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COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2), 99–114
VOWELS IN THE BUFFER: A CASE STUDY OF
ACQUIRED DYSGRAPHIA WITH SELECTIVE VOWEL
SUBSTITUTIONS
Maria Cotelli
I.R.C.C.S. S. Giovanni di Dio, Fatabene Fratelli, Brescia, Italy
Jubin Abutalebi
Vita Salute San Raffaele University, Milano, Italy
Marco Zorzi and Stefano F. Cappa
Vita Salute San Raffaele University and San Raffaele Scientific Institute, Milano, Italy
We report the case of a patient who recovered from a clinical picture of fluent aphasia to selective
dysgraphia. The features of the writing disorder were compatible with a graphemic output buffer
dysfunction (errors in all spelling tasks and for all type of material, affected by word length and consisting mostly of graphemic deviations), with the exception of the lack of transposition errors and position
preference. Further, the spelling disorder was selective for vowels, replicating the original observation
by Cubelli (1991). A similar, although milder, error pattern was also observed in reading tasks, in
particular for nonwords, suggesting that the locus of dysfunction involves a processing stage shared by
reading and writing. These findings support the notion that the consonant-vowel status is a property of
graphemic representations, and is compatible with that a common buffer is involved in spelling and
reading. We discuss the implications of selective vowel disorders for current models of the spelling
system.
INTRODUCTION
The investigation of patients with acquired
dysgraphia has played a crucial role in increasing
our understanding of the spelling system. All models of the spelling system (Campbell, 1983;
Caramazza, Miceli, Villa, & Romani, 1987; Ellis,
1982, 1988; Goodman & Caramazza, 1986;
Houghton & Zorzi, 1998) converge in postulating
a processing stage, called the “graphemic buffer”.
This structure is thought to hold the graphemic
representations computed temporarily, according
to dual-route models, by the lexical or the
sublexical phonology-to-orthography conversion
components, in preparation for subsequent, more
peripheral, spelling processes. The graphemic representations of both familiar and nonfamiliar words
are both held within this graphemic buffer during
the execution of the appropriate output processes,
that is the computation of specific letter shape
representations for written spelling, or the computation of letter name representations for oral spell-
Requests for reprints should be addressed to Prof Stefano F. Cappa, DIBIT, via Olgettina 58, 20132 Milano, Italy.
We wish to thank Dr Roberto Cubelli and Dr Lorella Algeri who referred the patient to us and contributed to the investigation in
many different ways.
 2003 Psychology Press Ltd
http://www.tandf.co.uk/journals/pp/02643294.html
99
DOI:10.1080/02643290244000158
COTELLI ET AL.
ing. In the case of written spelling, the abstract
letter-form has been suggested to include both
visually and motorically based representations
(Rapp & Caramazza, 1997).
Selective damage to the graphemic buffer
Several recent studies have indicated that the
graphemic memory store can be selectively involved
in cases of acquired dysgraphia (Aliminosa,
McCloskey, Goodman-Schulman, & Sokol, 1993;
Caramazza et al., 1987; Hillis & Caramazza, 1989;
Kay & Hanley, 1994; McCloskey, Badecker,
Goodman-Schulman, & Aliminosa, 1994; Miceli,
Silveri, & Caramazza, 1985; Piccirilli, Petrillo, &
Poti, 1992; Posteraro, Zinelli, & Mazzucchi,
1988). In their landmark study, Caramazza and coworkers (1987) have attempted to delineate the
specific features of the spelling disorders caused by a
selective functional lesion to the graphemic buffer
(henceforth GBD, graphemic buffer disorder).
First, the errors should be quantitatively and qualitatively similar in all spelling tasks, irrespective of
both the input modalities (written naming, writing
to dictation, spontaneous writing, and delayed
copying) and the output modalities (written spelling, oral spelling, or typing), because the graphemic
buffer is involved in each of these spelling tasks.
Second, the errors should be present for the spelling
of both familiar words and nonwords, as the buffer
holds both types of stimuli. Spelling performance
should therefore not be affected by linguistic factors, such as lexical frequency, grammatical class,
morphological structure, or concreteness. Third, as
the graphemic buffer is a temporary repository,
which can be conceived of as a working memory
storage system, characterised by limited space
capacity, word length may be expected to affect
spelling performance. Fourth, the spelling errors
expected from a buffer deficit should mostly consist
of graphemic deviations from the target words; they
should essentially take the form of substitutions,
deletions, additions, or transpositions of letters and
of various combinations of these error types. These
errors should result in the production of nonwords
(Miceli et al., 1985; Nolan & Caramazza, 1983).
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COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
Subsequently, Caramazza and Miceli (1990)
have suggested that the nature of the graphemic
representations within the graphemic buffer consists of more than a simple linear arrangement of
letter identities. According to this simplistic view,
the information contained in graphemic representations basically consists of the identity of individual letters and the specification of their correct
linear order. By analysing the errors produced by
their patient LB, the authors concluded that the
graphemic representations included in the
graphemic buffer have a multidimensional structure, which codes several different properties of
written words separately. In particular, LB’s errors
were constrained by the written syllabic structure:
For instance, words with a regular alternating CV
pattern (e.g., the CVCVCV structure of the Italian
word “TAVOLO,” table) were correctly spelled
more frequently than words with a more complex
syllabic structure (e.g., the VCCVCV structure of
the Italian word “ALBERO,” tree). Furthermore, a
different distribution of error types in simple and
more complex words was observed. Errors like
deletion, insertion, and adjacent-letter transposition were found to be uncommon for simple CV
words, when compared with words with more complex syllabic words. A further crucial characteristic
of the errors produced by LB was the presence of
letter substitutions: These errors virtually always
involved the substitution of a vowel for a vowel or of
a consonant for a consonant. The authors reported
also that the performance with geminate consonants was radically different from other CC patterns: Geminate consonants behaved like a single
functional unit, were more resistant to error, and
were never involved by some types of errors commonly described for other CC patterns. Finally, a
crucial observation was that it was the graphemic
structure, and not the phonological structure, that
determined the distribution of errors. In particular,
consonant or vowel clusters that corresponded to a
single phoneme behaved as two graphemic elements, and not as a single phonological unit. On the
basis of these observations, the authors concluded
that graphemic representations have a multidimensional structure that specifies, besides identity and position of the graphemes, gemination,
A STUDY OF ACQUIRED DYSGRAPHIA
graphosyllabic structure, and the consonant/vowel
status.
