.
This makes it all the more surprising that when P.G. did provide responses
in repetition, they were more likely to be fully correct than her responses in
dictation.
This difference in the rate of fully correct responses may reflect an
advantage for the correlated input-output condition, but perhaps only for
occasions when the input was sufficiently well-processed to elicit any response at
all.
In the reading and copying tasks, in which the input was a printed word,
P.G. was consistently able to provide a related response, indicating that a printed
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
86
word was a more reliable stimulus than a spoken word for engendering output for
this patient.
P.G. was far more likely, however, to provide a correct response in
the copying task, where input and output modality were the same, than in the
reading task where the input and output modalities were different, again
supporting the input-output correspondence hypothesis.
Notably, although the
stimuli for the copying task were presented in lower case, the patient wrote her
responses in upper case, indicating that her copying was orthographically, not
visually, mediated.
There was negligible support for the prediction that responses would be
more successful to high frequency words: there was no effect of frequency on
correctness in any task, and P.G. gave a higher rate of related responses to high
frequency words only in the dictation task.
Perhaps the frequency effect in
repetition was not found because of the large number of putative occasions when
the input was too degraded to specify even a related output in this task, but it is
more likely that the frequency manipulation used (less than 30 versus more than
50 per million) was not sufficiently powerful, and that a greater contrast might
have produced more striking results.
P.G.'s performance on repetition and reading in this experiment did not
show quite the same pattern as her performance on single-syllable words in these
tasks in Experiment 1.
In Experiment 2, her rate of completely correct responses
in both tasks was lower, her reading no longer showed an advantage over
repetition in the rate of correct responses produced, and she produced fewer,
rather than an equivalent number of, related responses in repetition than
reading.
These differences are presumably attributable to either or both of two
factors: the period of six months elapsing between the first and second
experiments, and the limitation of exposure to the task stimuli which occurred in
this experiment but not the previous one.
It thus appears that by the time of,
and/or under the conditions of Experiment 2, the information provided by the
orthographic stimulus in reading was no longer sufficiently well-specified to
elicit a fully correct pronunciation more often than that derived from the
auditory-phonological stimulus in repetition.
Nevertheless, P.G.'s higher rate of
related responses in reading versus repetition in Experiment 2 demonstrates that
the written word was still a better stimulus than the spoken word for yielding an
approximation to the phonological content of the target.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
EXPERIMENT 3:
87
READING ALOUD WORDS VARYING IN
THE PREDICTABILITY OF CORRESPONDENCE
BETWEEN ORTHOGRAPHY AND PHONOLOGY
In Experiment 1, P.G.'s and L.M.'s better performance on the repetition and
reading tasks compared with naming suggested that stimuli providing
phonological information facilitated spoken single word production.
Experiment
2 explored whether this facilitation was due to the closeness of the correlation
between input and output forms.
The results of this second experiment indicated
that while P.G.'s performance was more successful in conditions of matched than
mismatched input and output modality, the impact of such a correlation was
perhaps less apparent than the patient's considerable difficulties processing
phonological information, at both input and output.
A final experiment aimed to test the effect of varying the input-output
correlation in a reading task only, utilising orthographic stimuli which the
patients were able to process relatively well, and controlling for the nature of the
phonological processing across conditions of varying correlation.
A reading task
allows manipulation of the correlation between input (orthographic) form and
output (phonological) form in at least the following two ways.
Firstly, words which obey grapheme-to-phoneme correspondence (GPC)
rules and thus have a regular or typical spelling-to-sound relationship (Coltheart,
1978; Coltheart et al., 1993) may be considered to show a closer correlation
between orthography and phonology than words which are irregular in their
grapheme to phoneme correspondence.
The phoneme associated with each of the
graphemes in regular words is the most typical one in English orthography,
whereas the phoneme associated with at least one of the graphemes in an
irregular word is not the most typical translation of that grapheme.
At a
segmental level, therefore, the correlation between orthography and phonology
is closer for regular words than for irregular words.
Secondly, it is recognised that the extent to which the orthographically
similar "neighbours" of words agree or disagree with a word's pronunciation
affects reading performance (Glushko, 1979; Patterson & Morton, 1985; Plaut et al.,
1996), and this consistency may also be considered a measure of the closeness of
the correlation between orthography and phonology for any given word.
Although any part of a word might be chosen for such an analysis, the
orthographic "body" and its corresponding phonological "rime" (the vowel and
any following consonants in a one-syllable word) is the unit over which
consistency has most frequently been manipulated, so this was the unit over
which consistency was manipulated in this experiment.
It was hypothesised that
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
88
the closer the correlation between the orthography of a word and a particular
pronunciation of that orthographic string (on either regularity or consistency or
both), the more likely the patient would be to read that word correctly.
Materials,
Procedure
and
Scoring
P.G. and L.M. were invited to read 141 monosyllabic words; 75 of these were
regular in their grapheme to phoneme correspondence and 66
were irregular,
according to the formulation of GPC regularity proposed in the Dual-Route
Cascaded model of reading (Coltheart et al., 1993).
All of the words were regular in
the pronunciation of their constituent consonants and only varied on the
grapheme-phoneme
correspondence
of
the
vowel.2
Words were chosen on the
basis of vowel phonology alone because the patients' production of the vowel in
single-syllable words was generally more accurate than their consonant
production, so that putative differences in results could more reliably be
attributed to the experimental manipulations rather than to other disruptions in
speech production.
Furthermore, the majority of irregular monosyllabic words
are irregular only in the phonology associated with the vowel grapheme.
Three sets of regular words and three sets of irregular words were formed
which varied in the degree to which other words sharing the same orthographic
body also shared the same phonology.
Table 3:7 summarises the characteristics of
each set, referring to words in the orthographic body neighbourhood of the
target which have the same body pronunciation as "friends" and to those with a
different body pronunciation as "enemies".
include the target itself.
A target's "friends" are considered to
As shown in Table 3:7, across the three sets of regular
words, the average percentages of words in the orthographic body
neighbourhoods of the target words with the same body pronunciation as the
target were 55%, 87%, and 100% respectively.
Across the three irregular sets, the
corresponding values were 13% (where only the target itself, or the target and
2
I thank Max Coltheart for advising that two words I had classed as irregular (MOURN,
POUR) are in fact regular according to the GPC component of the DRC model (Coltheart et al.
1993), and that the word SOUR which I had classed as regular is considered irregular by the
DRC model.
I repeated the analyses of the patients' performances reclassifying these words,
but the results were not significantly different from those reported.
One further word, ROSE,
that I had considered regular, is irregular according to the DRC model on the basis of the
pronunciation of the final consonant, not the vowel, so the classification of this word was left
unchanged.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
one other word, shared the target body pronunciation), 37% and 100%.
89
(This last
set are irregular but consistent words).
All words came from orthographic body neighbourhoods of at least four
words, with an average body neighbourhood size of 12.1 words, except for the lastmentioned irregular set in which the average neighbourhood size was 1.3 words.
All sets were reasonably well matched for word frequency (Kucera & Francis,
1967) and number of letters, and for concreteness and imagability where ratings
were available (Gilhooly and Logie, 1980; Toglia & Battig, 1978).
The frequency,
length, concreteness and imagability measures matched across sets are also
shown in Table 3:7.
All the words were presented in one session in semi-random order.
Where
the list included two different words with the same body but different
pronunciations (e.g. PLEAD and DREAD), on half the occasions the word with the
regular pronunciation was presented first; on the other occasions the irregular
pronunciation occurred first; to balance for any priming effects of body
phonology (Seidenberg, Waters, Barnes & Tannenhaus, 1984).
the words aloud from cards at their own rate.
The patients read
Transcription was carried out in
situ and checked from a video of the experimental session.
A second listener blind
to the word's identity was asked to identify the vowel in any cases of uncertainty.
As in the two previous experiments, the patients' responses were scored
according to whether the whole word was produced correctly and according to
whether the response was phonologically related to the target.
In this
experiment, the measure of phonological relationship of theoretical interest was
the correctness or otherwise of the vowel, because only the vowel phonology was
manipulated to be regular or irregular for a given spelling pattern.
This
experiment was carried out 6 months after Experiment 1, at about the same time
that P.G. completed Experiment 2.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
90
Table 3:7. Characteristics of the stimuli used in Experiment 3
Characteristic of set
Regular G.P.C. Sets
Irregular G.P.C. Sets
N words
25
25
25
21
22
23
% body neighbourhood with
55
87
100
13
37
100
15
11
9.6
9.9
15
1.3
(6.3)
(4.1)
(4.1)
(3.6)
(6.4)
(0.4)
8.4
9.2
9.6
1.3
5.7
1.3
(4.5)
(3.9)
(4.1)
(0.5)
(4.4)
(0.4)
7
1.4
0
8.5
9.2
0
(4.5)
(0.5)
(0)
(3.4)
(4.3)
(0)
32.1
34.1
27.4
41.0
38.9
34.1
(49.3)
(41.1)
(35.9)
(49.6)
(67.8)
(46.7)
1589
1699
499
145
1008
48.8
(765)
(419)
(1019)
(69)
same pronunciation
Mean body neighbourhood size
(s.d.)
Mean number of friends
(s.d)
Mean number of enemies
(s.d.)
Mean
Frequency
(s.d.)
Mean summed frequency of friends
(s.d.)
(3388) (5974)
Mean summed frequency of enemies
1088
124
*
331
837
*
(1009)
(386)
*
(631)
(700)
*
4.4
4.3
4.4
4.4
4.5
4.7
(0.7)
(0.7)
(0.7)
(0.8)
(0.7)
(0.7)
418
480
489
522
468
511
(212)
(102)
(99)
(97)
(138)
(110)
462
520
497
534
498
508
(s.d.)
(110)
(70)
(70)
(76)
(98)
(88)
Example
plead
toe
keen
gross
dread
laugh
(s.d.)
Mean Length (letters)
(s.d.)
Mean
concreteness
rating
(s.d.)
Mean
imagability
rating
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
91
Results
The number of whole words produced correctly showed no significant main
effect of regularity in grapheme-to-phoneme correspondence.
There was also no
significant main effect of body neighbourhood consistency in an analysis
comparing the patients' completely correct responses on the two sets of
"consistent" words (in which the only phonology associated with all words in the
body neighbourhood was that of the target) with their performance on the four
sets of words in which there were competing phonologies associated with the
bodies. L.M. was, however, more likely to be correct in the consistent sets than
the other sets at a level approaching significance (χ 2 (1) = 3.29, p = 0.07). P.G.
showed a significant interaction between the effects of GPC regularity and
consistency of body pronunciation, producing fewer words correctly from the
least consistent irregular set than from the other two irregular sets (13% set vs.
100% set: χ 2 (1) = 6.13, p = 0.01; 13% set vs. 37% set: χ 2 (1) = 4.13, p = 0.04). The rate of
correct word productions for both patients is illustrated in Figure 3:11.
PG Regular GPC
PG Irregular GPC
LM Regular GPC
0.75
Proportion
Correct
LM Irregular GPC
0.5
0.25
0
0
Figure 3:11.
25
50
75
% Body Neighbourhood
with Same Pronunciation
100
Proportions of words varying in regularity of grapheme to phoneme
correspondences and percentage of body neighbourhood consistency which were
read aloud correctly by P.G and L.M. in Experiment 3.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
92
As in previous experiments, the completely correct production of words is
not necessarily the most sensitive measure; and in this experiment in particular,
it is the patients' performance on the vowels which should more directly inform
the experimental hypotheses.
The rate of vowels correctly produced by both
patients is shown in Figure 3:12.
PG Regular GPC
PG Irregular GPC
LM Regular GPC
LM Irregular GPC
Correct
0.75
Proportion
1
0.5
0.25
0
0
25
50
75
100
% Body Neighbourhood
with Same Pronunciation
Figure 3:12.
Proportions of words varying in regularity of grapheme to phoneme
correspondences and percentage of body neighbourhood consistency in which
the vowels were pronounced correctly by P.G. and L.M. in Experiment 3.
Both patients showed a significant effect of regularity in grapheme-tophoneme correspondence on the number of vowels correctly produced (P . G . : χ 2 ( 1 )
= 8.06, p < 0.01; L.M.: χ 2 (1) = 26.02, p < 0.01), and also a significant main effect of
body neighbourhood consistency in number of vowels produced correctly when
performance on the two entirely consistent sets was compared with performance
on the other four sets (P.G.: χ 2 (1) = 9.47, p < 0.01; L.M.: χ 2 (1) = 4.85, p = 0.03). Further,
the variables of regularity and consistency interacted: consistency made no
difference to the number of correct vowels produced across the regular GPC sets,
but both patients produced more correct vowels in the irregular consistent set
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
93
than in either of the other two sets (P.G.: 13% set vs. 100% set: χ 2 (1) = 6.77, p = 0.01;
37% set vs. 100% set: χ 2 (1) = 5.38, p = 0.02; L.M.: 13% set vs. 100% set: χ 2 (1) = 6.15, p =
0.01; 37% set vs. 100% set: χ 2 (1) = 5.14, p = 0.02).
More than half the patients' errors to words in the irregular sets (P.G.: 5 9 % ;
L . M . : 68%) involved "regularisation errors" in which the vowel was given the
pronunciation that would be predicted by typical grapheme-phoneme
correspondence rules (i.e. CROW → [kraU] to rhyme with "cow"; BREAK → [brik] to
rhyme with "beak"). The other vowel errors consisted of less systematic vowel
substitutions (e.g. SEW → [ s a U]; gauge → [goU ]).
Discussion
The patients' performance as measured by correct vowel production
provided clear support for the hypothesis that a closer correlation between the
orthography and phonology of a word would yield better performance in reading
aloud in these patients, as both manipulations of correlation strength had a
significant effect in the direction predicted.
Although these effects were not
significant in the analysis of completely correct words, this was perhaps to be
expected given the patients' severe difficulties with phonological output, and the
fact that this measure also reflected their success with the surrounding
consonants as well as with the vowels.
Nevertheless, even under this stringent
requirement, L.M. showed a trend towards a significant main effect of body
neighbourhood consistency on number of whole words produced correctly.
An important constraint on the interpretation of these results arises from
the unavoidable confounding of GPC regularity with proportion of body
neighbourhood agreeing in pronunciation.
Thus, the "regular" words used in
this experiment come from body neighbourhoods in which a greater proportion
of words agree in pronunciation than the corresponding proportions for the
irregular sets (Table 3:7).
This is not surprising given that "typicality" of
correspondence between graphemes and phonemes across the vocabulary of
English defines GPC regularity, and that what is typical for the vocabulary as a
whole is reflected in the orthographic bodies of the words used in this
experiment.
Indeed, if this were not the case, the representativeness of the
stimuli used in this experiment would be questionable.
This means, however, that although the patients performed better on high
orthography-to-phonology correlation words, it is not clear to what extent each
of the manipulations contributed to their success, even though some of the
interactions between the two variables were significant.
Thus, although P.G. read
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
94
significantly fewer words correctly from the least consistent irregular set, it was
not possible to assess her performance on r e g u l a r words from body
neighbourhoods in which the majority of other words also disagreed with the
target words in pronunciation. (An example of a regular word from such a
neighbourhood is SPOOK: the grapheme "oo" is pronounced [ U ] in all other words
which have the orthographic body OOK, such as LOOK, BOOK and HOOK, but is
otherwise typically pronounced [ u ] as in COOL, ROOM and FOOD.) Unfortunately,
there are not enough English words of this type to form a set of reasonable size,
especially when other word variables such as frequency and length need to be
taken into account.
Similarly, the patients' greater success in producing correct vowels in the
regular words in this experiment may not be attributable to GPC regularity alone,
as the higher proportion of body neighbourhoods agreeing in pronunciation
with the targets for those words may also have been implicated.
While the
relative contributions of GPC regularity and body neighbourhood consistency are
partially confounded in this experiment, the results still support the hypothesis
that a closer correlation between orthographic and phonological form leads to
better
performance.
The findings of Jared, McRae and Seidenberg (1990) indicate that
consistency effects in normal subjects' response latencies in reading single words
aloud depend not on the relative n u m b e r of friends and enemies a word has, but
on the relative f r e q u e n c i e s of those friends and enemies.
Thus the patients'
reasonably good performance on the irregular but consistent set compared with
the other irregular sets may be explained by the fact that, while the irregular
consistent words have few friends, they also have no enemies.
The mean summed
frequencies of friends of this group was 48.8 per million (Table 3:7), which, while
not high, is considerably higher than zero.
One prediction for this experiment had been that a correlation between
input and output form would facilitate performance.
Experiments 1 and 2
demonstrate this predicted facilitation when the stimulus was similar to the
response in some way (containing phonological information versus not in
Experiment 1, presented in the same versus different modality in Experiment 2).
The results of the current experiment indicate that, with regard to the quasiregular correspondences between orthography and phonology in English,
opposing correspondences between input and output, as well as supportive ones,
must be taken into account.
The pattern of consistency effects co-occurring with regularisation errors
which was observed in the reading performance of P.G. and L.M. has also been
reported of J.H., a case of non-fluent progressive aphasia described by Watt et al.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
(in press).
95
This pattern is typically associated with the disorder of surface
dyslexia, in which reading aloud is excessively influenced by the most typical,
consistently encountered pronunciation of a given spelling pattern, and also by
word frequency.
Surface dyslexic patients are therefore prone to reading errors
on lower frequency words with atypical pronunciations of one or more of their
orthographic components.
Accounts of surface dyslexia differ amongst various
theories of the procedures for translating orthography to phonology (for
example, see Coltheart et al., 1993 and Plaut et al., 1996, for two different accounts).
In the view proposed by Watt et al. (1996), as in Plaut et al. (1996), the procedure
for direct, non-semantic print-to-sound translation is shaped by both frequency
and consistency, and supports accurate reading of words (even low-frequency
ones) with typical correspondences, or of words (even those with atypical
correspondences) that are common and hence well-learned.
For accurate reading
of less common and atypical words, however, additional input is required from
word meaning to balance the strength of more standard correspondences
preferred by the direct procedure.
Watt et al. therefore attribute J.H.'s surface
dyslexia to reduced communication between semantic and phonological
representations, the impairment that also accounts for his severe anomia.
Patient J.H. showed a reasonably pure pattern of surface dyslexia, with
preserved nonword reading as well as frequency effects, consistency effects and
regularisation errors in word reading.
In contrast, P.G. and L.M. were severely
impaired on nonword reading from their first assessment on this task.
Thus,
while J.H.'s reading impairment may be attributed to a deficit affecting the nondirect reading procedure, an account of the reading deficit of P.G. and L.M. must
explain the impairment to both procedures.
The nature of the patients' reading
deficit will be taken up again in the general discussion.
GENERAL DISCUSSION
The current study aimed to investigate the nature of the language
impairment in non-fluent progressive aphasia, with particular reference to the
effects of different speaking tasks, and thus different inputs to the speech
production system.
The study has shown that the single word production of two
non-fluent aphasic patients was to some degree more successful when the
stimulus in a speaking task specified the required phonological output form,
although this was not the only factor related to the patients' success.
An account
of the patients' impairment in single word production must consider the
facilitatory effects of providing phonological information per se, and of
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
96
providing that information in a form closely correlated with the required output
form.
The review of cognitive neuropsychological studies of phonological
disruption in speech production in Chapter 1 observed that the dual-route model
of speech production described by McCarthy and Warrington (1984), and the
interactive activation model of speech production developed by Dell and
colleagues (Dell, 1986; Martin et al., 1994; Schwartz et al., 1994, etc.), both make
similar predictions about task differences in production.
Specifically, both
predict patterns of aphasic performance in which there are significant
differences between speech production in semantically-driven speaking tasks
compared with tasks which do not require semantic mediation.
Speech via the
"semantic" route may be selectively impaired in both models even without any
direct disruption to the semantic system itself.
This is consistent with the
performance of the two non-fluent progressive aphasic patients described here,
whose single word production was severely impaired in naming tasks and
conversational speech, but who showed little evidence of semantic impairment on
general neuropsychological testing, and made only rare semantic errors in
speaking tasks.
A second similarity between the two models is their prediction
that delivering phonological information directly to the level of phonological
output processing will assist speech production.
The model of Dell and his colleagues (especially as discussed by Martin &
Saffran, 1992; Martin et al., 1994; Schwartz et al., 1994) provides a more specific
account of the differences which may arise between tasks involving direct versus
semantically mediated activation of phonological representations for speech
production.
In the three-tier network of the latter model (see Chapter 1, Figure
1:3), the semantic nodes are activated first in semantically-driven tasks, while in
the single network
version, the nodes first activated in the repetition task (and
by analogy, in the task of reading aloud) are the phonological nodes.
If a global
processing deficit affects the network, different outcomes will necessarily be
predicted for tasks with differing entry points to the network.
There are at least
two global processing parameters which may be disrupted: rate of activation
decay and strength of connections between nodes.
In considering the
impairment of non-fluent progressive aphasic patients, the effect of weakened
connection strength bears particular examination because this predicts an error
profile similar to that of the two patients reported here.
As discussed in Chapter 1, the error profile associated with weakened
connection strength between nodes in simulations of the Dell model consists of a
high rate of neologistic errors and the tendency for errors to be perseverative
rather than anticipatory.
The inefficiently functioning network is unable to take
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
97
advantage of feedback connections which in an optimally functioning network
reinforce the production of real words under appropriate semantic specification.
This was the error pattern shown by Schwartz et al.'s (1994) jargon aphasic
patient, F.L.; and, like the errors of F.L., the most frequently produced speech
errors of P.G. and L.M. were neologisms phonologically related to the target item,
characterised by segment and syllable deletions, phonological substitutions, and
contextually related phonological errors.
whole
word
The patients also produced a number of
perseverations.
It is important to note, however, that while the errors produced by P.G. and
L.M. were similar to those of F.L. in terms of qualitative disruption to the spoken
word form, the overall presentation of the non-fluent progressive aphasic
patients differed from that of the jargon aphasic F.L. in two significant ways.
Firstly, F.L. was able to produce a high level of verbal output in conversational
speech (Schwartz et al., 1994), and secondly, F.L. showed a "rapid and near
complete recovery of language functions" within two years (Schwartz et al., 1994,
p. 62).
In contrast, P.G. and L.M. already showed a paucity of spontaneous speech
upon first presentation, and this situation only declined over time.
It is not
unreasonable to speculate that the speech data from F.L. (collected two months
after his aneurism) reflect a less severe weakening of connections within the
speech output system than that seen in P.G. and L.M. at the time of Experiment 1.
Further, while F.L.'s recovery implies the re-establishment of near-normal
activation in his speech processing, the progressive patients' decline suggested
only further weakening of these connections over time.
In a non-linear dynamic
system such as the Dell model, qualitative differences in outcome may arise as a
function of reducing only a single parameter.
The same global processing deficit
may therefore account for the differing clinical presentations of F.L. versus P.G.
and L.M., with the critical difference being one of degree.3
3
Simulations fitting the most recent version of the Dell model (Dell, Schwartz, Martin, Saffran, & Gagnon,
in press) to the patients' performances on the three tasks described in Experiment 1 indicate that a lesion
in connection strength (or weight) in this version of the model provided an excellent simulation of the
patients' data.
First, the naming version of the model was fitted to each patient's naming with the best
simulations arising from pure connection weight "lesions" with normal decay rate values.
Second, using
the parameters obtained from naming, the current version of the model for repetition also made good
predictions of the patients' repetition performance, although both patients underperformed slightly
relative to the models' predictions.
The implemented version of the model, however, differs from that described in Martin et al.,
(1994), and in the present report of P.G. and L.M., in assuming "perfect recognition" of the target word
for repetition.
Thus, it is assumed that activation begins at the lexical level rather than the
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
98
In addition to the qualitative similarity of their errors to those of F.L., the
performance of P.G. and L.M. is consistent with the predictions of the "weakened
connections" account in several ways.
Firstly, this account predicts that if the
build-up of activation is abnormally slow throughout the network, performance
in reading and repetition will be better than naming, because the stimulus in
each of the two former tasks directly activates the phonological nodes required
for output, while the activation required for naming must originate from the
semantic level.
P.G.'s and L.M.'s naming responses were less often correct, less
often phonologically related and more severely disrupted than their errors in
reading and, to some extent, repetition.
Secondly, the "weakened connections" account predicts that the risk of
semantic and lexical errors will be higher in naming than in repetition (and
reading), because in the naming task the selection of the correct lexical node is
vulnerable to noise at both these levels, while in repetition these levels do not
receive activation until a f t e r the target phonological nodes are activated, and any
such activation only builds up slowly subject to weak connections.
(Note,
however, that under these conditions any lexical misselection errors in naming
arise from f e e d f o r w a r d misselection, in contrast to the lexical misselection errors
that occur as a result of activation feeding back to the lexical level from the
phonological level under conditions of pathologically rapid decay.)
Approximately 10% of the patients' responses in the naming task were
visually/semantically related words or visually/semantically related neologisms
(P.G.: 10.5%; L.M.: 6.3%), while they produced none of these errors in the
phonological level, and that the correct lexical node is selected.
occur in the selection of phonological nodes for output.
Errors in repetition may therefore only
The patients' repetition was disrupted beyond
what might have been expected from their output deficit because of impaired auditory-phonological input
processing.
It is therefore not entirely appropriate to assume perfect recognition for these patients.
It was, however, concluded that the patients showed relatively normal processing of the
phonological information that is provided by orthographic stimuli with predictable spelling-sound
correspondences; therefore adequate recognition may be assumed for their reading.
Indeed, the model's
predictions of the patients' repetition were a near-perfect fit to their performance in reading.
It must be noted, however, that L.M.'s performance was very close to the pattern associated with
total breakdown in the model, a point at which the error pattern of the model is primarily influenced by
error opportunities rather than by the nature of the lesion in the model.
strongly arbitrate between a weight lesion and a decay lesion.
Thus, his performance does not
P.G.'s performance, however, unmistakably
corresponds to that of a weight lesion.
I am most grateful to Gary Dell for running the simulations and providing information on the
current version of the model.
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
repeating and reading tasks.
99
These errors were unlikely to be due to difficulties
in object identification because the patients were able to perform other tasks
relying on pictorial input to semantic processing (such as the Pyramids and Palm
Trees test of Howard & Patterson, 1992) within normal limits.
Thirdly, this account predicts that there will be frequent perseverative
errors because previously activated nodes are likely to be the targets' strongest
competitors for selection.
The patients did produce a higher rate of whole word
perseverations in naming than in the other tasks, consistent with the prediction
that noise at the lexical and semantic levels would be less likely to influence
response production in repetition and reading.
Although nearly 10% of L.M.'s
responses perseverated earlier responses or components of responses in the
repetition task, these were neologisms, suggesting that previously-activated nodes
at the phonological, not lexical, level were controlling production instead of the
target nodes.
Like the jargon aphasic patient reported by Butterworth (1979),
L.M. may have been substituting word-like utterances when a response was called
for, rather than giving no response.
Similarly, L.M. rarely gave no response in
the naming task, whereas P.G. produced a high rate of no responses in this task,
but L.M. produced many abstruse neologistic responses, whereas P.G. produced
few of these.
The "weak connections" account also makes the strong prediction that
perseverative segmental errors will outnumber anticipatory errors, but this
prediction is difficult to test in these data.
Because the tasks employed here only
required production of single items in citation speech, there is limited material to
provide anticipatory interference, whereas there is more opportunity for
perseverative interference from previous responses.
Notwithstanding, P.G. did
make a number of segment anticipation errors, although the ratio of these to
segment perseverations shown in Table 3:5 may be misleading because of the
number of "ambiguous" errors (which may have included contextual errors)
excluded from the tally.
A
comparison of perseverative and anticipatory errors
would be more appropriately made in samples of the patients' spontaneous speech.
While the concept of slow build-up of activation due to weakened
connections throughout the lexical network accounts for many aspects of the
patients' impaired single word production, some additional weakened connections
must be proposed beyond those specified in the model proposed by Dell, Martin
and colleagues.
These are connections which deliver information from
orthographic and auditory-phonological input t o the phonological nodes within
the Dell network.
Thus, although Dell's model does not incorporate processes for
reading aloud, this study suggests that the processes for directly activating
phonology from orthography are also vulnerable to weakened connections
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
100
because, despite the patients' well preserved orthographic input processing skills,
the target phonological nodes for output still do not always receive adequate
activation in this task.
Following the same reasoning, it is proposed that
connections delivering auditory-phonological input to the level of phonological
representation for output in the repetition task are also weakened.
It is in the transmission of information along putatively weakened
connections that a close correlation between input and output form would best
support the patients' output performance.
P.G.'s performance in Experiment 2
suggested an advantage for tasks in which input and output modality were the
same.
It might be supposed that, where there is no need for transcoding from one
modality to another, there is less potential for information loss under conditions
of inadequate transmission of activation.
In Experiment 3, both patients'
accuracy data reflected the supportive effects of a close correlation between
orthographic and phonological form, in this case because such a correlation
predicted the correct assignment of phonology based on the use of the direct,
non-semantic procedure in reading.
Hypothesising weakened connections, in the
"direct" routes from orthographic and auditory-phonological input to the
phonological levels used for output, and between nodes in the lexical network,
accounts for the patients' impaired reading of both nonwords (see Case
Descriptions, earlier) and words with atypical orthography-to-phonology
correspondences.
The co-occurrence of phonological input and output deficits in these
patients clearly raises the controversial question of whether there is a single
impaired level of phonological processing common to both input and output
(Allport, 1983; Allport & Funnell, 1981; Best & Howard, 1994; Howard, 1995; MacKay,
1987; Morton, 1979).
While these data do not resolve the issue, they are consistent
with the single-lexicon model proposed by Martin and Saffran (1992) and Martin
et al. (1994), in which the phonological nodes involved in output may also be the
entry point for phonological information to the network.
Thus in these patients,
phonology may be weakly activated for output in repetition not simply because
connections
delivering
peripheral
auditory-phonological
phonological level are weakened, but because the s a m e
input
to
this
representations
inefficiently activated by auditory-phonological input are required for output.
One final consideration is that the survey of the error processes producing
the responses classified as "phonologically related" in Experiment 1 indicated that
some of the errors made by these non-fluent progressive aphasic patients were
similar to those attributed to deficits of articulatory implementation or phonetic
disintegration in some cases of Broca's aphasia.
Rather than attempting to
delineate two separate levels of processing and provide an account in which
Chapter 3: Single Word Production in Non-fluent Progressive Aphasia
101
articulatory or phonetic deficits are additional to impaired phonological
processing, it may be more parsimonious to consider an alternative view of how
phonological representations for speech output are organised (Kaye, 1989).
Pate
et al. (1987), in discussing the interrelationships between various levels of speech
planning which may be considered "phonological", suggest that formalisms of
phonological representation arising from linguistic as well as psycholinguistic
study may assist our understanding of these phenomena.
As mentioned briefly in Chapter 1, current autosegmental theories of
phonological representation no longer deal with phonemes as units of
phonological organisation (Harris, 1994).
Instead, the stress and tone features of
the phonological form, as well as the features traditionally grouped into
phonemes (including voicing, nasality, and others) are all ascribed to
independently functioning levels or tiers in the representation.
Autosegmental
theories are motivated by the observation that articulatory gestures associated
with features such as voicing and nasality (phonation at the larynx, raising and
lowering the velum, etc.), as with stress- or tone-related features, may overlap in
time, and thus cannot be readily associated to a representation containing a series
of discrete units such as phonemes (Goldsmith, 1979).
Thus, in some views of
phonological representation at least, there is no distinction between phonological
and articulatory representations for speech production; in fact, the units of
p h o n o l o g i c a l contrast are "abstract characterisations of a r t i c u l a t o r y
(italics added)" (Browman & Goldstein, 1992, p. 155).
events
Deficits which have been
differentially described as phonological compared with articulatory
planning/phonetic disintegration may therefore all arise from complex patterns
of disruption within a many-tiered (multiple-level) phonological system.
This study represents the first attempt at a theoretical interpretation of
speech deficits seen in the non-fluent type of progressive aphasia.
Experimental
data have been presented from two non-fluent aphasic patients on various single
word production tasks and their performance has been considered from the point
of view of the interactive spreading activation model developed by Dell and
colleagues.
While the feature of interactive processing, and the potential for
globally weakened connections between nodes in the model, provide helpful
accounts of some aspects of the patients' performance, areas have been noted in
which such a model might be extended to account for other aspects of the patients'
single word production.
Further investigations of non-fluent progressive
aphasia are required to develop the account presented in this paper, and to
consider the patients' associated deficits in syntactic processing, phonological
input processing, and spontaneous speech.
Chapter 4
Familial Progressive Aphasia: Insights into
the Nature and Deterioration of Single Word
Processing
Virtually all the reports of progressive aphasia in the literature have been
cases of sporadic disease, with no significant family history.
Only two reports of
familial primary progressive aphasia are available (Morris, Cole, Banker, &
Wright, 1984; Neary, Snowden, & Mann, 1993b) , and neither of these provide a
systematic account of the patients' language breakdown.
The clinical descriptions
of these familial cases suggest that the aphasia was of the non-fluent type, with
speech production noted to be initially hesitant and dysfluent (Morris et al., 1984),
and containing phonological errors (Neary et al., 1993b).
There are only a few
further reports of language disruption c o n c u r r e n t with memory loss and general
cognitive decline, in familial Alzheimer's Disease (Bird et al., 1989; Breitner &
Folstein, 1984; Kennedy et al., 1995; Lampe et al., 1994),
and in familial dementia
with non-specific pathology (Kim, Collins, Parisi, Wright, & Chu, 1981) .
It seems
clear that aphasia is rare as the only presenting symptom in familial
neurodegenerative
disease.
The present chapter presents a longitudinal investigation of the language
deficits of R.B. and C.B., two brothers with primary progressive aphasia.
of the investigation were twofold.
The aims
The first aim was to document in detail the
clinical, neuropsychological and radiological findings in two new cases of
familial progressive aphasia.
