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Biomedical subjects

D Caplan

Publications and source records attributed to D Caplan.

At least 19 recordsLinked to original sources
PubMed1998

Sentence production by aphasic patients in a constrained task.

Sixty aphasic patients and 55 normal control subjects were tested on a sentence production protocol that required subjects to produce specific sentence types from semantic representations. Normal subjects produced the expected targets with great reliability. Analysis of the patients' performance indicated that patients had difficulty producing both grammatical forms and thematic roles. Patients had more trouble producing grammatical elements than content words, and showed differential difficulty on sentence types that had more grammatical elements and in which the order of thematic roles was non-canonical. The results provide evidence regarding the processing load imposed by different components of the sentence production process.

Adult↗
PubMed1998

Task demands and sentence comprehension in patients with dementia of the Alzheimer's type.

Patients with dementia of the Alzheimer's type (DAT) and matched normal controls were given three tests of syntactic comprehension in which nonlinguistic visual and memory task demands were varied. In all tasks, subjects were presented spoken semantically reversible sentences with a variety of syntactic structures and required to match the sentence to a picture. In the first experiment, subjects matched the spoken sentence to one of two pictures that appeared either before or immediately following the presentation of the sentence. The target picture depicted the spoken sentence correctly and the foil depicted the reversed thematic roles to those in the sentence (i.e., it was a syntactic foil). The second experiment employed a sentence video-verification task in which subjects were required to determine if the spoken sentence matched a videotaped depiction of the action in the sentence or a syntactic foil. In the third experiment, in different conditions, subjects were required to determine whether the spoken sentence matched a single picture or to choose the picture that matched the sentence from an array of two or three pictures. In this experiment, both lexical and syntactic foils were used. In all tasks, DAT patients were affected by the number of propositions in the presented sentence, but not by the syntactic complexity of the sentence. Control subjects also were unaffected by the syntactic complexity of the sentence; the number-of-proposition effect was present in some experiments in the control population. Comparison of performance across the one-, two-, and three-picture versions of the task showed that the magnitude of the effect of number of propositions increased as the number of pictures in the array increased. In addition, analysis of the data from each of the tasks separately showed that the effect of number of propositions only occurred when subjects were attempting to match the target to a syntactic foil (one-picture version) or to choose between the target and a syntactic foil (two- and three-picture versions). The results support the view that patients with DAT do not have disturbances affecting syntactic processing. In addition, they suggest that the effect of number of propositions arises at a stage of analysis that is partially separate from assigning sentence meaning, such as in holding a representation of the sentence in memory until the pictures can be analyzed and encoded and/or in comparing the results of the picture analysis with a stored representation of the sentence meaning.

Aged↗
PubMed1998

Rapid, automated assay for progesterone on the Abbott AxSYM analyzer.

We describe an automated assay for progesterone (P4) in human serum and plasma with the Abbott AxSYM random-access immunoassay analyzer. In this one-step competitive assay, P4 immobilized onto latex microparticles competes with sample P4 for binding to a conjugate of alkaline phosphatase (AP) and anti-P4 antibody. Total CVs ranged from 3.4% to 8.2% in multiple precision studies conducted according to the 20-day NCCLS EP5-T protocol. The detection limit (zero calibrator + 2 SD) was 0.10 microg/L across 36 experiments. Values for diluted samples were 83-116% of expected. Recovery of P4 added to serum specimens was 92-115%. Cross-reactivities with 43 natural and synthetic steroids were 0-6.3%. No significant interference was detected from bilirubin, protein, erythrocytes, hemoglobin, triglycerides, or cholesterol. In a multisite correlation study, AxSYM P4 results compared well with results from a commercial RIA method (n = 1156; r = 0.976; slope = 1.03; y-intercept = 0.04). Assay throughput is >80 tests per hour in batch mode, 60 tests per hour with mixed load list configurations.

Autoanalysis↗
PubMed1997

The use of contextual information by right brain-damaged individuals in the resolution of ambiguous pronouns.

Two experiments were conducted with the primary purpose of investigating the ability of right brain-damaged (RBD) individuals to use contextual information--at the level of the single sentence, in terms of the integration of information between clauses, and at the level of a minimal discourse (i.e., two sentences)--in the resolution of ambiguous pronouns. The investigation was extended to a group of left brain-damaged (LBD) and non-brain-damaged (NBD) individuals. Contrary to the prevailing view that RBD patients have difficulty in the use of contextual information to process language, both experiments were consistent in demonstrating that the RBD group was influenced by contextual information in a manner similar to that demonstrated by both the LBD and NBD groups.

Adult↗
PubMed1997

The use of contextual information related to general world knowledge by right brain-damaged individuals in pronoun resolution.