The model of the graphemic buffer put forth by
Caramazza and Miceli (1990) is in essence a model
of spelling representation (Shallice et al., 1995),
and has little to say about serial output processes. In
contrast, Houghton and colleagues have developed
a connectionist model of spelling in which the
“problem of serial order” in the production of letters
plays a central role in explaining spelling disorders
(Houghton, Glasspool, & Shallice, 1994; Shallice,
Glasspool, & Houghton, 1995). Indeed, problems
with the control of serial order are manifest in GBD
patients, because many aspects of the patients’
errors are strikingly similar to the kinds of errors
generally found in serial recall tasks (i.e., mis-orderings and substitutions). The model of Houghton
and colleagues is based on a connectionist architecture known as “competitive queuing” (CQ)
(Houghton, 1990). When a word is to be spelled, a
group of letter nodes in the CQ model are activated
in parallel, but with a gradient of activation over
them such that letters are more active the sooner
they are to be produced. Letters compete to be produced depending on their activation level. Under
disruption (in the form of noise added to letter activations), the model has been shown to account for
many basic features of the errors found in GBD,
such as word length effect, serial position curve, and
error types (Shallice et al., 1995). The CQ model,
however, could not account for the preservation of
the consonant/vowel status. This is because a
word was represented simply as a series of letters,
with no further structure other than a special marking of doubled letters (geminates). Glasspool and
Houghton (2002) have recently developed a successor of the model, which includes a representation of
the consonant/vowel status of letters. The revised
CQ model produces very detailed simulations of
GBD errors, including the preservation of CV
status.
Peripheral dysgraphia
Some agraphic patients appear to be affected at a
stage that follows the graphemic buffer. These
include disorders at a stage, defined as allographic,
which contains spatially coded representations of
letter shapes. These patients usually display dissociation between upper-case and lower-case writing
(Hanley & Peters, 1996, 2001), or letter case confusions (De Bastiani & Barry, 1989). This is considered to be followed by a stage characterised by the
selection of graphic motor patterns (Baxter &
Warrington, 1986; Zesiger, Pegna, & Rilliet,
1994). Patients with damage at this stage often
write shapes that are not real letters. If the patient
produces mostly letter substitution despite good
oral spelling, the disorder is considered to affect the
access to graphic motor codes from intact
allographic representations (Black, Behrmann,
Bass, & Hacker, 1989; Del Grosso Destreri et al.,
2000).
Dysgraphia with a selective deficit for vowels
Additional, direct evidence in favour of the hypothesis that the consonant/vowel status of graphemes
is represented in the spelling process was provided
by Cubelli (1991). The author studied the spelling
performance of two patients with a selective deficit
in writing vowels. His first patient, CF, had a transient dysgraphia after an ischaemic infarction
located in the left parietal lobe of the left hemisphere. When writing words, he omitted all vowels,
leaving a blank space between consonants or consonant clusters (e.g., TAVOLINO, little table →
T_V_L_N_). The second patient, CW, who had
an infarction in the subcortical region of the left
frontal lobe, produced errors that almost exclusively
involved vowels. His spelling abilities were investigated in depth: His spelling performance was
affected only by stimulus length, and not by input or
output modalities, lexical status, word frequency, or
word class, suggesting a deficit to the graphemic
buffer. The most frequent errors were letter substitutions, which, however, respected the consonant/
vowel status of the involved graphemes. In the writing tasks, CW produced 409 letters incorrectly,
with 340 of them (83%) consisting of letter substitutions. Vowels were significantly more affected
than consonants (e.g., DIETRO, behind →
DIATRO; AUTO, car → UUTO; VILONTA,
nonword → VELENTO). These two patients
provided the first clinical evidence that vowels can
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
101
COTELLI ET AL.
be selectively affected in a spelling disorder due to
brain damage.
We present here a new case of acquired
dysgraphia, characterised by selective vowel substitutions. Besides replicating the previous observations, this case study provided evidence for a
similar, although much milder, pattern of impairment in reading performance, thus providing
insight about the role of the graphemic buffer not
only for spelling but also for reading (Caramazza,
1997; Caramazza, Capasso, & Miceli, 1996;
Hanley & Kay, 1998; Hanley & McDonnell,
1997). We discuss how computational models of
spelling could explain a selective deficit for vowels
and we conclude that the pattern represents a challenge to these models.
CASE REPORT
Clinical background
LiB is a 39-year-old, right-handed woman, a textile
industry worker, with 8 years of schooling. In January 1996, she suffered an acute left hemispheric
cerebral haemorrhage. The CT scan showed a left
temporal haematoma, in the white matter adjacent
to the posterior corn of the lateral ventricle. A surgical evacuation was performed. Post-operatively,
the neurological examination disclosed slight
weakness of the right limbs, right homonymous
hemianopia, and a fluent aphasia with impaired
auditory comprehension. The first neuropsychological examination was carried out 3
months after the cerebral haemorrhage (April
1996). At that time the patient had already made a
good neurological recovery. The weakness of the
right limbs had resolved, and the aphasia was substantially improved. A formal language evaluation
with the Aachener Aphasie Test (Italian version,
Luzzati, Wilmes, & De Bleser, 1992) showed a
profile of mild Wernicke’s aphasia, associated with
a severe disorder of writing. Her performance in
reading tasks was qualitatively very similar to writing, but less severely affected. On Raven’s Colored
Progressive Matrices, a test of nonverbal intelli-
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COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
gence, LiB had a normal score (26/36 correct
responses).
