RESEARCH ARTICLE
SENTENCE PROCESSING IN FRONTOTEMPORAL DEMENTIA
Murray Grossman, Jina Rhee and Peachie Moore
(Department of Neurology, University of Pennsylvania, PA, USA)
ABSTRACT
Patients with frontotemporal dementia (FTD) have sentence comprehension difficulty. We examined the hypothesis that
both grammatical and resource factors contribute to their impaired sentence comprehension with a traditional, off-line
sentence comprehension task, and an on-line sentence processing procedure that minimizes task-related resources. This was
investigated in subgroups of FTD patients with Progressive Non-fluent Aphasia (PNFA; n = 5) who have effortful speech;
non-aphasic patients with an executive deficit (EXEC; n = 8); and Semantic Dementia (SD; n = 3) patients with poor
single word comprehension. The results were correlated with measures of executive resources. We found that PNFA patients
are significantly impaired in their off-line sentence comprehension, and that their performance correlated with auditoryverbal short-term memory. PNFA patients also demonstrated a pattern of slowed processing for the on-line sentence
measure. This is consistent with the hypothesis that information relevant for constructing sentence representations during
comprehension degrades in working memory as it is activated over an abnormally slowed time course. EXEC patients had
modest off-line sentence comprehension difficulty, and this correlated with performance on measures of working memory,
planning, and inhibitory control. On-line processing in EXEC patients demonstrated their insensitivity to sentence-based
information. This raises the possibility that a limitation in material-neutral executive resources not dedicated to grammatical
processing may play a role in their sentence comprehension deficit. SD patients’ pattern of on-line sentence comprehension
paralleled control subjects’ performance. We conclude that grammatical and executive components both contribute to
sentence comprehension, and that the profile of sentence comprehension difficulty varies across FTD subgroups depending
on the sentence processing component that is impaired.
Key words: frontotemporal dementia, progressive aphasia, grammar, working memory, comprehension
INTRODUCTION
Frontotemporal dementia (FTD) is a progressive
neurodegenerative condition affecting predominantly
prefrontal and temporal association regions of the
brain. These patients appear to be impaired in their
sentence comprehension (Grossman et al., 1996a;
Hodges and Patterson, 1996; Mesulam, 2001;
Snowden et al., 1996; Thompson et al., 1997;
Weintraub et al., 1990), but there has been limited
work evaluating the basis for their sentence
comprehension difficulty. It is particularly valuable
to assess sentence comprehension in patients with a
neurodegenerative condition such as FTD because
this provides converging evidence from the
perspective of a non-stroke disease process that
compromises cortical regions thought to be
important for sentence processing. Moreover, FTD
interferes with the functioning of cortical regions
important for sentence processing without damaging
the “innocent bystander” white matter pathways that
are compromised by stroke but are unrelated to
sentence processing. Comparative assessments of
subgroups of patients suffering from FTD also can
elucidate some of the components of sentence
processing from a unique perspective that is not
available in stroke patients. This is because the
compromised vascular supply typically causes
indiscriminate damage to portions of the frontal lobe
that subserve both language processes and nonCortex, (2005) 41, 764-777
language processes implicated in executive resources
such as working memory. In FTD, by comparison,
the selective anatomic distribution of the
neurodegenerative process may dissociate ventral
portions of left inferior frontal cortex thought to
contribute to grammatical processing from dorsal
portions of inferior cortex that appear to play a role
in verbal working memory (Cooke et al., 2003).
Other patients with FTD appear to have a limitation
in executive resources such as working memory and
planning without obvious sentence comprehension
difficulty (Grossman, 2002). The purpose of this
study was to evaluate the role of grammatical and
working memory components of sentence
comprehension in clinically-defined subgroups of
patients with FTD.
Sentence comprehension is a complex process
that is hypothesized to include several major
components. While the precise nature of these
components is debated, most theoretical approaches
distinguish between representations of grammatical
knowledge and executive resources such as
working memory that mediate the application of
grammatical knowledge to sentence material.
Briefly, one component involves the syntactic
structures that mediate long-distance linkages
between phrases in a sentence. According to some
linguistic theorists (Chomsky, 1981), sentence
structures with long-distance syntactic relations are
hypothesized to involve constituent movement. For
Sentence processing in frontotemporal dementia
example, this type of movement involving a
subordinate clause leaves an abstract, phonetically
unrealized placeholder in the vacated position or
“gap”. The sentence “The boyi from Boston that ei
chased the girl is friendly” thus contains a gap
denoted by e that represents the moved noun
phrase (NP) “the boy”. If a thematic position
contains a gap, such as the subject of the verb
“chased” in the above sentence, then the gap is
assigned the appropriate thematic role, and the
moved constituent receives its role indirectly
through co-indexation to the gap. This coindexation is denoted by the subscript i in the
sentence. Some investigators have attributed
sentence comprehension difficulty in non-fluent
Broca’s aphasia to degradation of grammatical
knowledge regarding long-distance dependencies of
this sort (Grodzinsky 1989; Grodzinsky et al.,
2000; Mauner et al., 1993).
The
second
component
of
sentence
comprehension is concerned with cognitive
resources such as working memory, inhibitory
control, and information processing speed (Frazier
and Friederici, 1991; Haarmann and Kolk, 1994).
Resources such as these appear to play a crucial role
in processing sentence material such as grammatical
structure, although it is unclear whether these
resources are material-neutral or dedicated to
sentence processing (Caplan and Waters, 1999; Just
and Carpenter, 1992; Salthouse, 1996). For
example, the long-distance linkage between a
displaced constituent and the co-indexed gap in a
sentence with a subordinate clause is formed in real
time by an operation termed “gap-filling” (Swinney
and Fodor, 1989). Gap-filling must be fast-acting
because reactivation of the displaced constituent at
the gap site occurs as soon as it is syntactically
licensed. If processing is slowed and the NP “the
boy” is not reactivated precisely at the point of the
gap, as occurs in patients with slowed lexical
retrieval such as Broca’s aphasia (Prather et al.,
1997) and Parkinson’s disease (PD) (Grossman et
al., 2002; Lee et al., 2003), then the gap-filling
process fails and sentence comprehension suffers.
Regarding working memory, if the head NP (in
the above example, ‘the boy’) cannot be retained
in working memory until constituent assignment
can be completed, then comprehension becomes
impaired (Grossman et al., 2000, 2002; Zurif et al.,
1995). The role of inhibitory control in sentence
comprehension is demonstrated in work examining
constituent role assignment in English. The first NP
of a sentence is typically assigned the subject role
since English is strongly word order-dependent, and
difficulty inhibiting canonical syntactic role
assignment in verbs with atypical syntactic-thematic
mapping interferes with comprehension (Geyer and
Grossman, 1994).