This study investigated the ability of right brain-damaged individuals (RBD) to use contextual information to resolve ambiguous pronouns. Subjects were presented with sentence pairs and required to resolve the ambiguous pronoun in the second sentence. Contrary to the prevailing view that RBD patients have difficulty using contextual information to integrate language, the RBD group demonstrated a normal pattern of response, demonstrating a sensitivity to the pragmatic information contained in the leading sentence. They responded more quickly to sentences with a pragmatically constrained preferred referent than to those sentences for which there was no preferred referent. As well, they chose the preferred referent significantly more often than the non-preferred referent. These results suggest that RBD patients can use contextual information at the level of a minimal discourse (i.e., two sentences).

Adult↗
PubMed1997

Working memory and on-line sentence comprehension in patients with Alzheimer's disease.

We examined the ability of patients with dementia of the Alzheimer's type (DAT) and normal controls to perform a sentence acceptability judgment task that required determining the referent for a reflexive pronoun. Performance on three different sentence types that differed in terms of syntactic complexity was assessed. Subjects performed the task alone and under two different dual-task conditions which required continuous, externally paced responses. DAT patients were more affected than controls by the dual-task conditions, but were not disproportionately impaired on the more complex sentence types. The failure of DAT patients to be disproportionately affected on the most complex sentence types in the dual-task conditions provides evidence for the separation of the processing resources that are used in sentence comprehension from those involved in other tasks.

Aged↗
PubMed1997

Determinants of sentence comprehension in aphasic patients in sentence-picture matching tasks.

The results of two studies of sentence comprehension in aphasic patients using sentence-picture matching tests are presented. In the first study, 52 aphasic patients were tested on 10 sentence types. Analysis of the number of correct responses per sentence type showed effects of syntactic complexity and number of propositions. Factor analysis yielded first factors that accounted for two-thirds of the variance in performance to which all sentence types contributed. Clustering analysis yielded groups of patients whose performances progressively deteriorated and in which performance was more affected by sentence types that were harder for the group overall. These results were very similar to those previously obtained using an enactment task. In the second study, 17 aphasic patients were tested on the same 10 sentence types using both sentence-picture matching and enactment tasks. Correlational analyses showed that performance on the two tests was significantly correlated across both subjects and sentences. The results provide data relevant to the determinants of the complexity of a sentence in auditory comprehension.

Adult↗
PubMed1996

An examination of impaired acoustic-phonetic processing in aphasia.

This research examines the nature of acoustic-phonetic impairments found in aphasia, and the reliability of patient performance on phoneme discrimination and identification tasks. Aphasic patients were tested on three phoneme discrimination tasks examining their ability to discriminate items on the basis of contrasts in sonorance, manner, place, or voicing using both spoken and synthetic stimuli. One of these tests involving the discrimination of spoken, one-syllable items was given to patients on three occasions over the course of 1 year to examine short- and long-term test reliability. In addition to these measures, patients were tested on three phoneme identification tasks using stimulus items drawn from the discrimination tests. The results of these tests show that aphasic patients may display stable patterns of performance on these measures over time and between tests. Furthermore, these findings suggest that discriminations of synthetic speech do not necessarily reflect patients' ability to discriminate spoken speech tokens. These results are interpreted as evidence that aphasics display stable, discrete impairments in acoustic-phonetic processing, and that these deficits may be measured reliably using phoneme discrimination and identification tasks using natural speech.

Adult↗
PubMed1996

Localization of syntactic comprehension by positron emission tomography.

Positron Emission Tomography (PET) was used to determine regional cerebral blood flow (rCBF) when eight normal right-handed males read and made acceptability judgments about sentences. rCBF was greater in Broca's area (particularly in the pars opercularis) when subjects judged the semantic plausibility of syntactically more complex sentences as compared to syntactically less complex sentences. rCBF was greater in left perisylvian language areas when subjects had to decide whether sentences were semantically plausible than when subjects had to decide whether syntactically identical sentences contained a nonsense word. The results of this experiment suggest that overall sentence processing occurs in regions of the left perisylvian association cortex. The results also provide evidence that one particular aspect of sentence processing (the process that corresponds to the greater difficulty of comprehending center-embedded than right-branching relative clause sentences) is centered in the pars opercularis of Broca's area. This process is likely to be related to the greater memory load associated with processing center-embedded sentences.

Adult↗
PubMed1996

The capacity theory of sentence comprehension: critique of Just and Carpenter (1992)

The authors review M.A. Just and P.A. Carpenter's (1992) "capacity" theory of sentence comprehension and argue that the data cited by Just and Carpenter in support of the theory are unconvincing and that the theory is insufficiently developed to explain or predict observed patterns of results. The article outlines an alternative to the capacity theory, according to which the unconscious, obligatory operations involved in assigning the syntactic structure of a sentence do not use the same working memory resource as that required for conscious, controlled verbally mediated processes.

Attention↗
PubMed1996

The measurement of verbal working memory capacity and its relation to reading comprehension.