Three months after this first neuropsychological
evaluation LiB was referred to our laboratory for an
in-depth examination of her linguistic abilities.
The experimental investigations described here
were all conducted during the summer of 1996. Her
language abilities were largely improved at the time
of the evaluation, with the exception of writing and
reading deficits, which were found to be stable.
Spontaneous speech
LiB’s spontaneous speech was fluent, with only a
few anomic pauses as investigated with the BADA
(Miceli, Laudanna, Burani, & Capasso, 1994).
Phonemic and verbal substitutions were rare. A
transcript of LiB’s production, in response to the
request to tell the story of Little Red Riding Hood,
is reported below:
Cappuccetto Rosso (The story of Little Red Riding Hood)
.. è andata per preparare il cestino...per preparare la pappa per
portare uova per la loro nonna, Hanno incontrato....’sto
olio.....lupo, e voleva andare a tirare dentro questa bambina... e
lei è riuscita a staccarsi. Però è riuscito ad entrare dentro nella ..
nella casa della nonna ... per mangiare, voleva mangiare e ha
cercato di mangiare un po’ di nonna. L’ha messa nella loro,
dentro la loro, allora è passato e diceva: “sono io la nonna”......
(...she was going to prepare the basket...to prepare the pap to
take the eggs to their grandma. They have met.... this oil.....wolf,
and he wanted to go to draw inside this girl....and she succeeded
to pull off. But he managed to enter in the.. in grandma’s
house...to eat, he wanted to eat, he tried to eat a little bit of
grandma. He put her in their, inside their, and then he passed
and said: “It’s me the grandma” .....)
EXPERIMENTAL INVESTIGATIONS
Table 1 reports LiB’s performance in single-word
processing tasks, and clearly indicates that her basic
impairment was in writing (only 62% correct). The
features of the writing disorder were in general
compatible with a graphemic output buffer dysfunction whereas allographic errors, letter sequence
errors, and micrographia never occurred. Fewer difficulties were present in reading and repetition. A
A STUDY OF ACQUIRED DYSGRAPHIA
Table 1. LiB’s performance in the repetition, the
reading, and the writing-to-dictation of single words
and nonwords
Task
Repetition
Reading
Writing
Correct responses
665/676
610/668
420/681
%
93
91
62
series of investigations was carried out to better
characterise her written language disorder.
Writing
A single researcher (MC) performed the analysis of
writing: In cases of doubt in the interpretation of a
letter, the evaluation was checked independently by
five native Italian speakers. In cases of disagreement
the error was not considered for the analysis.
Written spelling to dictation
The written spelling-to-dictation evaluation was
performed with a large corpus of single words (n =
681), which included sublists controlled for frequency, grammatical class, lexical status, concreteness, and stimulus length. LiB was invited to spell
to dictation 616 words and 65 nonwords, presented
in random order during the testing sessions. The
stimulus length of the words ranged from 2 to 13
letters. LiB wrote with her (dominant) right hand.
Her written production was motorically unimpaired, and was executed without any noticeable
delay after word presentation.
No reliable differences were observed between
her ability to write words and nonwords. LiB
spelled correctly a total of 420/681 stimuli (62%),
consisting of 380/616 words (62%) and 40/65
nonwords (62%). Neither the writing modality
(e.g., cursive or capital letters), nor lexical factors
(word frequency, grammatical class) affected her
spelling performance. The results for the controlled
sublists are presented in Table 2. Only the stimulus
length had a significant effect: LiB spelled correctly
359/539 (67%) stimuli (words and nonwords)
ranging from 2 to 7 letters, whereas she spelled
correctly only 61/142 (43%) stimuli ranging from 8
to 13 letters, χ2 = 26.59; p < .0001. It is, however,
important to notice that the length effect was abol-
Table 2. Results obtained by LiB on controlled sublists in the
writing-to-dictation tasks
Total stimuli
Lexicality
Words
Nonwords
Grammatical word class
Nouns
Adjectives
Verbs
Functors
Frequency
High
Low
Cursive
Capital letters
Correct responses
%
420/681
62
380/616
40/65
62
62
21/40
24/40
28/39
26/40
53
60
72
65
68/108
67/108
369/602
51/79
63
62
61
64
ished if the effective number of correct letters
within the total number of letters present in the
whole corpus of stimuli was considered (see Table
3), indicating that the error unit was the single letter
and not the whole word.
LiB’s errors were predominantly letter substitutions, followed by letter insertions, deletions, and
transpositions. These features were observed in the
written spelling-to-dictation of both familiar words
and nonwords. Although a more detailed error pattern analysis for writing to dictation will be reported
later, we will mention here that LiB made significantly more errors with vowels than with consonants. Her writing deficit was thus characterised by
the relatively selective substitutions of vowels (e.g.,
ENTRARE, to enter → INTRARE; DAVANTI,
in front of → DAVONTE; SIRBOLO, nonword
→ SIRBELE). A sample of her writing production
is reported in Table 4, and examples of her handwriting are reproduced in Figure 1 on page 105 (see
also Figure 4 on page 111 for examples of handwritten capital letters).