The second aim was to explore the single word
production and comprehension abilities of R.B. and C.B. in the context of the
interactive-activation model of speech production (Dell, 1986; Martin et al., 1994;
see Chapter 1, Figure 1:3)
which was applied to the investigation of sporadic non-
fluent progressive aphasia in Chapter 3.
It was shown in Chapter 3 that two patients with a sporadic non-fluent
progressive aphasia were more successful in reading and repetition tasks than in
naming, and it was hypothesised that this was because the phonological
information in the former tasks facilitated the formulation of a spoken response.
Further, it was proposed that the patients' graded deficits across naming,
102
Chapter 4: Familial Progressive Aphasia
103
repetition and reading, and the nature of their distribution of errors across tasks,
reflected an extreme form of the "weak connections" processing deficit in the Dell
model.
The investigation of familial progressive aphasia in the present study also
began with an experiment to compare single word production across tasks with
different input stimuli.
Because of their phonological difficulties in spontaneous
speech, the initial hypothesis was that R.B. and C.B. would show a "weak
connections" processing deficit similar to that claimed in the study of non-fluent
progressive aphasia in Chapter 3.
CASE DESCRIPTIONS
R . B . , a right-handed, 50 year old man, presented in 1995 with a two year
history of progressive difficulty in speaking and writing.
He had left school at 15
and managed his own security/importing company, with increasing assistance
from his wife.
He was still driving without difficulty and had good day-to-day
(episodic) and autobiographical memory.
In 1989 he had shown mood changes
attributed to depression, which had partially resolved but not quite returned to
normal.
His father had died at age 80, dementing in his last years, but there was
no other previous history of neurological or psychiatric disease in the family.
examination, R.B. showed no physical signs, and blood analysis was normal.
On
Pure-
tone audiometry indicated unimpaired hearing.
R.B.'s conversational speech, while generally fluent, showed somewhat
reduced phrase length and word finding difficulties.
and phonological paraphasias.
He made grammatical errors
General neuropsychological assessment,
summarised in Table 4:1, showed performance within the normal range on tests of
visuo-perceptual and spatial abilities including Object Matching (Humphreys &
Riddoch, 1984) , Line Orientation (Benton, Des Hamsher, Varney, & Spreen, 1983) ,
Rey Figure 4:Copy (Rey, 1941)
and subtests from The Visual Object and Space
Perception Battery (VOSP Warrington & James, 1991) .
Also within the normal
range were non-verbal problem solving (Raven's Progressive Matrices, Raven,
1962) ) and non-verbal memory (Warrington, 1984) .
In contrast, R.B.'s
performance was impaired on a range of language tests, most notably
comprehension of complex syntax (Test for the Reception of Grammar (TROG)
Bishop, 1989) , naming to confrontation, writing to dictation, and "fluency" tests
requiring the generation of words beginning with a particular letter or
exemplars of semantic category members.
His digit span of 4 digits forwards and 3
backwards was significantly reduced relative to normal.
Chapter 4: Familial Progressive Aphasia
Table 4:1.
104
Summary of general neuropsychological testing for R.B. and C.B.;
control data from Hodges and Patterson (1995).
R.B.
Global
Rating
Controls
(n=25)
June
Dec.
June
Mar.
1995
1995
1996
1996
mean
s.d.
15
11
4
11
29.2
1.0
Scale:
MMSE /30
Visuospatial
C.B.
Perceptual
Tests
VOSP: Fragmented Letters /20
19
*
13
18
19.3
0.8
VOSP: Dot Counting /10
9
*
10
*
9.9
0.2
VOSP: Cube Analysis /10
9
*
9
9
-
-
Object Match /40
39
40
*
40
37.3
3.1
Benton Line Orientation /30
25
*
15
19
27.4
4.0
Rey Figure 4:Copy /36
34
32
34
22
34
3.0
43.1
73.6
55.6
18.1
44.6
20.7
RMT Words /50
38
*
38
40
47.3
2.8
RMT Faces /50
40
*
44
45
-
-
Digit Span forward, backward
4,3
3,2
3,2
3,2
6.8
1.0
Pointing Span forwd, backwd
*
*
4,3
3,2
-
-
32
*
26
28
-
-
Fluencies:
Semantic Tests
living things ¶
2
0
0
28
58.3
12.3
Fluencies:
man-made ¶
3
1
0
35
55.4
8.6
Memory
&
Tests
Rey Figure 4:% Recall
Nonverbal
Reasoning
Ravens Prog. Matrices /36
Language
&
Fluencies: letters (FAS) ¶
N a m i n g ¶ /48
1
0
*
11
44.6
10.2
13
5
8
35
43.6
2.3
Reading: regular words /126
98
86
71
125
125.2
2.7
Reading: exception wds /126
68
62
48
101
123.6
3.1
TROG /80
65
65
55
49
78.8
1.8
P&PT: words /52
42
46
42
51
> 48
-
P&PT: pictures /52
49
45
47
52
> 48
-
Recognising Sounds: B&W /20
18
*
*
20
-
-
Recogn'ing
*
27
*
29
-
-
Sounds(Perry)/30
KEY: MMSE = Mini Mental State Examination (Folstein et al., 1975); VOSP = The Visual Object
and Space Perception Battery (Warrington & James, 1991); RMT = Recognition Memory Test
(Warrington, 1984); ¶ = Semantic Battery (Hodges & Patterson, 1995); TROG = Test for the
Reception of Grammar (Bishop, 1989); P&PT = Pyramids and Palm Trees (Howard & Patterson,
1992); B&W = Recognising Ordinary Sounds (Baddeley & Wilson, 1993) ; Perry = unpublished
test of environmental sound recognition.
Chapter 4: Familial Progressive Aphasia
105
A 99m Tc-HM-PAO SPECT scan revealed marked left fronto-parieto-temporal
hypoperfusion and possible right frontal changes.
As illustrated in Figure 4:1, an
MRI scan showed a degree of generalised left hemisphere atrophy involving the
frontal lobe (panels A and B) and, particularly, the polar and inferior regions of
the left temporal lobe (indicated by arrows).
Figure 4:1.
Coronally oriented T1 weighted MRI images of R.B. through the frontal
and temporal lobes from the pole (panels A & B) to the mid and posterior temporal
regions (panels C & D), showing global left hemisphere atrophy with particular
involvement of the polar and infero-lateral regions of the left temporal lobe.
In the 18 months following presentation, R.B showed some decline in
nonverbal reasoning and on all language tests; other neuropsychological test
scores remained stable (Table 4:1).
His word finding difficulties and phonological
errors in spontaneous speech increased.
Below is a sample of his spontaneous
speech from September 1996.
KC Has the airfield always been there, or is it new?
RB
oh God, they've been there, down there [ s I] all [D ] all the time
KC r i g h t
RB
yes, they've been like that [ s ] sort of
Chapter 4: Familial Progressive Aphasia
106
well I've I mean that's been that's God I dunno how long that's been
well, it's been round there [ s ] all the time
KC So, was it there during the war? During the last war?
RB
ah yeah, usually, see that's [ z ] really
KC Is it a training school?
RB
No, it ain't, I'm afraid
There's too much [ t ] [t ] too much [t ] 'cause like they've come [ ´ ] come
along here and then oh terrible really really [ t ] well some of them
some of them just come along like that [´ jÅN] that that's it, well that's it,
terrible
KC Do they come really close in?
RB yeah, some of them, yeah
KC Do they ever have any accidents?
RB
um I have [n ] not at the moment
I haven't see any see anyone at the moment um so I haven't [s ] that at the
moment
C . B . , R.B.'s older brother, also right-handed, presented with a strikingly
similar profile of language impairment in January 1996.
He was 57, had left
school at 15, and was still working part-time as a baker.
He was a keen golfer,
maintaining a consistent golfing handicap.
Unlike his brother, he had shown no
gradual changes in personality, but had been depressed in 1994 following the
death of a close family member.
In 1991 he had suffered from several episodes of
altered awareness suggestive of complex partial seizures.
epileptiform changes over the left temporal lobe.
carbamazapine there were no further attacks.
An EEG had shown
Following treatment with
On examination he showed no
physical signs, and his hearing, assessed using pure tone audiometry, was normal.
His general profile on neuropsychological testing is also shown in Table 4:1
for comparison with that of his brother.
Like R.B., C.B. showed normal
performance on non-verbal problem solving, non-verbal memory, and
nonverbal semantic processing.
His performance on visuo-perceptual tasks was
normal, but on two demanding tests of visuo-spatial ability, judgement of line
orientation (Benton et al., 1983)
and complex figure copying (Rey, 1941) , he
showed a mild degree of impairment.
His scores for single word reading and
writing to dictation, while just below the normal range, were better than those of
his brother, but in general he was impaired on the same range of language tests
as R.B.
Digit span was severely impaired (three forwards and two backwards).
Chapter 4: Familial Progressive Aphasia
107
Imaging with 99m Tc-HM-PAO SPECT revealed focal left temporo-parietal
hypoperfusion.
In comparison with R.B., C.B.'s MRI scan (see Figure 4:2) showed
much less marked left hemisphere atrophy.
Atrophy was confined in C.B.'s case to
the perisylvian region, with only a mild degree of left temporal lobe involvement
(indicated by arrows).
Figure 4:2.
Coronally oriented T1 weighted MRI images of C.B. through the frontal
and temporal lobes from the pole (panels A & B) to the mid and posterior temporal
regions (panels C & D), showing a mild degree of left perisylvian and temporal
lobe
atrophy.
Chapter 4: Familial Progressive Aphasia
108
An example of C.B. describing his language difficulties in March 1996 is
given below.
His word-finding difficulties and phonological errors are apparent
in this sample.
His production and comprehension of complex grammatical
structures was also impaired.
CB
As I say, I I'm not I'm [n ]
anything
I can do that but I can't I can't speak it
I can't ah [√ nd´spQn´ ] my words
[´nç ] stupid and I [Q n ] what what I
all about I can't [ç ] all that's [s ] see what I mean I'm I got all
but I can [d ] I can do these other things
you know, I can play golf
I can go there but I [k ] I have to take some- because I I I lose where I
go with the [kav ]
KC right, so somebody goes with you?
CB
somebody goes [ f ] [fŒs] [sEk´n] [T Œ ] I can go and I can do it
but I [k ] you know I can't you know but and the same and the same in
the...
I can still go in to do the baking
I can still do the baking
but but if he's [g I ] if er if they give me a [l ] a a list a list about the er
I can't do a list
if he says hundred [loU ] or fifty loaves or sixty loaves or sticks er I
can't do it
I can go and just get the get the machine and do and I do it
KC mhm mhm so some things some things are much better than than
other
things?
CB
yeah.
I can't you know it's ridiculous you know but I can't understand
what I'm you know
I can't understand what to say and say about it and what about and that
sort of thing
it's
peculiar
(tsk) so that's it
that's the [p´sItjueIS´n ] with me
Chapter 4: Familial Progressive Aphasia
109
INVESTIGATION OF SINGLE WORD PRODUCTION
Both patients were seen on three occasions.
R.B.'s language abilities were
first assessed in July 1995; follow-up investigations were carried out in June 1996
(Round 2) and September 1996 (Round 3).
C.B. performed the first round of
experiments described in this paper in March 1996; two further rounds of
language testing took place in July 1996 and September 1996.
EXPERIMENT 1: NAMING, REPETITION AND READING
This experiment was a replication of the first experiment performed by the
non-fluent progressive aphasic patients P.G. and L.M. reported by Croot et al. (in
press), and in Chapter 3 of this thesis.
The aim was to compare the brothers'
production of the same target words across naming, repetition and reading tasks.
These tasks differ in the extent to which the stimuli provide phonological
information; thus, in the single
network version of the model described by Martin
et al.(1994), they differ in the level at which activation begins in the lexical
network.
It was hypothesised that if R.B.'s and/or C.B.'s progressive phonological
disruption was due to a weakening of connections within the lexical network,
their reading and repetition performance should be superior to their
performance in naming.
Repetition should be as good as, or better than, reading,
because the phonological information provided by the spoken word arrives
directly at the phonological level, with no intermediate processing of
orthographic input required as in reading.
Additionally, a high ratio of nonword
to real-word errors was predicted because, when connections between the levels
are weakened, feedback loops are less effective in stabilising activation on the
phonological pattern of a word.
Patients with acquired phonological disruption are typically sensitive to
word length as a measure of phonological difficulty in production (Caplan et al.,
1986; Croot et al., in press; Pate, Saffran, & Martin, 1987; Wilshire & McCarthy,
1993) .
Words in this experiment were of one, two or three syllables, to enable
assessment of a length effect in the three word production tasks.
Chapter 4: Familial Progressive Aphasia
Materials
and
110
Procedure
As in Chapter 3, Experiment 1, the patients were asked to produce the same
180 words, of 1, 2 or 3 syllables (N=60 each) in picture naming, immediate
repetition and reading tasks.
Full details of the task stimuli and administration
procedure are given in Chapter 3.
For this experiment, and in all subsequent
experiments described in this chapter in which speech was elicited, the testing
sessions were videotaped.
Broad phonetic transcriptions were made of all spoken
responses in situ and these transcriptions were later checked against the video
recording.
Each brother performed the full version of this task on his first round of
testing, and C.B. also performed the full version on his third round.
R.B was tested
on one block of words in repetition and reading (n=60 per block) on his second
round of testing, and on one block in all three of the tasks on his third round of
testing.
The number of items was reduced after the first round for R.B. because of
restrictions on the time available for testing.
The classification of the patients' spoken responses followed the criteria
used in Chapter 3, Experiment 1, which were closely derived from those of Martin
et al. (1994).
1.
The categories used were as follows:
correct
2.
phonologically related neologism
3.
formal paraphasia (phonologically but not semantically related
word)
4.
phonologically and visually and/or semantically related word
5.
perseveration (including responses with considerable phonological
overlap with a preceding response, as well as perseverations of an
entire
6.
earlier
response)
visually and/or semantically related word with no phonological
overlap with the target, including semantic errors and descriptions of the
target
containing
semantic
information
7.
visually and/or semantically related neologism
8.
unrelated lexical item
9.
abstruse neologism (no evident relationship to the target)
10. no response.
Chapter 4: Familial Progressive Aphasia
111
Results
The percentage of each response type given in each task on each round for
R.B. is shown in Table 4:2, and for C.B is shown in Table 4:3.
With the exception of
R.B.'s performance in the naming task, in which he had a high rate of no
responses, the majority of errors produced by both patients in all tasks were
phonologically related to the targets.
As in Chapter 3, Cochran's Q, a nonparametric statistic for matched data
with a sampling distribution approximated by a chi-squared distribution (Winer,
1970) , was calculated to compare the rate of correct versus incorrect responses,
and of phonologically related versus unrelated responses, across the three tasks.
McNemar's Change Test was used to compare matched data between pairs of tasks,
and a simple Chi-squared statistic was calculated when the words were not
repeated in the conditions under comparison (i.e. length effects on all rounds and
task effects for R.B. on Rounds 2 and 3).
Chapter 4: Familial Progressive Aphasia
112
Table 4:2. Percentage of responses of each type given by R.B. in each task for the
three rounds of testing (naming not tested in June 1996).
% Responses
Round 1
Round 2
Round 3
July 1995
June 1996
September 1996
n task = 180
n task = 60
n task = 60
R.B.
target
Response Type
Name
Rpt
Read
Rpt
Read
Name
Rpt
Read
correct
22.2
90
81.7
55
28.3
3.3
55
15
6.1
8.3
15.6
38
36.7
3.3
45
23.3
0.6
1.1
1.1
5
20
3.3
0
13.3
0
0
0.6
0
5
1.7
0
0
0.6
0.6
0.6
1.7
0
0
0
3.3
6.1
0
0.6
0
1.7
0
0
1.7
0
0
0
0
1.7
0
0
1.7
0
0
0
0
1.7
0
0
0
0
0
0
0
3.3
1.7
0
0
64.4
0
0
0
1.7
86.7
0
41.7
100
100
100
100
100
100
100
100
phonologically
related
neologism
(e.g. propeller → [ pr´pEp´ ] )
formal
paraphasia
(e.g. whale →
phonologically
rail)
and
visually/
semantically related word
(e.g. palette →
painter)
perseveration
visually/semantically
related
word (e.g. sock → f o o t )
visually/semantically
related neologism
(e.g. goat → [hç ] )
unrelated
word
(e.g. barrel →
palm)
abstruse neologism
(e.g. zebra → [gÅvw´] )
no
response
Chapter 4: Familial Progressive Aphasia
113
Table 4:3. Percentage of responses of each type given by C.B. in each task on two
rounds of testing.
% Responses
Round 1
Round 3
March 1996
September 1996
n task =180
n task =180
C.B.
Response Type
target
correct
phonologically
formal
related
neologism
paraphasia
phonologically
and
visually/
Name
Rpt
Read
Name
Rpt
Read
61.7
85
87.2
27.8
52.2
68.9
22.8
10.6
10
29.4
30.6
21.1
5
3.3
1.7
14.4
8.9
7.2
3.9
0.6
1.1
6.7
5.6
0.5
1.1
0.6
0
6.1
1.7
2.2
6.1
0
0
3.3
0.6
0
1.1
0
0
4.4
0
0
0
0
0
1.7
0.6
0
0
0
0
2.8
0
0
2.2
0
0
3.3
0
0
100
100
100
100
100
100
semantically related word
perseveration
visually/semantically
related
word
visually/semantically
related
neologism
unrelated
abstruse
no
word
neologism
response
Chapter 4: Familial Progressive Aphasia
114
Production of Correct Responses
Both patients showed significant effects of task and length on the number
of correct responses produced, on each round of testing, in the directions
predicted by the hypotheses.
That is to say, reading and repetition always yielded
better performance than naming.
For R.B. the pattern of performance across
tasks was generally Name < Read < Repeat, whereas for C.B. the pattern that
evolved over time was Name < Repeat < Read.
of correct responses than longer words.
Shorter words elicited a higher rate
Analyses and significant effects are
summarised in Table 4:4.
Table 4:4.
Summary of significant length and task effects in the number of
responses produced correctly by R.B and C.B. over all rounds of testing on
naming, repetition and reading.
Table continues overleaf.
Task Effects
R.B.
July 1995
Name < Repeat = Read (Overall: Q(2) = 187.0, p < 0.01;
Name vs Repeat χ 2 (1) = 114.4, p < 0.01, Name vs Read χ 2 (1) =
C.B.
June 1996
94.4, p < 0.01)
Read < Repeat (χ 2 (1) = 8.78, p < 0.01; Naming not tested)
Sept 1996
Read < Repeat (χ 2 (1) = 22.0, p < 0.01; Naming at floor)
Mar 1996
Name < Repeat = Read (Overall: Q(2) = 50.0, p < 0.01;
Name vs Repeat χ 2 (1) = 27.1, p < 0.01, Name vs Read χ 2 (1) =
Sept 1996
33.8, p < 0.01)
Name < Repeat < Read (Overall: Q(2) = 79.9, p < 0.01;
Name vs Repeat χ 2 (1) = 24.3, p < 0.01, Repeat vs Read χ 2 (1) =
18.3, p < 0.01, Name vs Read χ 2 (1) = 62.0, p < 0.01)
Chapter 4: Familial Progressive Aphasia
Table 4:4.
Length
R.B.
115
Continued from previous page.
Effects
July 1995
1 > 3 syllables (Overall: χ 2 (2) = 17.6, p < 0.01;
June 1996
1 vs 3 χ 2 (1) = 17.5, p < 0.01)
1 > 3 syllables (Overall: χ 2 (2) = 15.3, p < 0.01;
Sept 1996
1 vs 3 χ 2 (1) = 14.6, p < 0.01)
1 > 3 syllables (Overall: χ 2 (2) = 10.5, p < 0.01;
1 vs 3 χ 2 (1) = 9.8, p < 0.01)
C.B.
1 > 2 = 3 syllables (Overall: χ 2 (2) = 33.4, p < 0.01;
1 vs 2 χ 2 (1) = 6.2, p = 0.013, 1 vs 3 χ 2 (1) = 31.7, p < 0.01)
Mar 1996
1 > 2 > 3 syllables (Overall: χ 2 (2) = 59.4, p < 0.01;
1 vs 2 χ 2 (1) = 18.4, p < 0.01, 2 vs 3 χ 2 (1) = 12.7, p < 0.01,
Sept 1996
1 vs 3 χ 2 (1) = 59.2, p < 0.01)
Production of Phonologically Related Responses
Following Croot et al. (in press) and Martin et al. (1994), the criterion of
one overlapping consonant or stressed vowel was used as the minimum basis for
categorising a response as phonologically related.
The comparisons between the
observed rate of phonologically related response-target pairs and the rate which
might be attained by chance (in a random distribution of responses to targets)
which are described in those papers were not carried out, however.
This was
because subsequent detailed analyses of the phonologically related errors
indicated that these responses were phonologically very close to the targets,
effectively ruling out the possibility that they were related to the targets only by
chance due to liberal categorisation criteria. The total number of
phonologically-related responses on any task was the sum of responses in the
categories of correct, phonologically related neologism, formal paraphasia and
phonologically
and
visually/semantically
related
responses.
The rate of phonologically related responses across tasks showed a similar
pattern to the rate of fully correct responses across tasks (i.e. Name < Read <
Repeat for R.B., and Name < Repeat = Read for C.B.), further supporting the
hypothesis that spoken and written words should be more successful than
pictures in activating phonological representations.
Table 4:5 summarises the
significant task effects and non-significant length effects in the brothers'
production of related responses over the three rounds of testing.
Responses were
more likely to be related in repetition and reading than in naming, although for
R.B. this pattern was somewhat attenuated at testing round 3 due to the shift in his
Chapter 4: Familial Progressive Aphasia
reading performance to no-response errors.
116
There were no significant length
effects in the number of related responses given by either brother, suggesting
that they were both managing to achieve partial activation of phonological target
representations even for longer words, although with decreasing chance of
being fully correct.
Table 4:5.
Summary of significant length and task effects in the number of
phonologically related responses produced by R.B and C.B. over all rounds of
testing on naming, repetition and reading.
Task Effects
R.B.
July 1995
Name < Repeat = Read (Overall: Q(2) = 246.0, p < 0.01;
Name vs Repeat χ 2 (1) = 125.0, p < 0.01, Name vs Read χ 2 (1) =
120.2, p < 0.01)
June 1996
Sept 1996
Repeat = Read (Binomial p= 0.063; Naming not tested)
Name < Read < Repeat (Name vs Read χ 2 (1) = 22.9,
p < 0.01, Read 50% responses related, Repeat 100% related
so at ceiling)
C.B.
Mar 1996
Name < Repeat = Read (Overall: Q(2) = 20.5, p < 0.01;
Name vs Repeat Binomial p < 0.01, Name vs Read
Sept 1996
Binomial p < 0.01)
Name < Repeat = Read (Overall: Q (2) = 54.1, p < 0.01
Name vs Repeat χ 2 (1) = 25.9, p < 0.01, Name vs Read
χ 2 (1) = 29.6 p < 0.01)
Length
R.B.
C.B.
Effects
July 1995
Non-significant
June 1996
Non-significant
Sept 1996
Non-significant
Mar 1996
Sept 1996
Non-significant
Overall χ 2 (2) = 10.0, p < 0.01 but multiple comparisons not
significant at alpha = 0.05/3
Rate of Word versus Nonword Errors
The weak connections account also predicts a majority of nonword errors.
Table 4:6 shows the percentage of non-correct responses which were word and
nonword errors in each task.
Non-responses are also shown because these were
Chapter 4: Familial Progressive Aphasia
so frequent in R.B.'s performance.
117
The "Word" total includes responses from the
formal paraphasia, phonologically and visually/semantically related word,
visually/semantically related word and unrelated word categories, and also
includes any perseverative responses which were words.
The "Nonword" total
sums over the three neologism response categories and also includes those
perseverations which were nonwords.
Table 4:6 shows that both patients
produced a majority of nonword errors, an outcome consistent with the effects of
weak connections within an interactive activation lexical network, although
some qualifications to this claim are noted below.
Table 4:6.
Percentages of word versus nonword errors and no responses given by
R.B. and C.B. on the first and third rounds of testing on naming, repetition and
reading.
% Errors
R.B.
C.B.
Name
Rpt
Read
Name
Rpt
Read
% words
9.4
11.0
21.1
27.6
25.7
21.9
% nonwords
7.8
89.0
87.9
66.7
74.3
78.1
% no response
82.8
0
0
5.7
0
0
100
100
100
100
100
100
% words
4.3
0
21.5
41.2
36.0
26.6
% nonwords
7.0
100
29.4
54.2
64.0
73.4
% no response
88.7
0
49.1
4.6
0
0
100
100
100
100
100
100
ROUND 1
ROUND 3
Discussion
R.B.'s and C.B.'s production of single words was less successful in naming
than in repetition and reading, both in terms of the number of words fully
correct and the number of phonologically related responses.
They also produced
Chapter 4: Familial Progressive Aphasia
more nonword than word errors.
118
In both these ways, their performance is
consistent with the predictions of a weak connections account of disruption to the
lexical network, and resembles the performance of the non-fluent progressive
aphasic patients previously reported by Croot et al. (in press).
The two brothers
did not, however, show an identical pattern of language decline.
While naming
remained the most difficult task for both, over time R.B.'s reading declined
relative to repetition, whereas C.B.'s repetition declined relative to reading.
Two caveats are also necessary about the interpretation of the nonword
error bias in the brothers' word production.
Firstly, R.B. did not show the
nonword error bias in naming, but it is difficult to assess the outcome of any
genuine attempts at production in naming because his non-response rate was so
high.
Similarly the nonword bias was reduced in R.B.'s reading in Round 3, where
he failed to give a response to nearly half the items.
the predicted nonword error bias, this decreased
Secondly, while C.B. did show
over time in naming and
repetition, which is not consistent with the hypothesis of a gradual weakening of
connection
strength.
The predictions about the effect of weak connections within the Dell lexical
network were derived from naming tasks in which normal subjects or patients
make responses to almost all the items (Dell et al., in press).
As already mentioned,
R.B.'s high non-response rate thus makes the interpretation of his naming
performance problematic.
Two further experiments were therefore designed,
with the aim of eliciting a higher response rate in R.B.'s naming.
These
experiments were also performed by C.B. to permit comparison of the brothers'
performance.
EXPERIMENT 2: NAMING ITEMS WITH PHONOLOGICALLY SIMPLE NAMES
If R.B.'s high non-response rate in the previous naming task was due to
difficulty in activating phonological representations sufficiently to support any
response, then simplifying the target phonological representation might
improve his performance.
A new naming task was therefore designed to
minimise phonological output processing by probing for picture names with a
simple CVC (consonant-vowel-consonant) structure.
A frequency manipulation
was introduced to test the hypothesis that higher frequency words would be
produced with fewer errors than low-frequency words (Dell, 1990) .
Chapter 4: Familial Progressive Aphasia
Materials
and
119
Procedure
A set of 50 pictures was compiled which have single-syllable names with a
CVC structure.
Based on the CELEX (Schreuder & Kerkman, 1987) spoken word
frequencies in British English, half the picture names were high frequency (25690 per million; mean 111.4) and half were low frequency (0-10 per million; mean
4.5).
Pictures were drawn from the same sources used for the naming task in
Experiment 1.
The majority of pictures (41/50) were taken from the Snodgrass &
Vanderwart (1980) set.
Using the norms provided with these pictures, the two
frequency groups were broadly matched on image complexity (high
frequency
mean complexity = 2.67, s.d = 0.63; low frequency mean complexity = 2.64, s.d. =
0.89) and name agreement (all > 80% agreement).
Both R.B and C.B. performed this task on their second round of testing
(June/July 1996).
Responses were scored according to the criteria used in
Experiment 1.
Results
The percentage of responses of each type produced by both R.B. and C.B in
Table 4:7 indicates that phonologically simple names had no impact on R.B.'s
ability/willingness to make naming attempts.
His 28% response rate to the CVC
naming set was not significantly higher than his response rate to the more
demanding naming task in Experiment 1 (more demanding because target names
were longer and more structurally difficult).
R.B. attempted to name 36% of
Experiment 1 pictures on Round 1 and 13% of these on Round 3 (Experiment 1
Naming-Round 1 vs CVC Naming: χ 2 (1) = 0.997, p = 0.32; Experiment 1 NamingRound 3 vs CVC Naming: χ 2 (1) = 3.67, p = 0.06).
Although the latter comparison
approaches statistical significance, it should be noted that the more difficult set
was named at a later point in time, and thus even with disease progression the
difference in response rate to the harder set only approached significance.
Chapter 4: Familial Progressive Aphasia
120
Table 4:7. Percentage of responses of each type given by R.B. and C.B. when
naming 50 pictures with phonologically simple (CVC) names.
% Responses
Response Type
target
correct
phonologically
formal
related
neologism
paraphasia
phonologically
and
visually/
R.B.
C.B
14
60
6
12
4
18
2
2
0
0
0
0
0
2
0
0
2
6
72
0
100
100
semantically related word
perseveration
of
entire
visually/semantically
response
related
word
visually/semantically
related
neologism
unrelated
abstruse
no
word
neologism
response
The results did, by contrast, support the hypothesis that higher frequency
words should be easier to produce.
R.B.'s rate of completely correct responses was
too low to yield an advantage for high frequency words (high = 5, low = 2,
binomial p = 0.23), but he produced significantly more related responses to high
than low frequency words (high = 10, low = 2, binomial p = 0.02).
C.B. produced
more correct responses to the pictures with high frequency names (high freq. =
19, low freq. = 11, χ 2 (1) = 5.33, p = 0.02), and was near ceiling in his production of
related responses (high freq. = 24, low freq. = 21, binomial p = 0.38), so showed no
significant effect of frequency among the latter.
Chapter 4: Familial Progressive Aphasia
121
Discussion
Simplifying the phonological structure of the target output in naming did
not assist R.B. to respond, as his non-response rate in this simpler task remained
near 80%.
With only a few exceptions, it seems R.B. was either not willing or not
able to provide a response in confrontation naming.
One explanation may be that
R.B. was able to detect and "edit out" errors by monitoring at a prespeech level
(Levelt, 1989) , and refused to respond when the probability of error was high.
This explanation, however, is not supported by his performance on other tasks,
where he might also have been expected to refrain from responding when likely
to make an error.
For example, while R.B. made no response to 72% of items in the
CVC naming task on Round 2, 40% of his responses in repetition and 42% of
responses in reading on the same round were nonword errors, and he had a
negligible non-response rate in these latter tasks (Tables 4:2 & 4:3).
The alternative explanation is that pictures simply failed to produce
sufficient phonological activation for R.B. to be c a p a b l e of producing any
response on most occasions in naming.
This explanation is consistent with the
weakened connections hypothesis proposed in Experiment 1 to account for R.B.'s
pattern of single word production across tasks and his nonword error bias.
If
activation is indeed transmitted weakly through the levels of the network, then in
a naming task, where activation begins at the semantic level, even
phonologically simple words may be insufficiently activated for production.
The following experiment describes a further attempt to explore the nature
of the brothers' naming deficits, using phonological cueing.
EXPERIMENT 3: NAMING WITH PROGRESSIVE PHONEMIC CUEING
If R.B.'s high non-response rate in naming was due to insufficient
activation of phonological representations from semantic/lexical levels, then
boosting activation directly at the phonological level should increase the
likelihood of a correct naming response, or at least of some attempt to respond.
Similarly for C.B.: to the extent that his deficits were the result of weakened
connections within the lexical network, his naming performance should be
assisted by the increased phonological activation provided by phonological cues.
Chapter 4: Familial Progressive Aphasia
Materials
and
122
Procedure
On the second round of testing (June/July 1996), R.B. and C.B. were asked to
name the same 180 pictures used in Experiment 1.
If after 5 seconds there was no
response, or an incorrect response, the experimenter provided a spoken cue of
the first phoneme of the target name.
If, after a further 5 seconds, the correct
response had not been given, then a cue containing the first two phonemes of the
word was given by the experimenter.
After a further 5 seconds, the first three
phonemes were provided and so on until the whole word had been spoken by the
experimenter.
This is an informal version of the gating paradigm of spoken word
recognition/production (e.g. Graham et al., 1995; Tyler, 1992) .
For example, for
the word ELEPHANT, the sequence of potential cues would be:
[...El...El´...El´f...El´f´...El´f´n...El´f´nt] .
Words ranged from a single phoneme in length (EAR, which was broken into the
two targets of its single diphthong [ I ] and [´ ]) to nine phonemes in length (e.g.
STETHOSCOPE, AMBULANCE).
In order to compare the rate of word versus nonword errors, each patient's
first spoken attempt was scored according to the criteria used for classifying
responses in Experiments 1 and 2.
The no response category was used if no
attempt was made before the experimenter had provided the entire word at the
conclusion of the incremental cueing.
Results
Table 4:8 gives examples of responses where cueing was successful or
unsuccessful for R.B., and where successive approximations to the target
produced a correct response for C.B.
It is intriguing to note that on some
occasions (e.g. IGLOO, in Table 4:8), C.B.'s successive responses appear to be more
influenced by his own previous attempts than by the phonological content of the
cue provided by the experimenter.
Chapter 4: Familial Progressive Aphasia
Table 4:8.
with
Examples of responses given by R.B. and C.B in Experiment 3, naming
progressive
phonological
cueing
R.B.
C.B.