Sentence comprehension difficulty is quite
evident in FTD patients with features of progressive
aphasia (Grossman et al., 1996a; Mesulam, 2001;
765
Snowden and Neary, 1994; Snowden et al., 1992;
Thompson et al., 1997; Weintraub et al., 1990).
With a single exception (Tyler et al., 1997),
assessments of sentence processing have involved
traditional, off-line measures mediated by executive
resources. Task-related resource demands confound
our ability to assess the relative contribution of
syntactic representations and executive resources to
sentence processing difficulty during off-line
measures used to examine these patients. To
circumvent this problem, the present study adopted
two strategies. First, we assessed sentence
comprehension with both off-line and on-line
measures. On-line measures of sentence processing
are designed to minimize task-related resources that
are present in off-line measures. We used an on-line
sentence processing technique pioneered by
Marslen-Wilson and Tyler (1980; Tyler, 1985, 1992;
Tyler et al., 1997). This method asks subjects to
detect a target word in a sentence that they hear.
Unbeknownst to subjects, the target word follows
an agreement violation on some occasions. Healthy
control subjects demonstrate their sensitivity to a
grammatical agreement when they are slower to
respond to a target word immediately following an
agreement violation compared to the target word
response immediately following a coherent
agreement. This sensitivity to a grammatical
agreement is not evident when target word
detection is performed outside of the temporal
window when the grammatical agreement is
activated, that is, when the target word occurs
several words after a grammatical agreement error
in a sentence. This emphasizes the limited time
window during which grammatical processing is
normally activated. In the one, published “on-line”
investigation of grammatical processing in a
progressive aphasic (Tyler et al., 1997), the
investigators monitored the latency to detect a
target word in a sentence with a grammatical
agreement violation. This patient was insensitive to
grammatical agreement violations with this
technique, paralleling the patient’s performance on
several off-line language measures.
Our second approach to examining grammatical
and resource aspects of sentence comprehension
focused on the evaluation of off-line and on-line
performance in three subgroups of FTD patients
who have relatively distinct patterns of progressive
cognitive difficulty. The nosology of FTD is
controversial. Some authors treat each form of
progressive aphasia and each non-aphasic cognitive
and social impairment as a relatively distinct subset
of FTD (Grossman, 2002; Hodges et al., 1999;
Neary et al., 1998; Snowden et al., 1996), although
others do not appear to distinguish between the
various forms of Primary Progressive Aphasia
(Mesulam, 2001). While it is well beyond the
scope of this report to address this controversy
(Grossman and Ash, 2004), we have adopted the
approach of investigating sentence comprehension
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Murray Grossman and Others
in three subgroups of patients with clinically
different patterns of progressive language and
cognitive difficulty. Patients with Progressive Nonfluent Aphasia (PNFA) present clinically with
effortful and at times dysarthric spontaneous
speech that is often characterized by the omission
of grammatical morphemes and verbs (Grossman,
2002; Grossman and Ash, 2004; Hodges and
Patterson, 1996; Mesulam, 2001; Snowden and
Neary, 1994; Snowden et al., 1992, 1996;
Thompson et al., 1997). PNFA is associated with a
neurodegenerative process centered in anterior
portions of peri-Sylvian cortex in the left
hemisphere, including left inferior frontal cortex,
left frontal operculum, and anterior superior
portions of left temporal cortex (Grossman et al.,
1996b, 1998, 2004; Lieberman et al., 1998; Nestor
et al., 2003; Turner et al., 1996).
The sentence comprehension deficit in patients
with PNFA has been demonstrated systematically
on tasks such as sentence picture-matching and
responses to probes of sentences (Grossman et al.,
1996b; Hodges and Patterson, 1996; Weintraub et
al., 1990). The basis for this deficit, however, is
unclear. According to one hypothesis, impaired
sentence comprehension is due to the degradation
of grammatical knowledge. Difficulty with sentence
comprehension from this perspective appears to
reflect directly the grammatical complexity of the
sentence material presented for comprehension. For
example, sentences containing an object-relative
subordinate clause were more difficult for these
patients to understand than sentences with a
subject-relative subordinate clause in a series of
four PNFA patients (Grossman et al., 1996b).
Consistent with this account, the case report
demonstrating grammatical insensitivity in the online study by Tyler et al. (1997) involved a patient
with PNFA. A second hypothesis attributes sentence
comprehension difficulty in PNFA to the limited
executive resources observed at times in these
patients. For example, PNFA patients have been
shown to have poor auditory-verbal working
memory (Grossman et al., 1996b). Difficulty
retaining crucial linguistic elements in working
memory during the course of sentence processes
such as gap-filling thus may play a role in their
sentence comprehension difficulty.
FTD patients with little clinical evidence of an
aphasia also appear to have impaired sentence
comprehension. The distribution of disease in these
patients is associated with dorsolateral prefrontal
cortex (Grossman et al., 2004; Miller et al., 1991;
Rosen et al., 2002). In a consecutive series of 28
patients with FTD, a significant sentence
comprehension impairment was often observed,
regardless of the presence of a clinically apparent
progressive aphasia (Grossman et al., 1996a).
Many of these non-aphasic patients had difficulty
on measures of executive functioning such as
planning and inhibitory control, presenting an
opportunity to assess the contribution of executive
resources to sentence processing in FTD. We
characterize this subgroup of non-aphasic FTD
patients as having a dysexecutive syndrome
(EXEC) because of their considerable executive
resource limitation (Grossman, 2002), although it is
important to point out that the presence of an
executive impairment is not diagnostic of FTD
since it is also seen in patients with other
neurodegenerative diseases such as Alzheimer’s
disease (AD) (Frisoni et al., 1995; Knopman et al.,
1989; Mendez et al., 1996; Pachana et al., 1996;
Perry and Hodges 1999) and corticobasal
degeneration (Massman et al., 1996; Pillon et al.,
1995; Pillon and Dubois, 2000). Some preliminary
evidence suggests that limited executive resources
contribute to the comprehension impairment in
FTD. In a study of single word comprehension, the
EXEC subgroup of FTD patients had greater
difficulty understanding verbs than nouns (Rhee et
al., 2001). The authors argued that verbs require
greater executive resources than nouns because of
the multiple types of information that must be
coordinated during verb use. Some support for this
claim came from the significant correlations that
were found relating verb comprehension difficulty
to performance on executive measures such as the
Stroop Test and the Trail Making Test Part B.
Patients with Semantic Dementia (SD) also
have a progressive form of aphasia. These patients
have profound difficulty with naming and single
word comprehension. This has been attributed to
their degraded representation of lexical and
semantic feature knowledge (Hodges et al., 1992,
1999; Hodges and Patterson, 1996; Snowden et al.,
1989, 1992, 1996). SD is associated with a
neurodegenerative process affecting ventral and
lateral portions of the left temporal lobe (Chan et
al., 2001; Galton et al., 2001; Grossman et al.,
2004; Mummery et al., 2000; Rosen et al., 2002).