Ninety-four subjects were tested on the Daneman and Carpenter (1980) reading span task, four versions of a related sentence span task in which reaction times and accuracy on sentence processing were measured along with sentence-final word recall, two number generation tasks designed to test working memory, digit span, and two shape-generation tasks designed to measure visual-spatial working memory. Forty-four subjects were retested on a subset of these measures at a 3-month interval. All subjects were tested on standard vocabulary and reading tests. Correlational analyses showed better internal consistency and test-retest reliability of the sentence span tasks than of the Daneman-Carpenter reading span task. Factor analysis showed no factor that could be related to a central verbal working memory; rotated factors suggested groupings of tests into factors that correspond to digit-related tasks, spatial tasks, sentence processing in sentence span tasks, and recall in sentence span tasks. Correlational analyses and regression analyses showed that the sentence processing component of the sentence span tasks was the best predictor of performance on the reading test, with a small independent contribution of the recall component. The results suggest that sentence span tasks are unreliable unless measurements are made of both their sentence processing and recall components, and that the predictive value of these tasks for reading comprehension abilities lies in the overlap of operations rather than in limitations in verbal working memory that apply to both.

Adolescent↗
PubMed1996

Location of lesions in stroke patients with deficits in syntactic processing in sentence comprehension.

Sixty patients, 46 with left-hemisphere strokes and 14 with right-hemisphere strokes, and 21 normal control subjects were tested for the ability to use syntactic structures to determine the meaning of sentences. Patients enacted thematic roles (the agent, recipient and goal of an action) in 12 examples of each of 25 sentence types, which were designed to test a wide variety of syntactic operations. Both right-and left-hemisphere damaged patients performed worse than control subjects on syntactically complex sentences, and left-hemisphere patients performed worse than right-hemisphere patients. Eighteen patients with left-hemisphere strokes underwent CT scanning to image the perisylvian association cortex. There was no difference between the performance of patients with anterior and posterior lesions, and no correlation between the degree of impairment and the size of lesions in different regions of the perisylvian cortex. These results are consistent with the view that syntactic processing involves an extensive neural system, whose most important region is the left perisylvian cortex. When these results are combined with those of other studies, the picture that emerges is one in which, within this cortical region, this system manifests features of both distributed and localized processing.

Adult↗
PubMed1996

Processing resource capacity and the comprehension of garden path sentences.

Three experiments explored the relationship between verbal working memory capacity and the comprehension of garden path sentences. In Experiment 1, subjects with high, medium, and low working memory spans made acceptability judgments about garden path and control sentences under whole sentence and rapid serial visual presentation (RSVP) conditions. There were no significant differences between subjects with different working memory spans in the comprehension of garden path sentences in either condition. In Experiments 2A and 2B, subjects with high and low working memory spans were tested on the same materials at three RSVP rates. There were no significant differences between subjects with different working memory spans in the magnitude of the effect of garden path sentences at any presentation rate. The results suggest that working memory capacity, as measured by the Daneman and Carpenter (1980) reading span task, is not a major determinant of individual differences in the processing of garden path sentences.

Aged↗
PubMed1995

On the nature of the phonological output planning processes involved in verbal rehearsal: evidence from aphasia.

This paper describes the performance of an aphasic patient, R.W., in producing the sounds of words and in verbal rehearsal. R.W. showed evidence of retained abilities to access aspects of the forms of spoken words but made numerous phonemic paraphasias in single word production tasks. He did not show features of dysarthria or apraxia of speech. This pattern indicates that his deficit affected a process that plans the phonological forms of spoken words. R.W.'s performances in short-term memory and metalinguistic tasks involving single words were consistent with impaired rehearsal functions. The pattern of results indicates that rehearsal requires planning of the phonological forms of spoken items and suggests that activating entries in the phonological output lexicon is not adequate to permit rehearsal to proceed normally.

Aphasia↗
PubMed1995

Issues arising in contemporary studies of disorders of syntactic processing in sentence comprehension in agrammatic patients.

This paper reviews recent studies of sentence comprehension in agrammatic patients. The conclusion is reached that more detailed study of individual patients is necessary to support hypotheses that have been presented concerning the deficit in these patients and that the rationale for studying comprehension in this group of patients is not well developed. A set of suggested criteria is presented for patient analysis in this field.

Aphasia↗
PubMed1995

Analysis of lesions by MRI in stroke patients with acoustic-phonetic processing deficits.

We tested 10 aphasic stroke patients for the ability to discriminate and identify English phonemes. All patients underwent MRI and had their scans analyzed morphometrically. Patients with impairments in acoustic-phonetic processing tended to have lesions involving the left posterior supramarginal gyrus and the bordering parietal operculum, an observation further supported by regression and correlation analyses. These results are interpreted as evidence that the region including the left posterior supramarginal gyrus and parietal operculum plays a significant role in acoustic-phonetic processing.

Adult↗