CUE
RESPONSE
CUE
RESPONSE
TARGET = UMBRELLA
TARGET = CANDLE
nil
[√ ]
nil
no
response
no
response
[√m ]
no
response
[√mb]
√mbrEl´ ()
TARGET = IGLOO
kQ kQb´lIm kQr´ kQ
kQp´l kQp´l kQn kQn
kQnd´l ()
TARGET = IGLOO
Es Esk´ Esk´l√ Esk´l√n
Esk´l√n Esk´noU
Esk´noU Esk´n´n Esk´n
Esk´noU E ..o h !
aI aI aIk´l´n aIk´l´n
aIk´l´n..aIk´n
[I]
aIk´l´n aIk´n´n aIk´n
[Ig]
Ig´n Ig´nmaI Ig´nI
[Igl]
aIk´n aIk´nlu aIk´ngu
aIk´ngu aIk´n
[Iglu] aIk´n aIk´nglu
aIk´nglu (X)
nil
nil
[I]
no
response
no
response
[Ig]
Igdu Igw√n
[Igl]
no
[Iglu]
no response
response
(X)
TARGET = TELESCOPE
nil
[t]
123
no
response
no
response
[tE]
no
response
[tEl ]
no
response
[tElI]
tElIfoUn
[tElIs]
tElIfoUt tElI
[tElIsk ]
tElIfoUt
[tElIskoU]
tElIgoUt tElIfoUt
[tElIskoUp] tElIfoUt tElIgoUt (X)
The hypothesis had been that the production of a correct response in
naming would be facilitated by the provision of phonemic cues if the difficulty in
the previous confrontation naming tasks was due to weakened connections
within the lexical network.
R.B.'s pattern of responses supported the weak
connections hypothesis whereas C.B.'s pattern of responses did not.
Table 4:9
shows that with the provision of phonemic cues, R.B. named an additional 37% of
targets correctly after his first attempt, thus giving more correct responses with
cueing on this test than he had produced in total (correctly and incorrectly) on
any previous naming test, even a year earlier.
C.B., by contrast, attempted to
correct his errors, and did reach the target on a further 25% of occasions, without
any cue being provided; but if his own approximations did not lead to a correct
Chapter 4: Familial Progressive Aphasia
124
production of the target, the subsequent provision of phonemic cues rarely
increased his success rate.
Table 4:10 shows that both brothers made more
nonword than word errors.
Table 4:9. Percentages of correct responses given before and after progressive
phonological cueing in naming, Experiment 3.
R.B. % correct
Stage at which response
produced
at each
C.B. % correct
cumulative
at each
stage
cumulative
stage
3.9
3.9
38.9
38.9
0
3.9
25
63.9
36.7
40.6
4.4
68.3
No cue: 1st attempt
No cue: after successive
approximations
During cueing, before
complete word given
Table 4:10. Effects of progressive phonological cueing showing the percentages
of word versus nonword errors and non responses.
% Error Type
Response Type
R.B.
C.B
% words
25.0
36.4
% nonwords
39.1
63.6
% no response
35.9
0
100
100
Discussion
The results of naming with phonemic cueing are consistent with the weak
connections hypothesis for R.B. because he produced (i) a greater number of
responses with cues, (ii) a greater number of c o r r e c t responses with cues, and
(iii) more nonword than word errors.
The results are more difficult to interpret
for C.B., because it seems that for him, a cue which should activate phonology was
of no benefit.
While this is contrary to the predictions from a weak connections
Chapter 4: Familial Progressive Aphasia
125
hypothesis, he d i d make more nonword than word errors in accord with such an
account.
Thus, across the range of tasks described in Experiments 1—3, support for
a weak connections account is stronger for R.B. than for C.B.
The predictions of the weak connections account for the two brothers were
further tested in a series of repetition tasks, described below as Experiments 4—6.
Because repetition tasks are proposed to provide a different entry point for
activation in the lexical network, such tasks generate different predictions from
those made for naming performance.
One final aspect to be noted about R.B.'s naming performance is that his
non-response rate — 37% even with cueing — was much higher than that of any of
the patients in the naming study reported by Dell et al. (in press).
It is possible
that his severe difficulties in naming are not simply due to weakened
connections, but to interacting global and local processing deficits (Martin &
Saffran, submitted) .
semantic disorder.
There is evidence that R.B. had an additional, albeit mild,
On general neuropsychological testing, summarised above (see
Table 4:1), R.B. performed more poorly than C.B. on both the 3 picture and 3 word
versions of the Pyramids and Palm Trees Test (Howard & Patterson, 1992) , a test of
associative semantics.
Thus, while R.B.'s linguistic performance was impaired by
weak connections t h r o u g h o u t the lexical network, a l o c a l impairment at the
semantic level would further compromise the level of activation entering the
network at the semantic level.
Corroborating evidence for R.B.'s semantic deficit comes from the
distribution of pathology evident on his MRI scans.
C.B.'s structural imaging was
simply characterised by generalised left hemisphere atrophy; but R.B.'s scan, in
addition to a mild degree of generalised left perisylvian atrophy, showed more
marked focal left temporal atrophy involving the inferolateral neocortex.
In
patients with semantic dementia, focal left temporal atrophy is associated with
primary semantic loss (Hodges & Patterson, in press) .
EXPERIMENT 4: IMMEDIATE WORD REPETITION
The Martin et al. (1994) account of repetition in the single
network version
of the Dell model proposes that activation from an auditorily presented word
begins at the phonological level of the network and spreads upwards to effect
lexical selection.
In an efficiently functioning network, the target word will gain
the highest activation and be selected for production.
If the connections are
weakened, then the reduced feedback from the lexical to the phonological level
may fail to activate/reinforce all of the correct target phonemes and therefore
result in a nonword error.
By contrast, if the activation building up at the nodes
Chapter 4: Familial Progressive Aphasia
126
is subject to rapid decay, selection of the lexical node for production will occur
under disproportionate influence from the semantic level and a semantic error
might arise.
Thus, the "signature" of weak connections in repetition (as well as in
naming) is a predominance of nonword errors, while the signature of rapid decay
in repetition is the occurrence of semantic errors.
Materials
and
Procedure
R.B. and C.B. were tested on the ADA Word Repetition Test (Franklin et al..,
1992), which manipulates word frequency, length and imageability (n=80).
words are 6 or 7 phonemes in length; short words have 3 or 4 phonemes.
Long
C.B.
performed the task on all three rounds of testing; R.B. performed it on his second
and third rounds of testing.
On the latter two rounds of testing, both brothers'
testing was distributed over two sessions to accommodate a delayed recall
condition which is described below as Experiment 5.
Results
Table 4:11 summarises the results from all testing rounds.
The decline in
number of correct responses over time reflects the progressive nature of the
language impairment.
Both R.B. and C.B. had more difficulty with longer words,
as in Experiment 1, and C.B. also made significantly more errors on the less
imageable words, but at no stage was there any effect of word frequency on the
patients' performance.
The brothers made more nonword errors than real word
errors on all rounds of this task (Word versus Nonword Errors: R.B. 6 vs 21 (Round
2), 7 vs 27 (Round 3); C.B. 5 vs 11 (Round 1), 9 vs 25 (Round 2), 14 vs 28 (Round 3)).
Chapter 4: Familial Progressive Aphasia
127
Table 4:11. Summary of immediate repetition performance of R.B. and C.B. on the
ADA Word Repetition Test.
R.B.
Testing Round
C.B
%
Significant
%
Significant
Correct
Effects
Correct
Effects
90
binomial
70
p = 0.04
High Imageability Words
87.5
not
Low Imageability Words
72.5
significant
TOTAL
80
ROUND 1
(R.B. July 95, C.B. March 96)
not tested
Short Words
Long Words
ROUND 2
(R.B. June 96, C.B. July 96)
Short Words
90
χ 2 (1) = 20.18,
67.5
χ 2 (1) = 4.11,
Long Words
42.5
p < 0.01
45
p = 0.04
High Imageability Words
67.5
not
70
χ 2 (1) = 6.15,
Low Imageability Words
65
significant
42.5
p = 0.01
TOTAL
66.3
56.3
ROUND 3
(R.B. & C.B. September 96)
Short Words
72.5
χ 2 (1) = 7.37,
67.5
χ 2 (1) = 12.83,
Long Words
42.5
p < 0.01
27.5
p < 0.01
High Imageability Words
57.5
not
60
χ 2 (1) = 5.01,
Low Imageability Words
57.5
significant
35
p = 0.03
TOTAL
57.5
47.5
Chapter 4: Familial Progressive Aphasia
128
Discussion
In contrast to the pronounced difficulty of R.B. and C.B. in repeating long
words, control subjects — whose overall accuracy is of course higher (maximum =
9/80 errors) — make almost all of their errors on short words (Franklin et al.,
1992).
Errors to shorter words may best be explained by the phonological
confusability between short words in the lexically dense neighbourhoods of short
words in the English language.
A higher error rate on long words is usually
attributed to the greater processing load required to produce larger phonological
chunks.
A number of patients with language impairment have been reported to
show an advantage for high imageability compared with low imageability words
(Franklin, Howard, & Patterson, 1995; Howard & Franklin, 1988; Martin & Saffran,
submitted) .
High imageability words are hypothesised to be more robustly
represented in the semantic system (Plaut & Shallice, 1993; Strain, Patterson, &
Seidenberg, 1995) , and even with the deterioration of semantic knowledge seen
in semantic dementia, the advantage for high imageability words usually
remains, or even increases (Knott, Patterson, & Hodges, submitted) .
This is
because the more weakly represented low imageability items are hypothesised to
be more vulnerable to any sort of damage in the system (although there are
occasional reports of a reverse advantage: Breedin et al., 1994; Cipolotti &
Warrington, 1996; Warrington, 1975) .
R.B., however, failed to show any semantic
effects, even by the third round of testing when nearly half of his responses
were incorrect.
This lack of advantage for highly imageable words suggests that,
in R.B.'s repetition of single words, very little information from the semantic
level was reaching the phonological level to augment segment activation at that
level, exactly as would be predicted under conditions of weak connections within
a lexical network.
The predominance of nonword versus word errors in R.B.'s
performance on all three rounds of this task as in previous tasks further supports
the weak connections hypothesis.
C.B.'s significant imageability effect is in direct contrast to the weak
connections prediction because it implies that connectivity within the lexical
network must be sufficiently strong to enable transmission of activation from the
phonological level to the semantic level and back again to facilitate phonological
selection for high imageability words.
Further, weak transmission of activation
from the phonological level to the semantic level and back would allow no
possibility of a semantic error, but C.B. did make a semantic error on this task.
In
Round 3 he repeated BUILDING as HOME, and in other repetition tasks performed
Chapter 4: Familial Progressive Aphasia
129
on this round he repeated SKI as SKATE, BALCONY as ARCH, LADLE as SPOON, and
TOASTER as BAKE, BAKING.
The imageability effect in C.B.'s immediate repetition, and his occasional
semantic errors, are less likely to be the outcome of weakened connection
strength than of rapid decay according to the parameters of the Dell lexical
network.
Nevertheless, the predominance of nonword errors in C.B.'s
performance on this and other tasks is
consistent with a weakening of
connection strength within the network.
To test the hypothesis that the pattern
of C.B.'s repetition performance reflects rapid decay in the lexical network, his
performance on delayed repetition tasks was investigated.
R.B. also performed
these tasks, and was expected to show evidence of weak connections.
EXPERIMENT 5: DELAYED WORD REPETITION
Method
and
Hypotheses
The brothers' immediate repetition was compared with their repetition
following a filled delay on Round 2 and an unfilled delay on Round 3, using the
words from the ADA Word Repetition Test described above.
Each word was elicited
once in each of two sessions on each round, with half the words repeated in the
immediate condition and half in the delay condition on each session.
In the filled
delay condition the brothers counted aloud from 1 to 5 before repeating the target
word, in the unfilled delay condition they repeated the target word at a nonverbal prompt from the experimenter after a 5-second interval.
The idea behind this manipulation was the hypothesis that, given a deficit
corresponding to rapid decay (rather than weakened connections), there would
be no disadvantage in the filled versus the unfilled delay condition, for the
following reason.
The production of speech in the filled delay condition is
presumed to interfere with the maintenance of the phonological activation
associated with the target word.
Under conditions of rapid decay in the network,
however, activation related to the target is not maintained at the phonological
level, but refreshed by activation feeding forward and then back from higher
levels.
By contrast, in the case where connections within the network are
weakened, a filled delay might seriously compromise repetition: while
phonological target activation is difficult to maintain during a filled delay, there
is insufficient activation to feed forward and then back to refresh the
phonological activation of the target from higher levels.
Chapter 4: Familial Progressive Aphasia
Results
and
130
Discussion
R.B.'s and C.B.'s performance in immediate repetition versus the two
delayed repetition conditions is summarised in Table 4:12.
Delay per se did not
impair performance, in the sense that there was no difference for either brother
between immediate repetition and repetition after an unfilled delay.
Repetition
in the filled delay condition for R.B., however, was significantly poorer than
immediate repetition, while for C.B. there was no disadvantage for repetition after
a filled delay.
Thus results for R.B are consistent with the predictions of a weak
connections hypothesis.
The fact that C.B.'s repetition was not impaired by
interference from counting suggests that, even in immediate repetition, C.B. was
not maintaining target activation primarily at the phonological level, but was
instead refreshing it from activation at higher levels.
Such feedback from
higher levels would be required to boost target activation at the phonological
level in the context of rapid decay.
Table 4:12. Summary of the brothers' immediate versus delayed repetition on
Round 2 and Round 3 under two different delay conditions.
Delay Condition &
Testing Round
ROUND 2
Immediate
R.B.
C.B
%
Significant
%
Significant
Correct
Effects
Correct
Effects
length
58
66
(see Table
4:11)
Filled Delay
Effect of Delay
ROUND 3
Immediate
31
nil
Significant
χ2 (1) = 20.25, p < 0.01
58
length
Effect of Delay
65
nil
Non-significant
χ2 (1) = 1.14, p = 0.29
imag
(see Table
4:11)
60
imageability
χ2 (1) = 5.01,
p = 0.03
Non-significant
χ2 (1) = 0.27, p = 0.60
48
(see Table
4:11)
Unfilled Delay
length,
length,
imag
(see Table
4:11)
54
length
χ2 (1) = 11.31,
p < 0.01
imageability
χ2 (1) = 4.07,
p = 0.04
Non-significant
χ2 (1) = 1.07, p = 0.30
Chapter 4: Familial Progressive Aphasia
131
In the delayed repetition tasks, R.B. continued to show no effects of
imageability, even though repetition performance in the filled delay condition
could potentially be facilitated by feedback support from lexical and semantic
levels.
C.B.'s performance was characterised by imageability effects in both
delayed repetition conditions, as well as in immediate repetition on both Round 2
and 3, suggesting that feedback from the semantic level contributed to
phonological activation in his performance on all repetition tasks.
EXPERIMENT 6: IMMEDIATE REPETITION OF TWO-WORD STRINGS
The previous experiments suggest that R.B.'s deficit in single word
production is consistent with weak connections in the lexical network, while
C.B.'s breakdown appears to have characteristics of both weak connections and
rapid decay.
The next experiment sought to test these hypotheses using
predictions derived from the work of Martin & Saffran (submitted).
These authors
investigated the immediate memory performance of a group of twelve subjects
whose fluent aphasia was due to CVA but whose language impairments varied in
the extent to which lexical-semantic versus phonological processing was
compromised.
The subjects' lexico-semantic abilities were assessed using word-
picture matching tests and synonomy judgement tests; their phonological abilities
were measured using phoneme discrimination and rhyme judgement tasks.
Martin and Saffran demonstrated that relatively efficient semantic processing
was associated with primacy effects in immediate memory, that is, with better
recall of the first item in a string, while relatively efficient phonological
processing was associated with recency effects (better recall of the final item in a
string).
Three assumptions underlie the predictions for the current experiment.
The first assumption is that of an interaction between serial position effects and
the level of most severe lexical impairment, following Martin and Saffran
(submitted).
The second is that the semantic and phonological processing
discussed by Martin and Saffran as the basis for immediate memory must
correspond somewhat directly to the maintenance of activation at semantic and
phonological nodes in the interactive activation model of Dell and colleagues.
It
follows from this that immediate memory function must be subject to the same
global processing parameters of connection strength and rapid decay which
govern the efficiency of language processing in the Dell model.
Finally, it was
assumed that phonological input activates the phonological level of the network
first, as in the single
network version of the model reported by Martin and
Saffran (1992) and Martin et al., (1994) and thus far invoked in this chapter.
Chapter 4: Familial Progressive Aphasia
132
Recall that under conditions of weakened connections in the model, there
is reduced feedback from the semantic level to phonological activation in
repetition.
In this case, repetition of the early part of a word string — that part
most supported by semantic processing — should be most impaired.
Under
conditions of rapid decay, when activation at the phonological level decays first
and is therefore more compromised than the semantic level, recall of final items
should be poor.
Thus, if R.B.'s language deficit were due to weakened connections,
his repetition should not be characterised by a primacy effect.
In contrast, if C.B.
was affected by rapid decay, he should show no recency effect.
Method
Ideally, an assessment of predictions concerning serial position effects
would rely on a minimum list length of three items, and indeed, if possible, more.
While this principle can be realised in studies of patients with reasonably
preserved immediate verbal memory (e.g., Knott et al., submitted), it is impossible
— or at least ill-advised — with patients like R.B. and C.B., as it would risk too high a
proportion of trials with no analysable output.
Two-word sequences were
therefore used, and the analyses to assess primacy and recency effects relied on
patterns of data for first/second word of each string, and for first/last phoneme
in the 2-word utterance.
Accordingly, the brothers were asked to repeat 80 two-
word strings derived from the target picture names in Experiment 2 (e.g. HAT,
SUN).
Each word in the string was thus of Consonant-Vowel-Consonant structure
to control for the difficulty of the beginning versus the end of the string.
In half
the strings both, words were drawn from the low-frequency set of CVC words; in
the other half, both words were from the high frequency set.
repeated phonemes within any string.
There were no
The word pairs were spoken by the
experimenter at the rate of approximately one word per second.
Incorrectly repeated pairs were scored (i) strictly, for whether the
phonemes were preserved in the c o r r e c t position in the response and, (ii) more
leniently, for whether each target phoneme was preserved in a n y position in the
string.
To evaluate the hypotheses regarding recall of the beginning versus the
end of the string, the correctness of the first word versus the second word was
compared, and the correctness of the first and last phonemes relative to the rest
of the phonemes in the string was examined.
Chapter 4: Familial Progressive Aphasia
133
Results
R.B. produced 20/80 pairs completely correctly and gave no response to 11
of the strings; C.B. only repeated 9/80 pairs correctly but attempted a response to
all 80 items.
The brothers differed in their relative performance on the first
versus the second word of the string.
Figure 4:3 shows that, on both the strict and
lenient scoring criteria, R.B.'s performance on the first and the second word was
similar (strict: χ 2 (1) = 0.55, p = 0.46; lenient: χ 2 (1) = 0). In contrast, C.B. was more
successful in repeating the first word in the pair than the second word (s t r i c t :
χ 2 (1) = 15.12, p < 0.01; lenient: χ 2 (1) = 10.42, p < 0.01).
a)
b)
50
% Errors (lenient scoring)
% Errors (strict scoring)
50
40
30
% Correct
CB
40
30
% Correct
20
10
1st
2nd
Word
Figure 4:3.
RB
20
10
1st
2nd
Word
Percentage of correct productions made by R.B. and C.B. on the 1st
versus the 2nd word in immediate repetition of two-word strings (Experiment 6),
using a) strict scoring criteria and b) lenient scoring criteria.
Chapter 4: Familial Progressive Aphasia
60
60
number correct (lenient scoring)
number correc (strict scoring)
a)
50
40
30
20
10
C
V
C
C
V
CB
50
40
30
20
10
C
60
C
V
C
C
V
Segment Position
C
C
V
C C V
Segment Position
C
60
number correct (lenient scoring)
number correct (strict scoring)
RB
Segment Position
b)
134
50
40
30
20
50
40
30
20
10
10
C
Figure 4:4.
V
C C
V
Segment Position
C
Number of correct segments produced by a) R.B. and b) C.B. on each
position in the two-word repetition task, using the strict and lenient scoring
criteria.
Next, a series of analyses was carried out to explore whether there were
primacy or recency effects at a phoneme level in the repetition of the two-word
strings. Under both the strict and the lenient scoring criteria there was an
overall effect of phoneme position on accuracy of repetition (R.B.: strict Q (5) =
16.95, p < 0.01; lenient Q (5) = 11.13, p = 0.049; C.B. strict Q (5) = 57.98, p < 0.01; lenient
Q (5) = 54.16, p = p < 0.01), illustrated in Figure 4:4. A series of McNemar's tests
comparing the correctness of phonemes at sequential positions along the string
revealed that on both measures, R.B.'s repetition of the final phoneme was
significantly poorer than of the penultimate phoneme (Position 5 vs Position 6:
strict binomial p < 0.01; lenient binomial p < 0.02).
Also on both measures, C.B.'s
repetition of the first phoneme in the string was significantly better than his
repetition of the second phoneme (Position 1 vs Position 2: strict binomial p < 0.01;
Chapter 4: Familial Progressive Aphasia
135
lenient binomial p < 0.01), and his repetition of the final two phonemes was
significantly poorer than of the fourth phoneme (Position 4 vs Position 5: strict
χ 2 (1) = 12.90, p < 0.01; lenient χ 2 (1) = 14.70, p < 0.01; Position 5 vs Position 6: strict
binomial p = 0.79; lenient binomial p = 1.0).
Thus, neither R.B. nor C.B. showed a
recency effect — in fact their repetition of the final phoneme(s) was significantly
p o o r e r than of preceding phonemes — and C.B. did show a significant primacy
effect.
Discussion
R.B. was impaired to a similar degree in the repetition of the first and
second words in the string.
This result is not entirely consistent with the
prediction that weakened connections throughout the network would result in a
poorer performance in repeating the first word.
In the Martin and Saffran
(submitted) framework, R.B.'s equivalently impaired performance on the first
versus second word would be associated with both phonological a n d semantic
deficits.
On the phoneme-by-phoneme serial McNemar's tests, however, R.B. did
fail to show a primacy effect, thus at this level there was no evidence of support
from semantic processing, and this effect supported the hypothesis about the
effects of weak connections in this task.
R.B.'s lack of recency effect may reflect
noisy patterns of phonological activation under weakened connections.
C.B. was more impaired in repeating the second (final) word, a pattern
Martin and Saffran found to be associated with impaired phonological processing,
and a pattern which would be predicted under conditions of rapid decay in a
network with the entry-point at the phonological level.
C.B. also showed a
primacy effect in the phoneme-position analyses, an effect attributed to
relatively efficient semantic processing in the Martin and Saffran framework.
Like R.B., C.B. also showed no recency effect in the phoneme-position analyses,
but C.B.'s repetition of the ends of strings was more severely impaired than that of
his brother.
C.B. made significantly more errors on phonemes in the final two
positions in the string, whereas R.B.'s performance only dropped significantly on
the final phoneme.
Further support for this account of the patients' deficits is found in
comparing R.B.'s and C.B.'s pattern of performance on this task with that of
patients reported by Dell et al. (in press) on a task of two-word repetition (Martin
and Saffran, submitted).
R.B.'s relative success on the first versus second word
(strict: 25% vs 18% correct) resembles that of L.H., one of the patients
characterised by Dell (in press) as having a pure "lesion" in connection strength.
On the two-word repetition test of Martin and Saffran (two- and three-syllable
Chapter 4: Familial Progressive Aphasia
136
words), L.H. repeated 81% of the first words correctly versus 65% of the second
words correctly.
In contrast, two other patients, G.L. and H.B.1 ,who were
characterised by Dell et al. (in press) as having "mostly decay" lesions, repeated
the first word much more successfully than the second (G.L.: 53% vs 11% correct;
H.B.:
64% vs 37% correct).
As this was the trend shown by C.B. (strict: 44% vs
14%), patients G.L. and H.B. lend further support to the claim that C.B.'s language
deficit involves rapid decay.
DISCUSSION OF WORD PRODUCTION
Experiments 1 to 6 investigated R.B.'s and C.B.'s word production in a range
of tasks including picture naming, naming with progressive phonemic cueing,
reading, immediate and delayed repetition of single words and repetition of twoword strings.
Overall, R.B.'s naming was less successful than C.B.'s, with a very
high non-response rate unless phonemic cues were provided.
Except in the filled
delay condition, however, R.B.'s performance in repetition was slightly, but
consistently, better than C.B.'s.
The two brothers, therefore, did not differ so
much in the outright severity of their language production impairments, as in
the particular language functions which were more or less severely affected.
This study sought to account for the brothers' impairments in terms of the
Dell interactive activation model of word production, in order to compare their
progressive phonological impairments with those of the two sporadic non-fluent
progressive aphasic patients reported in Chapter 3 of this thesis, and in Croot et
al. (in press).
Having tested predictions derived from the version of the Dell
model invoked by Martin and Saffran (1992) and Martin et al. (1994),
it was
concluded that R.B.'s performance was characteristic of weak connections within
the lexical network, while C.B. showed features of both weak connections and
rapidly decaying activation.
It was further suggested that R.B. must have had a
deficit localised at the level of semantic representations as well as a global
weakening of connection strength.
This additional impairment accounts for
R.B.'s drastically reduced output compared with C.B. in semantically-driven
speech tasks such as naming and category fluency (see Table 4:1), and his
impaired performance on the Pyramids and Palm Trees test of semantic
processing (Howard & Patterson, 1992).
1
G.L. and H.B. were tested a few years earlier on the tasks reported by Dell et al. (in press)
than on those reported by Martin and Saffran (submitted), but had stable Boston Diagnostic
Aphasia Examination Comprehension scores across the time interval.
Chapter 4: Familial Progressive Aphasia
137
These accounts are more complex than the one given for two patients with
non-fluent progressive aphasia, whose phonological errors and word-finding
difficulties in naming were attributed to a pure connection strength deficit (see
Chapter 3, and Croot et al., in press).
As in stroke-related aphasia (Blumstein,
1994) , it appears that a range of different types of phonological disruption may
be associated with progressive aphasia.
The present accounts of the brothers' language deficits are based on a
model of language processing in which the phonological nodes used for output
are the same nodes used for the entry of phonological information to the network.
Such a position does not entail the view that abnormalities of performance must
always be identical — either in severity or even pattern — across tasks which
stress receptive vs expressive spoken word processing.
This is because, even if
central phonological representations are shared between input and output, there
will be other elements of processing specific either to analysing a spoken word as
input, or to creating a spoken word in production.
Furthermore, unless a
receptive task is made very precise and difficult, for example, by subtle changes
of a single phonetic feature (Allport, 1983)
and/or by use of words from dense
phonological neighbourhoods, there is always the danger that receptive tasks
may be 'easier' than expressive tasks.
This is because a certain degree of noise or
approximation in phonological processing, which might perturb speech
production, is probably tolerable or indeed even efficient in processing of speech
input (Gaskell & Marslen-Wilson, 1996) .
Despite these caveats, the kind of theoretical position endorsed here does
mean that conclusions drawn on the basis of performance in expressive
phonological tasks (like naming and repetition) should generate some degree of
predictability about patterns of performance on receptive tasks.
converging evidence for these accounts of the brothers' speech
Thus, a source of
production
deficits should be their performance on tasks requiring knowledge of
phonological word forms and word meanings, but not requiring speech
production.
According to the contrasting view that there are separate sets of
phonological representations for word recognition and production (Howard &
Franklin, 1989), there would be no necessary link between a patient's abilities on
input and output tasks.
Chapter 4: Familial Progressive Aphasia
138
INVESTIGATION OF RECEPTIVE WORD PROCESSING
EXPERIMENT 7: PICTURE-NAME JUDGEMENT
If the entry-point of spoken stimuli to the Dell lexical network is the level
of phonological nodes, then abnormalities in the parameters of connection
strength and decay rate will have differing effects on the performance of
receptive tasks which are dependent on processing at different levels of the
network.
In this experiment, R.B.'s and C.B.'s abilities to make judgements about
the phonological versus the semantic properties of spoken stimuli were
compared.
The task was to decide whether a spoken stimulus was the correct name
for a simultaneously presented picture.
In different conditions, the distractor
stimuli were semantically related, phonologically related or unrelated to the
correct
names.
It was hypothesised that when connections are globally weakened in the
network, it should be more difficult to make semantically-based judgements than
phonologically-based judgements because activation from the spoken stimulus
must be transmitted further into the network to reach the level of semantic
processing, and this transmission is impeded by weak connections.
Under
conditions of rapid decay, however, it should be more difficult to make fine
phonological discriminations because the representation at the phonological
level begins to decay rapidly after input.
Given the interpretation thus far of a
connection-strength deficit for both RB and CB, plus selective abnormalities of
semantic representations for RB and of decay rate for CB, it was predicted (i) that
both patients would be somewhat impaired at semantic judgements, (ii) that this
semantic performance deficit would be substantially more severe for RB than CB
and (iii) that CB, but not RB, should have significantly sub-normal performance
when the task required fine phonological discriminations.
Procedure
The procedure for this experiment was derived from that of the auditory
lexical decision test performed by 3 conduction aphasic patients and 12 control
subjects and reported by Allport (1983).
On each trial of Allport's test, subjects
were asked to decide whether a spoken stimulus was the correctly pronounced
name of either of two pictures presented on that trial.
(Allport's subjects were
subsequently asked to select the picture which best matched the spoken stimulus,
but this subtask was not replicated in the experiment described in this chapter;
R.B. and C.B. were shown only one picture with the spoken stimulus.)
Allport's
Chapter 4: Familial Progressive Aphasia
139
distractors were phonologically related nonword mispronunciations of the
picture's name, departing from the correct name on the voicing, place or manner
of articulation of one of the consonant phonemes of the correct name.
One, two or
all three of these features were simultaneously altered as a measure of the
"phonological distance" of the distractor from the target.
In the experiment
which R.B. and C.B. participated in, there were five different distractor
conditions.
In one condition, nonword distractors directly modelled on those
described by Allport (1983) were used.
In other conditions, the distractors were
more difficult nonwords, or real words which were phonologically related,
semantically related or unrelated to the target (correct) picture name.
Each condition of the experiment was performed over two sessions, with
each picture shown once in each session: on one occasion with the correct spoken
name, and on the other with an incorrect spoken name.
In every session, half
the pictures were presented with their correct names and half with distractors,
and the brothers were asked to point to cards bearing the words YES and NO for
stimuli which were correct names and incorrect names respectively.
The names
and word distractors in the semantically related and unrelated conditions were
spoken by the experimenter.
The spoken stimuli in the conditions with
phonological distractors were recorded on audiotape and presented via
headphones to standardise pronunciation of the nonword distractor items.
Target
words and pictures were obtained from the naming materials used in Experiment
1, except for those in the condition with the more difficult nonword distractors.
C.B. performed all conditions of this experiment on Round 2 of his testing;
R.B. performed all but the phonologically related matched words (n=116) and
nonwords (n=116), on his Round 2, and the latter on Round 3.
Chapter 4: Familial Progressive Aphasia
140
Materials
Examples of the stimuli used in this experiment are given in Table 4:13.
A
description of these stimuli follows.
Table 4:13.
Examples of targets and distractors in the Picture Name Judgement
conditions in Experiment 7.
n
Example
distractors
Target
Distractor
Unrelated Word
90
pineapple
grasshopper
Semantically Related Word
90
pineapple
coconut
Phonologically Related Word
58
palette
palace
Phonologically Related Nonword
58
palette
[pQl´f]
place
20
boot
voice
20
beaver
20
radio
[bup]
[piv´]
[reIzioU]
20
handlebars
place & manner
20
whale
manner & voice
20
fountain
3 features changed
60
fish
[hQnd´lbaf]
[zeIl]
[faUst´n]
[nIS]
Difficult Phonologically Related
52
calculator
[tQlkj´leIt´]
Condition
(matched to phon. related words)
Phonologically Related Nonword
(full set)
1 feature changed
manner
2 features changed
place & voice
Nonword
The phonologically related distractors modelled on those of Allport (1983)
were derived from the words used in Experiment 1 (n=180).
Sixty of these words
had one consonant phoneme changed by one feature (20 place, 20 voice, 20
manner), 60 had a phoneme changed by two features (20 place and voice, 20 place
and manner, 20 voice and manner) and the rest contained a phoneme altered by
Chapter 4: Familial Progressive Aphasia
all three features from the corresponding phoneme in the target.
141
This
manipulation of the phonological distance of distractors from targets was
orthogonal to word length.
Also orthogonal to these manipulations, the altered
phoneme occurred equally in word-initial, -medial and -final positions.
This
condition of the experiment was also performed by four elderly hearing-matched
controls from the Applied Psychology Unit subject panel.
To allow a comparison between the brothers' performance on word and
nonword phonological distractors, a smaller set of phonologically related real
word distractors was created.
The distractor words were pictureable nouns like
the targets (but not possible names for the pictures), matched to the target on
spoken frequency in British English (Schreuder & Kerkman, 1987).
The N in this
condition was smaller than that for the nonword condition because word
distractors obviously impose serious selection constraints not encountered in
creating nonword distractors.
It was possible to find word distractors for 58 of the
1- and 2-syllable targets which met the following criteria: (i) each word distractor
was identical to both its target and the matched nonword in length and
consonant-vowel structure; and (ii) each word distractor was matched to the
corresponding nonword distractor in terms of the specific phoneme of the target
word altered, the degree of discrepancy (in number of features) from the target
word and even the type(s) of articulatory feature(s) changed.
A further set of 52 phonologically difficult targets and distractors was
created, with target items ranging from 3 to 5 syllables in length, of low spokenword frequency (mean = 2.5 per million).
Targets were different to those used in
Experiment 1 and the other conditions of the present experiment, although the
picture stimuli were obtained from the same naming tests as the pictures used in
Experiment 1.
As in the other phonologically related conditions, distractors
varied from the targets on only one phoneme, but in this set the only feature on
which the distractors differed was place of articulation.
In half of the distractors
the altered phonemes were word-initial and in half they were word-final; all
distractors were phonotactically legal nonwords.
The set of semantically related distractor names was composed of semantic
co-ordinates of 90 of the target words used in Experiment 1, 30 of 1 syllable, 30 of 2
syllables and 30 of 3 syllables.
Distractors were as closely matched as possible to
the targets on category representativeness (Battig & Montague, 1969) .