Table 3. Incidence of correct responses as a function of stimulus
length for the writing-to-dictation of words/nonwords
No. of
letters
Correct
responses
%
Correct
a
letters
%
2–7
8–13
359/539
61/142
67
43
2613/2814
1147/1241
93
92
a
Amount of correctly spelled letters within the total number of
letters provided by the stimuli.
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
103
COTELLI ET AL.
Table 4. Examples of LiB’s errors in the writing tasks
Item
(In English)
Written
uomo
ultimi
inutile
insomma
purtroppo
atteso
poi
successo
cospetto
sud
tatto
invidia
volonta
accordo
entrare
credi
ferrovia
nuova
beato
termina
cattivo
ogni
davvero
gruppo
davanti
entrare
piuttosto
giornali
vota
intanto
rigazzo
dottere
pano
bortuna
mettina
(man)
(last)
(unnecessary)
(in short)
(unfortunately)
(attended)
(then)
(success)
(presence)
(south)
(touch)
(envy)
(will)
(agreement)
(to enter)
(you believe)
(railway)
(new)
(happy)
(to finish)
(bad)
(every)
(really)
(group)
(in front of)
(to enter)
(rather)
(newspapers)
(to vote)
(meanwhile)
(nonword)
(nonword)
(nonword)
(nonword)
(nonword)
iomo
iltime
enotile
insemma
purtrappo
otteso
pui
siccesso
caspitto
sod
tatti
invedia
volento
eccarde
intrare
crodi
forrovia
niova
biato
tormina
cottivo
ogne
dovvero
groppa
davonte
intrare
piottosta
giarnali
veta
entante
rigazzi
dottero
pani
bertuna
muttina
Spontaneous writing
LiB was invited to describe her daily life in a written
narrative. Also in this task her written production
was fast, without noticeable pauses. In the sample,
the errors are underlined and followed by the
correct word in parentheses:
Prima salata (saluto) Gloria e totti (tutti); faccio la pipì cal (col )
cagnolino pui (poi) praparo (preparo) tè con biscotti. Pai (poi)
andiamo a trovare Gloria, col cagnolino. Quando ritorno a casa
chiuda (chiudo) gli occhi, poi comincia (comincio) a pulire un po’,
pachissimo (pochissimo); puoi (poi) camincio (comincio) a
mangiare.
104
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
( I first say hello to Gloria and all; I pee with the little dog then I
prepare tea with cookies. Then we go to see Gloria, with the little
dog. When I come back home I close the eyes, then I begin to
clean a bit, a little bit; then I begin to eat.)
The sample consists of 35 words (not taking into
consideration words formed only by one letter, such
as “a,” to or “e,” and ). LiB spelled incorrectly 11
words (31%), making 12 errors, most of them consisting of substitutions (n = 11/12; 92%), with only
one insertion. By dividing the words in two main
groups—words from 2 to 5 letters (n = 17) and from
6 to 10 letters (n = 18)—five errors affected shorter
words (42%), and seven (58%) longer words. All the
errors involved vowels.
Written naming
LiB was asked to write the names of 44 pictures of
objects and actions, controlled for frequency and
length. She spelled correctly 10 items (23%),
whereas 16 items (36%) were omitted. Within the
group of incorrect responses (18/44; 41%), she
produced 12 letter substitutions (67%), 5 of which
could be classified as semantically related to the
target (3 with letter substitutions) (28%), and 1
neologism (5%). All errors, except for two semantic
errors, resulted in the production of nonwords.
It is noteworthy that 11 of the 12 letter substitutions (91%) affected vowels (e.g., TORTA, cake →
TARTA; BANDIERA, flag → BANDIARA;
LAVARE, to wash → LAVARA), and only 1 was a
consonant substitution (PIANGERE, to cry →
MIANGERE). Similarly, in three of the five
semantically related errors, vowel substitutions
were found (e.g., CULLA, cradle → LETTINA,
instead of the semantically related word
LETTINO, little bed); VOLARE, to fly→
COLEMBA, instead of the semantically related
word COLOMBA, dove; and BOCCA, mouth →
LABBRI, instead of LABBRO/LABBRA, lip/
lips). Errors were not influenced by frequency or
word length.
Delayed copy
The patient was presented with 16 typewritten
stimuli, including 10 familiar words controlled for
frequency, grammatical class and length, and 6
A STUDY OF ACQUIRED DYSGRAPHIA
Figure 1. Samples of LiB’s handwritten words.
nonwords. She was allowed to look at each stimulus, presented individually, for 10 s, then the
stimulus was removed. She spelled incorrectly two
nonword stimuli (33%), producing one substitution
(SEGREMO, nonword → SEGRAMO) and one
deletion (PRI, nonword → PR_). Within the familiar words, three stimuli (33%) were not spelled
correctly, producing three substitutions (FERIE,
vacation → FERIO; MENTO, chin → MANTE)
and one insertion (NOVEMBRE, November →
NOVEMBRIE). All six errors involved selectively
vowels, most of them consisting of substitutions
(67%).
Oral spelling-to-dictation tasks were not carried
out, because of the unfamiliar nature of oral spelling
tasks for native Italian speakers. Italian, in contrast
to English, has a largely transparent orthographic
system: Oral spelling is thus unnecessary as a learning/teaching strategy, and most Italians have never
practiced oral spelling at school. The difficulty of
performing an oral spelling task has also been
observed in other investigations of Italian
dysgraphics, e.g., Caramazza et al. (1987) and
Posteraro et al. (1988).
Spelling errors analysis
In the present section we provide a detailed characterisation of the errors produced by LiB in the written spelling-to-dictation tasks (e.g., the tasks based
on the largest corpus of stimuli).