Sentence comprehension has been studied rarely in
these patients. One direct comparison of five SD
patients and two PNFA patients demonstrated
poorer lexical comprehension in the former
subgroup
but
more
impaired
sentence
comprehension in the latter subgroup (Hodges and
Patterson, 1996). This observation suggests that
poor sentence comprehension is not a general
consequence of any aphasic deficit, although this
remains to be confirmed.
In sum, we hypothesized that sentence
comprehension difficulty would be relatively
widespread in FTD, using an off-line measure of
sentence comprehension. We also expected to
observe poor on-line sentence processing
performance in FTD subgroups, but we expected
the pattern of performance to vary depending on
the specific component of sentence processing that
is compromised in these patients. Specifically, we
expected PNFA patients to show sentence
comprehension difficulty related to limited
Sentence processing in frontotemporal dementia
executive resources for sentence material. The
contribution of limited information processing
speed in PNFA was expected to emerge from
inspection of the time course of agreement
sensitivity during on-line sentence processing.
Evidence to support the activation of syntactic
information over an abnormally slowed time course
in PNFA thus would come from sensitivity to a
grammatical agreement that is observed only after
a temporal delay between the grammatical
agreement and the target word. To the extent that
sentence comprehension depends in part on
executive resources, we also expected sentence
processing difficulty in EXEC patients due to their
material-neutral executive limitations. Correlations
of sentence comprehension accuracy with
performance on independent measures of executive
functioning were expected in EXEC patients. We
did not expect sentence processing difficulty in SD
patients for our on-line assessment of sentence
comprehension because of their relatively preserved
grammatical processing and executive resources.
METHODS
Subjects
We assessed 16 mildly demented, right-handed,
native English-speakers who were diagnosed with
FTD, according to published criteria (McKhann et
al., 2001; The Lund and Manchester Groups, 1994).
The patients were recruited from the Department of
Neurology at the Hospital of the University of
Pennsylvania. FTD patients were screened for
severity of dementia, and participation was restricted
to mildly and moderately impaired patients,
according to Mini-Mental State Exam (MMSE)
scores (Folstein et al., 1975). We excluded patients
with other causes of dementia such as AD, PD,
vascular disease or hydrocephalus, psychiatric
disorders such as primary depression or psychosis,
medical illnesses or metabolic conditions that may
have resulted in encephalopathy, and/or other
medical conditions that may have an impact on
cognitive performance. None of the subjects were
taking sedating medications at the time of testing,
although some of the patients were taking small
doses of non-sedating anti-depressants (e.g.,
sertraline) or neuroleptics (e.g., quetiapine).
We subdivided the FTD patients into three
subgroups. This subdivision was based on
published consensus criteria (Neary et al., 1998)
modified following a reliability assessment to
improve inter-rater agreement (Davis et al., 2001;
Price et al., 2001). Briefly, PNFA (n = 5) included
the subgroup of FTD patients with effortful speech
that was dysarthric and/or telegraphic, but with
relatively preserved comprehension of single word
meaning; Dysexecutive (EXEC) patients (n = 8)
included the subgroup of FTD patients with
767
TABLE I
Mean (± SD) demographic features of patients
with frontotemporal dementia
Progressive Dysexecutive
non-fluent
syndrome
aphasia
(n = 5)
(n = 8)
Age (years)
Education (years)
MMSE (max = 30)
66.4 (± 6.6)
16.8 (± 3.0)
12.2 (± 2.2)
Semantic
dementia
(n = 3)
62.0 (± 7.5) 70.7 (± 10.5)
14.5 (± 2.5) 14.7 (± 2.3)
21.3 (± 6.2) 17.0 (± 3.6)
impairments of planning, selective attention,
motivation, and/or inhibition; although there was
no evidence for a progressive aphasia, most
patients had a disorder of social comportment,
Semantic Dementia (SD) (n = 3), also known as
Progressive Fluent Aphasia, included the subgroup
of FTD patients with fluent, prosodically melodic
speech that was devoid of content at times and
contained word-finding pauses, circumlocutions,
and semantic and phonemic substitutions,
associated with impaired confrontation naming and
some difficulty understanding single words.
Demographic features of the FTD patient
subgroups are summarized in Table I. The FTD
patients were compared to 17 healthy, elderly,
right-handed, native English-speakers. The FTD
patients were matched with the healthy control
subjects for age [control subjects’ age = 70.7
(± 12.8) years, χ2 (3) = 5.21, n.s.] and education
[control subjects’ education = 16.4 (± 3.5) years, χ2
(3) = 2.70, n.s.]. Unfortunately, there is no widely
accepted measure that we can use to compare FTD
subgroups for their overall dementia severity. Table
I nevertheless provides one reflection of overall
dementia severity with the MMSE (Folstein et al.,
1975). According to this measure, the patients had
a dementia that is mild or moderate in its severity.
Materials
On-line sentence processing: Based on a
paradigm developed by Marslen-Wilson and Tyler
(Marslen-Wilson and Tyler, 1980; Tyler, 1985, 1992;
Tyler et al., 1997), each trial began with a brief
auditory warning signal 1000 msec before the
presentation of a target word. Then another brief
warning signal was heard 1000 msec prior to the
presentation of a sentence. Subjects were instructed
to press a button as soon as the target word was heard
in the sentence. This button press stopped the
computer’s clock that had been initiated at the
beginning of the target word in the sentence. Without
informing the subjects, 48 sentences contained a
grammatical agreement violation prior to the target
word. An equal number of sentences containing
correct grammatical agreements prior to the target
word were also administered. These sentences are
provided in the Appendix. The agreements were
divided among subject-verb pluralization agreements
(e.g., ‘The child were sad when it was time to leave’),
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Murray Grossman and Others
determiner-noun agreements (e.g., ‘These flower
would look beautiful in a small vase’), and quantifier
(Q-float) agreements (e.g., ‘The duck all ran toward
the boy carrying the bread’). We examined these
agreements because they sample a variety of longdistance syntactic dependencies that have been
studied in patients with Broca’s aphasia (Linebarger
et al., 1983). Half of the grammatical agreement
violations (and half of the sentences with a correct
grammatical agreement) immediately preceded the
target word, and the remaining were separated from
the target word by about four syllables. This
condition allowed us to establish whether sensitivity
to a grammatical agreement occurred only in the
immediate vicinity of a grammatical agreement
violation or following a delay. In half of the
grammatical agreements, moreover, the agreementtarget word combination was distributed in the first
half of the sentence, and the remainder occurred in
the second half of the sentence (although the target
word was never the last word in a sentence). This was
in order to reduce the likelihood that patients would
develop an expectation about the location of the target
word in the sentence. Because there was a difference
between groups in the absolute latency to respond to
a target word [χ2 (3) = 18.01; p < .001], we report
“difference scores” calculated as the difference
between the latency to respond to a target word
following a grammatical agreement violation
compared to the latency to respond to a target word
following a correct grammatical agreement. These
sentences were embedded in another 192 sentences
that were presented as fillers, including sentences
with a selection restriction agreement or a mass/count
quantifier agreement. Half of these filler items were
correct and half had an agreement violation.