The
distractors were also matched on length and spoken frequency in British English
(Schreuder & Kerkman, 1987).
The semantic co-ordinates were also used as
distractors in the unrelated condition, pseudo-randomly assigned to the targets
such that no members of a target-distractor pair were semantically related but
Chapter 4: Familial Progressive Aphasia
pair members were of similar length.
142
To restrict phonological similarity, target-
distractor pair members did not share an initial letter nor a stressed vowel.
Results
The rates of correct responses given by each brother in each condition of
this experiment are shown in Table 4:14.
These reports support the predictions in
a convincing, indeed dramatic form: R.B. rejected the phonologically related
distractors much more successfully than the semantically related distractors; C.B.
showed the reverse pattern.
Table 4:14.
Results from the Picture Name Judgement Tasks, all conditions, for R.B.
and C.B.
Distractor Condition
R.B.
C.B.
% Correct
% Correct
Targets
Distractors
(Hits)
(Correct
Overall
Targets
Distractors
(Hits)
(Correct
Rejections)
Overall
Rejections)
Unrelated Word
90.0
98.9
94.4
100
100
100
Semantically
78.9
56.7
67.8
100
93.3
96.7
Related
98.3
89.7
94.0
100
72.4
86.2
Related
100
100
100
98.3
93.1
95.7
100
94.4
97.2
97.8
81.7
89.7
96.2
75.0
85.6
92.3
7.7
50.0
Related
Word
Phonologically
Word
Phonologically
Nonword (matched to
phon. related words)
Phonologically
Related
Nonword (full set)
Difficult
Phonologically
Related Nonword
Chapter 4: Familial Progressive Aphasia
Table 4:15.
143
Errors on the picture name judgement task with the full set of
phonologically-related nonword distractors, in the different phonological
manipulation conditions (length, number and type of feature changed in
distractors).
Number of Errors
Manipulation
R.B.
C.B.
1 syllable
1
6
2 syllables
3
9
3 syllables
6
18
one
9
20
two
0
9
1
4
Place
5
9
Voice
3
7
1
4
Length
(all distractors, n = 60 per length)
Number of Features Changed
(all distractors, n = 60 per change)
three
Type of Feature Changed
(1-syllable distractors, n= 20 per type)
Manner
In the phonologically related conditions, both brothers were sensitive to
the difficulty of the phonological discrimination required, making more errors
on longer items than shorter items.
The number of errors made in the condition
with the full set of phonologically related nonword distractors, on words of each
length are shown in Table 4:15.
This table also shows that both R.B. and C.B. made
more errors on distractors with fewer articulatory features changed from the
target, and that distractors with place of articulation changes and voicing
changes were harder for the brothers to detect than changes in manner of
articulation.
In the difficult phonologically related set, in which the distractors
combined the most difficult of all three manipulations (long words, in which
distractors vary only on place of articulation), R.B.'s performance dropped away
from the near-ceiling level he showed on the other phonologically related
conditions, and C.B. accepted almost all distractors as correct.
R.B.'s performance
on the full set fell just below the control range, as none of the four controls
scored less than 98.3% correct on this set.
R.B. and C.B. were also significantly
Chapter 4: Familial Progressive Aphasia
144
better at detecting phonological errors when these occurred in nonwords than in
words (R.B.: binomial p < 0.01, C.B.: χ 2 (1) = 5.26, p = 0.02).
DISCUSSION OF RECEPTIVE WORD PROCESSING
The brothers' performance on the various conditions of the picture-name
judgement experiment confirmed the hypotheses about the deficits affecting
their lexical processing.
Both R.B. and C.B. made errors on the close semantic
distractors, but while C.B. accepted only a few of these distractors as appropriate
names for the pictures, R.B. accepted nearly half these distractors as appropriate.
It had been hypothesised that some semantic errors would arise as a consequence
of globally weakened connection strength, and that R.B.'s performance would be
considerably poorer than C.B.'s on this task due to an additional semantic level
impairment.
Not only was this prediction upheld; but R.B.'s semantic deficit is
apparent also from the fact that he even made errors in the condition where the
distractor names were completely unrelated to the target names.
The hypothesis
that C.B.'s ability to make fine phonological discriminations would be impaired
due to rapid decay was supported by his impaired performance on all conditions
requiring the detection of phonologically-related distractors, with almost no
distractors being correctly rejected in the most difficult of these conditions.
In
comparison, R.B.'s performance on phonologically-related distractors was barely
below that of the three controls on the full nonword set.
The experiments in this chapter have been testing a model of language
processing in which there is a single phoneme level shared by input and output
language processing, the s i n g l e - n e t w o r k version of the Dell interactive
activation model reported by Martin and Saffran (1992) and Martin et al. (1994).
Dell et al. (in press) have, however, also simulated repetition using a model that
assumes separate levels of phonemes at input and output (the p e r f e c t - r e c o g n i t i o n
version; see Chapter 1).
In these simulations, it is assumed that the lexical target
for repetition is recognised correctly; that the first stage of production in
repetition is the activation of the lexical level; and that errors in repetition must
therefore arise only in the incorrect selection of phonemes for output.
Using
parameters derived from the patients' naming performance, simulations based on
the perfect repetition assumption provide the best fit to the patients' repetition —
providing the patients have unimpaired word recognition.
performance
on
the
phonological-distractor
conditions
R.B.'s good
in
picture-name
judgement suggests the perfect recognition assumption is appropriate for his
repetition, and thus that perhaps a two-lexicon view is most consistent with R.B.'s
performance.
Chapter 4: Familial Progressive Aphasia
145
C.B.'s performance, however, may be more consistent with the single
network model.
In the same series of analyses which showed that a perfect
recognition model is the best fit to the repetition of patients with good word
recognition, Dell and colleagues also showed that such a model over-predicted the
repetition performance of a patient, N.C., who had a word-recognition deficit.
Similarly, in simulations of the repetition of two non-fluent progressive aphasic
patients with word recognition deficits, the naming parameters combined with
the perfect recognition assumption over-predicted repetition performance (Croot
et al., in press; Chapter 3, Footnote 2).
C.B.'s performance on all the phonological-
distractor conditions of the picture-name judgement experiment indicate that his
word recognition is far from perfect; thus the most parsimonious account of C . B . ' s
language disorder would involve a model of language processing which does not
require separate input and output phonological representations.
It is apparent, therefore, that testing the predictions of a single
phonological lexicon model against the performance of these two patients has not
shown clear support for such a model against the claims of a model with separate
input and output phonological representations.
Instead, it has highlighted the
confounding issue in neuropsychological research on the question.
In the
neuropsychological literature to date, the support for one account versus the
other may depend more on the integrity of the input phonological processing in
the patients tested than on the discovery of a testable theoretical prediction that
would cast the deciding vote.
GENERAL DISCUSSION
The present study investigated the progressive language deficits of two
brothers with primary progressive aphasia.
The study has implications both for
theories of normal speech production and its breakdown, and for the
understanding of progressive aphasic syndromes.
While some of these
implications have been noted in the discussion sections above, a few of the
broader issues remain to be considered below.
The investigations of language production in the present chapter, and in
the study of non-fluent progressive aphasia in the previous chapter, demonstrate
that the Dell interactive activation model is appropriate for characterising the
deficits of patients with progressive aphasia as well as deficits observed in strokerelated disease.
In degenerative cases, however, while predictions about language
performance at any one point in time are relatively straightforward, predictions
about the likely pattern of decline are much more complicated.
This is because,
while both processing parameters of connection strength and decay rate may be
Chapter 4: Familial Progressive Aphasia
146
implicated in the aphasic profile of the patient, there is no guarantee that the
ratio of one to the other will remain constant over time.
Thus, the extent to which
these parameters may change relative to one another longitudinally remains an
important question for future research.
In C.B.'s case, the characteristics of rapid
decay in his speech production became more evident over time with the
emergence of imageability effects in immediate repetition on his second round of
testing and the appearance of semantic errors by the third round.
The longitudinal investigation of aphasia in degenerative disease
complements the study of language processing in patients recovering from
stroke.
In both situations, the relative efficiency of different components of the
language system changes over time.
A model which can account for patterns of
recovery a n d degeneration both strengthens its own claim to generalisability,
and supports the assumption that a continuity exists between normal and the
pathological language systems (Dell et al., in press).
Martin and colleagues (1994) reported a longitudinal study of the naming
and repetition performance of a patient, N.C., whose language disorder following
a stroke was consistent with rapid decay in the lexical network.
As N.C. recovered,
his aphasic profile evolved from that typical of deep dysphasia (semantic errors
and imageability effects in immediate repetition), to that of conduction aphasia,
in which semantic influences in repetition are absent but phonological errors
remain, and in which repetition of nonwords is severely impaired.
C.B., the
brother in the present study hypothesised to have a rapid decay impairment,
showed a language pattern which evolved in the reverse order to that of N.C.
Initially, C.B. made only phonological errors in immediate repetition, but over
time, semantic influences became more apparent.
Although not reported in the
results section of the current paper, on Round 1 C.B.'s repetition of nonwords was
significantly poorer than repetition of words matched closely on phonological
structure.
Furthermore, if N.C. and C.B. demonstrate that complementary patterns
of language recovery and decline can be explained with reference to a
mechanism of rapid decay in the Dell model of production, it would be predicted
that patients will also be reported who show a complementary pattern of recovery
to those already described with weakened connection deficits (Croot et al., in
press; Dell et al., in press; Schwartz et al., 1994).
Thus, with a sufficiently specified
model of language processing, the pattern of i m p a i r m e n t shown by patients with
degenerative disease may contribute to predictions about r e c o v e r y from singleinsult disease.
Although the model based on two global parameters provides a useful
account of the brothers' language deficits, it has been argued that R.B. must also
have an additional deficit specifically at the level of semantic representations.
Chapter 4: Familial Progressive Aphasia
147
This was necessary to account for his disproportionately impaired naming, and
his impaired performance on even non-verbal semantic tests.
Converging
evidence was available from structural brain imaging, which showed that R.B.
had focal atrophy of the left infero-lateral temporal lobe, a region known — from
patients with semantic dementia (Hodges et al., 1992, Snowden et al., 1989) and
activational PET studies (Martin, Wiggs, Lalonde, & Mack, 1996; Mummery,
Patterson, Hodges, & Wise, 1996)
— to be associated with semantic processing.
At this point in its development, the model of Dell and colleagues
incorporates the assumption that the parameters of connection strength and
decay rate apply globally throughout the network; that is, they affect each level
equally (Dell et al., in press).
R.B.'s severe semantic impairment might therefore
be localised at a level of semantic processing prior to the semantic layer of the
Dell lexical network, or may need to be explained in a version of the model in
which the parameters of connection strength and/or decay rate may be locally
impaired at one or two layers of the network (Martin & Saffran, submitted;
Schwartz et al., 1994).
It should be noted, however, that even in naming with
phonological cueing — in which his response rate was higher than in any other
naming task — R.B.'s response rate was lower than that of any of the patients fitted
to the Dell model.
The model does not therefore claim, a priori, to generalise to
such a pattern of performance.
The fact that the concept of weak connections
predicts so many aspects of R.B.'s performance speaks instead to the explanatory
strength of the model in accounting for patterns of aphasic performance beyond
those it has experienced.
As Dell et al. (in press) point out, the central challenge
in applying this model to patients with semantic difficulties lies in understanding
what their non-responses in naming can tell us.
As emphasised at the beginning of this chapter, very few cases of familial
progressive aphasia have been reported previously, which makes it difficult to
draw conclusions about the syndrome in familial versus sporadic progressive
aphasia.
In comparison to the brothers reported by Neary et al. (1993b) who were
in their early sixties at presentation, C.B., and particularly R.B., presented at a
younger age (57 and 50 years, respectively), but otherwise showed a fairly similar
clinical profile with phonological disruption an early characteristic.
The ten
patients reported by Morris et al. (1984) ranged from 56 to 74 years of age at onset,
but not all presented with an isolated aphasia; in some cases the aphasia cooccurred with memory loss and behavioural and/or personality change.
The
clinical description of the language deficits in these cases, as initially hesitant,
anomic, paraphasic and dysfluent, is consistent with the language changes
observed in R.B. and C.B.
Chapter 4: Familial Progressive Aphasia
148
It would therefore appear, on the basis of current limited evidence, that
familial progressive aphasia is perhaps more typically non-fluent, with
prominent breakdown in phonological processing (although as discussed above,
one of the brothers reported in this study had an additional semantic
impairment).
Although not the focus of the present study, both brothers also
showed morpho-syntactic deficits in spontaneous speech.
The MRI scans of R.B. and C.B. suggest that pathology is somewhat
differently distributed in the two brothers; a finding also noted of the brothers
reported by Neary and colleagues.
At autopsy, one brother reported by Neary et
al. (1993b) showed bilateral fronto-temporal atrophy more marked in the right
hemisphere; the other had frontal, temporal, frontoparietal and lateral
parietal/occipital atrophy of the left hemisphere.
Histology showed spongiform
change with mild gliosis but no Pick cells, Pick or Lewy-type inclusions nor
neurofibrillary tangles.
Post-mortem examination of four members of the family
reported by Morris et al. (1984) revealed focal cerebral atrophy in the left
anterior perisylvian regions, with neuritic plaques normally associated with
Alzheimer's Disease, neuronal depigmentation and depletion, as well as Lewy Body
inclusions, although Pick cells and Pick inclusion bodies were not seen.
Previous studies of patients with sporadic progressive aphasia have
distinguished two major syndromes: progressive non-fluent aphasia and
progressive fluent aphasia (Hodges et al., 1992, Hodges & Patterson, 1996).
R.B.'s
and C.B.'s marked phonological disruption sets them apart from the fluent
semantic dementia patients (Snowden et al., 1993; Hodges et al., 1992; Graham et al.,
1994; Knott et al., submitted) and also from a progressive anomic patient F.M.
(Graham et al., 1995), as none of these patients made outright phonological errors
in speech.
Similar to the non-fluent sporadic patients, the brothers showed
primary breakdown in phonological processing, but presented with somewhat
more fluent speech.
In terms of reported aphasic patterns, R.B.'s language profile
fits the description of the "mixed" type of progressive aphasia reported by
Mesulam & Weintraub (1992) and Snowden et al., (1992), in which both
phonological and semantic abilities are progressively compromised.
C.B. has
shown something more like a conduction aphasia progressing to deep dysphasia.
The study reported in this chapter may represent the first attempt to provide a
theoretical account of both types of progressive syndrome.
Chapter 5
Review of Phonological Processing Abilities
In Dementia of the Alzheimer Type
It has been known that Alzheimer's Disease (AD)1 may cause language
deficits since the clinico-pathological characteristics of the disease were first
described by Alois Alzheimer in Tubingen in 1906 (Alzheimer, 1911/1991) .
A
range of studies conducted in the succeeding ninety years — most of them in the
last thirty years — demonstrate conclusively that not all language functions are
equally impaired in Dementia of the Alzheimer Type (DAT), and that the severity
and pattern of language deficits varies from patient to patient and with disease
progression.
Nonetheless, the literature reflects an overwhelming consensus
that phonological and syntactic aspects of language processing are relatively
preserved in DAT, while the lexico-semantic and pragmatic aspects are more
severely impaired.
In her review of language in dementia, Hart (1988, p. 109)
notes that this conclusion "is fast approaching the status of dogma", but that it has
not
gone
unchallenged.
The present review argues that phonological processing is not necessarily
preserved in DAT.
While there is a vast literature on the semantic abilities of
patients with DAT (for review, see Greene & Hodges, 1996), there are, instead,
almost no studies which have specifically focused on the status of phonological
abilities in DAT.
Nevertheless, other investigations of language and cognitive
function in DAT, and clinical descriptions of language in dementing syndromes in
general, provide oblique evidence that phonological breakdown does occur in
some patients with DAT.
There are two broad types of evidence against the claim
that phonology is relatively preserved in the disease.
Firstly, among the various studies that conclude that phonological
processing is relatively preserved, only in some instances does this mean
preserved relative to normal.
1 In this thesis, the term Alzheimer's
In other studies, phonology is only judged as
Disease (AD) is reserved for pathologically proven
cases; the terms Dementia of the Alzheimer Type (DAT) and probable AD describe clinically
diagnosed cases.
149
Chapter 5: Phonological Processing in DAT 150
preserved relative to other aspects of cognition, most frequently, as already noted,
relative to lexico-semantic and pragmatic aspects of language.
The indications
that phonology is impaired relative to normal are found in clinical descriptions
which note the disrupted production of sounds in spontaneous speech, and in the
phonological errors sometimes reported in single word or sentence production
tasks.
There are even occasional reports of patients with sporadic probable AD
and pathologically-confirmed familial AD manifesting specific phonological
difficulties.
Secondly, recent interest in progressive aphasia — especially non-fluent
progressive aphasia — has demonstrated that phonological processing may indeed
be compromised in patients with progressive dementing syndromes.
In rare
cases, these patients are found to have Alzheimer pathology at autopsy.
This review will therefore suggest that, contrary to the "dogma",
phonology may not only be impaired relative to normal in some patients with
DAT, but that, in some patients, phonological problems may even emerge earlier
than those in the lexico-semantic and pragmatic domains.
Alzheimer's Disease is a
clinically heterogeneous entity, with different cognitive functions differentially
impaired across patients and over time — and phonological processing may be one
of the functions compromised.
Further, it will be shown that phonological
breakdown in AD is associated with an atypical distribution of pathology in
perisylvian language areas which have long been known for their involvement
in
phonological
processing.
For the purposes of this review, as elsewhere in the thesis, "phonological
processing" is taken to mean all levels of processing involving the production
and comprehension of speech sounds, embracing the articulatory levels of
production as well as the more strictly linguistic-phonological functions related
to lexical retrieval and encoding.
The present literature survey is deliberately
inclusive of both levels because, as discussed in Chapter 1, it is frequently
impossible to determine from a clinical description of disrupted speech whether
the disruption occurs at a linguistic-phonological level of organisation, or a
motor-articulatory level.
Further, as is no guarantee that a principled distinction
between the two sources of error has been made in reported studies, and errors
arising at both levels of speech output processing may be acoustically
indistinguishable, it would be premature to narrow the focus at this point in the
investigation.
Several types of abnormal utterance were therefore noted in this search
for signs of phonological disruption in DAT.
These included series of
approximations to a phonological target (conduit d'approche responses), and the
Chapter 5: Phonological Processing in DAT 151
"classic" phonological paraphasias in which there is addition, substitution and/or
deletion of phonemes.
non-fluent
and/or
Also noted were references to Broca's aphasic-type,
dysarthric
speech,
to
"phonetic
disintegration"
(Ajuriaguerra
& Tissot, 1975) , which is the mistiming or misarticulation of components of the
sound structure at a sub-phonemic level (see Chapter 1), and palilalia, the
meaningless immediate repetition of a syllable or word which is thought to persist
even after the catastrophic breakdown of the phonological system in dementia
(Appell, Kertesz, & Fisman, 1982) .
THE SOURCE OF THE "DOGMA": EVIDENCE SUGGESTING
THAT PHONOLOGY IS UNIMPAIRED IN DAT
Connected
Speech
A range of group studies analysing phonological production in both
spontaneous speech and single word production tasks have concluded that
phonology is n o t impaired in Dementia of the Alzheimer's Type.
Looking first at
those studies which have analysed conversational or narrative speech, Appell and
colleagues (1982)
reported that 25 DAT patients made no phonological paraphasias
or conduit d'approche responses.
A further 9 DAT patients, with Mini Mental State
Examination (MMSE) scores (Folstein, Folstein, & McHugh, 1975)
ranging from
13—21, were phonologically unimpaired relative to controls on a 10—20 minute
interview, also making no phonological errors (Glosser & Deser, 1990) .
Blanken, Dittmann, Haas and Wallesch (1987)
Likewise,
found that 10 DAT patients showed
no more difficulty finding content words in conversation than controls, making
an average of around one or fewer phonological approximations to a target in the
course of a 5—10 minute interview.
(1985)
Nicholas, Obler, Albert & Helm-Estabrooks
reported that DAT patients did not produce a higher rate of phonologically
unrelated neologisms, phonologically-related word or non-word errors than
controls, in their description of the Cookie Theft picture from the Boston
Diagnostic Aphasia Examination (BDAE) (Goodglass & Kaplan, 1972) .
Two studies which classified the language of patients with DAT according to
the aphasia subtypes of the Western Aphasia Battery found no patients with
Broca's or Transcortical Motor Aphasia, the subtypes characterised (among other
features) by the production of phonological errors (Kertesz, Appell, & Fisman,
1986; Price et al., 1993) .
respectively.
These studies looked at groups of 25 and 20 patients
Moreover, Kertesz and colleagues retested their patients after a year
and found no change in fluency had occurred over that time, despite the fact that
the patients were at a sufficiently late stage of the disease to be hospitalised.
Chapter 5: Phonological Processing in DAT 152
Blanken et al. (1987) , however, note that some language difficulties may
only be apparent in testing situations, not spontaneous speech.
If so, then in the
spontaneous speech samples analysed by the above authors, the patients may
have been able to avoid phonological errors by monitoring and restricting their
output; that is, allowing patients to determine the content of speech output may
obscure any phonological output deficits which are present.
Several studies of
single word production have, however, also concluded that phonology is
unimpaired in DAT.
Naming
In one of the first formal naming studies, Martin and Fedio (1983)
reported
that 14 patients with DAT made no phonological errors on the Boston Naming Test
(BNT) (Kaplan, Goodglass, & Weintraub, 1976) .
(1983)
Similarly, Bayles and Tomoeda
reported that 11 mild DAT patients made no phonemically related errors
naming twenty coloured pictures, while even the moderately impaired subjects
only made 3 such errors (the total for the group).
(1989)
Smith, Murdoch & Chenery
also showed that 18 subjects with moderate to moderately-severe DAT
(MMSE scores ranging from 4—9) made an average of less than 1 phonemically
related error and less than 1 phonologically distant neologism per subject on
visual and tactile naming tests, and that this was not different to the control rate
of these types of error.
Hodges, Salmon and Butters (1991)
performed a more
comprehensive naming study in which they compared patients with DAT,
Huntington's Disease and controls.
The DAT patients (n = 52) made a slightly
higher rate of phonological errors on the BNT (around 6%) than the moderately
impaired group reported by Bayles and Tomoeda (3%) in coloured picture-naming,
but this was still not significantly different to the phonological error rate of the
controls.
A subgroup of the DAT patients was also studied longitudinally, and
again there was no significant increase in the rate of phonological errors over a
3-year period.
Other researchers report near-error-free performance on
repetition (Grossman et al., 1996; Marcie, Roudier, Goldblum, & Boller, 1993)
and
reading (Lambon Ralph, Ellis, & Franklin, 1995) , indicating that DAT did not
compromise the production of phonological forms in the single word production
tasks in these studies.
Articulation
Two studies have concluded that the articulatory processes of speech
production, as measured by specific dysarthria/articulation scales, are also
unimpaired in DAT.
Cummings, Benson, Hill and Read (1985)
reported that 30 DAT
patients showed no impairment on the "mechanical" aspects of speech output
Chapter 5: Phonological Processing in DAT 153
(loudness, pitch, articulatory precision, rate, intelligibility), and made no more
literal or verbal paraphasias than matched controls.
and Boyle (1987)
patients
had
Murdoch, Chenery, Wilks
also found that none of a group of 18 institutionalised DAT
articulatory
impairments.
Receptive Word Processing
Finally, there is evidence that receptive word processing may be
unimpaired in DAT.
Grossman and colleagues (1996)
Zatorre and Growdon (1993)
and Kurylo, Corkin, Allard,
reported no significant difference between DAT
patients and controls on phoneme discrimination (n= 25 DATs in the former study,
n=19 in the latter).
Bayles and Boone (1982)
found that 35 patients with DAT were
poorest relative to controls on a test requiring them to correct sentences
containing semantic errors, and less impaired at detecting phonological errors
(in which lexical stress, phrasal intonation or the identity of a single phoneme
was incorrect).
In this latter study, however, it is not clear whether or not the
patients performed within normal limits in detecting phonological errors.
While
DAT patients are poorer than controls at detecting speech in noise (Gates et al.,
1995) , this is attributed to attentional/executive deficits rather than impaired
language
input
processing.
Reviews
Reviews of language in DAT invariably claim that phonological processing
is preserved, but several of these reviews are superficial in their survey of
literature to support this claim, citing only one or two studies as evidence
(Flicker, Ferris, Crook, Bartus, & Reisberg, 1986; Lee, 1991; Miller, 1989; Walcoff,
1991) .
Furthermore, one of the patients who is cited as evidence for preserved
phonological processing in AD in a number of these reviews did not h a v e
Alzheimer's Disease, and the same is likely of a second widely-cited patient.
The first of these patients, H.C.E.M. (Whitaker, 1976) , was able to correct
phonological errors in sentences given as targets for echolalic repetition even
when she could no longer understand them.
Post-mortem analysis showed
nonspecific atrophy (lacking AD pathology), a fact noted in the original case
report.
Lee (1989), supposedly reviewing language change in AD, extrapolates
from H.C.E.M.'s performance that "m a n y patients with severe disorders are able to
recognise and correct phonological error" (italics added).
The other frequently
cited patient, W.L.P., (Schwartz, Marin, & Saffran, 1979) , had well-preserved
phonology and syntax in the context of marked semantic deterioration.
Although
not labelled as such at the time — the term was not introduced until the late 1980s
(Snowden, Goulding, & Neary, 1989)
— W.L.P. is now widely regarded as one of the
Chapter 5: Phonological Processing in DAT 154
first patients reported with the syndrome of semantic dementia, which occurs in
the context of severe focal temporal lobe atrophy which is almost always
secondary to non-Alzheimer pathology (non-specific microvaculation or Pick's
Disease) (Hodges, Garrard, & Patterson, in press) .
Thus Flicker and colleagues
(1986, p. 314), in citing only the performance of W.L.P., exceed the conclusions
justified by data from one patient (let alone one with potentially non-Alzheimer
pathology!) in claiming that phonological operations are "especially
resistant to
the dementing process" in senile DAT (italics added).
With the exception of the review by Hart (1988), even those reviews which
are more probing reach the orthodox conclusion that: "language production
during early AD is fluent, with preserved syntax and phonology" (Cohn, Wilcox, &
Lerer, 1991, p. 453) ; "preserved phonology" extends through early and middle
stages of DAT (Thompson, 1987, p. 148) ; "there are no deficits of phonetic
articulation...equally interesting is the preservation of phonology" in the early
stages of senile DAT (Patel & Satz, 1994, p. 7) .
There is no doubt that many
empirical studies, surveyed above, suggest that phonological processing is
unimpaired in DAT.
There are, however, also studies which indicate that aspects
of phonological processing may in fact be impaired in patients with DAT.
CHALLENGING THE DOGMA:
HINTS THAT PHONOLOGICAL PROCESSING MAY BREAK DOWN IN DAT
Early Reports
Earlier reports of language in dementia, while emphasising that
semantic/conceptual levels of speech are most disrupted, do not suggest that
phonological processing is normal.
For instance, Stengel (1964, p. 30)
noted the
tendency of demented patients to "produce new words" (neologisms) and gives as
one example a phonological paraphasia (cigarette → cigaroot).
overview from the same year, Critchley (1964)
In a similar
suggested that demented patients
may exhibit "phonetic" errors, producing speech at an unduly high pitch, and
"phonemic" errors, prolonging diphthong glides or adding an [s] or [t] or final
schwa sound in the pronunciation of words.
In a more empirical investigation, a
large battery of language tests was administered to 32 French-speaking subjects
with senile-dementia, and a detailed analysis of the errors carried out (Irigaray,
1973; reviewed by Obler, 1981).
While Irigaray concluded that "phonological and
morphosyntactic levels of language were relatively preserved...while semantic
and pragmatic realms are disturbed" (Obler, 1981, p. 379), she nonetheless noted
that patients gave "paraphonic" responses on several tasks; words that were
phonologically related to the target.
Similarly, Ajuriaguerra and Tissot (1975)
Chapter 5: Phonological Processing in DAT 155
and Constantinidis, Richard and Ajuriaguerra (1978)
observed that while
phonological paraphasias are much rarer than semantic paraphasias, the former
do occur in the speech of patients with senile dementia, as do elements of
"phonetic disintegration", or inaccuracy in articulating certain phonemes.
None of these early studies, however, distinguished between dementias of
differing etiologies.
There is therefore no guarantee that the patients reported
with disrupted production of speech sounds actually had Alzheimer's Disease.
They may instead have had multi-infarct dementia, Pick's Disease, Huntington's
Disease, or Parkinson's Disease, any of which may be associated with phonological
and/or motor disruption to speech output (Bayles & Tomoeda, 1983; Cummings,
Darkins, Mendez, Hill, & Benson, 1988; Gordon & Illes, 1987; Hier, Hagenlocker, &
Shindler, 1985; Holland, McBurney, Moossy, & Reinmuth, 1985)
Even in more recent studies, where a diagnosis of probable Alzheimer's
Disease is reached by more restrictive exclusionary criteria, such as those of the
National Institute of Neurological Disorders and Stroke-Alzheimer's Disease and
Related Disorders Association (NINCDS-ADRDA) (McKhann et al., 1984) , patients
diagnosed with DAT may prove to have non-Alzheimer pathology at autopsy.
The
accuracy of initial clinical diagnosis relative to neuropathology using the
NINCDS-ADRDA criteria is around 86%, rising another 5% or so when follow-up
clinical data are taken into account (Becker, Boller, Lopez, Saxton, & McGonigle,
1994) : high accuracy, but not perfect.
The possible inclusion of non-Alzheimer
patients presents a problem of interpretation for all studies which lack autopsy
confirmation of the diagnosis.
This is particularly true of instances in which one
patient of a series of patients has unusual speech production, or when a low rate
of phonological error is reported as the average for a group of patients with no
indication of individual variability.
Nevertheless, the range of studies which d o
report disruption of speech sounds in DAT patients suggests that surely not all of
these patients have dementias of other aetiologies, especially as AD is by far the
most common cause of dementia.
Connected
Speech
Contrary to the conclusions of Appell et al. (1982), Glosser and Deser (1990)
and Blanken et al. (1987) which were discussed above, some researchers report
that phonological disruption may occur in spontaneous speech in DAT.
Dager, Berg and Hyde (1990)
Loebel,
rated 8/32 DAT patients with MMSE scores ranging
from 18—24 as having a severe impairment in fluency on the basis of a 45 minute
interview.
These patients were reported to make numerous and prolonged
hesitations, paraphasias and repetitions of syllables and words, and/or to be
agrammatic or neologistic, with monotonous tone and nearly unintelligible
Chapter 5: Phonological Processing in DAT 156
speech.
Illes (1989)
found that in answering autobiographical questions, DAT
patients at both early and moderate stages of disease made no more conduits
d'approche than controls, but did produce a higher rate of phonemic paraphasias
and neologisms.
Of the 19 "florid phase" patients studied by Gavazzi, Luzzatti and
Spinnler (1986) , one was classed as a Broca's aphasic and described as having a
dysarthria of moderate severity; one of 33 non-hospitalised patients reported by
Kertesz and colleagues (1986)
also had a Broca-type aphasia.
A further patient,
Case 3 reported by Shuren, Geldmacher and Heilman (1993) , was described as
having moderately slow spontaneous speech, with word-finding difficulty and
occasional phonemic and semantic paraphasias.
This patient had probable AD
determined by NINCDS-ADRDA criteria and an MMSE score of 23/30.
Even Blanken
et al. (1987), in their study reporting negligible rates of phonological error in
DAT, commented that one DAT patient from a pilot study who was not included in
their experimental sample showed lexical access disturbances and made phonemic
paraphasias.
One final study which investigated the characteristics of a four-minute
sample of conversational speech in DAT (Romero & Kurz, 1996)
found that
"phonematic structures" were unimpaired in more than 95% of a large sample
(n=63) of mildly to moderately impaired DAT patients.
Romero and Kurz also
reported that this figure had not declined significantly after 1 year follow-up of
all 63 subjects.
In the same study, however, a striking 30% of subjects were
impaired on the articulatory/prosodic measure, and the proportion of patients
impaired on this measure increased significantly over the following year.
Unfortunately, there is not enough information provided in the study to
determine whether the patients' difficulties were articulatory as well as prosodic
in nature, and it is possible that only prosodic disruption was observed, and that
these were due to word-finding difficulties associated with semantic impairment.
Word and Sentence Production Tasks
The literature is similarly inconclusive about the rate of phonological
errors made by DAT patients in single word production tasks.
In many naming
studies, the nature of the errors is simply not reported, so it is not possible to
assess the phonological integrity of responses (Huff et al., 1987; Margolin, Pate,
Friedrich, & Elia, 1990; Mitrushina, Uchiyama, & Satz, 1995; Rebok, Brandt, &
Folstein, 1990) .
In others, phonological errors are grouped with a range of other
error types, so the specific proportion of phonological errors cannot be extracted
(e.g. Gavazzi et al., 1986).
Finally, even in studies which use the same naming test,
and where phonological errors are systematically analysed, the results are rather
inconsistent.
Thus, although Martin and Fedio (1983)
found that DAT patients
Chapter 5: Phonological Processing in DAT 157
made no phonological errors on the BNT, the patients tested by Hodges and
colleagues (1991)
on the BNT made an average of 6% of phonological errors, and
Price et al. (1993) note that at least 7 of the 20 patients they tested on the BNT made
phonemic errors.
Some of this inconsistency must arise from comparing patients
at different stages of disease severity across studies; but it almost certainly also
occurs because of the heterogeneity of the disease itself, with phonological
processing more impaired in some patients than in others.
Although some researchers claim that impairments in phonological
processing and speech production only occur late in DAT, there is no consensus
on this point either.
Cummings et al. (1985)
noted impaired repetition and a
progressive decline in speech pitch and intelligibility late in the course of DAT.