In the first place, it must be underlined that two
of the errors resulted in illegal graphemic sequences
for Italian orthography (e.g., SOSTANZA, substance → SOSTANRA). In a few instances, one of
the graphemes of double consonant clusters corresponding, in Italian orthography, to a single phoneme was also affected by substitution errors (e.g.,
FINISCE, it finish → FINIGRE). Both these
features indicate that the errors are graphemic,
rather than phonological in nature.
The distribution of spelling errors as a function
of letter position in words/nonwords was assessed
using the Wing and Baddeley method (see Figure
2). These authors proposed (1980) that the letter
position within words/nonwords might affect the
liability to errors within the graphemic buffer.
Errors were expected to occur more frequently for
letters located in the middle positions of the stimuli, because of a so-called “read-out failure” from
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
105
COTELLI ET AL.
the graphemic buffer. Our results, reported in Figure 2, indicate that error rates are distributed in a
somewhat equal manner for initial, medial, and
final letter positions. Thus, we did not observe
“read-out” errors in LiB. Other patients with
graphemic buffer deficits failed to show the middle
position effect (Aliminosa et al., 1993; De Partz,
1995; Katz, 1991). Recently, Schiller et al. (2001)
reported two dysgraphic patients, whose spelling
errors most often occurred in the final part of
words, suggesting that different types of impairment to the graphemic buffer may result in contrasting patterns of position effects.
The most striking aspect of LiB’s spelling errors
was represented by the significant occurrence of
letter substitutions. In the entire corpus of
responses, a total of 295 letters were not produced
correctly, with 283 (96%) of the errors represented
by letter substitutions. From Table 5, it appears that
within the spelling-to-dictation of familiar words,
the incorrect responses (e.g., BEATO, happy →
BIATO) were overwhelmingly represented by letter substitutions (263/270; 97%), followed by only a
few insertions (6/270; 2%; e.g., TIZIO, fellow →
TIZZIO). A similar error pattern was observed for
the writing to dictation of nonwords, in which letter substitutions (e.g., BORTUNA, nonword →
BERTUNA) were the most common error type
(20/25; 80%), followed by insertions (4/25; 16%;
for example, ARVE, nonword → ARVEN). Transpositions of letters never occurred and only two
deletions (BRO, nonword → BR_, and STRADA,
road → ST_ADA) were present within the entire
corpus.
The substitution, insertion, and deletion errors
always respected the consonant/vowel status of the
involved graphemes. A predominant 85% of the
Wing and Baddeley’s method (1980) was utilised to conform
letter positions in words/nonwords of different length. This
method assigns a position between A and E in a word of any
length, according to the following pattern:
Number
of letters
3
4
5
6
7
8
9
10
11
12
A
B
C
K
K
K
K
K+1
K+1
K+1
K+1
K+2
K+2
K
K
K
K
K
K+1
K+1
K+1
K+1
K
K
K+1
K
K+1
K
K+1
K
K+1
D
E
K
K
K
K
K
K+1
K+1
K+1
K+1
K
K
K
K
K+1
K+1
K+1
K+1
K+2
K+2
Figure 2. Distribution of LiB’s errors in the writing-to-dictation
task as a function of letter position in words/nonwords.
errors (250/295) affected vowels (as indicated in
Table 6a), whereas only 15% involved consonants,
χ2 = 284.9; p < .0001. In Table 6b, the incidence of
these errors is reported by considering the number
of incorrect letters within the whole corpus of
letters administered (divided by their consonant/
Table 5. The general distribution of the various error types (substitutions, insertions, deletions, and
transpositions) made by LiB in the writing-to-dictation of words/nonwords
Substitutions
Insertions
Deletions
Transpositions
Total
106
Words
%
Nonwords
%
Total
%
263
6
1
0
270
97.0
2.0
0.4
0.0
20
4
1
0
25
80.0
16.0
4.0
0.0
283
10
2
0
295
96.0
3.0
0.7
0.0
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
A STUDY OF ACQUIRED DYSGRAPHIA
Table 6. (a) Incidence of vowels and consonants within LiB’s entire corpus of incorrect letters
(n = 295) obtained from her errors in the writing-to-dictation of words/nonwords; (b)
Incidence of writing errors selectively affecting vowels and consonants within the whole corpus
of letters administered in the spelling-to-dictation tasks, shared by their vowel/consonant status
(1850 vowels and 2205 consonants, for a total of 4055 letters)
(a)
Incorrect letters
Vowels
Consonants
%
250/295
45/295
(b)
Writing errors
%
250/1850
45/2205
13.5
2.0
85
15
vowel status), and a similar pattern emerges. Moreover, it is noteworthy that within the group of vowel
errors, 99% (247/250) were selective vowel substitutions, that is, vowels were substituted for other
vowels. Within the consonant errors, 80% (36)
were selective consonant substitutions, as indicated
in Table 7. Vowel-for-consonant substitutions and
vice versa were never observed. The dissociation
between vowels and consonants found in LiB’s
spelling performance leads to the further characterisation of her “graphemic buffer” dysgraphia as
being relatively selective for vowels.
Table 8. Results obtained by LiB on controlled sublists in the
reading tasks
Stimuli
Total stimuli
Lexicality
Words
Nonwords
Grammatical word class
Nouns
Adjectives
Verbs
Functors
Frequency
High
Low
Correct responses
%
610/668
92
542/583
68/85
93
80
36/40
34/40
31/39
37/40
90
85
79
93
80/98
76/98
82
78
Reading
The assessment of reading skills in a patient with an
ascertained damage to the graphemic buffer offers
the opportunity to gain more insight into an important issue: does the reading performance reflect the
spelling difficulties, suggesting that a common
buffer is involved in both reading and writing?
