Gayle DeDe

A study of syntactic processing in aphasia I: Behavioral (psycholinguistic) aspects

This paper presents the results of a study of syntactically based comprehension in aphasic patients. We studied 42 patients with aphasia secondary to left hemisphere strokes and 25 control participants. We measured off-line, end-of-sentence, performance (accuracy and reaction time) in two tasks that require comprehension--enactment and sentence-picture matching--and in grammaticality judgment, with whole sentence auditory presentation. We also used sentence-picture matching and grammaticality judgment as tasks in two self-paced listening studies with the same patients to measure on-line performance. In each task and presentation format, we presented sentences that tested the ability to assign and interpret three structural contrasts chosen to examine different basic syntactic operations: actives and passives, subject and object extracted relative clauses, and reflexive pronouns and matched sentences without these elements. We examined these behavioral data to determine patterns of impairment in individual patients and in groups of patients, using correlational analyses, factor analyses, and analyses of variance. The results showed that almost no individual patients had stable deficits referable to the ability to interpret individual syntactic structures, that a variety of structural features contributed to sentence processing complexity both on-line and off-line, that correct responses were associated with normal on-line and errors with abnormal performance, and that the major determinant of performance is a factor that affected performance on all sentence types. The results indicate that the major cause of aphasic impairments of syntactically based comprehension are intermittent reductions in the processing capacity available for syntactic, interpretive, and task-related operations.

A study of syntactic processing in aphasia II: Neurological aspects

This paper presents the results of a study of the effects of left hemisphere strokes on syntactically-based comprehension in aphasic patients. We studied 42 patients with aphasia secondary to left hemisphere strokes and 25 control subjects for the ability to assign and interpret three syntactic structures (passives, object extracted relative clauses, and reflexive pronouns) in enactment, sentence-picture matching and grammaticality judgment tasks. We measured accuracy, RT and self-paced listening times in SPM and GJ. We obtained magnetic resonance (MR) and 5-deoxyglucose positron emission tomography (FDG PET) data on 31 patients and 12 controls. The percent of selected regions of interest (ROIs) that was lesioned on MR and the mean normalized PET counts per voxel in ROIs were calculated. In regression analyses, lesion measures in both perisylvian and non-perisylvian ROIs predicted performance. Patients who performed at similar levels behaviorally had lesions of very different sizes, and patients with equivalent lesion sizes varied greatly in their level of performance. The data are consistent with a model in which the neural tissue that is responsible for the operations underlying sentence comprehension and syntactic processing is localized in different neural regions in different individuals.

Teaching self-cues: A treatment approach for verbal naming

Background: Very few treatment studies have examined the effects of training individuals with anomia to self-generate phonological cues. There is evidence that treatments using written language can improve phonological access for some patients. Such approaches are most effective when the patients are taught strategies to facilitate oral reading of targets. Aim: The goal of the present study was to evaluate the effects of a naming treatment designed to teach a chronic nonfluent aphasic to generate self-cues based on partial access to the written form of words and tactile (placement) cues. Methods: Therapy focused on naming items using a modified cueing hierarchy that incorporated written naming and tactile cues. An AB design was used to examine treatment effects in an individual with aphasia and apraxia of speech. Outcomes and Results: Verbal naming improved in target compared to control items. Generalisation was observed to verbal and written naming on standardised measures but not to novel stimuli with initial target and control phonemes. Testing 6 weeks post-treatment revealed limited loss of treatment gains. Conclusions: The results provide qualified support for the treatment programme.

Task-independent and task-specific syntactic deficits in aphasic comprehension

We present 42 case studies of aphasic syntactic comprehension performances in sentence-picture matching and object manipulation, examining the data for the existence of deficits referable to particular syntactic structures, or such structures in a single sentence form, in both tasks. No deficits affected performance on all sentence types that contained a particular structure in both tasks. Most deficits affected single sentence forms in only one task, and no isolated deficits occurred. The implications of the pattern of performance for the nature of aphasic deficits are discussed.

Construct validity and reliability of working memory tasks for people with aphasia

Background: Although several studies have examined working memory in people with aphasia, there is little information about the psychometric properties of tasks used to measure working memory in this population. Aims: The aims of this study were (1) to examine the construct validity, internal consistency, and test-retest reliability of several working memory tasks and (2) to determine which tasks were feasible to use with people with a wide range of aphasia severities. Methods & Procedures: In experiment one, non-brain-damaged adults (n = 47) completed a set of working memory tasks that were designed for use with people with aphasia. The tasks included 1-back, 2-back, listening span and forward and backward versions of picture span and square span. Construct validity was assessed by correlating performance on the new tasks with a composite score based on three well-established working memory tasks with known psychometric properties. Ten older adults completed the testing battery twice to measure test-retest reliability. Internal consistency was estimated using split-half reliability. In experiment two, people with aphasia (n = 12) completed the new working memory tasks. Outcomes & Results: The picture span tasks demonstrated acceptable test-retest reliability, internal consistency, and construct validity. Controls showed ceiling effects on 1-back and people with aphasia showed floor effects on listening span. Both the square span tasks and n-back showed poor internal consistency for people with aphasia and age-matched controls. Conclusions: A composite score based on the forward and backward versions of picture span provides a measure of verbal working memory with acceptable construct validity, internal consistency and test-retest reliability and can be completed by non-brain-damaged adults and people with aphasia.