Most of the hospitalised DAT patients who were retested by Kertesz and colleagues
(1986) after a year had also declined in repetition ability.
Obler and Albert (1984)
In contrast, however,
reported that repetition of phrases containing low
frequency words (as in "the vat leaks" from the BDAE) was already impaired by
mid-stage DAT, with patients producing errors that were "phonetically related
jargon".
This situation only deteriorated in later stages of the disease as higher
frequency items were also affected.
Emery and Breslau (1988) also observed
pronunciation errors in 15/21 DAT subjects repeating the most difficult sentence
in the WAB Repetition test ("pack my box with five dozen jugs of liquid veneer").
While all seven of the severely demented patients in the study may have been
among these fifteen who made phonological errors, the other eight in the
phonologically impaired group would not have been at a late stage of disease.
One study by Biassou et al. (Biassou et al., 1995)
directly addressed the
question of phonological disruption in DAT and reported a clear impairment.
Sixteen DAT patients, diagnosed under the NINCDS-ADRDA criteria and with MMSE
scores above 10, made more speech errors in sentence repetition than controls.
The DAT patients' errors were predominantly nonwords diverging from the
targets at word-initial positions (e.g. meaty → veaty, brown →
→ krimpanzee).
trown, chimpanzee
The patients also made more non-environmentally influenced
errors, and more phoneme additions than controls.
Biassou and colleagues
suggest the difficulty was in retrieval of the lexical phonological form.
and Hodges (1991)
Funnell
reached the same conclusion in a single case study of the
naming of a 58 year-old woman with DAT.
Mary's naming (27.3% correct) was
significantly impaired relative to reading (92.7% correct) and repetition (98.2%
correct), but she showed good (although not perfect) comprehension of pictures
she failed to name (75% correct).
Funnell and Hodges concluded that this woman
had impaired access to the phonological lexicon from semantic descriptions.
Chapter 5: Phonological Processing in DAT 158
PHONOLOGICAL DISRUPTION IN HISTOLOGICALLY-CONFIRMED
ALZHEIMER'S DISEASE
Familial Alzheimer's Disease
The most convincing evidence for phonological disruption in familial AD
comes from the study of Kennedy et al. (1995) , who reported two siblings with
impaired speech production in a kindred of 7 affected individuals spanning 2
generations.
The patients, Cases II.5 and II.6, were non-identical twins who met
the NINCDS-ADRDA criteria for probable AD, and had an older sibling for whom
AD had been confirmed by autopsy.
The twins began showing marked difficulties
with speech production in the year before their MMSE scores fell to 16/30 and
15/30 respectively.
Their speech problems were noted to be more marked in
spontaneous speech, but were also documented in single word reading and
repetition tasks (to an equivalent degree in the two tasks).
The patients made
more errors on sentence and cliché repetition than on repetition of single words,
although their auditory-verbal short-term memory span for digits exceeded the
length of the short phrases.
Errors included phonemic substitution, omission, and
repetition errors, false-starts (e.g. b-b-brown) and stammering speech.
As
articulation was noted to be unimpaired, a phonological, rather than articulatory
level of impairment was implicated.
Speech difficulties were reported in another series of familial AD cases
described by Morris, Cole, Banker and Wright (1984) .
The ten affected family
members were described as having initially hesitant, anomic, paraphasic and
dysfluent language, which evolved to global aphasia and mutism over an average
course of 8 years.
Post-mortem findings for 4 members of the family showed focal
cerebral atrophy in the left anterior perisylvian region, with typical Alzheimertype neuritic plaques, as well as neuronal depigmentation, depletion and Lewy
Body inclusions.
Given the mixed pathology present in these cases, however,
some of the observed difficulty in speech may arise from motor problems
associated with the Parkinsonian pathology (Broussolle et al., 1992; Cummings et
al., 1988) .
Sporadic Alzheimer's Disease
There is also a growing number of reports of phonological disruption in
the context of histologically confirmed, non-familial AD.
patients reported by Neary et al. (1986)
difficulties producing fluent speech.
Several of the 18
had biopsy-confirmed AD and had
One is described with stammering, palilalic
speech, two had speech limited to monosyllables and stereotyped utterances, and
two further patients are reported with dysprosodic speech and mild dysarthria in
Chapter 5: Phonological Processing in DAT 159
the context of more general motor difficulties.
Six of the 42 patients with
pathologically confirmed AD described by Mendez, Selwood, Mastri and Frey
(1993)
had speech disturbances including dysarthria, decreased verbal output
and reiterative speech acts.
It is not clear from the report, however, how many of
the patients had specifically dysarthric output rather than reduced or
echolalic/palilalic speech.
Five of the 23 pathologically-confirmed AD cases
reported by Goodman (1953)
were described as having language deficits, Cases 4
and 6 with involvement of phonology.
Case 4 was initially hesitant although with
no overt speech defects, and later "her productions bore little resemblance to
words...she had difficulty repeating her own name and was unable to count
spontaneously or repeat numbers" (p. 119).
Case 6 developed speech deficits six
months after onset of behavioural and personality changes.
This patient made
paraphasic errors and groped for words, and was described as having "variable
motor
aphasia".
The final, and perhaps most convincing group of patients who demonstrate
that phonological deficits may occur in autopsy-confirmed AD are those who
p r e s e n t with an insidious non-fluent progressive aphasia.
In these patients,
disruption to the fluent production of speech, with syntactic omissions and
phonological errors, is the first manifestation of AD.
A selective deterioration in
speech fluency may proceed for several years in isolation from other cognitive
deficits — including the lexico-semantic deficits claimed by some to be so
pervasive in DAT.
Three such non-fluent progressive aphasic patients have been
reported.
Green, Morris, Sandson, McKeel, and Miller (1990)
described a woman (Case
8) who presented at age 74 with a three year history of slow, effortful, hesitant
speech.
On examination she showed a mild orofacial apraxia, slowed motor
performance and speech with monotonous prosody.
(1993)
Karbe, Kertesz and Polk
reported that one patient (Patient 2) of a series of 10 who had slow,
hesitant and sometimes agrammatic speech containing phonemic paraphasias,
had shown diffuse AD pathology at autopsy.
age 55 and died at 58.
This male patient had presented at
While the accounts of these two patients are extremely
brief, there is more detail provided by Greene, Xuareb, Patterson and Hodges
(1996)
about patient A.S.
A.S. presented at 66 years of age with a history of hesitant and syntactically
impoverished speech stretching back five years.
On neuropsychological testing,
he made phonological errors in naming, repetition and reading, and was unable
to provide rhymes in a task designed to tap knowledge of the sound structure of
words.
The following is an example of his spontaneous speech describing his
garden (Greene et al., 1996, p. 1076).
Chapter 5: Phonological Processing in DAT 160
Yeah, but I can't do it now, but...my wife has...done very well.
She's
made...a picture in her [plaU´z]...and she sat some seed for the...er...
the...[p´teIp´z ] and had been [wIn ] out of this [w Œ D] ...We gave some, the
[meIb´z ]...and they said...lovely
Examples of phonological errors in naming include elephant → [wEl´ ] and tortoise
→ [t Å k ´ s ].
One year after presentation, A.S. died of myocardial infarction, and
autopsy confirmation of AD was obtained.
Distribution of Pathology
A striking point about these pathologically-confirmed AD cases with
prominent phonological impairment is that the distribution of pathology is
consistently atypical for AD.
The most common pattern of neurodegeneration in
AD is early involvement of the transentorhinal region, with pathology then
extending into limbic structures and isocortical association areas (Braak & Braak,
1991; Hodges & Patterson, 1995) .
By contrast, however, in Goodman's (1953) Case 4,
the degeneration was marked in both frontal and temporal areas, especially
perisylvian areas, and in Case 6 the severe temporal atrophy was accompanied by
a high number of Alzheimer-type cells in Broca's Area.
Post-mortem examination
of Case 8 reported by Green and colleagues (1990) showed Alzheimer pathology
disproportionately present in left inferior parietal cortex, whereas the nonfluent progressive aphasic reported by Karbe et al. (1993, p. 198) had widespread
cortical and subcortical neuritic plaques and neurofibrillary tangles, in "vast"
and "overwhelming" numbers in the left middle frontal gyrus.
Patient A.S.
(Greene et al., 1996) was found to have pathology throughout perisylvian
language areas, but s p a r i n g the medial temporal lobe; the familial cases of Morris
et al. (1984) also showed focal anterior perisylvian pathology.
Further patients with atypically distributed pathology and phonological
disruption are reported by Ross et al. (1996)
biparietal syndrome.
under the rubric of progressive
Case 1, with autopsy-confirmed AD had severe neuronal loss,
neuritic plaques and neurofibrillary tangles in bilateral parietal cortex, and Cases
2 and 3 showed marked parietal hypoperfusion on SPECT scans.
All three had
severe phonological disruption in spontaneous speech and were unable to
perform tasks requiring phonological abilities, such as rhyme production and
phoneme blending.
Finally, while autopsy-confirmed data from the probable
familial cases II.5 and II.6 described by Kennedy et al. (1995) have not been
reported, PET scans of these patients revealed hypometabolism with a parietal
emphasis, and frontal hypometabolism more marked on the left.
While the
distribution of pathology in perisylvian language areas including Broca's area
and the supramarginal and angular gyri may be atypical for AD, reports of
Chapter 5: Phonological Processing in DAT 161
phonological deficits associated with widespread neuronal loss in these areas are
hardly surprising (see Chapter 1, Figure 1:5).
SUMMARY
Many reports of the language changes across the course of DAT suggest
that phonological processing is unscathed by the disease, at least until the final
stages in which there may be complete dissolution of language abilities
resembling global aphasia.
Whitaker (1976) proposed that it is the automaticity
and non-volitional nature of phonemic (and syntactic) functions which permits
their preservation in the face of cognitive breakdown.
The fruits of a further
twenty years of research on language in DAT, however, indicate that while
phonology does not appear to be systematically affected in all patients with AD, it
is definitely impaired in some, and these are likely to have an atypical
distribution of pathology focussed in perisylvian areas.
The present review suggests that phonological impairment in DAT may
have been difficult to detect when it did occur because group testing
methodologies are not most suitable for its detection, and because a priori
assumptions excluded direct investigation of the issue.
In the many studies using
group testing methodologies, atypical performances and low levels of individual
impairment may have been obscured by the more typical performance of the
group.
By contrast, studies with a narrower focus on individual cases with
familial disease, or with unusual progressive syndromes such as PPA, have
facilitated the detection and documentation of phonological impairment in some
cases of AD.
Further, the assumption from group studies that phonological
processing is intact in the disease has meant that tests targeting phonological
abilities are frequently omitted from assessment batteries which are designed
instead to enable maximum accuracy in the diagnosis or staging of the disease for
the greatest number of patients (Becker et al., 1994; Bracco et al., 1990; Cahn et al.,
1995; Cohn et al., 1991; Haxby, Raffaele, Gillette, Schapiro, & Rapaport, 1992;
Stevens, 1992) .
The same assumption has meant that few studies have deliberately
investigated the nature of phonological errors in DAT speech production; instead
such errors are not reported, or are pooled with other responses.
A clear
exception to this trend is the experimental repetition study of Biassou and
colleagues (1996), and the positive finding of phonological errors in DAT in the
latter study exposes the invalidity of assuming a priori that phonological
processing is preserved.
Thus evidence is gradually mounting that phonological impairment may
occur in AD.
Clinical descriptions of phonologically disrupted speech had been
Chapter 5: Phonological Processing in DAT 162
noted for patients who later had autopsy-confirmed AD in group studies (Price et
al., 1993), and reports of familial disease (Kennedy et al., 1995; Morris et al., 1984)
and primary progressive aphasia (Green et al., 1990; Karbe et al., 1993 ; Greene et
al., 1996).
At this stage, however, accounts of the patients' phonological
disruption are predominantly anecdotal and impressionistic.
Some
neuropsychological testing results and phonological error rates are given by
Kennedy et al. (1995) and Greene et al. (1996), but in comparison with the
extensive literature on semantic abilities in DAT, we know very little about the
effects of the disease upon phonological processing.
The phenomenon of
phonological breakdown in DAT is overdue for empirical study: the initial stages
of one such study are reported in Chapter 6.
Chapter 6
An Investigation of Phonological Disruption
in Atypical Dementia of the Alzheimer Type
As the review in Chapter 5 shows, there is a strong claim in the literature
that phonological processing is preserved in DAT, at least relative to lexicosemantic processing, and/or until late stages of the disease.
By contrast, the
present chapter describes 13 patients with either probable or autopsy-confirmed
AD who, atypically, showed striking phonological disruption.
Furthermore, this
disruption was evident early in the disease, either in combination with more
generalised cognitive deficits, or as one of the central features of what initially
appeared to be an isolated progressive aphasic syndrome.
The first aim of the
chapter is, therefore, to support the conclusion that phonological impairment
m a y occur in atypical presentations of DAT, with data from several hitherto
unreported cases, and with further data from a number of the previously noted
cases.
The second aim is to evaluate and develop the limited accounts of
phonological disruption in DAT which have been proposed.
There has been almost no discussion of the nature of the phonological
breakdown which occurs in DAT because it is so rare in the general population of
DAT patients.
Furthermore, among the studies which h a v e
demonstrated
phonological disruption in DAT (discussed in Chapter 5), most had a
predominantly clinical focus, and thus attempted no analysis of the cognitive
processes involved in the reported speech breakdown (e.g. Green et al., 1990;
Greene et al., 1996; Mendez et al., 1993; Ross et al., 1996; Karbe et al., 1993). Two
groups of researchers (Kennedy et al., 1995; Biassou et al., 1995) have, however,
speculated on the source of phonological errors produced by patients with DAT,
making reference to descriptive models of speech production.
(See Chapter 5 for
details of the patients described in these studies.)
Two Accounts of Phonological Errors in DAT
In the first account, Kennedy and colleagues (1995) attributed the
phonological errors of two patients with probable familial AD to a deficit at a level
of phonological processing per se.
Two of the patients from a single kindred,
163
Chapter 6: Phonological Disruption in Atypical DAT
164
cases II.5 and II.6, made phonological errors in reading and repetition as well as
spontaneous speech; Kennedy et al. therefore concluded that the deficit was not
specific to either a semantically-driven or a direct route to speech output, and
must therefore be located at a level of speech processing common to all
production tasks.
As the patients did not appear to make articulatory-phonetic
errors in the production of sounds, the authors concluded that post-phonological
representation and production of language was intact, and that the impairment
must lie in the phonological system itself.
This system is implemented in the
simulations of Dell and colleagues (Dell, 1986; Dell et al., in press) as the level of
phonological nodes, and the impaired process approximates phonological
retrieval/encoding.
In this chapter, the deficit hypothesised by Kennedy and
colleagues is referred to in general terms, as a phonological processing deficit.
This is to avoid confusion with the terminology of Biassou and colleagues, and
because Kennedy and colleagues did not invoke a specific model of phonological
processing in their account of the brothers' deficits
In the second account, that of Biassou and colleagues, the disruption was
also thought to apply to all types of speech output.
Biassou et al. (1995) proposed
that the phonological errors observed in a group of 16 unselected sporadic DAT
patients on a sentence repetition task were due to a deficit in a process they call
"lexical phonologic retrieval" (1995, p. 2169).
According to Biassou et al., this
process entails retrieval of a version of the lexical form which is somewhat
abstract but partially specified as to a word's initial consonant, stressed vowel, and
perhaps pattern of consonants and vowels within syllables (CV structure).
This
representation corresponds approximately to a lemma in some theories of speech
production (e.g. Levelt, 1989), and to the level of lexical nodes in Dell's interactive
activation model of production (Dell, 1986) — although there is no consensus
across theories as to the precise nature of information which is represented at
this level.
Biassou's position, does however, grant this intermediate lexical
representation between semantics and a fully-specified phonological form a
greater phonological specification than many theories (c.f. Astell & Harley, 1996;
Badecker, Miozzo, & Zanuttini, 1995; Butterworth, 1989; Levelt, 1989) .
In the Biassou et al. study (1995, p. 2167), the patients made a higher
proportion of their total errors on word-initial consonants than did controls (e.g.
The brown dog ate the... → The trown dog ate the...).
It was also claimed that the
patients showed a trend towards making more errors than controls on stressed
vowels and CV structure, but as the error rates reported in favour of these claims
did not reach statistical significance at α = 0.1, the study presented in this chapter
did not examine the rates of those two error types.
Biassou and colleagues
concluded that the DAT patients were more impaired than controls at retrieving
Chapter 6: Phonological Disruption in Atypical DAT
165
the lexical representation because they made more errors on phonological
information putatively (in their framework) represented at the lexical level.
They also argued that the patients' production of "pseudoword" errors (nonwords)
implied failed lexical retrieval because such items do not appear in the lexicon.
An alternative view would attribute such errors to phonological level
impairment.
For example, in the interactive activation network of Dell and
colleagues discussed previously in this thesis, nonword errors occur as a result of
noisy activation of the phonological nodes, even though an appropriate lexical
item has been selected (Schwartz et al., 1994).
Nonword errors were not,
therefore, considered as evidence of a failure to retrieve a lexical-level
representation in the study in the present chapter.
Biassou and colleagues argued instead that the patients' phonological
errors did n o t arise from a primary deficit at the level of phonological processing.
The stage of processing which follows lexical retrieval in Biassou et al.'s model is
that of "phonemic planning", in which detailed phonological information is added
in a left-to-right fashion to the retrieved lexical representation.
This phonemic
planning process corresponds roughly to the phonological encoding process of
Levelt (1989), in which a fully specified phonological representation is accessed
and "spelled out"
(see Figure 1:2), to the process described by Dell (1986) whereby
phonological nodes are activated and selected for production, and to the
processing level putatively impaired in the familial patients reported by Kennedy
et al. (1995).
Because of the left-to-right nature of the phonemic planning
process, Biassou et al. hypothesised that deficits at this phonological level should
result in environmentally induced phonological errors, i.e. segment
anticipations, perseverations, and exchanges.
They argued that the DAT patients
in their study were relatively unimpaired at this level because they did not differ
from controls in their proportion of these environmentally-induced phonological
errors.
Biassou and colleagues did concede, however, that some errors of
phonemic planning may have arisen as a secondary consequence of the lexical
phonologic retrieval deficit, and that a mild phonemic planning deficit in DAT
could not be ruled out.
Thus, these two accounts of the source of phonological errors in the speech
production of DAT patients differ in the hypothesised locus of deficit.
In the
account given by Kennedy et al (1995), the deficit is attributed to the level of
phonological processing per se; in the account of Biassou et al. (1995), it is in the
retrieval of an abstract lexical representation which is partially specified for
phonological
information.
It should be stressed that the production of phonological errors in DAT is
rarely reported in the literature.
The predominant linguistic impairment in DAT
Chapter 6: Phonological Disruption in Atypical DAT
166
is usually claimed to be a word-finding deficit related to the patients' semantic
breakdown.
For contrast with the accounts of phonological errors in DAT outlined
above, the following section describes the type of account usually given for the
word-finding deficits which occur in the speech production of DAT patients.
Word-finding Deficits in DAT
In this chapter, the notion of "word-finding difficulty" is used to describe
occasions when the correct phonological target is not activated at all; thus in
conversation, patients omit words, or produce circumlocutions or semantic errors
or speech that is empty of content words (Appell et al., 1982; Glosser & Deser,
1990).
In more constrained tasks such as naming or category fluency, patients
with word-finding difficulty make no response, or make circumlocutions and
semantic errors (Bayles, 1982; Hodges et al., 1991).
This type of word-finding
disruption is frequently attributed to an impaired access to phonological
representations from semantics (e.g. Astell & Harley, 1996; Margolin, Pate,
Friedrich, & Elia, 1990) .
An illustrative single case study of the typical word-
finding deficit occurring in DAT is described by Funnell and Hodges (1991).
Funnell and Hodges reported that Mary, a 58-year-old woman with
presumed AD, had relatively preserved comprehension of items she could not
name, thus ruling out a primary semantic impairment as the cause of her naming
deficits.
She only named 27% of a set of 55 pictures correctly, but was able to give
correct definitions for 75% of pictures not named.
Further, impaired naming to
definition and an absence of visual errors in picture naming indicated that the
naming deficit was not due to impaired visuo-spatial processing of pictorial
naming stimuli, as had been the case for some of the DAT patients reported by
Kirshner, Webb and Kelly (1984) .
Funnell and Hodges also proposed that Mary's
near-perfect performance on reading and repetition indicated relatively
unimpaired phonological processing.
In the context of relatively preserved
visuo-spatial, semantic and phonological processing, Funnell and Hodges (1991, p.
177) attributed Mary's anomia to a "disorder of access from semantic descriptions
to the phonological lexicon".
Their demonstration that Mary's naming improved
when she was given phonological cueing supported this account, showing that a
small amount of phonological information was able to boost activation of the
phonological target sufficiently for production.
The Present Study
This chapter reports on four aspects of phonological processing in the
group of atypical DAT patients described below.
The first study explored the
nature of the patients' deficit in spontaneous speech, the second, the extent to
Chapter 6: Phonological Disruption in Atypical DAT
which phonological disruption occurred in non-propositional speech tasks.
167
A
third experiment investigated the patients' deficits in single word production, and
a final experiment considered the receptive word processing of a subgroup of the
patients.
CASE DESCRIPTIONS
The patients described in this chapter presented to a Memory Disorder
Clinic at Addenbrooke's Hospital and were willing to participate in a longitudinal
study of memory and language disorders in dementia.
come from 13 patients.
The data included here
Ten of these, who were given an original diagnosis of
probable AD (subsequently confirmed at autopsy in two cases) made phonological
errors in spontaneous speech and on neuropsychological language tests.
The
language performance of three additional patients with phonological disruption
originally fit the pattern of primary progressive aphasia, but these cases showed
Alzheimer-type pathology at autopsy.
(John R. Hodges).
All diagnoses were made by a neurologist
Diagnoses of probable AD were made according to the NINCDS-
ADRDA (National Institute of Neurological and Communicative Disorders and
Stroke and the Alzheimer's Disease and Related Disorders Association) inclusion
and exclusion criteria (McKhann et al., 1984).
These criteria include dementia
established by clinical examination, decline in memory and performance
affecting two or more areas of cognition as documented by neuropsychological
testing, no disturbance of consciousness, and an absence of systemic disorders,
other brain diseases, and psychiatric disorders which might account for the
dementia.
The patients classified as having probable AD were in many ways very
atypical.
Seven patients presented to the memory clinic with non-fluent aphasic
symptoms which dominated the clinical picture but were accompanied by other
cognitive deficits which could not be explained on the basis of their language
disorder (e.g. impaired memory, perceptual difficulties etc.; see Table 6:6:3 and
discussion of general neuropsychological profile below), and/or with a decline in
activities of daily living.
The remaining 3 DAT patients presented with features of
a progressive bi-parietal syndrome (severe visuo-spatial deficits often including
visual disorientation and simultanagnosia, dyspraxia and dysgraphia), and
developed phonological disruption with progression.
It should be noted that these
patients presented over a 4—5 year period during which time approximately 200
patients were assessed in the memory clinic.
Diagnoses of primary progressive aphasia followed the criteria proposed by
(Mesulam & Weintraub, 1992, Weintraub & Mesulam, 1993): progressive language
Chapter 6: Phonological Disruption in Atypical DAT
168
deficits in the context of preserved non-linguistic cognitive abilities for at least
two years, with activities of daily living otherwise unaffected over the same
period, again, occurring in the absence of disturbances of consciousness or other
systemic disorders or brain disease.
Because of difficulty in determining what
constitutes relative preservation of non-linguistic cognitive abilities, the
diagnosis of primary progressive aphasia was reserved for patients who
performed
within
the
normal
range
on
non-language-based
neuropsychological
tests (see also Chapter 2).
Six of the patients reported in this chapter have already been described in
the literature, although only in one case with detailed attention to the
phonological deficit.
P.G., one of the two non-fluent progressive aphasic patients
reported by Croot et al. (in press) and in Chapter 3 of this thesis, died several
months after the investigations described in those reports, and post-mortem
examination revealed extensive AD pathology (see Table 6:4).
A.S., reported by
Greene et al. (1996), is discussed in Chapter 5 as one of the three patients noted in
the literature whose non-fluent progressive aphasia was associated with
Alzheimer-type pathology.
An example of the conversational speech of P.G.
appears in Chapter 3, and a small sample of conversation from A.S. is given in
Chapter 5.
Chapter 5 also mentions patients N.K., J.G. and J.M. who had notable
phonological breakdown in the context of a progressive biparietal syndrome
(Ross et al., 1996).
Finally, P.B.'s surface dyslexic pattern of reading is reported by
Patterson & Hodges (1992) , where his non-fluent speech is also noted.
Four of the patients reported in this chapter were not tested on the
experimental tasks in the present investigation of phonological disruption in
atypical DAT because of disease severity at the beginning of the study (P.B., J.G.,
and J.M.), or sudden death (A.S.).
Instead, other results are reported which
illustrate these patients' phonological disruption in picture naming and reading
tasks.
These alternative data were collected prior to the commencement of the
present study as part of a larger longitudinal study of language and memory in
dementia being conducted by John R. Hodges and Karalyn Patterson (e.g. Hodges &
Patterson, 1995; Hodges & Patterson, 1996; Patterson et al., 1994a & 1994b) , and
clearly add weight to the argument for phonological breakdown in some atypical
cases of AD, because both P.B. and A.S. had autopsy-confirmed diagnoses of the
disease.
Some of the background demographic information about the patients, and
their difficulties on first presentation at the Memory Disorder Clinic, are
summarised in Tables 1 and 2 respectively.
There are roughly equal numbers of
men and women, from a range of occupational backgrounds.
handed and had a minimum of 9 years' education (Table 6:1).
All were rightTable 6:2 shows the
Chapter 6: Phonological Disruption in Atypical DAT
169
relatively young age of the group: 10 of the 13 patients first noted speech and
language difficulties before the age of 65.
Each of the ten patients who were
given a diagnosis of probable AD were nevertheless noted to have atypical
symptoms for AD because of profound aphasia in most cases, and because of the
apraxic, visuo-spatial and aphasic difficulties in the bi-parietal cases.
In three
cases (P.G., A.S. and P.B.), the aphasia was the only presenting symptom and the
diagnosis of primary progressive aphasia was given, although these patients were
subsequently shown at autopsy to have Alzheimer-type pathology.
Table 6:1.
Summary of demographic information about the patients.
Subject Sex Pref.
Hearing
Hand
Years
Previous
Educ'n Occupation
M.T.
F
R
unimpaired
9
shop assistant, catering
V.B.
F
R
unimpaired
10
waitress
G.D.
M
R
unimpaired
10
dock worker
R.S.
M
R
wore hearing aid ¶
11
company
C.M.
M
R
10
sales
S.W.
F
R
— 80 dB < 2000 Hz **
no hearing aid ¶
11
care
K.M.
M
R
9
factory
worker
N.K.
F
R
13
physical
educ'n
J.G.
M
R
13
garden
J.M.
M
R
no hearing aid ¶
no hearing aid ¶
11
lecturer, art college
P.G.
F
R
11
secretary
A.S.
M
R
wore hearing aid ¶
wore hearing aid ¶
13
cannery
worker
P.B.
M
R
no hearing aid ¶
12
company
director
—50—70 dB > 4000 Hz*
no hearing aid ¶
Mean
11
(s.d.)
(1.4)
manager
representative
assistant
teacher
design
KEY: ¶ = audiometric data not available; unimpaired hearing indicates hearing
intact to -30dB from 500-8000 Hz; ** = severe to profound loss; * = moderately
severe loss; > = above, < = below.
Chapter 6: Phonological Disruption in Atypical DAT
Table 6:2.
Summary of information about patients at presentation.
Subject A g e Presenting
MT
VB
66
56
Length
of Family
RS
61
65
History
Diagnosis
Symptom(s)
History
of
severely reduced
18 months
mother (d. 66 yrs)
DAT with severe
speech output,
became vague in
aphasia
impaired
later years
writing
grammatical errors in
12 months
language
GD
170
word-finding & phono-
9 months
Dementia
mother had dementia DAT with severe
in final years
aphasia
nil
non-fluent
logical errors, compre-
progressive
hension problems
or DAT
word-finding & phono-
18 months
nil
aphasia
DAT with unusual
language disorder
logical errors, memory
problems
CM
77
word-finding and
12 months
memory problems
SW
52
memory problems and
subsequent
mother (d. 83 yrs)
DAT with profound
demented in late 70s a p h a s i a
2 years
father (d. 86 yrs)
DAT with marked
demented late in life a p h a s i a
severe
aphasia
KM
64
word-finding and
9 months
nil
memory deficits
NK
54
impaired
writing,
spelling,
praxis,
DAT with progressive aphasia
12 months
nil
atypical DAT; biparietal
syndrome
visuoperception
JG
53
impaired praxis &
visuospatial
JM
68
3 years
nil
abilities
impaired praxis &
parietal
5 years
nil
writing
PG
74
loss of speech fluency
atypical DAT, bi-
atypical DAT, biparietal
2 years
nil
syndrome
syndrome
non-fluent
pro-
gressive aphasia
AS
66
speech faltering with
5 years
nil
non-fluent
pro-
gressive aphasia
phonological errors,
writing problems
PB
71
word-finding &
6 years
phonological errors
mother (d. 87 years)
mixed primary
demented late in life progressive
mean
63.6
28.2 months
(s.d.)
(8.1)
(21.9 mths)
aphasia
Chapter 6: Phonological Disruption in Atypical DAT
171
The patients' performance on general neuropsychological testing,
summarised in Table 6:3, was heterogeneous.
For example, the patients who were
reported by Ross et al. (1996) as having progressive biparietal syndrome (N.K., J.G.
and J.M.) showed comparatively poorer performance at presentation on visuospatial and perceptual tests such as Object Matching (Humphreys & Riddoch,
1984), Line Orientation (Benton, 1983) and copying the Rey complex figure (Rey,
1941). By contrast, P.G. and P.B., two of the patients initially diagnosed with
primary progressive aphasia, performed within normal limits on two memory
tests, the recall of the Rey figure and Warrington's Recognition Memory Test
(1984).
(A.S., the third patient diagnosed with progressive aphasia was in the
impaired range on many tests, but had a 5 year history of language decline before
presentation for assessment.)
Other patients performed within the impaired
range on almost all tasks at presentation (e.g. V.B. and G.D.).
Chapter 6: Phonological Disruption in Atypical DAT
Table 6.3 in separate file
172
Chapter 6: Phonological Disruption in Atypical DAT
Table 6.3 (continued) in separate file
173
Chapter 6: Phonological Disruption in Atypical DAT
174
The distribution of pathology (identified either by in vivo MRI and/or
SPECT imaging or by post-mortem analysis), although somewhat heterogeneous
across these 13 patients, is consistently atypical for Alzheimer's Disease, focusing
mainly on the perisylvian regions of the left hemisphere, rather than the more
characteristic medial temporal regions.
Details of the location and nature of
pathology are given in Table 6:4.
Table 6:4.
continues
Summary of imaging or neuropathological data for the patients.
overleaf.
S u b j e c t Nature
M.T.
V.B.
G.D.
C.M.
and
Distribution
of
Pathology
Source
i) mild atrophy only (poor quality image)
i) MRI
ii) marked left temporoparietal hypoperfusion
ii) SPECT
i) moderate diffuse atrophy
i) MRI
ii) severe left temporal hypoperfusion, left parietal hypoperfusion
ii) SPECT
i) moderate global atrophy especially left perisylvian areas
i) MRI
ii) marked left temporoparietal hypoperfusion, mild bilateral
ii) SPECT
parietal
R.S.
Table
hypoperfusion
i) moderate global atrophy, greater in left hemisphere
i) MRI
ii) bilateral temporoparietal hypoperfusion
ii) SPECT
mild general cerebral atrophy with moderate medial temporal
Post-mortem
involvement, moderate-severe neuronal loss in medial and lateral
neuropathology
temporal lobe.
L hemisphere
Numerous plaques and tangles especially in
temporal pole and Broca's area
S.W.
K.M.
i) minimal atrophy only
i) MRI
ii) bilateral temporoparietal hypoperfusion
ii) SPECT
i) general atrophy most marked left temporal lobe
i) MRI
ii) severe left temporal hypoperfusion, less marked hypoperfusion
ii) SPECT
in left parietal area
N.K.
generalised cerebral atrophy, especially superior parietal lobules
Post-mortem
and medial occipital (visual) cortex; neuronal loss greatest in
neuropathology
parietal cortex but moderate in medial temporal areas; widespread
L hemisphere
neuritic plaques and tangles with concentration in parietal areas
J.G.
i) Focal left temporoparietal hypoperfusion, right parietal
i) SPECT
hypoperfusion (at presentation)
ii) mild generalised atrophy, focal parietal atrophy, preserved
medial temporal complex (2 years post-presentation)
ii) MRI
Chapter 6: Phonological Disruption in Atypical DAT
Table 6:4.
Continued from previous page.
S u b j e c t Nature
J.M.
175
and
Distribution
of
Pathology
Source
i) Biparietal hypoperfusion (at presentation)
i) SPECT
ii) asymmetrical atrophy, especially left temporal and parietal
ii) MRI
areas (2 years post-presentation)
P.G.
moderate cerebral atrophy, especially frontal and parietal areas,
Post-mortem
widespread plaques and tangles especially superior parietal lobule, neuropathology
A.S.
P.B.
medial temporal regions and temporal pole
L hemisphere
moderate cerebral atrophy, especially in frontal & parietal areas;
Post-mortem
neuronal loss, neuritic plaques & neurofibrillary tangles in peri-
neuropathology
sylvian frontal & parietal areas, but sparing medial temporal lobe
L hemisphere
mild general atrophy with severe temporal lobe involvement
Post-mortem
(especially the pole and anterior 2/3), severe neuronal loss in
neuropathology
temporal pole.