LiB was asked to read aloud single words. She
was administered a total corpus of 668 words, controlled for lexicality, grammatical class, frequency,
abstractness, and stimulus length. The correct
responses that LiB made while reading are shown
in Table 8. She read correctly 92% of the words
Table 7. Proportions of the various error types (substitutions,
insertions, and deletions) distributed selectively as a function of the
consonant/vowel status of letters
Substitutions
Insertions
Deletions
Total
Vowels
(%)
247
2
1
250
99
0.8
0.4
85
Consonants
36
8
1
45
(%)
80.0
18.0
1.0
15.0
from the entire corpus (610/668). Among them,
93% of correct responses were for real words (542/
583). Non-word reading was more affected: LiB
correctly read 80% of the stimuli (68/85). A
lexicality effect was thus present, χ2 = 15.73; p <
.0001. There was no reliable difference between
high- and low-frequency words. By dividing the
whole corpus of stimuli into two groups of different
stimulus length (from 2 to 7 letters and from 8 to 13
letters), no significant length effect was found, χ2 =
0.07; p < 0.78 (see Table 9).
Table 9. Incidence of correct responses as a
function of stimulus length within the reading
of words/nonwords
Stimulus
2-7
8-13
Correct responses
%
462/505
148/163
91
91
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
107
COTELLI ET AL.
Figure 3. A CV constraint can be implemented in a CQ model by adding a bias to the activation of all vowel letters in vowel positions (left)
and all consonant letters in consonant positions (right). Activation is in arbitrary units (adapted from Glasspool & Houghton, 1998).
Error pattern analysis in reading
LiB’s error pattern in reading was very similar to
that observed in spelling. Letter substitutions were
the leading error type. She read a total of 133 letters
incorrectly. Among these errors, 98.5% consisted of
letter substitutions (131/133), with only a few letter
insertions (2/133: 1.5%) (Table 10). In word reading, letter substitutions were 98% of the errors
(110/112 (e.g., PUDORE, shame → PODORE;
PENSIERO, thought → PENSIERE); only two
letter
insertions
were
observed
(e.g.,
COSCIENZA, conscience → COSCHIENZA).
All errors (21/21) in nonword reading were letter
substitutions (e.g., SUMILE, nonword →
SAMILE; STIGHE, nonword → STIGRE).
Transpositions and deletions never occurred in
reading. The analysis of incorrect responses in reading words and nonwords yield the following results:
59% of errors in word reading resulted in real words
(24/41), while 41% resulted in nonwords (17/41),
χ2 = 2.39; p = .122, n.s. Errors in nonword reading
never resulted in real words.
Also in reading, the substitutions and insertions respected the consonant/vowel status of the
involved phonemes. Similarly to the spelling tasks,
in which 85% of the errors affected vowels and
only 15% affected consonants, in reading 84%
(112/133) of the errors involved vowels whereas
only 16% (21/133) involved consonants, χ2 =
124.53; p < .0001, as indicated in Table 11a. As in
the case of writing, the selectivity of the errors is
confirmed when considering the number of incorrect letters within the whole corpus (see Table
11b). Again, within the group of vowel errors, all
(112/112; 100%) were formed by selective vowel
substitutions, that is, vowels were substituted only
with vowels (see Table 12).
The nonwords were divided into two main
groups according to stimulus length (from 2 to 5
letters and from 6 up to 9 letters: 35% (13/37) of the
Table 10. The general distribution of the various error types (substitutions, insertions, deletions, and
transpositions) made by LiB when reading words/nonwords
Words
Substitutions
Insertions
Deletions
Transpositions
Total
108
110
2
0
0
112
%
98.0
1.7
0.0
0.0
84.0
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
Nonwords
21
0
0
0
21
%
100.0
0.0
0.0
0.0
15.7
Total
%
131
2
0
0
133
98.5
1.5
0.0
0.0
100.0
A STUDY OF ACQUIRED DYSGRAPHIA
Table 11. (a) Incidence of vowels and consonants within the total amount of incorrect letters
(n = 133) obtained from LiB’s errors in the reading tasks; (b) Incidence of reading errors
selectively affecting vowels and consonants within the whole corpus of letters read in the reading
tasks, shared by their vowel/consonant status (1917 vowels and 1985 consonants, for a total of
3902 letters)
(a)
Incorrect letters
Vowels
Consonants
%
112/133
21/133
84
16
Table 12. Proportions of the various error types that occurred in
the reading tasks (substitutions and insertions), distributed
selectively as a function of the consonant/vowel status of letters
Substitutions
Insertions
Total
Vowels
%
Consonants
%
112
0
112
100
0
19
2
21
90
10
100
longer nonwords were not correctly read. For the
shorter nonwords the percentage of errors was 9%
(see Table 13 for a comparison between spelling
and reading performance). These findings lead to
the conclusion that LiB’s reading impairment mirrors the writing disorder, although at a lesser level of
severity, and might thus share the same underlying
dysfunctional mechanism.
Table 13. Distribution of LiB’s errors in writing and in reading
as a function of stimulus length for words and nonwords
Stimulus length
(in letters)
Words
3–7
8–13
Nonwords
2–5
6–9
Errors in writing
———————
No.
%
Errors in reading
———————
No.
%
156/476
80/140
33
57
26/423
15/160
6.0
9.0
7/38
18/27
18
67
4/48
13/37
8.0
35
As indicated, a marked stimulus “length effect” occurred in
2
the writing of both words, χ = 27.19; p < .0001, and
2
nonwords, χ = 15.52; p < .0001, whereas in the reading
2
tasks this “length effect” was found only for, χ = 9.38;
p < .01. No significant “length effect” was observed in the
2
reading of familiar words, χ = 1.85; p < .17, ns.