The sentences were divided into four equal
blocks of stimuli. Each block contained an equal
number of randomly-ordered grammatical violations
and control items without a violation, as well as a
proportional number of filler items of each type
with a violation and filler items of each type
without a violation. A stimulus sentence containing
an agreement violation and its paired control
sentence featuring the corresponding coherent
agreement were placed in different blocks, and these
were administered during two, randomly-ordered
testing sessions separated by about one month most
patients. To encourage subjects to listen to the entire
sentence and not perform just a lexical detection
task, subjects’ knowledge of the content of 10% of
the correct sentences in each block was probed
randomly after a target word response had been
elicited. A training procedure was used to introduce
subjects to the word detection paradigm, to
familiarize subjects with the response modality, and
to make them aware that they would be probed for
their knowledge of sentences during the course of
stimulus sentence presentation.
The stimuli were digitized by MacRecorder v16
software, stimulus presentation was controlled by
PsyScope v1.1b9 software (Cohen et al., 1993),
and a Macintosh 1400 laptop computer was used to
administer the stimuli and record responses.
Responses were analyzed by examining the
latency between the onset of the target word and
the subject’s response to its occurrence, as
indicated by the subject pressing the space bar of
the computer. Latencies to respond to the target
words were analyzed once extreme response
latency outliers had been omitted (i.e., > 10,000
msec and < 100 msec), and responses had been
filtered with a two-standard deviation filter based
on each subject’s mean response latency. About 5%
of items were screened out in all groups.
Additional materials: We administered
independent measures of off-line sentence
comprehension and executive processing to the
FTD patients, including the following:
Off-line sentence comprehension (Grossman et
al., 1996a): This measure of aural sentence
comprehension requires subjects to answer a simple
probe question about a semantically unconstrained
sentence (n = 12) containing a transitive verb. Onethird of the sentences had a simple transitive
structure (e.g., ‘The large white puppy nipped the
small brown poodle. Which dog did the nipping?’),
one-third contained a center-embedded subordinate
clause (e.g., ‘The car that hit the truck is green.
Which vehicle did the hitting?’), and one-third
contained a sentence-final subordinate clause (e.g.,
‘The eagle chased the hawk that is fast. Which bird
did the chasing?’). Half of the subordinate clauses
were subject-relatives and half object-relatives.
Digit span (Wechsler, 1987): Forward digit span
measures auditory-verbal short-term memory, or
the ability to retain phonological information for a
brief period of time. Reverse digit span measures
working memory, or the ability to manipulate the
auditory-verbal information that has been retained
transiently. We report the maximum number of
digits repeated correctly in the order of
presentation (forward digit span) and in an order
reversing the order of presentation (reverse digit
span). One patient did not perform this task.
Category naming fluency (Mickanin et al.,
1994): This measure of mental organization
requires subjects to name as many different
animals as possible in 60 sec. One patient did not
perform this task.
Trail Making Test Part B (Reitan, 1958): This
assesses mental planning and switching by asking
subjects to produce a continuous line between an
ascending series of alternating numbers and letters
randomly distributed on a page. We report the last
item completed (maximum 25) and the amount of
time required to complete this task, with a maximum
5 minute trial. Two patients did not perform this task.
Stroop Test (Stroop, 1935): This measure of
inhibitory control asks subjects to name the color
of the font in which a color name is printed, where
the font color does not correspond to the printed
Sentence processing in frontotemporal dementia
color name. We report the total number of items
completed (n = 80 items), the number of errors,
and the amount of time required to complete this
task, with a maximum trial of 5 minutes. Two
patients did not perform this task.
769
subjects. PNFA patients were significantly more
impaired than EXEC patients in their overall
sentence comprehension accuracy (U = 3.0,
p < .01), but SD patients did not differ statistically
from PNFA patients or EXEC patients. Analyses of
individual patient performance profiles with zscores are summarized in Table II. All five (100%)
of the PNFA patients differed significantly from
healthy control subjects (at least at the p < .01
level) in their off-line sentence comprehension
performance. Three (37.5%) of the eight EXEC
patients differed significantly from control subjects,
and only one (33%) of the three SD patients
differed significantly from control subjects. These
findings
emphasize
widespread
sentence
comprehension difficulty in FTD.
A comparison of subtypes of sentences in FTD
showed that comprehension of grammatically
demanding sentences containing subordinate clauses
are significantly more difficult than grammatically
simple sentences (z = 2.15, p < .05), although there
was no difference for object-relative compared to
subject-relative sentences. FTD patient subgroups
tended to differ in their comprehension of sentences
containing a subordinate clause (χ2 = 5.15, p < .07).
PNFA patients (20% correct) had more difficulty than
EXEC patients (38% correct) for the sentences with a
grammatically-demanding subordinate clause (U =
4.5, p < .05). The FTD subgroups did not differ
statistically in their comprehension of grammatically
simple sentences (PNFA: 40% correct, EXEC: 62%
correct, SD: 51% correct). These findings suggest
that the PNFA subgroup of FTD patients is
consistently impaired in their off-line sentence
comprehension, and this is related in part to the
grammatical complexity of the sentence stimuli.
Moreover, the non-aphasic EXEC subgroup appears
to encounter difficulty understanding grammatically
complex sentences as well.
Statistical Considerations
Because of the small numbers of subjects in the
FTD subgroups, we used non-parametric statistical
tests. The Kruskal-Wallis and Mann-Whitney U tests
were used to make comparisons between groups, the
Wilcoxon test was used to make comparisons within
a group, and the Spearman rho test was used to
assess correlations between measures within a group.
We also evaluated individual patient performance
profiles to assess the consistency of performance
profiles within each FTD subgroup. These were
derived from z-score analyses comparing FTD
patients to the performance of the healthy control
subjects on the same measures. Z-scores used to
characterize the performance of FTD patients for the
off-line sentence comprehension task were in
comparison to 27 previously evaluated, age- and
education-matched healthy seniors.