L hemisphere
Plaques and tangles especially in temporal pole,
inferior occipitotemporal junction and inferior parietal area
ANALYSIS OF SPONTANEOUS SPEECH
The first investigation of the patients' phonological processing was
concerned with the degree of phonological disruption in spontaneous speech.
Unlike the DAT patients reported in the spontaneous speech studies of Appell et al.
(1982), Glosser & Deser (1990), and Blanken et al. (1987), these patients were all
noted on assessment to make phonological errors in speech production.
One aim
was to compare the rate of phonological errors in these patients' speech with
their rate of lexico-semantic errors, because more typical presentations of DAT
are characterised predominantly by lexico-semantic deficits.
A second aim was to
characterise in more detail the nature of the phonological deficits, in order to
evaluate the accounts of phonological errors in DAT proposed by Kennedy et al.
(1995) and Biassou et al. (1995).
Although not specifically derived from an empirical study of spontaneous
speech, both these accounts would predict that these patients should have faulty
production of phonological word forms in spontaneous speech.
Kennedy et al.'s
account of local phonological disruption would predict the occurrence of frank
phonological errors.
Biassou's lexical retrieval deficit would predict a number of
errors on the initial consonant and stressed vowel but that, if these features of a
word emerge intact, the rest of the word should have a high chance of being
successfully
produced.
Chapter 6: Phonological Disruption in Atypical DAT
176
Finally, to the extent that the patients have word-finding difficulties in
addition to their phonological deficits, it was expected that on occasions there
would be below-threshold activation of the phonological target from the semantic
specifications of the patient's intended message in conversational speech.
On
these occasions, the patient would be expected to omit words required by the
context, or to produce circumlocutions or semantically-related errors.
Method
Samples of Conversational Speech
Samples of conversations between the patient and one or two
experimenters, which had been systematically video-taped during breaks in
general neuropsychological testing in order to obtain naturalistic speech
samples, were transcribed and analysed for the occurrence of phonological and
word-finding errors.
Conversational samples from ten of the patients were
analysed (as video-taped samples from J.G., J.M., and P.B. were not available).
The
topic was usually the patient's holidays or family, although the conversation with
R.S. was about his previous job, the conversation with S.W. was about where she
used to live, and that with N.K. was about the neuropsychological testing
materials.
At the time of the conversation, none of the conversational partners
knew the analysis was to take place.
Most of these speech samples were recorded
on the patients' first assessment for phonological disruption, with the exception
of those from K.M. (second round of testing, 6 months after presentation), and V.B.
(second round of testing, 12 months after presentation), and all were transcribed
by the author to achieve consistency of criteria.
A sample of audio-taped
conversation with P.B., two years after his first presentation and 18 months
before the beginning of the current study, had been transcribed by Naida
Graham, a research assistant to John R. Hodges and Karalyn Patterson at that time.
Because it was not possible to ensure consistency of transcription, this sample is
not included in the analysis, but an extract is given in Table 6:5 to demonstrate
that his production errors were very similar to those of the other patients.
Chapter 6: Phonological Disruption in Atypical DAT
Table 6:5.
177
Example of P.B.'s speech; errors are shown in b o l d font according to
the categories described below (omissions are not indicated).
u m and a h (laughs) this is a funny one.
were
and, a n d we u h we we um we were teaching, w e
teaching a sort of [ S ç l ] u h sort of thing u h for f o r the for the [ S ] for the
( u n i n t e l l i g i b l e ) and it was absolutely [ d
dru], absolutely down.
In in the u h in the [ m ´] a h after breakfast, but it's down (laughs) [ ´ n ] the and I say and
and I I get a lot of [ U D i] I I had I said I'll g o come and there's there's a lake [ ´ D Q] that
u m that [ √n ] [bU ] and [ T ] thing with the u h this the u h the water course [ d r Q] up here
somewhere.
Word counts for each patient's speech sample were obtained using the
Microsoft Word 5.1a word counting function (Microsoft Corporation, 1991); "word"
status was therefore accorded to any material bordered by spaces/full
stops/commas in the typed transcript.
Thus, incomplete portions of words
represented in the International Phonetic Alphabet, and fillers represented
orthographically as "um", "er" etc. were all counted as individual words.
Where a
word or words were presumed to be omitted, the presumed omissions were not
added to the total because there was no way of estimating how many words were
actually omitted.
The amount of speech produced in conversation varied considerably across
patients depending on the severity of their speech production deficits.
The actual
volume of output, however, was not of interest because there was no control for
the length of the conversational sample obtained from each patient, but details of
the number of words in the sample analysed for each patient are given in Table
6:6.
The measures of interest were, firstly, the overall rate of error as a measure
of the degree of impairment to conversational speech, and secondly, the nature of
the errors, with the most important question being the degree of phonological
impairment present in the spontaneous speech of these patients.
Table 6:6.
each patient.
Characteristics of the sample of conversational speech analysed for
Percent errors is the ratio of total errors to total words, with single
word yes/no responses excluded from the word total.
N.K. M.T.
V.B.
P.G.
G.D.
R.S.
C.M. S.W. K.M.
A.S
Total words produced
64
72
110
67
343
239
200
348
630
227
Total without yes/no
60
45
74
54
318
166
184
341
596
214
Total errors
40
20
31
21
111
42
40
62
97
31
66.7
44.4
41.9
38.9
34.9
25.3
21.7
18.2
16.3
14.5
Percent
errors
Chapter 6: Phonological Disruption in Atypical DAT
178
The overall rate of error in each patient's sample of conversational speech
was calculated as the ratio of total errors to total words, expressed as a percentage.
Single word yes/no responses were excluded from the word total (see Table 6:6)
because, in the case of the most impaired patients, these responses did not reflect
the patient's overall word production so much as the number of questions asked
by the experimenter.
The total number of errors was the sum of errors in each of
the categories described below.
Error Categories
Two types of errors in the patients' word production were scored as
phonologically disrupted errors.
In the first, classified here as "false start"
errors, only the initial sound(s) of a word were produced, and often another
attempt followed immediately afterwards or within a few words.
(Strings of such
attempts are known as successive phonemic approximations, or as "conduit
d'approche" responses when the attempts increasingly approximate the correct
target (see Chapter 1))
resulting
in
The second type was frank phonological errors, usually
nonwords.
Several types of error were scored as word-finding errors, indicating a
failure to produce the required phonological target at the moment when it was
required.
These were word or phrase repetitions, speech fillers (such as um, er,
you know), circumlocutions, semantic errors, and omissions (occasions where a
word which was needed to complete an idea was missing, with none of the other
phenomena
present).
Extracts of the analysed conversations with N.K., G.M., S.W., and K.M. are
shown in Table 6:7, to illustrate the various types of error, and something of the
range of the severity of impairment in spontaneous speech (with N.K. most
impaired and K.M. one of the least impaired).
Errors are shown in b o l d font
according to the following key:
i)
ii)
Phonologically Disrupted Errors:
[phonetic
brackets] = false start errors
[phonetic
brackets
with
underline] = frank phonological error
Word-finding errors:
u n d e r l i n e = repetitions of words or phrases
* =
speech fillers
i t a l i c s = circumlocutions and semantic errors
( O M I T ) = word omitted or idea incomplete but with none of the other
phenomena present
Chapter 6: Phonological Disruption in Atypical DAT
Table 6:7:
179
Examples of conversational speech from N.K., G.D., S.W. and K.M.,
showing errors in b o l d font.
1) N.K.
N.K.
K.C.
N.K.
K.C.
N.K.
K.C.
N.K.
K.C.
N.K.
mm try [ oU´] you'd'e ( O M I T ) you gotta
a h * [ j´] you you you new n e w [lÅ ]
lotta [ b´ b´] er* you you [ g´] ah* [ av]
cards
lose a lot of cards?
yeah er* you y o u no
[ j´] you ( O M I T ) you've got have a new
n e w [ u u √nz]
I use a lot of cards?
yes
yes?
a h * right, and these are er* er* er*
new ones!
These are new ones?
yes
2) G.D.
K.C.
G.D.
K.C.
G.D.
K.C.
G.D.
K.C.
G.D.
K.C.
G.D.
and who's coming to visit you?
my [ s] ah* [f ] [s] er* [ s] s i s t e r
e r * [ l´bE]
your wife's coming?
wife that's [ w ]
mhm
yeah
what time did you say she was
going to come?
that I couldn't tell you, really I
was I was
that's right
'cause I [ SoU SoU] know
but I reckon it's gonna be 'bout two
3) S.W.
4) K.M. (about a visit to Ireland)
N.G.
S.W.
K.M.
N.G.
S.W.
N.G.
S.W.
N.G.
S.W.
Did you grow up in London?
Yes! I'm a Londoner, yes
Right from the [ b ] right from the [ T Π]
you know* from the bottom to the
t o p (shakes head)
What part of London are you from?
the city, but in the [ m] [I] right, right,
well no not in the [ s] right in the
middle of the city, but its in the city
yes, that's where Old [ bIzi ] Where Old
Bill B i l l is you know*, the er* yes
So you're from that one square mile
that's the city, are you?
yes I mean er* me Dad was [ bç] born in
in that part of the world but [ Im Imi ]
you know* immediately you e r *
Where are the Cockneys from? Is that
near there?
In the middle of ( O M I T )
In the middle of the city
I think is what they ( O M I T )
I'm not too sure though
yeah we went up the ( O M I T )
what the heck did we call that?
when you go over oh! [ bl´ bla ] er*, no
the stone. What was that? and er* I
asked u m * I said "[ w´ ] Where can I get
a .....paper?" and er* "oh!" the ( O M I T )
"oh!" said one of them — only young
people — and they got hold of me
h a n d er* not e r * not e r * me arm
[ ´nç] er* er* never said nothing, took
us up.....'bout ooh three or four
hundred yards, something like that,
s o m e t h i n g and got me a [ p] she [ st ]
did — paid for it as well, she did, yeah
(laughs)
see they got the cor* whatever
they got the ( O M I T ) on the s o u t h
there, the [ s] south west. No I
don't
know. er* they (OMIT) I don't
know, it
was somewhere you can go er*
you can
go right round
can't think of the name of it
Chapter 6: Phonological Disruption in Atypical DAT
180
Results
Figure 6:1 shows the overall rate of errors produced by each patient (with
yes/no responses excluded from the total number of words as described above),
and Table 6:8 shows the percentage of each subtype of error which was produced.
Although the quality and amount of speech produced by any of the patients would
be expected to vary with context and occasion, it was the author's impression from
regular interaction with these patients over several testing sessions that these
samples did reliably reflect the "typical" characteristics of the patients output
deficits.
100
%
errors
80
60
40
20
0
NK MT VB PG GD RS CM SW KM AS
Figure 6:1.
Rate of errors made by ten DAT patients in spontaneous speech
(removing yes/no responses from total number of words).
Chapter 6: Phonological Disruption in Atypical DAT
181
In Table 6:8, patients are ranked from left to right according to severity of
spontaneous speech, and it is apparent that while all patients produced errors of
almost all types, there is no relationship between any particular type and the rate
of errors overall.
(The only exception to this is that the patients with most
severely impaired output made few phrase repetitions or circumlocutions,
presumably because they were no longer able to produce phrase-length
utterances.)
This ranking according to severity of output in spontaneous speech
is used throughout the remainder of this chapter to organise the presentation of
material from these 10 patients in tables and figures.
Table 6:8.
Percentages of different types of error produced by each patient.
% Error Types
N.K. M.T.
V.B.
P.G.
G.D.
R.S.
C.M. S.W. K.M.
A.S
Phonological
false starts
20
0
3.2
4.8
25.2
14.3
22.5
38.7
18.6
6.5
15
50
9.7
14.3
47.8
31
20
12.9
11.3
22.6
repetitions 22.5
20
16.1
4.8
5.4
2.4
5
8.1
2.1
6.5
repetitions
7.5
5
6.5
0
2.7
0
0
3.2
4.1
0
30
25
54.8
57.1
10.8
40.5
35
12.9
42.3
32.3
circumlocutions
0
0
3.2
0
0.9
4.8
5
1.6
2.1
3.2
semantic
errors
0
0
3.2
4.8
0.9
0
2.5
1.6
1
0
omissions
5
0
3.2
14.3
6.3
7.1
10
21
18.6
29
frank
phon.
errors
Lexico-semantic
word
phrase
speech
fillers
Chapter 6: Phonological Disruption in Atypical DAT
182
Figure 6:2 shows the percentage of phonologically disrupted versus wordfinding errors produced by each patient, with patients again ranked according to
overall severity.
This figure shows very clearly the pattern, also documented in
Table 6:8, that although a considerable percentage of the patients' total errors
involved inadequate activation of a phonological target, the proportion of
phonological errors was not related to general severity of output deficit.
phonologically
word-finding
disrupted
error
100
% total errors
80
60
40
20
0
NK MT VB PG GD RS CM SW KM AS
Figure 6:2.
Rates of phonologically-disrupted and word-finding errors produced
in spontaneous speech.
Discussion
This analysis of a sample of conversational speech from these ten patients
shows that their spontaneous speech disruption reflected a combination of
phonological and word-finding deficits, not simply word-finding difficulty as is
claimed to be more typical for DAT patients in general.
The extent to which each
type of impairment affected their speech differed across patients, and was not
simply related to severity.
Spontaneous speech may not be an optimal measure of
word-production difficulty, however, because the patients are somewhat free to
avoid words and constructions which they may find difficult to produce.
The patients made at least two types of phonological error in spontaneous
speech.
In the false-start errors, only the beginning of a word was activated,
Chapter 6: Phonological Disruption in Atypical DAT
183
whereas in the frank phonological errors, the phonological target showed some
other disruption.
The false-start errors appear to reflect an opposite problem to
that of the patients reported by Biassou et al. (who made half their phonological
errors on sounds in word-initial position) because, in such errors, the beginning
was the o n l y part of a target word's phonology available.
Thus, in false start
errors, at least some of the phonological information hypothesised by Biassou and
colleagues to be represented at the lexical level was retrieved, but the full
phonological form could not be specified.
By contrast with Funnell and Hodges'
(1991) patient Mary, who had difficulty accessing phonology from semantics, and
who could frequently be cued to retrieve the full form with an initial phoneme,
the patients in this study h a d retrieved the initial sound on the false-start
occasions, but this did n o t guarantee retrieval of the full phonological form.
Thus, the pattern of these patients' errors in spontaneous speech suggests they
had difficulty in producing a fully-specified phonological form, implying a
deficit at the level of phonological processing itself.
This account is more like
that of Kennedy et al. (1995) than that of Biassou et al. (1995).
Like the patients in
this study, the phonologically impaired cases reported by Kennedy et al. also made
a high rate of false-start errors.
In addition, however, the range of error types summarised as word-finding
difficulty indicated that on many occasions there was not sufficient phonological
activation for the patients even to attempt a target.
These word-finding
difficulties suggest the same sort of impaired access to phonological
representations from semantics as described by Astell and Harley (1996), Funnell
and Hodges (1991) and Margolin et al. (1990).
In conversational speech, the production of utterances is semanticallydriven.
According to Hughlings Jackson (1874) , this is the most propositional
form of speech production.
The next analysis considered the phonological
integrity of the DAT patients' speech in common production tasks which are not
propositional.
ANALYSIS OF SERIES SPEECH
Non-propositional speech tasks involve the production of overlearned
forms which have become linguistically familiar through frequent use.
Such
tasks include counting, and reciting well-known nursery rhymes or series such
as the days of the week, months of the year or alphabet.
The completion of idioms
and familiar phrases, the use of certain social greetings and clichés ("How are
you?", "Fine, thanks"), and swearing are also examples of non-propositional
speech (Lum & Ellis, 1994) .
Chapter 6: Phonological Disruption in Atypical DAT
184
Some aphasic patients are reported to show preservation of these types of
speech in the context of other severe language losses (Cummings, Benson, Walsh,
& Levine, 1979; Trojano, Fragassi, Postiglione, & Grossi, 1988) .
This preservation
may occur because the overlearned nature of the utterances makes them less
vulnerable to acquired brain damage, or because of the contribution an
unimpaired right hemisphere makes to their production (Ingvar & Schwartz,
1974) .
Another theory suggests that the memory representations for overlearned
speech series are represented more strongly at a phonological level than those
used to produce propositional speech (Van Lancker, 1987) , or that, because the
sequence of phonological information is invariable for any series, it comes to be
represented as a single unit or "giant word" in the phonological lexicon (Lum,
1996; Swinney & Cutler, 1979) .
By any of these accounts, production of non-
propositional speech in DAT should be relatively unimpaired if the patients'
predominant aphasic difficulties are associated with lexico-semantic deficits
leading
to
word-finding
difficulties
in
semantically-driven/propositional
speech.
By contrast, a disruption to the phonological structure of words in nonpropositional speech tasks would implicate a deficit at the phonological level if
such utterances are primarily represented at this level.
With regard to the specific accounts of phonological breakdown in DAT
considered above, it is difficult to make predictions from Biassou et al.'s account
because not enough is known about exactly how non-propositional series are
represented with regard to two-stage theories of lexical access.
Kennedy et al.'s
account, describing a deficit at the level of phonological processing per se,
predicts that the patients' production of overlearned series would be impaired.
Method
and
Results
Nine of the patients were asked to count from 1 to 20 and to say the days of
the week, months of the year, and alphabet.
If they appeared uncertain of the
task requirements, the patients were cued with "Monday" for the days of the week,
"January" for the months, and "A-B-C" for the alphabet.
N.K. was only asked to do
the counting task; R.S. was only willing to count from 1 to 10; P.G. was not willing
to attempt the days of the week.
Patients' performance on these tasks is reported
for the same round on which the sample of spontaneous speech was obtained.
The patients' responses are shown in Tables 9 to 12, in approximate order of
increasing difficulty, which was as follows: counting < days of the week < months
of the year = alphabet.
The downward sequence of uninterrupted ticks indicates
how far any one series was unimpaired for each patient, and the column ends at
the point at which the production of that series was discontinued.
The ranking of
Chapter 6: Phonological Disruption in Atypical DAT
185
patients from left to right according to overall error rate in spontaneous speech
highlights the tendency for the more impaired patients to discontinue the
production of any of the series at an earlier point than the less impaired patients.
Thus, the patients' degree of impairment in these tasks mirrors the extent to
which they were impaired in spontaneous speech.
The tasks were not performed in the same order by each patient; the order
of task performance is shown together with the patients' initials in the column
titles in each of Tables 9—12 (e.g. PG/T2 in the counting task means P.G. performed
this task second, after attempting the months, where her column is headed
PG/T1).
Order of task performance indicates whether interfering material from
other speech series in the patients' responses was perseverative or not.
The
lightly-shaded boxes in Tables 9-12 contain intrusive material perseverated from
earlier tasks.
In some cases such interference was perseverative (e.g. V.B.'s
production of months while counting); in others it was not (e.g. G.D.'s switch to
counting while saying the months of the year).
Table 6:9.
Eight DAT patients' performance counting from 1 to 20.
The code beside
each patient's initials indicates the order of task performance (T1 = 1st task, T2 =
2nd task, T3 = 3rd task, T4 = 4th task), the shaded box indicates material
perseverated from an earlier task.
1
2
3
4
5
NK/T1
MT/T4
VB/T4
PG/T2
GD/T4
CM/T1
SW/T4
KM/T4
dZQ
dZQdZu´ri
10, 10
10,10
4, 4
February
tatS, Qt´l
6
7
8
9
1 0
1
1
1
1
1
1
1
1
1
2
1
2
3
4
5
6
7
8
9
0
7, 7
9, 9
10, 10
7, 7, 8
9, 10
7, 7
11, 11
20
Chapter 6: Phonological Disruption in Atypical DAT
Table 6:10. Six DAT patients' performance saying the days of the week.
MT/T1
VB/T1
GD/T1
CM/T2
SW/T1
KM/T1
´ndi
n´
n´
n√m
Mon
n√mbeI
Tue
tu
Wed
weI,
w√ndeI, 2,
3, 3, f, 4,
f, 3, f
Thur
Fri
Sat
phon
error on
[d] in day
phon
error on
[d] in day
Sunday
TŒndi
Friday
Sunday
phon
error on
[d] in day
Saturday
Sun
Table 6:11. Seven DAT patients' performance saying the months of the year.
MT/T2
VB/T2
PG/T1
GD/T2
CM/T3
SW/T3
KM/T2
dZQdZu´ri
Jan
Monday
March
dZQnj´
5 of the
m´
wErEri,
dZQdZu´ri
mQ,mQdZ
mQd
mQdZ´ri
um March 1 3 , 1 4 , 1 5 ,
no
16,17,
18,18,19,
20,21,22
Feb
Mar
June
dZQndri
June
dZQnri
June , dZQ
June , n o
Apr
May
, May, P,
Q,R,S,T,U
June
July
Aug
Sept
dZeI s´, tsEk´n
t´ri father
Saturday
Oct
Nov
Dec
July,
August
186
Chapter 6: Phonological Disruption in Atypical DAT
Table 6:12. SevenDAT patients' performance saying the alphabet.
MT/T3
VB/T3
PG/T3
GD/T3
CM/T4
SW/T2
A
vE vE very
April
and um
B
C
D
E
F
G
G,B,B,
G,H
187
KM3
eIp´l, ´t´l
, G,G,
dZEn, G,11
H
I
J
say, s´,
H,A,A,
January
January
January, f a
A, , 1 1
it's run
out of gas
K
L
M
N
O
P
Q
R
S
T
Discussion
The DAT patients were clearly impaired in the production of overlearned
series, which, according to Lum and Ellis (1984) and Lum (1996), depends heavily
on phonological processing if carried out non-propositionally.
Lum and Ellis
(1984) demonstrated that counting was performed more automatically than
reciting the days of the week or the months of the year in a group of 28 aphasics
of stroke aetiology.
The DAT patients in the current study were also more
successful on the counting task (especially from 1—10) than on the other tasks,
suggesting that their production was facilitated by greater automaticity of a task.
Nevertheless, even on a task such as counting from 1—20, which normal subjects
perform flawlessly, several patients made repetition errors (N.K., M.T., P.G., S.W.,
K.M.) and V.B. perseverated material from the months of the year.
Thus, some
patients were clearly impaired on this most automatic and well-learned of speech
tasks, although perhaps only in V.B.'s case did the disruption in counting clearly
Chapter 6: Phonological Disruption in Atypical DAT
188
implicate phonological impairment rather than possible memory or attentional
deficits.
The phonological errors on the days and months tasks may perhaps have
been due to the phonological difficulty of some individual items because of their
length and/or the presence of consonant clusters (e.g. Wednesday, Saturday,
January, September), in the same way that polysyllabic items elicit more errors
than monosyllabic words in single word production tasks (see Chapter 3 of this
thesis).
The same cannot have been true of errors in the alphabet task, however,
as all the names of individual letters of the alphabet are monosyllabic (with the
exception of W, which none of the patients reached).
Lum and Ellis (1994) suggest that one explanation for the patients' deficits
on these series speech tasks may be that the patients are not, in fact, performing
them non-propositionally.
Patients may be stopping to think, for example, about
what comes after Thursday.
In that case, access deficits from semantics to
phonology, as described by Funnell and Hodges (1991), might also contribute to
impaired
performance.
In conclusion, there are some difficulties in interpreting the patients'
performance on these tasks, due to differing theoretical accounts of the extent to
which non-propositional series are uniquely represented at the phonological
level, and to some uncertainty about the degree to which the tasks were
performed non-propositionally by these patients.
Nevertheless, because series
speech tasks are so well-rehearsed, the predictability of one phonological form
from the preceding one is extremely high, yet this did not enable these patients to
produce these series correctly.
Furthermore, while the high level of
interference between tasks for some patients perhaps indicates that these tasks
should not have been performed without a break between them, the interference
also provides a further demonstration of the patients' impairments.
The strong
predictability from one item to another which is assumed to operate in the normal
phonological system for overlearned sequences not only fails to constrain
production to the correct phonological form, it fails to the extent that other
material which normally requires different constraints may be introduced.
SINGLE WORD PRODUCTION
The above analyses of the speech production of the atypical DAT patients
show that they made phonological errors in both propositional and nonpropositional speech tasks, and that their output in spontaneous speech was
characterised by both word-finding difficulty and phonological impairment.
In
single word production tasks, too, the patients' performance would be expected to
Chapter 6: Phonological Disruption in Atypical DAT
reflect both types of deficit.
189
Thus, in a semantically-driven task such as naming,
both word-finding and phonological errors should arise, whereas in repetition
and reading tasks, errors should be predominantly phonological because the
phonological information in the task stimuli facilitates activation of the target
form and thus avoids most word-finding difficulty.
Compared with the analysis of
spontaneous speech, single word tasks allow the rates of phonological versus
word-finding disruption to be quantified with more certainty because the targets
are closely constrained.
The patients' performance on single word production
also provides a further opportunity to test the hypothesis of Biassou and
colleagues that phonological errors in DAT reflect impaired retrieval of lexical
representations with word-initial phonological specification.
This hypothesis
was not upheld by the pattern of errors produced by the atypical DAT patients in
spontaneous
speech.
In Biassou's account, the absence of environmentally-influenced errors (as
well as the relative intactness of the ends of words compared with the
beginnings) was interpreted to mean that phonemic planning was relatively
unimpaired.
In single word repetition, however, the absence of
environmentally-influenced errors may simply reflect a comparative lack of
short term memory load in this task.
Some of the sentences in the Biassou et al.
study were at least 9 words long and contained centre-embedded subordinate
phrases, thus the involvement of immediate memory processes in the
phonological errors generated in this study cannot be ruled out.
In the present
study the patients' performance on single word repetition will indicate whether
their phonological output processing is disrupted in the absence of such a shortterm memory confound.
Method
Naming, Repetition and Reading: 9 Patients
Nine of the DAT patients performed the experiment described in earlier
chapters (see Experiment 1, Chapter 3), in which the same 180 words are elicited
in naming, repetition and reading tasks presented over three testing sessions.
Five of the patients (M.T., V.B., G.D., R.S. and K.M.) performed this task on two
rounds of testing, and longitudinal results are reported for these patients in a
separate section below.
Because of restrictions on time available for testing, S.W.
only performed one round of the experiment (n = 60 per task), and on Round 2 of
testing, V.B. and G.D. also only produced 60 items per task.
N.K. was unable to
complete the whole task, so her results are based on 45 items in naming, 60 in
repetition, and 27 in reading, produced in one session (with no repetition of items
Chapter 6: Phonological Disruption in Atypical DAT
across tasks).
190
As on previous administrations of this test, the patients' responses
were transcribed in situ and transcriptions were later checked against a video
recording of the testing session.
Responses in all tasks were categorised according to the criteria developed
from those of Martin et al. (1994) and described in full in Chapter 3, for the first
experiment with non-fluent progressive aphasic patients.
As in the earlier
experiments reported in this thesis, the first response was the one scored.
Tables
showing the rates of all ten response-types produced by each patient in each of
the three tasks, on all rounds of testing reported here, are given in Appendix I.
The text will focus on various subsets of these responses, created to approximate
the phonological disruption and word-finding categories used earlier in the
analysis of the patients' spontaneous speech.
The measure of responses showing
phonological disruption was obtained by summing the percentage of responses in
the formally-related neologism and formal paraphasia categories.
The measure of
word-finding difficulty was calculated from the sum of the visually/semantically
related word, visually/semantically related neologism and no response categories.
In addition, the responses in the formally a n d
visually/semantically-related
category were equally distributed between the phonologically-disrupted and
word-finding error measures.
Not included in the measures of phonological
disruption and word-finding difficulty were errors in the categories unrelated to
the targets — unrelated words, abstruse neologisms and perseverations.
It had not
been possible to distinguish the phonologically and semantically unrelated
utterances in spontaneous speech because the patients' targets could not reliably
be known when they made errors.
False start errors were scored for incorrect productions in which the
patient produced a minimum of the correct initial phoneme of the target (with or
without additional phonological information) then immediately made another
attempt which also began with the target phoneme.
As a measure of likely
success at retrieving the whole target, the number of targets correctly produced
within three attempts was also noted.
Picture Naming: DAT Patients compared with Elderly Controls
To ensure that the DAT patients were not simply showing age-related
deficits in naming (as demonstrated by (McKendrick & Armstrong, 1995) , of
elderly patients on the Boston Naming Test), the naming subtest of this
experiment was also performed by 10 controls from the Applied Psychology Unit
subject panel.
Controls were matched to the patients on age and years of
education and approximately matched on degree of hearing loss (relevant to the
section below on Receptive Word Processing).
As a group, the controls were
Chapter 6: Phonological Disruption in Atypical DAT
191
slightly older than the patients, although the difference did not reach statistical
significance (t 2 1 = 1.53, p = 0.14). A summary of demographic information about
the controls is provided in Table 6:13; the rates of all ten response-types produced
by each control in this task are given in Appendix II.
Control data were only
obtained for naming because this is consistently the most difficult of the three
tasks, and, as expected, most of the control subjects performed near ceiling.
Control responses were only transcribed in situ as there were few phonological
errors.
Table 6:13.
Summary of demographic information about the control subjects.
Subject Sex
Age
Hearing
Years
Previous
Educ'n Occupation
C1
M
50
unimpaired
10
computer
C2
M
66
unimpaired
11
graphic
C3
F
68
unimpaired
9
civil
C4
M
80
unimpaired
11
traffic
C5
M
62
—55—70 dB > 2000 Hz*
10
laboratory
C6
M
76
—50—80 dB > 4000 Hz*
9
meter
C7
F
56
—45-55 dB > 4000 Hz*
11
clerk
C8
M
82
—45—70 dB > 1000 Hz*
11
telephone
C9
F
78
—35—70 dB > 4000 Hz*
11
machine
C10
F
79
—35—80 dB > 2000 Hz**
11
secretary
Mean
69.7
10.4
(s.d.)
(11.1)
(0.8)
engineer
artist
servant
engineer
technician
reader
engineer
operator
KEY: unimpaired hearing indicates hearing intact to -30dB from 500-8000 Hz;
** = severe to profound loss; * = moderately severe loss; > = above.
Chapter 6: Phonological Disruption in Atypical DAT
192
Results
Picture Naming:
DAT patients compared with elderly controls
Controls named an average of 92.7% of the 180 pictures correctly (s.d. = 7.5,
range = 78.3% to 99.4% correct).
This mean is, however, skewed by the
comparatively poor performance of two controls (C9 and C10).
C9 named 80% of
items correctly, C10 named 78.3% correctly; none of the other controls named
fewer than 92% of items correctly.
Although the performance of controls in this
study supports the finding of McKendrick & Armstrong (1995) that elderly
controls do not necessarily perform perfectly on picture-naming tasks, it is
nevertheless clear from Figure 6:3 that all the DAT patients still performed well
below the control range.
Figure 6:3 also shows that the patients produced a much
higher rate of phonologically disrupted errors than controls.
100
Correct
Phonologically Disrupted
Responses
60
%
80
40
20
0
NK
Figure 6:3.
MT
VB
PG
GD
RS
CM
SW
KM Control
Mean
Rates of correct responses and phonologically disrupted errors
produced in picture naming by nine DAT patients, and corresponding mean rates
of these two response types given by the control group.
Chapter 6: Phonological Disruption in Atypical DAT
193
Naming, Repetition and Reading: 9 Patients
Figure 6:4 shows the rate of correct responses produced in the first (and in
some cases, only) testing round for 7 of the 9 patients on the naming, repetition
and reading tasks.
For two patients, V.B. and K.M., the results shown are from
their second round of testing, to allow comparison with the severity of their
spontaneous speech impairment (as noted earlier, spontaneous speech samples
for K.M. and V.B. were only available from Round 2).
The patients' ranking from
left to right according to severity of impairment in spontaneous speech shows
that their relative ability to produce single words correctly follows roughly the
same trend as the relative severity of their spontaneous speech deficit.
The only
exception is C.M., whose single word production, especially in naming, might
have been expected to have been somewhat better on the basis of his spontaneous
speech
sample.
100
Name
% Correct Responses
Repeat
75
Read
50
25
0
NK
Figure 6:4.
MT
VB
PG
GD
RS
CM
SW
KM
Percentage of correct responses produced by nine DAT patients in the
naming, repetition and reading tasks.
Figure 6:4 also shows same the task effect found for the other
phonologically-impaired patients reported in this thesis: repetition and reading
were better preserved than naming (see Appendix III for formal statistical
comparisons of correct responses across tasks for each
of the nine patients)1 . If
there was a difference between repetition and reading, reading was likely to be
1 The task order of Name-Repeat-Read used in this figure, and throughout the chapter, follows
the order used in earlier chapters.
Chapter 6: Phonological Disruption in Atypical DAT
194
the more impaired unless the patient had a hearing difficulty (as was the case for
P.G., R.S., and C.M.).
V.B. was tested on naming and reading and did not produce
any responses correctly in these tasks.
As in the other single-word production
tasks reported in this thesis, shorter words were more likely than longer words to
be produced correctly.
In Figure 6:5, the ranking of patients according to severity of spontaneous
speech deficit shows that, in single word production as in spontaneous speech, the
likelihood of the patients showing phonological disruption versus word-finding
difficulty was not related to severity of overall output deficit (compare Figure 6:2).
Instead, the probability of activating at least some part of the phonological target
was related to the speaking task: some approximation to the phonological target
was more likely in repetition and reading than naming, presumably because the
facilitatory effect of phonological information in the stimuli for the former two
tasks minimises word-finding difficulty.
However, the production of some
unrelated utterances even in repetition and reading by the patients with the
more severe output deficits (N.K., M.T., V.B.) suggests they were unable to benefit
from such information on some occasions.
The rate of unrelated utterances
produced by any individual is indicated in Figure 6:5 by the shortfall between the
rate of phonologically disrupted plus word-finding errors and the total errors
produced (100%).