(b)
Writing errors
%
112/1917
21/1985
5.8
1.1
DISCUSSION
The first point to consider is the locus of functional
impairment in LiB’s writing disorder. Most of the
features of LiB’s spelling performance are consistent with the criteria for graphemic buffer (GB)
dysfunction delineated by Caramazza and coworkers (1987). These are: the presence of spelling
errors for both familiar words and nonwords, the
lack of frequency effects, and the similar spelling
performance in the various experimental tasks
(written spelling-to-dictation, spontaneous writing, written naming, and delayed copying).
There are, however, some atypical aspects that
deserve careful consideration. In the first place, the
significant word length effect (WLE), as assessed
on the basis of the number of correct words, disappeared when single letters were considered. A
WLE has been reported both in patients with GB
and in those with post-graphemic (PG) impairments (Del Grosso Destreri et al., 2000; Hanley &
Peters, 2001; Zesiger et al., 1994). Rapp and
Caramazza (1997) reported an abolition of the
effect if the number of letters was considered in
their two PG cases, but not in two previously
reported GB patients. The latter conclusion was
based on the fact that the error rate increased much
faster than stimulus length in the reported data.
This however does not seem to apply to all patients
(see, for example, case TH, Schiller, Greenhall,
Shelton, & Caramazza, 2001), and thus cannot
probably be considered as a distinctive feature.
Second, the error distribution curve was flat,
whereas most GB cases show a U-shaped function.
It has already been mentioned that serial order
effects appear to be heterogeneous in GB patients,
probably reflecting different mechanisms of
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
109
COTELLI ET AL.
dysfunction (interference, fast decay, defective activation; Schiller et al., 2001). A third atypical feature
is that LiB’s incorrect responses were overwhelmingly represented by letter substitutions (97%).
Letter insertions were few (2%) and transpositions
of letters never occurred. Although patients vary in
the relative proportion of error types, with substitutions as the most frequent error, most patients produce a relatively high number of transposition
errors. For instance, the proportion of letter transpositions was 17% in patient LB (Caramazza et al.,
1987; Caramazza & Miceli, 1990) and 22% in
patient AS (Jonsdottir, Shallice, & Wise, 1996).
However, in other cases (such as the patient
reported by Posteraro et al., 1988) transpositions
were quite rare, indicating that in this respect also
there is a high degree of heterogeneity.
Nevertheless, the prevalence of substitutions
and the lack of transposition errors must lead to the
careful consideration of a possible post-graphemic
(PG) locus of impairment (Black et al., 1989; Del
Grosso Destreri et al., 2000). This possibility
appears to be unlikely given the specificity of the
disorder for vowels, which cannot be accounted for
by visual or motor similarity. An inspection of the
direction of errors (Table 14) indicates that the
most vulnerable vowel is O (substituted by A or E),
followed by A (substituted by O): The errors are
thus bidirectional in the case of A and O, and unidirectional from O to E. By comparing the performance on the same letters in cursive and capital
form, visual and motor factors in error generation
may be ruled out, since similar errors occurred also
in capital-letter writing tasks, in which the letters
are quite dissimilar (see Table 14b and Figure 4 for
handwritten examples). It is also noteworthy, from
this point of view, that in patients with PG disorders the errors may involve V to C substitution
(Rapp & Caramazza, 1997)—and may result in
orthotactically illegal sequences (Del Grosso
Destreri et al., 2000). An attempt was made to
apply the procedure described by Rapp and
Caramazza to assess the relationship between target and errors. Unfortunately, the stroke similarity
metrics could not be applied, given the unavailabil1
We wish to thank an anonymous reviewer for this suggestion.
110
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
a
Table 14. (a) Confusion matrix of vowel errors in writing tasks
(words and nonwords); (b) confusion matrix of vowel errors in
capital letter writing tasks (words and nonwords); (c) confusion
matrix of vowel errors in reading tasks (words and nonwords)
(a)
A
E
I
O
U
A
E
I
O
U
Total
497
9
0
60
1
567
5
419
7
6
2
439
0
19
399
1
0
419
66
35
2
451
6
560
0
6
9
16
84
115
(b)
A
E
I
O
U
A
E
I
O
U
Total
49
1
0
7
0
57
0
46
0
0
0
46
0
7
27
0
0
34
6
7
0
44
2
59
0
3
1
2
4
10
(c)
A
E
I
O
U
A
E
I
O
U
Total
541
2
0
19
3
565
8
443
13
7
0
471
0
5
406
2
1
416
16
26
3
446
3
494
3
0
0
1
81
85
a
The columns report the observed responses for each target
vowel.
ity of the patients for further testing. We have thus
applied only the visuospatial similarity metrics onto
the relatively small number of errors observed in
capital writing: only 1 out of 30 errors (increasing to
6 with a less stringent criterion) could be considered
as visuospatially similar to the target.
Finally, phonological-articulatory similarity in
term of position does not appear to affect the errors,
since I and E are anterior, A central, and O and U
posterior.
Taken together, these affects appear to be fully
compatible with a categorical disorder for vowels in
the GB. In this case, the probability of producing an
error is expected to be independent from the position or the length of a word1. The present observation replicates the observation of a selective deficit
for vowels in writing, which has been reported
only once in the literature (Cubelli, 1991). The
A STUDY OF ACQUIRED DYSGRAPHIA
Figure 4. Handwritten samples of capital letter writing. The item word is followed by the error and the handwritten sample.
graphemic buffer has typically been conceived as a
sort of working memory storage system, where
graphemic representations are temporarily held
in preparation for further, more peripheral spelling
processing. The production of correct words/
nonwords by combining letter sequences essentially
implicates that several properties of the orthographic representations have to be considered, in
particular the identity of the letters and their serial
position. However, if letter identity and letter position were the only specified properties, in the case
of letter substitution errors all the following possibilities would be expected (given the target word
COGNITIVE):
COGNITIVE → ROGNITIVE
COGNITIVE → AOGNITIVE
COGNITIVE → CAGNITIVE
COGNITIVE → CRGNITIVE
In other words, each letter would have the same
possibility of being substituted by an another one.