RESULTS
Off-line Sentence Comprehension
FTD patient subgroups were impaired relative
to control subjects to different extents in their
overall sentence comprehension [χ2 (2) = 5.59;
p < .06]. PNFA patients (mean z-score = – 4.16)
and SD patients (mean z-score = – 3.30) differed
from control subjects at least at the p < .01 level,
while the EXEC patients (mean z-score = – 1.50)
approached differing significantly from control
TABLE II
Individual FTD patient performance profiles1
NPNFA
EXEC
SD
1
Case
Off-line
sentence
comp
On-line
sentence
comp
Digits
forward
(digits)
Digits
reverse
(digits)
Category
naming
(min)
Stroop
err/complet
(max = 80)
Stroop
time
(secs)
Trails B
completed
(max = 24)
Trails B
time
(secs)
P1
P2
P3
P4
P5
E1
E2
E3
E4
E5
E6
E7
E8
S1
S2
S3
– 2.58
– 7.62
– 3.30
– 4.74
– 2.58
– 2.58
– 2.58
– 1.14
– .42
– 1.86
– 2.58
1.01
– 1.86
– 7.62
– 1.14
– 1.14
– 1.44
– 2.62
– 1.02
– 3.79
– 6.20
.59
– 1.94
.09
.69
– 4.70
1.65
– .26
1.69
– .41
– .19
1.90
5
0
3
2
3
7
4
7
7
6
4
6
4
7
–
5
2
0
0
0
0
0
2
4
4
3
2
5
3
4
–
4
0
2
2
5
0
1
11
12
10
8
11
11
6
0
–
10
73/80
–
0
8/13
0
16/16
80/80
0/80
5/80
0
47/80
0/80
1/80
0
–
5/80
193
–
300
247
300
73
194
110
170
300
200
180
260
300
–
262
2
1
6
4
6
–
4
24
24
1
2
24
11
16
–
10
300
300
300
300
300
–
300
120
164
300
300
156
300
100
–
300
Off-line sentence comprehension is the z-score of total sentence comprehension compared to 27 age- and education-matched control subjects; on-line sentence
comprehension is the z-score of [(grammatical incorrect near)-(grammatical correct near)] – [(grammatical incorrect distant)-(grammatical correct distant)]
compared to age- and education-matched control subjects participating in this study; Stroop err/complet is the number of errors produced (reading the word
instead of naming the font color) for the number of items completed.
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Murray Grossman and Others
Fig. 1 – Mean (± SD) on-line grammatical processing “difference scores” in healthy control subjects and patients with
frontotemporal dementia1.
On-line Sentence Processing
We examined sensitivity to grammatical
agreements in sentences in healthy control subjects
and subgroups of FTD patients by evaluating the
“difference score,” that is, the latency to respond to
a target word following an incorrect agreement
minus the latency to respond to a target word
following a correct agreement. The “difference
score” for a target word in the temporal window
immediately following an agreement should be
positive in subjects sensitive to a grammatical
agreement because of the delay to respond to a
target word immediately following an incorrect
grammatical agreement. However, the “difference
score” for a target word separated from an
agreement by four syllables should be close to zero
in subjects with a normal rate of grammatical
processing since there is no delay associated with a
target word following an incorrect grammatical
agreement. This is because the target word is
presented at a point that is beyond the brief
temporal window when grammatical processing is
normally activated.
1 A “difference score” is the difference in the latency to detect a target word
following a grammatical agreement violation compared to the latency to
detect a target word following a correct grammatical agreement. “Near”
refers to the difference score in the immediate vicinity of the grammatical
agreement; “distant” refers to the difference score separated from the
grammatical agreement by four syllables.
As summarized in Figure 1, control subjects
demonstrated their sensitivity to grammatical
agreements by showing a significantly greater
latency in their response to a target word in the
immediate temporal window following a
grammatical agreement violation compared to a
correct grammatical agreement (z = 3.62,
p < .001). However, there was no difference when
the target word was separated by several syllables
from the grammatical agreement (z = .11, n.s.),
demonstrating that control subjects’ rapid processing
of a grammatical agreement is complete by this
delayed point of a sentence. The “difference score”
for their responses to a target word immediately
following a grammatical agreement was significantly
greater than the “difference score” for the latency to
respond to a target word separated from a
grammatical agreement by a delay of several
syllables (z = 2.30, p < .03). Thus, healthy control
subjects are sensitive to grammatical agreements in
a sentence, and this occurs in the brief temporal
window during which information about the
grammatical agreement has been rapidly activated.
The statistical assessment of SD patients must
be interpreted cautiously because of the small
number of patients constituting this subgroup.
These patients generally resembled healthy control
subjects in their on-line sentence processing. Figure
1 thus shows a greater delay in SD patients’
response to a target word following a grammatical
Sentence processing in frontotemporal dementia
agreement violation compared to a correct
grammatical agreement that approached statistical
significance in the immediate temporal vicinity of
the grammatical agreement (z = 1.60, p = .10).
SD patients’ “difference score” did not differ from
control subjects’ “difference score” in this rapid,
immediate time window for grammatical
processing (z = .37, n.s.). SD patients did not show
a difference in their latency to respond to a target
word following an incorrect grammatical agreement
compared to a correct grammatical agreement when
it occurred at a point that is delayed by several
syllables following the grammatical agreement (z =
.53, n.s.). Again, SD patients’ “difference score”
for responding to a target word following a
grammatical agreement by several syllables did not
differ from control subjects’ “difference score”
following a delay (z = .27, n.s.). Individual patient
analyses summarized in Table II showed that all
three SD patients did not differ from control
subjects in their sensitivity to grammatical
agreements in this on-line task. While statistically
significant differences were not found because of
the small number of subjects, the performance
trends suggest that SD patients generally resemble
healthy control subjects in their on-line sensitivity
to grammatical agreements.
The PNFA subgroup of progressive aphasics,
however, did differ from control subjects. As
summarized in Figure 1, these patients appeared to
be particularly sensitive to a grammatical
agreement in the delayed time window, suggesting
slowed information processing speed for
constructing grammatical structures. PNFA patients
thus differed from control subjects in their
“difference score” for delayed sensitivity to a
grammatical agreement (z = 2.00, p < .05), but did
not differ from control subjects in their “difference
score” for sensitivity to a grammatical agreement
in the temporal window immediately following the
grammatical agreement (z = .51, n.s.). Within-group
analyses showed that PNFA patients’ latency to
respond to a target word following a grammatical
agreement violation compared to a correct
grammatical agreement was significant only when
the target word was separated from the agreement
by four syllables (z = 2.02, p < .05). PNFA
patients’ “difference score” was not significant in
the immediate temporal vicinity of the grammatical
agreement (z = .51, n.s.). PNFA patients also
showed a significantly greater “difference score”
for a target word separated by several syllables
from a grammatical agreement compared to the
“difference score” immediately following a
grammatical agreement (z = 2.02, p < .05). An
analysis of individual patient performance profiles,
summarized in Table II, revealed this pattern of
slowed sensitivity to a grammatical agreement to a
statistically significant extent (at least at the
p < .01 level) in three of five PNFA patients. While
there is some individual variability, these
771
observations are consistent with the hypothesis that
the sentence comprehension impairment in PNFA is
related in part to abnormally slowed grammatical
agreement activation during sentence processing.