Chapter 6: Phonological Disruption in Atypical DAT
195
Phonologically-Disrupted
a) Name
Word-finding
Errors
100
% Errors
75
50
25
0
NK
b) Repeat
MT
VB
PG
GD
RS
CM
SW
KM
MT
VB
PG
GD
RS
CM
SW
KM
MT
VB
PG
GD
RS
CM
SW
KM
100
% Errors
75
50
25
0
NK
c) Read
100
% Errors
75
50
25
0
NK
Figure 6:5.
Rates of phonologically disrupted and word-finding errors produced
by nine DAT patients in the single word production tasks of naming, repetition
and
reading.
By contrast with phonological disruption and word-finding difficulty in
these tasks, the production of false start errors w a s related to overall severity of
speech impairment.
The more impaired patients made repeated attempts at targets
more frequently than the less impaired patients did (Figure 6:6a), but were, on the
Chapter 6: Phonological Disruption in Atypical DAT
196
whole, less likely to be correct within three attempts (Figure 6:6b), although
neither of the curves in Figure 6:6a and Figure 6:6b change consistently as a
function of overall severity.
Figure 6:6a
shows false starts as a proportion of all
responses; the same trend is present when false starts are considered as a
a)
b)
80
80
60
60
% Correct within 3 attempts
40
20
20
Figure 6:6.
SW
KM
GD
R
S
CM
PG
SW
KM
GD
R
S
CM
PG
0
NK
M
T
VB
0
40
NK
M
T
VB
% Responses containing False Start Errors
percentage of total errors (not shown).
a) Percentage of responses containing false start errors from nine
DAT patients, pooled across the single word production tasks, and b) percentage of
false start errors which were followed by a correct production of the target
within the next two attempts.
No single task consistently elicited more false start errors than the others
(Figure 6:7), although the tasks of naming and reading were more likely to elicit
successive attempts than repetition.
This bias probably reflects the fact that in
the former tasks, a visual stimulus remains present throughout the attempt to
produce the target, whereas in repetition the stimulus is a transient acoustic
event.
The production of false start responses suggests that, on at least some
occasions where the whole target word could not be activated, the initial segment
did receive enough activation to be produced.
Moreover the trend towards a
Chapter 6: Phonological Disruption in Atypical DAT
197
correlation between rate of false starts and severity of output deficit suggests that,
if anything, the level at which this information is represented actually holds up
rather well under the effects of the linguistic disruption, rather than being one
of the first to break down.
100
Name
Repeat
% Errors
80
Read
60
40
20
0
NK
Figure 6:7.
MT
VB
PG
GD
RS
CM
SW
KM
Rates of false start errors as a percentage of total errors in naming,
repetition and reading for nine DAT patients.
Longitudinal Testing on Naming, Repetition and Reading: 5 Patients
Five of the patients performed the three single word production tasks on
two occasions from 6 to 14 months apart (M.T., G.D., K.M.: 6 months; R.S.: 10 months;
V.B.: 14 months).
Over time, the patients' likelihood of producing a correct
response decreased (Figure 6:8), except for R.S. whose percent correct in
repetition barely changed over 10 months, and K.M. whose rate of correct
productions did not decrease during the first 6 months after presentation.
The pattern of phonologically disrupted versus word-finding errors
produced by the patients on the two rounds of testing is illustrated in Figure 6:9.
Over time, if the rate of phonologically-disrupted errors changed for any patient
in any task, it decreased.
For M.T. and V.B., the two patients' whose language
production was most impaired, the rate of utterances with neither phonological
nor semantic relationship to the target increased in all tasks (unrelated errors
are the shortfall between the rates of phonologically disrupted and word-finding
errors shown in Figure 6:9 and 100%).
The increase in word-finding errors
Chapter 6: Phonological Disruption in Atypical DAT
198
shown by some patients from Round 1 to Round 2 in reading is due to a higher
non-response rate to items in that task over time.
a) Name
% Correct Responses
100
75
50
25
0
1st 2 n d
MT
1st 2 n d
VB
1st 2 n d
GD
1st 2 n d
RS
1st 2 n d
KM
1st 2 n d
VB
1st 2 n d
GD
1st 2 n d
RS
1st 2 n d
KM
1st 2 n d
VB
1st 2 n d
GD
1st 2 n d
RS
1st 2 n d
KM
b) Repeat
% Correct Responses
100
75
50
25
0
1st 2 n d
MT
c) Read
% Correct Responses
100
75
50
25
0
1st 2 n d
MT
Figure 6:8.
Percentage of correct responses produced by five patients in naming,
repetition and reading over two rounds of testing.
Chapter 6: Phonological Disruption in Atypical DAT
199
Phonologically-Disrupted
a) Name
Word-finding
Errors
% Errors
100
75
50
25
0
1st 2 n d
MT
1st 2 n d
VB
1st 2 n d
GD
1st 2 n d
RS
1st 2 n d
KM
1st 2 n d
VB
1st 2 n d
GD
1st 2 n d
RS
1st 2 n d
KM
1st 2 n d
VB
1st 2 n d
GD
1st 2 n d
RS
1st 2 n d
KM
b) Repeat
% Errors
100
75
50
25
0
1st 2 n d
MT
c) Read
% Errors
100
75
50
25
0
1st 2 n d
MT
Figure 6:9.
Rates of phonologically-disrupted and word-finding errors produced
by five patients over two rounds of testing on naming, repetition and reading.
Chapter 6: Phonological Disruption in Atypical DAT
Naming and Reading Data from Previous Testing:
200
4 patients
Four of the patients with phonological disruption in the context of autopsyconfirmed AD (A.S., P.B.) or probable AD (J.G., J.M.) could not be tested on the
matched single word production tasks in the current study because of disease
severity or sudden death, as noted above under Case Histories.
Data on these
patients' naming and reading abilities were, however, available from general
neuropsychological testing carried out before the beginning of the present study.
A.S. and P.B. carried out the naming and reading tests on one occasion each, on
the first assessment.
J.G. and J.M. completed the tasks on three rounds of testing
each, with testing rounds approximately 6 months apart.
The four patients' responses in the naming and reading tasks were
classified according to criteria used for scoring the other single word production
tasks described in this thesis, following Martin et al. (1994) and described fully in
Chapter 3.
Tables showing the proportions of each response type given by the
patients in each task are shown in Appendix IV.
The percentages of
phonologically disrupted errors compared with word-finding errors were
calculated from subgroups of these 10 response types, according to the procedure
outlined earlier in this chapter for the single word production tasks performed by
the group of 9 DAT patients.
False start errors were not analysed for this
subgroup of patients because it is not certain they were transcribed at the time of
testing.
The naming task was a subtest of the Semantic Battery (Hodges & Patterson,
1995) and contained 48 pictures from the Snodgrass and Vanderwart (1980) corpus
with names ranging from 1-5 syllables in length.
Elderly control subjects named
an average of 90.1% of pictures correctly (s.d. = 4.8) on a computerised version of
this test (Patterson et al., 1994); none of these four DAT patients scored above 40%
correct (Figure 6:10).
Further, a considerable proportion of the errors for 3 of the
DAT patients contained phonological disruption.
P.B. did not show a high rate of
phonological disruption because most of his errors, (classed as word-finding
errors) were non-responses (Appendix IV).
Chapter 6: Phonological Disruption in Atypical DAT
201
50
% Correct
40
30
20
10
0
AS-1
Figure 6:10.
PB-1
JG-1 JG-2 JG-3
JM-1 JM-2 JM-3
Percentages of correct responses produced in the Semantic Battery
naming test (Hodges & Patterson, 1995) by the four patients who were not assessed
on the matched single word production tasks in this study.
Phonologically
Word-finding
disrupted
errors
100
%Errors
75
50
25
0
AS-1
Figure 6:11.
PB-1
JG-1 JG-2 JG-3
JM-1 JM-2 JM-3
Percentages of phonologically disrupted versus word-finding errors
produced by four DAT patients on the Semantic Battery naming test.
Chapter 6: Phonological Disruption in Atypical DAT
202
The data on the patients' reading performance, summarised in Figures 6:12
and 6:13 below, were derived from their results on the "Surface" List (Patterson &
Hodges, 1992).
This list contains 252 monosyllabic, monomorphemic words, of
which half are irregular in orthography-to-phonology correspondence and half
are regular.
The results presented here refer to the patients' performance on the
126 regular words in the set only, for consistency with the results from the 180word reading task performed by the other DAT patients, in which all words had
regular
orthographic-phonological
correspondences.
Elderly
control
subjects
read an average of 125.2/126 (s.d. = 2.7) of regular words from the "Surface" List
correctly.
The DAT patients each made at least 10% errors on this task (Figure
6:12).
The patients were much more successful in reading the "Surface" List than
at naming the Semantic Battery items, an effect which is presumably attributable
both to the phonological information provided by orthographic stimuli in the
reading test, and to the fact that it only contained monosyllabic words.
As was the
case for the group of 9 DAT patients on the 180-item test, the majority of the
patients' errors in reading were phonologically-disrupted rather than wordfinding errors, again because the phonological information at input facilitated
the production of appropriate phonological information at output, even if a fully
correct response was not produced.
Neither J.G. nor J.M. showed a great decline in performance on either task
over three rounds of testing (with an interval of 1 year between the first and
third rounds) as measured by the percentage of correct responses they produced
(Figures 6:10 and 6:12).
However, the types of errors they produced did change
somewhat over time (Figures 6:11 and 6:13), with a trend towards responses which
showed less phonological relationship to the target (more word-finding errors in
J.G.'s naming and more unrelated responses in both J.G.'s and J.M.'s reading).
however, did not show this trend in naming, reflecting perhaps the
heterogeneity of the breakdown of language processing in AD.
J.M.,
Chapter 6: Phonological Disruption in Atypical DAT
203
100
% Correct
75
50
25
0
AS-1
Figure 6:12.
PB-1
JG-1 JG-2 JG-3
JM-1 JM-2 JM-3
Percentages of correct responses produced in reading 126 regular
words from the "Surface" List (Patterson & Hodges, 1992) by four of the DAT
patients who did not perform the matched single word production tasks in this
study.
Phonologically
Word-finding
disrupted
errors
100
% Errors
75
50
25
0
AS-1
Figure 6:13.
PB-1
JG-1 JG-2 JG-3
JM-1 JM-2 JM-3
Percentages of phonologically disrupted versus word-finding errors
produced by four DAT patients reading the regular words from the "Surface" List.
Chapter 6: Phonological Disruption in Atypical DAT
204
Discussion
The results of the experiments described in this section quantify the
phonological disruption and word-finding deficits in this group of atypical DAT
patients in the production of specified single word targets.
All patients showed
evidence of both phonological and word-finding impairment, with no consistent
relationship between overall severity of impairment to spontaneous speech and
the degree of one type of impairment compared to the other.
Patients with more
severely affected output did, however, produce more responses without any
semantic or phonological relationship to the target, and were on the whole more
likely to make false start errors.
The factor which most facilitated the production of the phonological target
in these tasks was, as for the other progressive aphasic patients reported in this
thesis, the nature of the task stimuli.
The atypical DAT patients were more likely
to produce a correct response in reading and repetition than in naming, and, if
not a fully correct response, to produce a phonologically-related attempt,
indicating that at least some part of the target word's phonology had been
activated.
Thus, the availability of phonological information at input
circumvented word-finding difficulties, whereas in the purely semantic task,
naming, there was frequently not enough activation of the appropriate
phonological form to support a target-related response.
Longitudinal data were available for seven of the patients (M.T., V.B., G.D.,
R.S., K.M., J.G. and J.M.).
Even though the tests were different for J.G. and J.M., and
follow-up testing occurred at different intervals for different patients, the
longitudinal results suggest that the rates and patterns of decline differed for
individuals, with K.M.'s performance barely deteriorating over 6 months whereas
G.D.'s declined noticeably over the same period, and V.B.'s reading and repetition
performance fell precipitously over a year.
the more impaired patients deteriorated faster.
There is some hint, therefore, that
In terms of pattern of errors
occurring over time for individual patients, the rates of phonological versus
word-finding difficulties did not show a systematic pattern, but the number of
unrelated
responses
increased.
These results support the claims of Biassou et al. (1995) and Kennedy et al.
(1995), apparently unique in the literature, that DAT patients can be shown to
make phonological errors on experimental speech production tasks.
Further, the
repetition condition in the current study demonstrated these errors in the
absence of the short-term memory load imposed by Biassou and colleagues' task of
repeating long, and sometimes syntactically complex, sentences.
The nature of
the phonological disruption in the speech of patients reported in this chapter is,
Chapter 6: Phonological Disruption in Atypical DAT
205
however, more consistent with the account of a phonological level processing
deficit reported by Kennedy and colleagues' for the phonological errors in two
familial cases of DAT, than with an account where the retrieval of a partially
phonologically specified lexical representation is the most impaired (Biassou et
al., 1995), with subsequent phonological processing relatively spared.
In the study by Biassou and colleagues, 50% of phonological errors in the
patients' sentence repetition occurred on word-initial segments whereas, in the
present study, the three most impaired patients produced false start errors on
around 50% of single word responses (Figure 6:6).
Thus, in the present study,
N.K., M.T. and V.B. often retrieved the initial sound, and sometimes made further
phonological errors in the production of the rest of the word, or generated no
appropriate phonology (making word-finding or unrelated errors).
The less
impaired patients in this study made some false start errors in which only the
initial sound was retrieved, but otherwise each produced frank phonological
errors, suggesting that subsequent phonological processing was also impaired.
The unselected group of DAT patients reported by Biassou et al. may simply
manifest a different output deficit to that shown by the patients reported in this
chapter, who were selected for inclusion on the basis of their evident
phonological
difficulties.
Biassou et al.'s claim that phonological errors could occur in word
repetition as the consequence of a deficit restricted to the level of lexical retrieval
would not, however, be made by all models of speech production, including the
interactive activation model of Dell and colleagues which has been used as an
explanatory framework for phonological errors elsewhere in this thesis.
In the
single network version of the Dell model implemented by Martin et al., (1994), the
spoken stimulus presented in repetition activates the phonological nodes first,
and lexical selection deficits potentially occur under conditions of weakened
connections or rapid decay throughout the network.
As the patients in the study
by Biassou et al. (1995, p. 2166) were reported to make an extremely high rate of
nonword errors relative to controls ( χ 2 (1) = 90.93, p < 0.001), and nonword errors
are the signature of weakened connections in the network, it is the prediction of
deficits under weakened connections in the Dell network which are relevant to
the claims of Biassou et al. (1995).
If connections within the Dell network are sufficiently weakened that
selection of a lexical node is significantly compromised, then activation feeding
back to the phonological nodes for output will be even more compromised.
Under
these conditions the network would not produce the pattern reported by Biassou
and colleagues, in which there are a high number of nonword errors with
phonological disruption predominantly occurring at the beginnings of words.
Chapter 6: Phonological Disruption in Atypical DAT
206
For example, the two patients reported in Chapter 3 of this thesis, who had
phonological deficits characterised by weak connections, were more impaired on
production of the ends of words than the beginnings (see Figure 3:9) — including
P.G., a confirmed case of AD and one of the patients reported in the present
chapter.
Our non-replication of the results of Biassou and colleagues in the present
study may reflect task differences between single word and sentence production;
and the mismatch between predictions from the Dell network and the patients'
performance on the study of Biassou et al. may arise because the Dell network at
this point in time only claims to model single word production.
An alternative
possibility, however, is that a Type I error occurred in the Biassou et al. study.
It
is not possible to determine from the report of that study how powerful the
demonstration of a word-initial error bias in the patients' production actually
was, because the number of errors made by patients and controls was not
reported.
Instead, the study compared proportions of errors between word-
positions and across groups to demonstrate the DAT patients' relative impairment
at the word-initial position.
As the design included only 30 sentences repeated by
17 neurologically intact controls (mean age = 70.4 years, s.d. = 10.2 years), the
control error pool is unlikely to have been very large, assuming that normal
elderly controls do not frequently make phonological errors in sentence
repetition.
The controls' proportions of different error types in that study might
therefore have been proportions of very small N's and thus unreliable.
RECEPTIVE WORD PROCESSING
The atypical DAT patients reported in this chapter showed evidence of
phonological disruption and word-finding deficits in conversational and nonpropositional speech, as well as in the production of single words.
Because it
seemed important to investigate the integrity of r e c e p t i v e processing of
phonological information in DAT, a subgroup of the patients performed a picture
name judgement task using the same items as the three single-word production
tasks described above.
The receptive task given to the DAT patients was one
condition of the experiment described in this thesis in Chapter 4, Experiment 7:
the condition with the full set of phonologically related nonword distractors.
Chapter 6: Phonological Disruption in Atypical DAT
207
Method
V.B., M.T. and K.M. performed the picture name judgement task with the
full set of phonologically related nonword distractors which was described in
Chapter 4.
All patients performed the task shortly after the second round of
testing on the single word production tasks.
The task was not given to the patients
who had not been included in the single word production experiment (A.S., P.B.,
J.G., J.M.), nor to those for whom no audiometric information was available (Table
6:1).
On his first attempt at this task, G.D. performed at chance level, and as his
performance on phoneme discrimination was also at chance (FAAF = 21/100, Table
6:3), his results are not reported here.
As described fully in Chapter 4, this task with the full set of
phonologically-related non-word distractors contained 360 items in total.
The 180
targets were the 1-, 2- and 3-syllable words from the 3-task experiment described
above; the distractor picture names were nonwords varying from the correct
names by one consonant phoneme altered by one, two or three articulatory
features (place, voicing and manner).
Orthogonal to word length and number
and type of features changed, this task also manipulated the position in which the
altered phoneme occurred in the word.
Thus, one third of the altered phonemes
were word-initial, one third were word-medial and the remaining third occurred
in word-final position.
(See Table 4:13 for examples of distractors in this task.)
The task was performed over two sessions, with each picture shown only once per
session, accompanied by either the correctly pronounced name or the distractor
pronunciation.
Half the spoken items on any one session were correct, and all
items were presented on audiotape, over headphones.
The full non-word picture name judgement task was also performed by six
of the control subjects who had performed the picture-naming task (Table 6:13).
Data from the four with unimpaired hearing (C1, C2, C3 and C4) were used as
control data for V.B. and M.T. who also had no hearing loss; data from the two men
(C5 and C6) with moderately severe hearing loss in the same ranges as K.M.
provided a measure of control for his performance.
Chapter 6: Phonological Disruption in Atypical DAT
Results
The DAT patients accepted more nonwords as correct pronunciations than did
controls (Figure 6:14).
These differences were shown to be statistically
significant using a McNemar's change test to compare the number of nonword
errors made by M.T. (who performed best of the patients with no hearing loss)
and the poorest of the controls with no hearing loss (C1), and comparing the
nonword errors of K.M with those of the poorest control with matched hearing
loss (C5) (M.T. vs C1: χ 2 (1) = 10.6, p < 0.01; K.M. vs C5: χ 2 (1) = 7.8, p < 0.01).
25
Words
% Errors
20
Nonwords
15
10
5
0
C1
Figure 6:14.
C2 C3 C4 MT VB
No Hearing Loss
C5 C6 KM
Hearing Loss
Percentages of errors made by DAT patients M.T., V.B. and K.M.
compared with hearing-matched controls in picture name judgement.
208
Chapter 6: Phonological Disruption in Atypical DAT
209
Characteristics of the incorrectly accepted nonwords are shown in Table
6:14.
The patients' likelihood of error increased with target length, and decreased
with the number of feature changes made, showing that they were sensitive to
distractor difficulty.
Alterations in place of articulation and voicing were more
difficult to detect than changes in manner of articulation.
Finally, the patients
were more successful in detecting changes occurring late rather than early in
the
distractor.
Table 6:14.
Errors made by M.T., V.B. and K.M. on the picture name judgement task
in the different phonological manipulation conditions (length, number, type and
position of feature changed in distractors).
Number of Errors
Manipulation
M.T.
V.B.
K.M.
1 syllable
1
14
4
2 syllables
4
13
12
3 syllables
13
17
11
one
12
20
14
two
4
14
10
2
10
3
Place
6
8
6
Voice
5
8
3
1
4
4
initial
9
19
10
medial
8
12
10
final
1
10
6
Length
(all distractors, n = 60 per length)
Number of Features Changed
(all distractors, n = 60 per change)
three
Type of Feature Changed
(1-syllable distractors, n= 20 per type)
Manner
Position of Phoneme Changed
(all distractors, n = 60 per position)
Chapter 6: Phonological Disruption in Atypical DAT
210
Discussion
The phonological deficits of these three DAT patients were clearly not
restricted to production tasks, as they also made errors on this picture name
judgement task, for which no production was required.
Their performance was
sensitive to task difficulty: longer words were more difficult to process at input as
at output, and the smaller the phonological "distance" between targets and
distractors (when fewer features were changed, or the change involved place or
voicing), the less likely the patients were to detect the change.
One intriguing finding was that the patients were more likely to make
errors when the distractor differed from the target word at the beginning, rather
than the end, of the stimulus.
This contrasts with other studies which have shown
that normally the beginning of a word is perceived more accurately than the
later parts (Cole, Jakimik, & Cooper, 1978; Marslen-Wilson & Welsh, 1978;
Stemberger, Elman, & Haden, 1985) .
An interpretation of the reverse trend in
these DAT patients' picture name judgement assumes that when the patients are
able to perform the task successfully, they do so by activating the phonological
form of the picture name upon presentation of the picture, and comparing the
incoming phonological stimulus with the correct representation.
On occasions
when the patients were slow or unable to activate the correct phonological
representation upon being shown the picture, however, they would have been
unable to monitor the spoken stimulus for error until that stimulus itself activated
the appropriate phonological representation.
On such occasions, word-initial and
-medial changes would have been more difficult to detect "on-line", but wordfinal changes would have been detectable with reference to an activated
phonological representation, thus explaining the patients' greater chance of
making errors on distractors in which the phonological changes occurred early,
rather than late in the stimulus.
If this interpretation of the position of change effect in the patients'
picture name judgement is correct, the patients' performance in this receptive
task supports the findings from their production data.
Presentation of a picture
in either naming or picture name judgement fails to provoke adequate activation
of the appropriate phonological representation.
The patients' relatively greater
success in word repetition, and better detection of word-final changes in picture
name judgement suggests, by contrast, the relatively efficient activation of stored
phonological representations from spoken input (Figure 6:8).
Chapter 6: Phonological Disruption in Atypical DAT
211
GENERAL DISCUSSION
The aims of this chapter were to demonstrate the phonological disruption
occurring in a series of patients with an atypical presentation of probable or
autopsy-confirmed Alzheimer's Disease, and to evaluate and develop the limited
accounts of phonological errors in DAT given by Kennedy et al. (1995) and Biassou
et al. (1995).
The patients described in this chapter showed deficits at the level of
phonological processing, but they also showed the word-finding deficits reported
as typical of the language impairments in DAT (Greene & Hodges, 1996) .
There
was no systematic relationship between the degree of phonological and wordfinding deficit and disease progression or severity of impairment to spontaneous
speech.
Both deficits were implicated in all cases, and, where longitudinal data
were available, at each testing session.
The degree of each type of deficit, and of
other co-occurring cognitive impairment, is apparently determined by the extent
and distribution of AD pathology and the relative involvement of brain structures
subserving
different
cognitive
functions.
The phonological disruption in these 13 patients was associated with an
atypical distribution of neuropathology, as it was in the only other two cases
reported in the literature in which phonological errors and non-fluent speech
occurred in the context of pathologically confirmed AD (Green et al., 1990, Case 8;
Karbe et al., 1993, Patient 2; see Chapter 5).
In all reported cases of DAT with
phonological disruption, therefore, pathology has involved perisylvian areas in
the frontal and/or parietal cortex, with medial temporal areas implicated to a
greater or lesser degree.
In contrast to the typical progression of DAT, in which
pathology spreads from entorhinal cortex to association cortex (Braak & Braak,
1991) , in the patients who presented with a history of prominent language
disruption, pathology may have originated in structures somewhat
topographically distant from medial temporal areas.
In the case of patient A.S.,
for example, after a history of non-fluent progressive aphasia lasting over 5
years, he was at the time of his death only beginning to manifest non-linguistic
cognitive deficits on neuropsychological testing (Table 6:3).
Neuropathological
examination of A.S. showed that neuritic plaques and neurofibrillary tangles
were distributed throughout frontal and parietal cortex, but medial temporal areas
were spared.
Serial functional imaging is likely to prove most effective in future
investigations of the spread of the pathological process in these atypical cases of
DAT.
Structural imaging using magnetic resonance (MRI) is less sensitive to
regional foci in DAT as in progressive aphasic syndromes (Sinnatamby, Antoun,
Freer, Miles, & Hodges, 1996) : in most of the cases reported in this chapter, MRI
Chapter 6: Phonological Disruption in Atypical DAT
212
showed only generalised atrophy, whereas single photon emission computed
tomography (SPECT) detected specific areas of hypoperfusion indicating
compromised neuronal activity (Table 6:4).
Neuropsychological testing to track
the spread of pathology in these cases is of some value, but only to the extent that
non-linguistic tests are available for functions with known brain loci, and if
their administration does not rely greatly on verbal instruction.
In this group of patients, phonological disruption was most often associated
with presenile onset of dementia.
Ten of the 13 patients experienced speech and
language difficulties before the age of 65 (mean age of onset = 63.6 years, s.d. = 8.1
years; see Table 6:2).
This finding is interesting with regard to the claim made by
several groups that a younger age of onset is associated with more predominant
general language difficulties in DAT (Faber-Langendoen et al., 1988; Lawlor,
Ryan, Schmeidler, Mohs, & Davis, 1994; Seltzer & Sherwin, 1983) , because this
claim is still controversial.
For example, Cummings et al. (1985) reported little
correlation between the presence of aphasia and the age of dementia onset, and
Bayles (1991)
reported that older age at disease onset was associated with greater
language impairment.
Similarly, both younger age at onset and language
impairment are frequently reported in the context of familial AD (Breitner &
Folstein, 1984; Kennedy et al., 1995; Lampe et al., 1994), although again, not
consistently (compare Farlow et al., 1994; Knesevich, Toro, Morris, & LaBarge,
1985) .
The study presented in this chapter supports the claim that language
deficits are associated with earlier age of onset in DAT; specifically, that
p h o n o l o g i c a l aspects of language may be impaired in early-onset sporadic cases.
The patients' deficits in spontaneous speech, non-propositional speech,
single word production and receptive word processing all suggest there are at
least two aspects of word production which are impaired in this atypical
presentation of DAT.
As previously hypothesised by Astell & Harley (1996),
Margolin et al. (1990), Funnell & Hodges (1991) and others, the patients have
impaired activation of phonological representations from semantic specifications
in conversational speech, picture naming, or picture name judgement.
As was
also true of the two patients reported by Kennedy et al. (1995), the patients
reported in this chapter also showed impaired processing at the phonological
level, leading to errors in the production of overlearned series and in single word
repetition and reading.
Notably, however, the two patients reported by Kennedy
and colleagues were from a kindred with familial AD associated with a known
genetic defect, whereas all the cases reported in this chapter were sporadic.
This study did not support the hypothesis of Biassou et al. (1995), that
phonological errors in DAT arise from impaired retrieval of a lexical
representation specified for initial phoneme, stressed vowel and CV structure.
Chapter 6: Phonological Disruption in Atypical DAT
213
Part of the evidence against such an account of the patients' phonological errors
in the present study was their production of false start errors, demonstrating
intact retrieval of word-initial phonemes on many occasions.
It may be that
Biassou et al. simply did not include such data for analysis in their study; they
note that "v o i c e d or silent hesitations were ignored" (p. 2166, italics added), and
only the better of two responses was scored.
In two other studies, of sentence and
phrase repetition respectively in DAT, Holland, Boller and Borgeois (1986) , and
Bayles, Tomoeda and Rein (1996)
similarly did not count phonological errors in
scoring.
The precise nature of the information represented at the lexical or lemma
level in speech production models is still controversial, and as Biassou and
colleagues proposed a very specific separation of information between the lexical
and "phonemic planning" levels, it would be valuable to replicate their study to
assess the reliability of their observed pattern of data.
Since Biassou's results
came from an unselected group of DAT patients, their phonological errors in
sentence repetition may in fact reflect a different type of deficit to those of the
patients in the current study, whose phonological errors were part of their
general clinical presentation.
Thus, it would also be of interest to test atypical
patients such as the ones in the present study on sentence repetition tasks.
Whereas the majority of studies which have investigated cognitive
functioning in DAT have been group studies (see Chapter 5), this chapter presents
a series of single cases.
This allows a more precise characterisation of the
heterogeneity of phonological breakdown arising in this atypical type of DAT.
This study, which includes unpublished data on the phonological disruption of 5
previously reported cases together with data from 9 new cases, increases what is
known of the possible clinical presentations and course of DAT.
The speech data from these atypical DAT patients are also suitable for
testing and developing detailed models of speech production such as the
interactive activation model of Dell and colleagues explored elsewhere in this
thesis.
However, the heterogeneity of speech disruption in DAT is likely to be
comparable with that seen in stroke-related aphasia and primary progressive
aphasia, and thus the same account will not necessarily apply to all patients.
The
network described by Dell and colleagues (Dell et al., in press) explains a wide
variety of aphasic production using one architecture but with varying ratios
between values of its two processing parameters of connection strength and
decay rate.
Similarly, accounts of the phonological disruption in these atypical
DAT patients using the Dell model are likely to involve different degrees of deficit
in the two processing parameters from one patient to another.
For example, P.G.
was interpreted in Chapter 3 to have a pure connection strength deficit, whereas
Chapter 6: Phonological Disruption in Atypical DAT
V.B. and G.D. made a high rate of the false start/conduit d'approche responses,
considered to reflect rapid decay in speech production (see the account of the
progressive aphasic patient C.B. in Chapter 4).
214
Table 6:3. Summary of general neuropsychological testing results from each patient at first assessment, with control data from
Hodges and Patterson (1995). Table continues overleaf.
MT
VB
GD
RS
CM
SW
KM
NK
JG
JM
PG
AS
PB
Controls
Months prior to present
study
Global Rating
MMSE /30
0
12
0
0
0
36
6
18
0
0
30
0
0
mean
s.d.
29.2
1.0
140.5
2.4
Scales
n/a
16
2
8
7/12
21
17
14
10
7
28
8
DRS /144
60
n/a
n/a
64
n/a
116
n/a
79
68
56
116*
89
Visuospatial &
Perceptual
Tests
Object Match /40 †
37
34
34
31
n/a
38
34
23
26
27
37*
30
39
37.3
3.1
Line Orientation /30
15
25
0
17
n/a
17
0
0
0
0
29
17
27.8
27.4
4.0
Rey Figure Copy /36
12.5
27
7.5
21
16
22
24.5
1
5
0
29
7.5
33
3 4
3.0
Memory Tests
Rey Figure Recall
0
8
2.5
0
3.5
0
7.5
0
0
13
2.5
17
16.5
7.5
RMT: Words /50†
Faces /50†
n/a
33
n/a
n/a
n/a
28*
19*
25*
26
28
28
43
43
30
33
34
26
39
23
28
46*
36
26
n/a
n/a
42
47.3
n/a
2.8
0
2
4
2
2
2
4
0
3
2
6
3
4
3
3
2
4
2
3
2
4
4
3
0
3
n/a
6.8
(fwd)
1.0
Digit Span:
Forwards
Backwards
(WAIS
perf
IQ=
107)
KEY:
MMSE = Mini-mental State Examination (Folstein et al., 1975), DRS = Dementia Rating Scale (Mattis, 1992)
WAIS = Wechsler Adult Intelligence Scale — Revised (Wechsler, 1981)
Object Match = Humphreys and Riddoch (1984), Line Orientation = Benton et al. (1983), Rey Figure = Rey (1941),
RMT = Recognition Memory Test (Warrington, 1984)
n/a = not available
* = result from testing session 6 months after first assessment
Chance Level of Performance: † = 0.5
172
Table 6:3.
Continued from previous page.
MT
VB
GD
Months prior to present
study
Language &
FAAF /100 ‡
Semantic
0
Tests
62
12
0
RS
CM
SW
KM
NK
JG
JM
PG
AS
PB
0
0
36
6
18
0
0
30
0
24
Controls
mean
s.d.
93
21
73
n/a
n/a
99
n/a
n/a
n/a
79*
n/a
93
n/a
n/a
F l u e n c i e s ¶ : living things
man-made
letters (FAS)
1
2
0
14
7
0
8
6
2
11
7
11
n/a
n/a
n/a
30
28
50
14
11
11
24
18
13
18
11
10
5
13
2
37
32
11
11
7
0
3
1
n/a
58.3
55.4
44.6
12.3
8.6
10.2
Picture Naming ¶ /48
1
34
14
19
n/a
45
33
28
32
16
39
18
11
43.6
2.3
Reading: regular words /126
exception wds /126
nonwords /40
55
39
14
112
93
36
66
59
n/a
122
107
36
n/a
n/a
27
126
122
38
126
118
36
124
20
29
106
96
23
110
94
15
126
122
28*
109
79
13
111**
63**
34**
125.2
123.6
39.3
2.7
3.1
0.9
TROG /80‡
48
56
47
42
n/a
74
66
45
54
44
60
60
62
78.8
1.8
P&PT: words /52 †
pictures /52†
44
44
41
46
23
40
46
43
n/a
n/a
46
n/a
41
41
36
n/a
39
n/a
38
n/a
50
n/a
n/a
42
n/a
n/a
> 48
> 48
KEY:
FAAF = The Four Alternative Auditory Feature Test (Foster & Haggard, 1987)
¶ = Semantic Battery (Hodges & Patterson, 1995)
TROG = Test for the Reception of Grammar (Bishop, 1989)
P&PT = Pyramids and Palm Trees (Howard & Patterson, 1992)
n/a = not available
* = result from testing session 6 months after first assessment
** = result from testing session 24 months after 1st assessment
Chance Levels of Performance: † = 0.5; ‡ = 0.25
173
Chapter 7
Conclusions and Implications for Future
Research
The goal of this thesis was to investigate phonological disruption in the
language abilities of patients with neurodegenerative disease.