Caramazza and co-workers (1987, 1990) were the
first to remark, investigating the spelling performance of their dysgraphic patient LB, that only the
first and the third alternatives were actually
observed. Their observation resulted in the identification of another important property of graphemic
representations, namely the vowel/consonant
status.
The preservation of vowel/consonant status in
GBD implies that CV information is available in
some form. Caramazza and Miceli (1990) proposed
that CV status is represented in an abstract “CV
template,” separately from letter identity (also see
Miceli, 1993; Tainturier & Caramazza, 1996):
C V C C V C V C V
|
| | | | | | | |
áGñ áOñ áGñ áNñ áIñ áTñ áIñ áVñ áEñ
consonant/
vowel level
of representation
graphemic
level of
representation
Glasspool and Houghton (1997, 2002) discuss the
nature of “categorical constraints” (such as the CV
status) in the more general context of serial behaviour. They distinguish two possible sources of categorical response biasing in CQ-type models:
external and internal. In the case of external constraint, the response bias comes from an explicit
representation of the template to which the
sequence must conform. This form of constraint
has often been used in connectionist models of
speech production (e.g., Dell, Burger, & Svec,
1997; Hartley & Houghton, 1996). Glasspool and
Houghton (2002) used a global biasing of all C or V
responses in the competitive queue to favour consonants or vowels at different points in the recall process (see Figure 3). In the case of internal constraint,
the response bias is produced by the partial activation of items sharing the same status of the target
due to the similarity of their internal representations. For instance, Glasspool, Shallice, and
Cipolotti (1999) suggested that letters have a
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
111
COTELLI ET AL.
distributed internal representation, which includes
a CV dimension. Whatever the exact nature of such
constraint, it will cause a systematic bias on activation levels in the queue of a CQ model, which,
under noise disruption, will show typical GBD
errors but with a preservation of CV status
(Glasspool & Houghton, 2002). Current CQ models, however, cannot account for a selective deficit
for vowels. The level of noise can change the relative proportion of error types, but it cannot differentially affect consonants and vowels. Thus, a
revised CQ model should incorporate an explicit
distinction between consonants and vowels, as
proposed by Caramazza and Miceli (1990). For
instance, CV information can be part of the orthographic representation itself, as in Houghton and
Zorzi’s (1998, 2002) connectionist model of
spelling.
In addition to the explicit coding of CV status in
the orthographic representation, one might also
postulate that vowels and consonants are stored in
different ways, or in different loci, within the spelling system. Cubelli (1991), reporting the first two
cases of selective vowel deletion (case CF) or substitution (case CW) in writing concluded that, when
the identity of a grapheme is unspecified because of
a brain lesion, residual information about the consonant/vowel status may affect error production.
When the “identity defect” is selective for vowels,
this would result in their deletion, or substitution
with other vowels. The observation of the converse
dissociation would be crucial to support this
hypothesis. To the best of our knowledge, a selective disorder of consonant writing has never been
reported.
In contrast to the single dissociation in spelling,
however, a double dissociation between consonant
and vowels has been reported in oral production. It
has been repeatedly observed that phonological
errors affect consonants more often than vowels
(Béland, Caplan, & Nespoulous, 1990). Romani
and co-workers (Romani, Granà, & Semenza,
1996) have reported the case of a patient with conduction aphasia who made more errors on vowels
(56%) than on consonants (44%). Recently,
Caramazza and co-workers (Caramazza, Chialant,
112
COGNITIVE NEUROPSYCHOLOGY, 2003, 20 (2)
Capasso, & Micelli, 2000) have reported two
patients, with a comparable clinical picture, who
showed a clear-cut double dissociation between
consonant and vowel errors in repetition. These
observations support the hypothesis that consonants and vowels are processed by two distinct neural mechanisms, which can be affected selectively by
brain damage.
LiB’s error pattern in reading indicates that the
locus of dysfunction involves a processing stage,
which is shared by spelling and reading, and is
compatible with the hypothesis that a common
graphemic buffer is involved in both reading and
spelling. It must, however, be underlined that,
according to several case studies of patients whose
spelling disorder was attributed to a damage to the
graphemic buffer (Caramazza et al., 1996; Friedman & Kohn, 1990; Jonsdottir et al., 1996; Katz,
1991; Tainturier & Caramazza, 1994), a mild deficit in reading words and much greater difficulties
in reading nonwords should be expected. An
exception is case JH (Hanley & Kay, 1998), who
had normal nonword reading.
The significant length effect on nonword reading, described here in our case, fits with the
hypothesis of a common buffer, in that a “buffer
effect” should become more evident in reading
“long” nonwords (see Table 13), which presumably should increase the memory load of the
graphemic buffer. It is particularly striking that
the errors in the reading tasks were also selective
vowel substitutions. The cooccurrence of vowel
substitutions in reading and writing leads to the
conclusion that the consonant/vowel opposition is
not only a reality within the spelling system but
also extends to the reading system. This fits well
with recent experimental data suggesting that the
categorisation of consonants and vowels into
separate domains is crucial for the assembly of
phonology (Berent & Perfetti, 1995) and for computational models of reading (Zorzi, Houghton,
& Butterworth, 1998).
Manuscript received 19 December 2001
Revised manuscript received 10 July 2002
Revised manuscript accepted 28 August 2002
A STUDY OF ACQUIRED DYSGRAPHIA
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