EXEC patients resembled neither control
subjects nor PNFA patients in their pattern of
grammatical agreement sensitivity. EXEC patients
thus differed from control subjects for their
“difference score” in the immediate temporal
vicinity of the grammatical agreement (z = 1.98,
p < .05). EXEC patients also differed from PNFA
patients for their “difference score” when there is a
delay between the grammatical agreement and the
target word (z = 2.05, p < .05). Within-group
analyses showed that EXEC patients’ latency to
respond to a target word immediately following a
grammatical agreement violation does not differ
from their latency immediately following a correct
grammatical agreement (z = 1.40, n.s.), showing
their insensitivity to a grammatical agreement in a
normal, rapid time window for grammatical
processing. EXEC patients also did not differ in
their latency to respond to a target word following
an incorrect grammatical agreement compared to a
correct grammatical agreement when the target
word followed the grammatical agreement by
several syllables (z = .70, n.s.). Table II shows
some individual variability in these patients as
well. These findings suggest that EXEC patients
are abnormal in their on-line sentence processing
performance, possibly due to a deficit that equally
affects sentences with grammatical agreement
violations and correct grammatical agreements. We
return to the basis for the sentence processing
impairment in EXEC patients below when we
consider their performance on executive measures.
Relationship between Sentence Processing
and Executive Measures
Mean (± SD) performance on measures of
executive resources is summarized in Table III. We
found that the subgroups of FTD patients differ in
their performance on several executive measures,
according to Kruskal-Wallis tests. This included
digit span forward, digit span reverse, and category
naming fluency.
We also observed different correlation patterns
in subgroups of FTD patients, as summarized in
Table III. It should be noted that we did not
examine correlations in SD patients because there
were too few patients in this subgroup. PNFA
patients were found to have a significant correlation
between off-line sentence comprehension accuracy
and digit span forward. To assess the possibility
that auditory-verbal short-term memory is related to
retaining information mentally from two nonadjacent sentence segments, we specifically
examined the correlation of digit span forward with
each type of sentence frame used in the off-line
sentence comprehension procedure. We found that
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Murray Grossman and Others
TABLE III
Neuropsychological test performance in FTD patient subgroups, and correlations between neuropsychological performance and sentence
comprehension in FTD patient subgroups1
Test2
PNFA
Mean (± SD)
performance
EXEC
SD
Mean (± SD)
Correlation3
Correlation3
Off-line
On-line
performance
Off-line
On-line
sentence
sentence
sentence
sentence
3
3
3
comprehension comprehension
comprehension comprehension3
Digits forward*
2.60 (± 1.8)
Digits reverse*
.40 (± .9)
Category naming*
1.80 (± 2.0)
Stroop completed
18.60 (± 34.7)
Stroop time
260.00 (± 51.2)
Trails B completed
3.60 (± 2.6)
Trails B time
300.00 (± .00)
Sentence comp@
4.80 (± 2.9)
.92*
.54
– .81
.29
– .06
.50
–
–
.31
.35
.05
.11
– .1
– .10
–
– .05
5.62 (± 1.4)
2.87 (± 1.5)
8.75 (± 3.7)
62.50 (± 33.6)
185.27 (± 73.2)
12.83 (± 10.5)
234.28 (± 83.1)
8.50 (± 1.8)
.42
.98*
.26
.28
– .13
.79*
– .80*
–
– .12
– .12
– .24
.43
– .07
.25
.03
– .09
Mean (± SD)
performance
6.00 (± 1.4)
4.00 (± .0)
5.00 (± 7.1)
40.00 (± 56.6)
281.00 (± 26.8)
13.00 (± 4.2)
233.33 (± 115.5)
6.00 (± 5.2)
Notes:
1. We did not include correlations for SD patients since only 3 patients were assessed.
2. Kruskal-Wallis tests compared FTD patient subgroup performance. Subgroups differed significantly at least at: * = p < 0.05 level, @ p < 0.06 level.
3. Spearman rho correlations examined the relationship between performance on neuropsychological tests, off-line sentence comprehension, and on-line
sentence comprehension. To develop a single number representing on-line sentence processing, we used the formula [(grammatically incorrect-near –
grammatically correct near) – (grammatically correct distant) – (grammatically correct distant)]. * = significant correlation at least at the p < 0.05 level.
Correlations could not be assessed between the time to complete the Trails B task and sentence processing in PNFA because all patients took the maximum time
(300 secs) to complete the Trails B task.
digit span forward correlated significantly with the
comprehension of sentences containing a centerembedded subordinate clause (r = .92, p < .05),
where the subordinate clause separates the
beginning and the end of the matrix sentence. This
finding implicates auditory-verbal short-term
memory in the sentence comprehension difficulties
of PNFA patients. By comparison, digit span
forward performance was not correlated with the
comprehension of sentences with a terminallylocated subordinate clause.
In EXEC patients, by comparison, off-line
sentence comprehension accuracy was correlated
significantly with Trails B accuracy, Trails B
latency, and reverse digit span. These findings
suggest that resource-related limitations in planning
and working memory contribute to EXEC patients’
sentence comprehension difficulty.
DISCUSSION
We and others have shown that FTD patients
have difficulty understanding sentences (Grossman
et al., 1996a, 1996b; Hodges and Patterson, 1996;
Snowden and Neary, 1994; Snowden et al., 1992,
1996; Tyler et al., 1997; Weintraub et al., 1990).
Our previous work is representative of most of
these studies in the use of off-line assessments of
sentence comprehension: A simple question probed
the patients’ comprehension of a sentence that has
a grammatically simple structure or a subordinate
clause, or patients matched grammatically simple
sentences or grammatically complex sentences to
one of several pictures. At least two major
hypotheses have been considered as the basis for
the sentence comprehension deficit in these
patients. On the one hand, a critical aspect of
understanding a sentence is the ability to construct
its grammatical representation, and this may be
impaired in some FTD patients (Grossman et al.,
1996b). Comprehension of a sentence also appears
to require executive resources such as working
memory, inhibitory control, and information
processing speed. Since executive resources such
as these are limited in some FTD patients (Boone
et al., 1999; Elfgren et al., 1993; Hodges and
Patterson, 1996; Jagust et al., 1989; Lindau et al.,
1998; Miller et al., 1991; Razani et al., 2001), an
executive impairment is another potential cause of
sentence comprehension difficulty in these patients.
We have found it difficult to discriminate between
these accounts in our previous studies of sentence
comprehension in FTD for at least two reasons.
First, off-line measures of sentence comprehension
depend in part on task-related resources, and this
has made it difficult to examine the executive
processes contributing specifically to sentence
comprehension. Second, FTD patients participating
in previous group studies often have been
heterogeneous: Averaging across subgroups of FTD
patients with different patterns of clinical difficulty
thus may have obscured our ability to determine if
the basis for impaired sentence comprehension
differs across FTD subgroups.
In the present study, we evaluated clinical
subgroups of FTD patients with a traditional, offline measure of sentence comprehension, and with
an on-line assessment of grammatical sensitivity
that minimizes task-related resource demands.