As well as reviewing
the background literature, the thesis presents new empirical data on, and a
theoretical interpretation of, the phonological breakdown observed in
i) the single word production of two patients with non-fluent progressive aphasia,
ii) the word production and receptive word processing of two patients (who were
brothers) with a somewhat more fluent primary progressive aphasia, and
iii) the speech production and receptive word processing of a series of thirteen
patients with an atypical presentation of Dementia of the Alzheimer Type.
These
investigations represent pioneering work in this area, because, apart from material
published from this thesis (the experiments in Chapter 3 and some of the data from
three patients reported in Chapter 6), there are, to date, no other experimental and
theoretical accounts of phonological breakdown in progressive aphasic syndromes.
The first aim of the thesis was to give a principled account of the patients'
phonological impairments with reference to models of normal speech production.
The phonological deficits of the non-fluent and familial progressive aphasic patients
were explained with reference to the interactive activation model of production
described by Dell (1986) and colleagues (e.g. Martin & Saffran, 1992; Martin &
Saffran, submitted; Martin et al., 1994; Schwartz et al., 1994; Dell et al., in press).
The
deficits of the atypical DAT patients with progressive aphasia were explored within a
more descriptive framework, and it was concluded that these patients showed deficits
in both the retrieval of phonological representations of words from semantic
specifications, and in phonological encoding in all production tasks.
These accounts,
and limitations of these accounts, are summarised in the first section of this chapter.
The second aim was to consider how the patient data from these studies might,
reciprocally, inform models of normal phonological processing in speech
production.
Many of the implications of the data have already been noted in the
215
Chapter 7: Conclusions and Implications for Future Research
216
General Discussions of each experimental chapter in the thesis; these are summarised
in the second section of this chapter, and several broad issues emerging from the
work as a whole are discussed.
The chapter concludes with some suggestions for
future approaches to the study of phonological disruption in aphasia.
ACCOUNTS OF PHONOLOGICAL DISRUPTION
IN NEURODEGENERATIVE DISEASE
Non-fluent
Progressive
Aphasia
Chapter 3 described three experiments investigating the spoken single word
production of two patients with non-fluent progressive aphasia, P.G. and L.M.
In
Experiment 1, a task effect (reading ≥ repetition ≥ naming, both in proportion of
correct responses and in proportion of phonological approximations to the target
word) suggested that phonological information available from task stimuli facilitated
the patients' speech production.
A length effect reflected the increased difficulty of
phonological processing required for long words compared with shorter words.
Experiment 2, comparing P.G.'s performance across repetition, reading, copying and
writing to dictation tasks, demonstrated that a correspondence between input and
output modality also facilitated her performance.
Experiment 3 showed that the two
patients' access to appropriate phonology in reading was positively related to the
degree of correlation between orthographic and phonological forms.
These results
were interpreted as reflecting an abnormality in one of the two global processing
parameters in the interactive spreading activation model of speech production
described by Dell (1986) and colleagues: pathologically weakened connections
between
nodes.
This account of non-fluent progressive aphasia is confined to processing at
the lexical access stages of speech production, and is not precise about the nature of
articulatory processing which occurs subsequent to phonological retrieval/
encoding.
Some of the patients' phonological errors, however, fit the description of
the phonetic disintegration errors attributed to impaired articulatory processing.
Furthermore, both P.G. and L.M. had lesions in the frontal and/or parietal regions
overlapping the anatomical areas which have been implicated in articulatory/motor
output deficits in several stroke-related aphasic syndromes.
Thus a comprehensive
account of these non-fluent aphasic patients' deficits would need to specify the
extent to which articulatory impairments are also involved, and the manner in
216
Chapter 7: Conclusions and Implications for Future Research
which phonological encoding and articulatory deficits are related.
217
The issue of the
relationship between phonological and articulatory deficits in models of speech
production is discussed below.
Other
Primary
Progressive
Aphasic
Syndromes
Chapter 4 described a longitudinal investigation of the language deficits of
R.B. and C.B., two brothers with primary progressive aphasia.
Experiments 1—6
assessed word production in picture naming, naming with progressive phonemic
cueing, reading, immediate and delayed repetition of single words, and repetition of
two-word strings.
Experiment 7 investigated receptive word processing using a
picture-name judgement task with phonologically related, semantically related, and
unrelated
distractors.
R.B. was less successful in naming than C.B., and made more errors to
semantically related distractors in the input task, whereas C.B. was more impaired
than R.B. in repetition tasks and in detecting phonological distractors at input.
At
presentation, both patients had features of the pattern suggesting weakened
connections within the Dell lexical network, including a task effect of repetition =
reading > naming, and a predominant proportion of nonword errors in all tasks.
However, R.B.'s broader neuropsychological profile, the infero-lateral temporal
focus of his atrophy, and his pattern of performance on further naming and picture
name judgement tests, indicated that he had an additional semantic impairment
which could not be attributed to the effects of globally weakened connections within
the lexical network.
Furthermore, C.B.'s nonword error bias in production decreased
over time, and he began to produce semantic errors in repetition, two signatures of
an abnormality in the other parameter of the Dell network: rapid decay of activation.
It was concluded, therefore, that the mixed type of progressive aphasia presented by
R.B., and the conduction-type aphasia progressing to deep dysphasia shown by C.B.,
required more complex accounts than those given for the non-fluent progressive
aphasic patients in Chapter 3.
The functional account of R.B.'s production deficits in Chapter 4 did not
explore in detail the nature of his semantic deficit.
In future cases of mixed
progressive aphasia, it would be valuable to investigate further the relationship
between the integrity of semantic processing abilities and the functioning of the
lexical network in speech production.
Such investigations are currently being
pursued in stroke aphasia (Martin & Saffran, submitted) and semantic dementia
217
Chapter 7: Conclusions and Implications for Future Research
218
(Knott et al., submitted); and the investigation of mixed progressive aphasia provides
a further context in which to address the issues raised in these investigations.
Dementia
of
the
Alzheimer
Type
The majority of patients diagnosed with probable Alzheimer's Disease do not
have prominent phonological impairments; but Chapter 6 reported phonological
disruption in 13 patients with probable or autopsy-confirmed Alzheimer's Disease.
These impairments were evident across a range of speaking contexts including
spontaneous speech, the production of overlearned series (such as counting or
reciting the alphabet), and single word production in naming, repetition and
reading tasks.
The patients' speech production showed evidence both of word-
finding deficits (difficulty activating phonological representations from semantic
specifications) and of specific phonological-level deficits, although the degree of
each type of deficit was not systematically related to the overall severity of
spontaneous speech disruption.
The
performance of three of the patients on a
receptive word processing task supported the interpretation that, in these atypical
cases of DAT, phonological representations were more effectively activated by stimuli
containing phonological input than by semantic specifications.
The patients'
phonological disruption was manifested by false start errors (with rates especially
high among the more impaired patients), and by frank phonological errors.
This
pattern was not consistent with a primary impairment in retrieving an abstract
lexical representation partially specified for phonological information (as proposed
by Biassou et al., 1995).
The study in Chapter 6 is probably the most comprehensive report on
phonological disruption in DAT to date.
Several previous studies (see review in
Chapter 5) have reported only single cases (e.g. Greene et al., 1996), or negligible
empirical data on the phonological output deficits (Green et al., 1990; Karbe et al.,
1993), or have omitted to provide quantitative data on errors which are described
qualitatively (Biassou et al., 1995).
Because the empirical investigations of
phonological disruption in DAT are still in the early stages, there is room for
considerable theoretical development of the accounts of such disruption, and for the
collection of a broader base of empirical data.
In this regard, there is a key role for
single case studies which document individual patterns of phonological disruption,
and thus avoid the loss of detailed information suffered by some syndrome-based
group studies of non-progressive aphasia (see Chapter 1).
218
Chapter 7: Conclusions and Implications for Future Research
219
One starting point would be to explore the mechanisms behind the patients'
false start errors and their frank phonological errors.
In the Dell interactive
activation model, the false start errors would arise from activation of the
phonological nodes representing the initial part of the word only, while the frank
phonological errors would reflect noisy activation of the whole word form, such that
incorrect segments would sometimes be selected for production and/or correct
segments fail to be selected.
Other models of production, however, suggest more
differentiated levels of output processing at which these errors might arise.
For
example, in the model of Levelt and Wheeldon (1994; see Figure 1:2), the false starts
could arise from partial/interrupted phonological lexical retrieval and/or from
partial/interrupted syllable retrieval.
The other phonological errors may reflect
faulty processing at any of the levels of phonological encoding shown in Figure 1:2.
Further, most of the atypical DAT patients reported in Chapter 6 had pathology
distributed in anatomical areas associated with articulatory impairment (see Chapter
1), and thus a close investigation of their errors would probably reveal articulatory
deficits in addition to the linguistic-phonological deficit in many cases.
One clear
problem in the investigation of phonological output errors is that their
interpretation depends on the model used, and there is a pressing need for the
rapprochement of models which account for the phonological stages of lexical
retrieval in speech production and those which describe the articulatory stages of
speech motor processing.
A second important area for investigation is the relationship between the DAT
patients' phonological deficits and their pattern of impaired and preserved function
in other areas of cognition.
Such investigations are essential because DAT is a
heterogeneous disorder, and may present complex patterns of associated deficits with
disease progression.
For example, both semantic memory impairment (Patterson et
al., 1994) and immediate memory impairment (Shallice & Warrington, 1977) ) may
compromise phonological output processing in speech; and the potential roles of
other cognitive processes (for example, attentional and executive functions) remain
unclear.
Studies of phonological disruption in DAT must therefore assume the
possibility of underlying interactions between deteriorating cognitive systems, as
well as primary deficits in phonological/articulatory processing.
Complex
interactions between cognitive subsystems over time have been demonstrated in
developmental language disorder in children (Bishop, in press) ; it will likewise be
essential to tease these interactions apart to understand the heterogeneous patterns
of deficit in speech production reported for DAT patients.
219
Chapter 7: Conclusions and Implications for Future Research
220
THEORIES OF NORMAL PHONOLOGICAL PROCESSING
Dell's
Interactive
Activation
Model
of
Production
Generalisability of the Model
The interactive activation model of Dell and colleagues was developed from
normal speech error data (Dell, 1986), and from the production errors of patients
with stroke-related aphasia (Dell et al., in press).
The investigations of phonological
disruption in non-fluent progressive aphasia and other progressive aphasic
syndromes, described in Chapters 3 and 4 of this thesis, demonstrate that this
particular model is able to generalise to the language production of patients with
progressive
disease.
The experimental investigations in Chapters 3 and 4 provided evidence for the
generalisability of the Dell model, firstly in demonstrating that it could account for
patterns of speech production in aphasic syndromes which it had not previously
encountered.
Secondly, the model provided a coherent interpretation of the
production deficits in one case where the quality of the speech errors was changing
over time (C.B.'s progression from a conduction-type aphasia to a deep dysphasia).
Thirdly, the response rate in naming tasks of one patient, R.B., was much lower than
that of any of the patients reported by Dell et al. (in press), and thus the model would
not necessarily claim to generalise to his performance.
The fact that a hypothesised
deficit in connection strength within the Dell network did in fact predict many
aspects of R.B.'s performance also speaks to the explanatory power of the model.
Fourthly, although the network was primarily implemented as a model of single word
production (e.g. Dell et al., in press), it was able to make sensible predictions about
two word repetition performance (Chapter 4).
Some Limitations of the Model
Despite its success in giving an account of R.B.'s and C.B.'s two-word repetition,
the interactive activation model of Dell and colleagues does not claim to be a model of
multiple word production.
One implication of this is that, although the
perseverations of P.G. and L.M. in Chapter 3 were attributed to weak connections
within the lexical network (such that activation for the current target was not
always sufficient to override activation from a previous target), this effect has not
been reproduced in simulations of the model.
At present, each single word
production attempt is assumed to be independent of other attempts in simulations
220
Chapter 7: Conclusions and Implications for Future Research
221
(Dell et al, in press), thus perseverative effects do not occur from one item to the
next.
A second implication is that the model is not sufficiently detailed to account for
the changes in phonological form associated with connected speech compared with
citation form.
Thus, the Dell framework has one level of phonological nodes, and
activation of these corresponds to the separate processes of phonological lexical
retrieval and phonological encoding described in other models.
A more detailed
model of the processes which occur in continuous speech is that of Levelt and
Wheeldon (1994), shown in Figure 1:2.
The model is also limited in regard to describing relationships with other
cognitive processes.
It simulates the two levels of lexical selection hypothesised to
occur in speech production: the retrieval of the lemma and the activation of the
phonological word form (which, as described above, is approximately equal to
phonological encoding).
Accounts of other aspects of cognitive processing which
are hypothesised to occur outside this network therefore remain descriptive.
For
example, the discussion of the non-fluent patients' reading in Chapter 3 suggested
that a global weakening in connection strength might also compromise the
transmission of information from orthographic input to the lexical network, but at
present this hypothesis cannot be tested by simulation as the network does not
attempt to model orthographic input processing.
A second example from Chapter 3 is
the suggestion that weakened connection strength may impair processes subsequent
to phonological encoding such as articulatory implementation.
Within the
framework of the current Dell model, and given the sparse theory about the
relationship between linguistic-phonological and articulatory processes in speech
output, this must also remain a hypothesis.
Global versus Local Processing Deficits
The additional semantic deficits of R.B. reported in Chapter 4 also raised the
issue of whether local, as well as global, processing deficits might compromise the
efficiency of activation patterns within the network.
While this possibility has also
been mooted to account for the production deficits of some stroke-related aphasic
patients (c.f. Martin & Saffran, submitted; Schwartz et al., 1994), one attraction of the
model to date has been its considerable explanatory power achieved with a simple
architecture and few processing parameters.
The incorporation of local processing
deficits might undermine the function of global processing deficits within the
network, thus removing the explanatory power of such deficits, especially with
221
Chapter 7: Conclusions and Implications for Future Research
222
regard to their non-linear effects upon production in tasks with different entrylevels to the network.
Advantages of Processing Accounts
As noted in Chapter 1, connectionist models such as that of Dell and colleagues
represent a theoretical advance over descriptive models, in their attempt to specify
the processing mechanism(s) involved in a particular cognitive function, rather
than simply identifying the functional components involved.
In Chapters 3 and 4,
the model of Dell et al. offered a theoretically precise way of characterising the
different speech production deficits that emerged in different tasks.
For example,
the deficit in connection weight shown by P.G. (Chapter 3) could explain both the
higher rate of errors, and the different profile of errors, that arose in her naming
compared with her repetition and reading, even though all three tasks activated the
same level of phonological nodes for output.
By contrast, although the model of
Caplan and colleagues (1986; see Chapter 1) also described a level of phonological
lexical representations common to all output tasks, this model would need to propose a
number of separate deficits to account for quantitatively or qualitatively different
error patterns across tasks.
The implementation of processing accounts of aphasic deficits in
connectionist architectures requires theoretical precision.
This allows the
formulation of specific testable predictions about other aspects of the patients'
performance.
In Chapter 4, the weak connections deficit hypothesised for R.B.
predicted his poor naming compared with repetition and reading, the facilitation of
his naming with phonological cueing, the lack of an imageability effect in his
repetition, and the severe disadvantage he showed in a filled versus an unfilled delay
condition in repetition.
The rapid decay deficit hypothesised for C.B. predicted his
imageability effect in repetition, his lack of disadvantage under conditions of filled
delay in repetition, and his better repetition of first versus second word in a twoword repetition task.
As predictions from the model may potentially be supported by
converging evidence from simulations of the computational model (see Chapter 3,
Footnote 2), a further strength of this type of account is that hypotheses about the
consequences of particular deficits are testable on not one, but two fronts.
Applications of the Continuity Assumption
It was noted in Chapter 4 that the pattern of progression of C.B.'s language
impairment was the converse of the pattern of recovery shown by patient N.C. after a
222
Chapter 7: Conclusions and Implications for Future Research
stroke (Martin et al., 1994).
223
The model's account of both the progression and the
recovery pattern supports the assumption that there is a c o n t i n u i t y between normal
and pathological processing (Dell et al., in press), allowing both types of production
to be described by the same model.
Significantly for the cognitive
neuropsychological enterprise, this assumption justifies the study of impaired
production in the development of models of normal production.
(The continuity
assumption in processing accounts is thus similar to the assumption of s u b t r a c t i v i t y
(Ellis & Young, 1988) in accounts based on double dissociations between patients with
selective cognitive impairments.
Subtractivity implies that the impaired system
reveals the functioning of the normal system minus the impaired component.)
Under the continuity assumption, one application of the Dell model might be
in the generation of reliable predictions about the quantitative and qualitative
changes in speech production which might be expected with alterations in the
parameters of connection weight and decay rate over the course of a patient's
recovery or decline.
These predictions would be of value in understanding cognitive
decline in progressive disease, and in constraining expectations about the possible
extent and course of recovery after stroke.
It is already possible to predict these
changes using simulations, and to test these simulations empirically against data
from both deteriorating and recovering patients.
For example, the studies of
progressive aphasia in Chapters 3 and 4, together with investigations of strokerelated aphasia (Dell et al., in press; Gagnon & Schwartz et al, 1996; Martin & Saffran,
1990; Martin & Saffran, 1992; Martin et al., 1994; Schwartz et al., 1994) and semantic
dementia (Knott et al., submitted) are beginning to provide the empirical verification
for the model's predictions.
What is not yet known is the time course which may be
associated with different types of deficit, nor the rate at which the ratio of the two
processing parameters of connection strength and decay rate might change relative
to one another over time.
Models
of
Phonological
and
Articulatory
Processing
Chapter 1 reviewed syndrome-based approaches to studying phonological
breakdown, and discussed the largely separate endeavours which have arisen to
describe linguistic-phonological deficits and articulatory-motor impairments.
The
former tend to be described in the context of psycholinguistic models of lexical access
and phonological encoding, and the latter in motor-speech theories of speech
production.
The theoretical problems associated with this division are twofold.
223
Chapter 7: Conclusions and Implications for Future Research
224
Firstly, it is not always clear whether the two types of theory are dealing with the
same or different phenomena, and secondly, it is not clear how to reconcile the two
approaches to provide a functional account of phonological and articulatory
production deficits in the one model.
The first of these difficulties needs to be addressed with precise descriptions of
the articulatory/phonological deficits which arise in all the classic aphasic
syndromes associated with non-progressive aetiology.
Such descriptions are
potentially available from instrumental measures of articulatory movement and
airflow, computational analyses of the acoustic properties of speech (voice-onset
time, spectral properties etc.), and analyses of linguistic structure guided by
autosegmental, rather than phoneme-based theories of phonology.
Analyses of
phonological/articulatory disruption using these techniques are well underway (see
Chapter 1), but there is still a tendency to measure articulatory-type phenomena in
patients assumed to have articulatory deficits, and linguistic-type phenomena in the
speech output of patients assumed to have linguistic-phonological deficits.
It would
instead be valuable to assume that the patients may show elements of both types of
deficit, and to describe their speech disruption using techniques from both
approaches.
Only when there is comparable data across the range of patients will it
be possible to determine to what extent phenomena explained as linguistic in one
account is the same as, or different from, something considered articulatory in
another.
Further, once there are precise descriptions of the range of phonological
deficits occurring across aphasic syndromes, it will be possible to use single case
methodologies to investigate systematic patterns of association and/or dissociation
between deficits.
This will allow further development of a model which embraces
both broad types of processing.
The study of articulatory/phonological disruption in progressive cases would
similarly benefit from detailed descriptions of the patients' production deficits.
Such
cases provide an additional type of information to that which is available from the
study of non-progressive cases.
Longitudinal investigations of progressive cases, as
in Chapter 4, reveal changes in the pattern of disruption with disease progression,
and therefore have the potential to illuminate relationships between different
functional processes.
Progressive cases therefore provide the opportunity to
compare theoretically important functions, both within individual patients over
time, and between patients with diverging patterns of deficit.
224
Chapter 7: Conclusions and Implications for Future Research
Neuroanatomical
Localisation
of
Phonological
225
Processing
The potential for understanding the neuroanatomical sites and/or networks
involved in phonological processing has increased with the development of
sophisticated scanning techniques
PET.
such as functional and structural MRI, SPECT, and
However, as apologists for cognitive neuropsychology argued a decade or so ago,
associating a particular function with a particular brain site does not provide a
theory of how we carry out that function (Ellis & Young, 1988; Shallice, 1988) .
It is
necessary to have a well-articulated theory of the function before asking where in
the brain it may be carried out.
One clear application of the rapprochement of
articulatory and phonological accounts of speech production deficits advocated above
would be in guiding hypotheses for functional imaging experiments with normal
speakers, and in guiding the selection of experimental tasks for such studies.
CONCLUDING REMARKS
Accounts of phonological disruption, and of phonological processing in
normal speech production, will benefit from the detailed description, on a case-bycase basis, of the articulatory, acoustic and linguistic characteristics of
phonologically disrupted speech in aphasia.
At present, it seems necessary to refrain
from making a priori assumptions about which type of disruption is likely to be
associated with particular aphasic syndromes or lesion sites.
The study of patients with progressive aphasic syndromes has much to
contribute to this endeavour.
Firstly, studies of such patients are a potential source
of converging evidence for theories derived from the investigation of phonological
disruption in non-progressive aphasia.
In fact, some patients with progressive
pathologies may present with purer and more theoretically informative patterns of
language breakdown than patients with non-progressive disease.
Secondly,
longitudinal studies of progressive aphasic cases may uniquely reveal the complex
interrelationships between functional systems, as these are differentially affected
during the course of the disease.
225
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Appendix I
This Appendix contains the percentage of responses of each type given by
the phonologically-disrupted DAT patients in Naming, Repetition and Reading.
(The corresponding data for P.G. appear in Chapter 3, Table 3:3.)
NK (June 94)
Response Type
target
correct
phonologically
related
Name
Repeat
Read
n= 45
n=60
n=27
2.2
48.3
3.7
15.6
36.7
40.7
4.4
6.7
3.7
8.9
3.3
3.7
17.8
3.3
14.8
13.3
0
3.7
0
0
3.7
15.6
0
0
11.1
1.7
11.1
11.1
0
18.5
100
100
100
neologism*
formal
paraphasia*
phonologically
and
visually/
semantically related word*†
perseveration
visually/semantically
related
word†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
250
Appendix I
251
MT
Round 1 (Dec 94)
Response Type
target
correct
phonologically
related
Round 2 (June 95)
Name
Repeat
Read
Name
Repeat
Read
n=180
n=180
n=180
n=180
n=180
n=180
2.2
25.6
23.9
1.1
10
6.1
18.3
47.2
44.4
6.7
42.2
36.1
6.1
16.7
23.3
2.2
12.8
15.6
0.6
3.9
1.7
1.1
1.1
8.9
5
2.8
11.1
13.9
14.4
11.1
0
0
6.7
0
0
7.8
0
0.6
5
0.6
1.1
4.4
1.1
0.6
1.1
2.8
3.9
13.3
1.7
0.6
6.1
10.6
8.9
25.6
2.2
0
58.3
6.1
12.8
100
100
100
100
100
100
neologism*
formal
paraphasia*
phonologically
and
visually/
2.2
semantically related word*†
perseveration
visually/semantically
related
word†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
Appendix I
252
VB
Round 1 (June 94)
Response Type
target
correct
phonologically
related
Round 2 (Aug 95)
Name
Repeat
Read
Name
Repeat
Read
n=180
n=180
n=180
n=60
n=60
n=60
15
92.2
55
0
41.7
0
27.2
5
33.9
23.3
30
31.7
8.9
2.8
7.8
8.3
18.3
10
0
2.2
0
0
3.3
0
0
10
3.3
13.3
10
0
0.6
0
0
0
2.2
0
0
0
0
0
0.6
0
0.6
8.3
1.7
6.7
4.4
0
0
8.3
5
13.3
25
0
0
18.3
0
25
100
100
100
100
100
100
neologism*
formal
paraphasia*
phonologically
and
visually/
2.2
0
semantically related word*†
perseveration
visually/semantically
related
word†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
Appendix I
253
GD
Round 1 (Jan 96)
Response Type
target
correct
phonologically
related
Round 2 (July 96)
Name
Repeat
Read
Name
Repeat
Read
n=180
n=180
n=180
n=60
n=60
n=60
23.3
68.9
48.9
15
53.3
28.3
17.8
26.7
43.3
21.7
35
40
2.2
1.7
5.6
5
8.3
8.3
5
2.8
2.2
10
2.2
0
0
6.7
0
1.7
26.7
0
0
13.3
0
3.3
9.4
0
0
15
0
8.3
0.6
0
0
0
0
0
2.8
0
0
3.3
0
0
10
0
0
10
0
5
100
100
100
100
100
100
neologism*
formal
paraphasia*
phonologically
and
visually/
3.3
5
semantically related word*†
perseveration
visually/semantically
related
word†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
Appendix I
254
RS
Round 1 (Sept 94)
Response Type
target
correct
phonologically
related
Round 2 (July 95)
Name
Repeat
Read
Name
Repeat
Read
n=180
n=180
n=180
n=180
n=180
n=180
42.8
65
76.7
20
61.1
39.4
29.4
22.2
22.8
30
26.7
43.9
5.6
10.6
0.6
7.8
8.9
12.2
1.7
0
2.2
2.8
0
0
1.7
0.6
2.2
7.8
0
0
4.4
0
0
1.1
0
0
0.6
0
0
1.7
0
0
2.8
0
0.6
1.7
0.6
0
3.9
0
0.6
6.1
0
0
26.1
0
0
100
100
100
100
100
100
neologism*
formal
paraphasia*
phonologically
and
visually/
1.7
2.8
1.1
semantically related word*†
perseveration
visually/semantically
related
word†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
Appendix I
CM (Feb 96)
Response Type
target
correct
phonologically
related
Name
Repeat
Read
n=180
n=180
n=180
11.7
46.1
63.9
7.22
28.9
23.3
1.7
21.1
10.0
2.8
1.1
0
2.8
1.1
0
33.3
0
0
5.0
0
0
5.0
1.7
0
6.1
0
0.6
24.4
0
2.2
100
100
100
neologism*
formal
paraphasia*
phonologically
and
visually/
semantically related word*†
perseveration
visually/semantically
related
word†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
255
Appendix I
SW (Nov 94)
Response Type
target
correct
phonologically
related
Name
Repeat
Read
n=60
n=60
n=60
55
91.7
66.7
15
6.7
20
3.3
0
0
5
1.7
3.3
0
0
0
10
0
6.7
5
0
1.7
0
0
0
0
0
0
6.7
0
1.7
100
100
100
neologism*
formal
paraphasia*
phonologically
and
visually/
semantically related word*†
perseveration
visually/semantically
related
word†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
256
Appendix I
257
KM
Response Type
target
correct
phonologically
related
Round 1 (Nov/Dec 94)
Round 2 (May/June 95)
Name
Repeat
Read
Name
Repeat
Read
n=180
n=180
n=180
n=180
n=180
n=180
61.1
95.6
92.8
57.8
93.3
92.8
6.1
4.4
7.2
10.6
3.9
6.1
0.6
0
0
0.6
1.7
0
0
0
2.8
0.6
1.1
2.2
0
0
1.7
0
0
8.9
0
0
12.8
0
0
0
0
0
1.7
0
0
0
0
0
0
0.6
0
0
0
0
0.6
0
0
11.7
0
0
11.7
0
0
100
100
100
100
100
100
neologism*
formal
paraphasia*
phonologically
and
visually/
8.9
semantically related word*†
perseveration
visually/semantically
related
word†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
Appendix II
This Appendix contains the percentage of each type of response given by
control subjects in picture naming.
Control Subjects
Response Type
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
98.9
99.4
93.9
95.6
96.1
92.2
97.2
95
80
78.3
0.6
0
1.7
1.7
2.2
4.4
0.6
1.1
5
11.1
0
0
0
0
0
0
0
0
0.6
0.6
0.6
0
1.7
2.2
0.6
1.7
1.7
3.3
.8
3.3
perseveration
0
0
0
0
0
0
0
0
0.6
0
visually/semantically
0
0.6
2.8
0.6
1.1
1.7
0.6
0.6
5
4.4
0
0
0
0
0
0
0
0
1.7
2.2
0
0
0
0
0
0
0
0
0.6
0
0
0
0
0
0
0
0
0
0.6
0
0
0
0
0
0
0
0
0
3.3
0
100
100
100
100
100
100
100
100
100
100
target
correct
phonologically
related
neologism*
formal
paraphasia*
phonologically
and
visually/semantically
related word*†
relatedword†
visually/semantically
related
neologism†
unrelated
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
258
Appendix III
This Appendix contains the formal statistical comparisons of rates of
correct responses given in the three tasks of naming, repetition and reading by 9
patients with probable or autopsy-confirmed AD, discussed in Chapter 6, and
illustrated in Figure 6:4.
Subject
N.K.
M.T.
Overall
Success
Comparison
Repeat
vs
Rpt > Rd = N
n/a
Binomial
Binomial
Binomial
p < 0.01
p < 0.01
p = 0.5 NS
Q (2) = 49.2
χ 2 (1) = 35
χ 2 (1) = 0.09
χ 2 (1) = 33.6
p < 0.01
p < 0.01
p = 0.76 NS
p < 0.01
n/a
Binomial
Binomial
N = Rd
p < 0.01
p < 0.01
0 correct
Q (2) = 20.2
χ 2 (1) = 7.3
χ 2 (1) = 2.2
χ 2 (1) = 19.3
p < 0.01
p < 0.01
p = 0.14 NS
p < 0.01
Q (2) = 88.1
χ 2 (1) = 65.6
χ 2 (1) = 20.4
χ 2 (1) = 28.9
p < 0.01
p < 0.01
p < 0.01
p < 0.01
Q (2) = 49.7
χ 2 (1) = 17.3
χ 2 (1) = 6.8
χ 2 (1) = 42.4
p < 0.01
p < 0.01
p < 0.01
p < 0.01
Rd > Rpt > N
Q (2) = 107.1
χ 2 (1) = 49.0
χ 2 (1) = 12.3
χ 2 (1) = 84.8
p < 0.01
p < 0.01
p < 0.01
p < 0.01
Rpt > Rd = N
χ 2 (2) = 20.5
χ 2 (1) = 20.6
χ 2 (1) = 11.4
χ 2 (1) = 1.71
p < 0.01
p < 0.01
p < 0.01
p = 0.19 NS
Q (2) = 91.7
χ 2 (1) = 49.6
Binomial
χ 2 (1) = 51.3
p < 0.01
p < 0.01
p = 1 NS
p < 0.01
Rpt = Rd > N
V.B.
Rpt > Rd = N
P.G.
Rpt = Rd > N
G.D.
Rpt > Rd > N
R.S.
Rd > Rpt > N
C.M.
S.W.
K.M.
KEY:
Order of Task
Rpt = Rd > N
Name
vs
Repeat
Read
Name
vs
Read
N = Name
Rpt = Repeat
Rd = Read
n/a = not available because too few responses in naming and reading to test
NS = not significant at α = 0.05/3 = 0.017 (Bonferroni correction for multiple
comparisons)
259
Appendix IV
This Appendix contains the percentage of each type of response given by
A.S., P.B., J.G. and J.M. in the picture naming and reading tasks included in their
general neuropsychological testing, the Semantic Battery naming test (Hodges,
Graham & Patterson, 1994) and the "Surface" List, (Hodges &
AS
Response Type
Patterson, 1995).
NAMING
(n=48 one- & two-syllable words)
PB
JG
JG
JG
JM
JM
JM
Round
1
Round
1
Round
1
Round
2
Round
3
Round
1
Round
2
Round
3
35.4
14.6
37.5
29.2
29.2
29.2
35.42
25
10.4
2.1
20.8
12.5
2.1
10.4
12.5
25
4.2
2.1
4.2
8.3
12.5
6.3
0
0
20.8
8.3
16.7
14.6
14.6
6.3
14.6
18.8
0
0
8.3
4.2
0
0
0
0
visually/semantically
related word†
16.7
25
4.2
8.3
2.1
20.8
12.5
20.8
visually/semantically
related neologism†
4.2
0
4.2
2.1
0
6.3
2.1
4.2
unrelated
2.1
0
0
2.1
8.3
2.1
2.1
0
4.2
0
4.2
16.7
8.3
4.2
6.3
0
2.1
47.9
0
2.1
22.9
14.6
14.6
6.25
100
100
100
100
100
100
100
100
target
correct
phonologically
neologism*
formal
related
paraphasia*
phonologically and
visually/semantically
related word*†
perseveration
abstruse
word
neologism
no response†
KEY:
* = phonologically disrupted errors
† = word-finding deficit
260
Appendix IV
READING
(n=126 one-syllable words)
JG
JG
JG
JM
261
AS
PB
JM
JM
Round
1
Round
3
Round
1
Round
2
Round
3
Round
1
Round
2
Round
3
86.5
84.1
84.1
89.7
81.0
87.3
79.4
79.4
4.0
10.3
4.0
2.4
4.8
6.4
7.1
9.5
7.9
4.8
10.3
5.6
10.3
6.4
10.3
7.9
1.6
0.8
0.8
0.8
1.6
0
3.2
0.8
perseveration
0
0
0.8
0.8
0.8
0
0
0
visually/semantically
related word†
0
0
0
0
0
0
0
0
visually/semantically
related neologism†
0
0
0
0
0
0
0
0
unrelated
0
0
0
0.8
0
0
0
1.6
0
0
0
0
1.6
0
0
0.8
0
0
0
0
0
0
0
0
100
100
100
100
100
Response Type
target
correct
phonologically
neologism*
formal
related
paraphasia*
phonologically and
visually/semantically
related word*†
abstruse
word
neologism
no response†
KEY:
100
100
100
* = phonologically disrupted errors
† = word-finding deficit