Utilization of Prosodic Information in Syntactic Ambiguity Resolution

Two self paced listening experiments examined the role of prosodic phrasing in syntactic ambiguity resolution. In Experiment 1, the stimuli consisted of early closure sentences (e.g., “While the parents watched, the child sang a song.”) containing transitive-biased subordinate verbs paired with plausible direct objects or intransitive-biased subordinate verbs paired with implausible direct objects. Experiment 2 also contained early closure sentences with transitively and intransitive-biased subordinate verbs, but the subordinate verbs were always followed by plausible direct objects. In both experiments, there were two prosodic conditions. In the subject-biased prosodic condition, an intonational phrase boundary marked the clausal boundary following the subordinate verb. In the object-biased prosodic condition, the clause boundary was unmarked. The results indicate that lexical and prosodic cues interact at the subordinate verb and plausibility further affects processing at the ambiguous noun. Results are discussed with respect to models of the role of prosody in sentence comprehension.

Lexical and Prosodic Effects on Syntactic Ambiguity Resolution in Aphasia

The purpose of this study was to determine whether and when individuals with aphasia and healthy controls use lexical and prosodic information during on-line sentence comprehension. Individuals with aphasia and controls (n = 12 per group) participated in a self-paced listening experiment. The stimuli were early closure sentences, such as “While the parents watched(,) the child sang a song.” Both lexical and prosodic cues were manipulated. The cues were biased toward the subject- or object- of the ambiguous noun phrase (the child). Thus, there were two congruous conditions (in which both lexical cues and prosodic cues were consistent) and two incongruous conditions (in which lexical and prosodic cues conflicted). The results showed that the people with aphasia had longer listening times for the ambiguous noun phrase (the child) when the cues were conflicting, rather than consistent. The controls showed effects earlier in the sentence, at the subordinate verb (watched or danced). Both groups showed evidence of reanalysis at the main verb (sang). These effects demonstrate that the aphasic group was sensitive to the lexical and prosodic cues, but used them on a delayed time course relative to the control group.

Effects of Verb Bias and Syntactic Ambiguity on Reading in People with Aphasia

Background: The Lexical Bias Hypothesis claims that people with aphasia (PWA) have difficulty understanding sentences when the verb’s argument structure bias conflicts with the sentence structure. This hypothesis can account for comprehension deficits that affect simple sentences, but the role of verb bias has not been clearly demonstrated in temporarily ambiguous sentences. Aims: This study examined how verb bias affects comprehension of temporarily ambiguous and unambiguous sentences using self-paced reading. Methods & Procedures: PWA and controls read sentences that contained sentential complements (e.g., The talented photographer accepted (that) the fire could not have been prevented). The main verb was biased to take a direct object (e.g., accepted) or a sentential complement (e.g., admitted). In addition, the sentential complement was either introduced by the complementiser that (i.e., unambiguous) or unmarked (i.e., ambiguous). Results: The reading times of PWA were affected more by verb bias than by the presence of the complementiser, whereas the control group’s reading times were more affected by the presence or absence of the complementiser. Conclusions: The results were generally consistent with the Lexical Bias Hypothesis, and showed that a mismatch between verb bias and sentence structure affected the processing of unambiguous and temporarily ambiguous sentences in PWA.

Rasch models of aphasic performance on syntactic comprehension tests.

Responses of 42 people with aphasia to 11 sentence types in enactment and sentence–picture matching tasks were characterized using Rasch models that varied in the inclusion of the factors of task, sentence type, and patient group. The best fitting models required the factors of task and patient group but not sentence type. The results provide evidence that aphasic syntactic comprehension is best accounted for by models that include different estimates of patient ability in different tasks and different difficulty of all sentences in different groups of patients, but that do not include different estimates of patient ability for different types of sentences.

Factor analysis of aphasic syntactic comprehension disorders

Background: Many people with aphasia have impaired sentence comprehension. Previous studies using factor analysis have suggested that a single factor accounts for performance on measures of sentence comprehension (e.g., Caplan, Baker, & Dehaut, 1985). However, this work has been limited to measures of accuracy on single sentence comprehension tasks. This research was supported by grants from NIDCD (DC00942 to David Caplan and DC007564 to Gayle DeDe). We are grateful to Sue Kemper for comments on an earlier draft and suggestions regarding CFAs. Aims: The purpose of this study is to further examine the factor structure underlying aphasic sentence comprehension using accuracy, reaction time (RT), and on‐line measures using both exploratory and confirmatory factor analyses. Methods & Procedures: A total of 42 people with aphasia and 40 non‐brain‐damaged controls were tested on 11 sentence types and five tasks. Accuracy and RT data are reported for the whole sentence presentation version of sentence–picture matching, and accuracy data are reported for object manipulation. Confirmatory factor analyses examining measurement invariance across groups and tasks are presented. Exploratory factor analyses of on‐line syntactic processing are also presented. Outcomes & Results: Results indicated that one‐factor models best account for accuracy and RT data. Measurement of factors was partially invariant across groups and tasks. Factor structures suggestive of syntactic processes emerged in the analyses of on‐line measures. Conclusions: This study suggests that syntactic processes may load on separate factors during on‐line parsing and that syntactic processes do not dissociate when the parsers output is used in the service of a task at the end of the sentence.