PNFA patients have obvious clinical difficulty in
their sentence expression, including labored speech
with agrammatic features (Thompson et al., 1997).
The present study confirmed earlier reports that
these patients also have sentence comprehension
difficulty during off-line assessments (Grossman et
al., 1996b; Hodges and Patterson, 1996; Snowden
and Neary, 1994; Snowden et al., 1992; Tyler et
Sentence processing in frontotemporal dementia
al., 1997; Weintraub et al., 1990). Each of the five
PNFA patients participating in this study differed
significantly from control subjects’ off-line
sentence comprehension. Inspection of the pattern
of correlations associated with their sentence
comprehension difficulty begins to demonstrate
some of the factors contributing to their
impairment. In particular, the off-line assessment of
sentence comprehension was correlated with
forward digit span, a measure of auditory-verbal
short-term memory that emphasizes factors such as
the transient retention of phonological material but
requires little mental manipulation. Previous
observations have suggested that PNFA patients
have an auditory-verbal short-term memory
limitation (Grossman et al., 1996b), and that
phonological representations are degraded in PNFA
(Croot et al., 1998; Thompson et al., 1997).
Auditory-verbal short-term memory may be
necessary during sentence comprehension to
support long-distance syntactic dependencies so
that information from the beginning of a sentence
can be retained, possibly in a phonological format,
until reactivation at an appropriate point later in the
sentence (Martin and Romani, 1994). We found
some evidence consistent with a limitation in this
mechanism when we observed that forward digit
span in PNFA patients correlates with the
comprehension of sentences featuring a centerembedded clause more strongly than with sentences
featuring a terminal subordinate clause. We found
no correlation between executive measures and the
on-line measure of sentence processing because the
latter minimizes task-related resource demands.
PNFA patients were sensitive to a grammatical
agreement during an on-line assessment of sentence
processing, suggesting relatively preserved
knowledge
of
grammatically-mediated
dependencies in sentences. However, PNFA
patients differed from control subjects in the time
course of processing a grammatical agreement.
Control subjects thus showed sensitivity to a
grammatical agreement only in its immediate
temporal vicinity, that is, when the processes
implicated in the grammatical agreement are
rapidly activated. By comparison, PNFA patients’
were sensitive to a grammatical agreement only
when the target word followed the grammatical
agreement by several syllables. While PNFA
patients did not differ from control subjects in their
“difference score” in the immediate vicinity of a
grammatical agreement, within-group comparisons
showed that PNFA patients’ responses were
significantly prolonged to words following a
grammatical agreement violation compared to a
correct grammatical agreement only when a delay
separated the grammatical agreement from the
target word. This performance pattern was present
in 3 of 5 PNFA patients, so the somewhat
inconsistent group statistical results may have been
due in part to the small number of PNFA patients
773
we examined. Another factor contributing to
individual differences is that there is some
variability in the clinical manifestation of PNFA:
Some patients are predominantly agrammatic in
their speech, but others are predominantly
dysarthric in a manner suggesting a modalityspecific disorder of word formation and
articulation. Regardless of this within-group
variability, grammatical agreement knowledge does
not appear to have been degraded in PNFA.
Instead, our observations are consistent with the
hypothesis that comprehension difficulty in some
PNFA patients is due to a resource-related
limitation in grammatical processing. One
consequence of PNFA patients’ slowed processing
of grammatical agreements in sentences may be
that they cannot re-activate a co-indexed NP in a
rapid and temporally coordinated fashion at the
location of the gap from which the NP has been
displaced. This resembles in part the pattern
demonstrated by Broca’s aphasics, who also show
delayed gap-filling (Swinney et al., 1996; Zurif et
al., 1993). Given the apparent contribution of
limited auditory-verbal short-term memory to
PNFA patients’ sentence comprehension difficulty,
it is possible that slowed grammatical activation
may allow phonological information in limited
auditory-verbal short-term memory to become
degraded during the course of gap-filling before it
can be used to build a sentence representation.
Additional work will be needed to define the
precise relationship between slowed activation and
limited working memory in PNFA, and to make
direct comparisons between PNFA patients and
Broca’s aphasics.
EXEC patients do not have clinically obvious
language difficulties. Nevertheless, previous work
has suggested that this subgroup of FTD patients
has subtle impairments of sentence comprehension
(Grossman et al., 1996a). The off-line assessment
of comprehension in the present study confirmed
this impression, where non-aphasic EXEC patients
were accurate at understanding only about 51% of
sentences. Some hints about the basis for this
impairment may come from the correlation pattern
seen for EXEC patients’ off-line sentence
comprehension. In particular, their sentence
comprehension was related to measures of
executive resources such as reverse digit span, a
measure of working memory that involves a mental
manipulation component, and accuracy and speed
on the Trails B test, a measure of switching and
inhibitory control. Working memory plays an
important role in manipulating information retained
transiently during processes such as gap-filling
that are necessary for constructing complex
sentence representations or sustaining on-going
comprehension during sentence processing.
Planning and inhibitory control contribute to the
flexibility needed to process non-canonical longdistance syntactic dependencies that often occur in
774
Murray Grossman and Others
a sentence. It is noteworthy that the executive
limitations contributing to poor sentence
comprehension also appear to play a role in the
word comprehension deficit in this subgroup of
FTD patients (Rhee et al., 2001). In that study,
FTD patients performed a word-picture matching
task for verbs and nouns alone and during
concurrent performance of a secondary task. EXEC
patients were significantly impaired on the wordpicture matching task during secondary task
performance but not when performed alone. By
comparison, PNFA patients were significantly
impaired with verbs regardless of the presence of a
secondary task. Verb comprehension accuracy in
EXEC patients also correlated significantly with
measures of switching and inhibitory control such
as Trails B and Stroop tests.
We found that EXEC patients differ from
control subjects and PNFA patients in their on-line
sensitivity to grammatical agreements in sentences.
Unlike control subjects, EXEC patients were
somewhat insensitive to grammatical agreements in
the immediate temporal window of a grammatical
agreement; unlike PNFA patients, EXEC patients
were insensitive to grammatical agreements
following a delay of several syllables. The presence
of a sentence processing abnormality in EXEC
patients on a task that minimizes task-related
resource demands suggests that their limited
executive resources may contribute to impaired
sentence processing. Given the broad-based nature
of an impairment that is not restricted to the
temporal window associated with processing a
grammatical agreement, however, it is not clear that
the deficit in EXEC patients is due to a limitation
in resources specifically implicated in sentence
processing, but may apply equally to other
materials. In this context, we cannot rule out the
possibility that the on-line word-monitoring task
requires divided attention, and task-related resource
demands may have contributed to their on-line
performance as well. We may not have observed a
correlation between on-line sentence processing and
our measures of executive functioning because of
the limited battery of executive measures
administered to these patients. Regardless of the
basis for their difficulty, these observations suggest
that non-aphasic patients with FTD also can have
sentence comprehension deficits, albeit due to a
different source of impairment, and raise the
possibility from a different perspective that
executive resources contribute to sentence
processing. Additional work with on-line sentences
is needed to evaluate the hypothesis that materialneutral resource limitations in EXEC patients
contribute to their sentence processing difficulties.
Although SD patients demonstrated impaired
sentence comprehension as a group during an offline measure, this deficit was due in large part to
the poor performance of only one of the three SD
patients we examined. The SD patients tended to
resemble control subjects in their on-line pattern of
sentence processing. Unfortunately, this could not
be demonstrated with statistical reliability because
of the small number of subjects we studied.
Nevertheless SD patients do not appear to have a
major sentence processing deficit, confirming
earlier observations of Hodges and Patterson
(1996). Stroke patients with Wernicke’s aphasia
also have difficulty understanding single words, but
these patients show relatively preserved processing
of structural aspects of sentences (Swinney et al.,
1996; Zurif et al., 1993). These findings emphasize
that all language deficits will not necessarily lead
to impaired sentence comprehension. This is not to
say that SD patients fully understand sentences,
since their single word comprehension difficulty is
likely to interfere with sentence comprehension.
Our observations appear to suggest that SD patients
are able to process in part the structure of
sentences. Additional comparative work with SD
patients and Wernicke’s aphasics will be needed to
evaluate the patterns of sentence processing in
these two patient groups.
Several caveats should be kept in mind when
interpreting our results. While we have reasonable
clinical and imaging evidence to support the claim
that these patients indeed have a frontotemporal
form of dementia, we have histopathologic proof of
FTD only in a small number of patients
participating in this study. FTD is a relatively rare
disorder, and additional studies are needed with
larger numbers of patients in each subgroup. We
surveyed a range of grammatical forms in the online assessment that have been assessed in Broca’s
aphasia due to a stroke, and specific grammatical
structures should be evaluated in FTD in greater
detail. With these caveats in mind, our observations
are consistent with the hypothesis that grammatical
and resource components contribute to sentence
processing. It appears that the pattern of
comprehension difficulty varies across FTD
subgroup, depending on the sentence processing
component that is compromised. PNFA patients
appear to have slowed activation of grammaticallyrelevant processes, allowing material needed to
build a sentence representation to degrade in their
somewhat limited auditory-verbal short-term
memory. While EXEC patients do not have a
clinically obvious aphasia, some of these patients
are impaired in their sentence comprehension as
well. Comprehension accuracy during an off-line
measure correlated with performance on measures
of executive functioning, and these patients were
also impaired in an on-line assessment of sentence
processing. These observations suggest that the
limited executive resources in EXEC patients may
compromise sentence processing. The relatively
preserved sentence comprehension of SD patients
emphasizes the selective nature of language
processing impairments that can lead to impaired
sentence comprehension.
Sentence processing in frontotemporal dementia
Acknowledgements. This work was supported in part
by the US Public Health Service (AG15116, NS35867,
NS44266and AG17586). We express our appreciation to
Marcia Linebarger for her help in creating the sentence
materials.
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e-mail: [email protected]
(Received 4 December 2002; reviewed 3 February 2003; revised 2 February 2004; accepted 3 February 2004; Action
Editor Jordan Grafman)
Sentence processing in frontotemporal dementia
APPENDIX
EXPERIMENTAL SENTENCE STIMULI1
This child (children) can read almost anything
interesting.
This (These) flower would look beautiful in a
small vase.
These (This) mice ate cheese and scraps from
the dinner table.
These kittens (kitten) had two bowls of milk
this morning.
These (This) books will not be easy for boys to
read.
This (These) dog can find lost shoes, keys,
toys, and jackets.
This (These) picture may be extremely valuable
today.
This large closet (closets) will hold everything
that we bought at the mall.
I had (has) to throw it out even though this
soggy pizza cost alot of money.
The city owns these blue and red buses (bus)
that need to be repaired soon.
Before they constructed too many houses on it,
this (these) tall hill looked lovely and very friendly.
Although we left the directions to her house at
home, this (these) map will show us how to get
there.
Even though we thought they looked fresh and
sweet, these (this) apples were too mushy and sour
to eat.
I have many errands to run before I go to the
party, but these silk dresses (dress) need to be
cleaned very quickly.
Although it is very wet and slushy outside
today, these (this) boots should keep my feet warm
and dry.
Because of the fire that engulfed the gallery or
the museum, this (these) photograph may be ruined
for good.
The trees (tree) will all look beautiful in the
spring.
The girls (girl) all hoped to be invited to his
house.
The ducks (duck) all ran toward the boy
carrying the bread.
The boys (boy) may each take one candle from
that big box.
The children (child) all jumped on to the wagon
at once.
The cars (car) will all be covered with lovely
flowers.
The children (child) can each take one cookie
from the jar.
The girls (girl) may each buy one item at the
school store.
Even though there was still a lot to be done at
work, the parents (parent) should have both gone
to the baseball game yesterday.
777
In order to be eligible for college financial aid,
the teenagers (teenager) had all sent in their
applications by March 1st.
The weather may be causing some delays, but
the flights (flight) from Boston should have both
landed by the end of the day.
After the children leave at the end of the school
day, the English teachers (teacher) will all go to the
very long meeting.
Even though the final history exam was quite
difficult, the students (student) should all be able to
answer that question.
Even though they cannot attend the reception
this evening, Fran and the children (child) will all
be at the early morning ceremony.
When we returned from the movie we found
that the windows (window) had all been
completely broken by a burglar.
After spending the day playing in the snow, the
kittens (kitten) should all drink a bowl of warm
milk.
The cows (cow) were sick after eating the
poisoned hay.
The tree was (were) in full bloom when we
visited you.
The books (book) were much too long for me
to read in one night.
The children (child) were sad when it was time
to leave.
The kids were (was) much too rowdy to sit
through the entire movie.
The bus and the cars (was) were close to the
busy roadside.
The teachers (teacher) have done a very good
job this year.
The buildings (building) are too close together
in this city.
The three beautiful brown and white spotted
horses (horse) are running around the corral
quickly.
That radio is (are) too loud to play on the train.
That old car and pick-up truck were (was) not
in very good condition.
Even though they are tall and strong, the trees
(tree) are not surviving the strong storm.
The fluffy white kittens and rabbits were (was)
bought from a pet store.
The two proud and happy grandmothers
(grandmother) are in the warm kitchen.
The small red and black birds have (has) left us
for the winter months.
When they are tired, the tiny black and tan
striped kittens (kitten) go to sleep quickly at night.
1
The error corresponding to each control sentence involves substituting
the word in parentheses for its preceding word. Target words are
underlined: the “near” target immediately follows the grammatical
agreement, and the “distant” target follows the grammatical agreement by
about four syllables.