Biomedical subjects

David Caplan

Publications and source records attributed to David Caplan.

12 recordsLinked to original sources

PubMed2003

Training with cognitive sequences improves syntactic comprehension in agrammatic aphasics.

A major open question in cognitive neuroscience concerns the modularity of language: does human language rely, in part, on neural processes that are not language specific? Such reliance would predict that learning should transfer between non-linguistic and linguistic domains via this common neural basis. To test this prediction, we studied effects of non-linguistic cognitive sequence training on syntactic comprehension of six left-hemisphere damaged aphasic patients. Syntactic comprehension impairment was quantified before and after 10 weeks of training on a non-linguistic sequence processing task. This task used a transformational rule specifically corresponding to the transformation required for understanding a particular type of sentence referred to as relativised. Non-linguistic sequencing improved significantly with training (day effect: F(9,45)=3.7, <0.005). Moreover, a significant transfer of this improvement was observed for relativised, but not active nor passive sentences (pre-post x type interaction: F(2,10)=4.72, <0.05). The specificity of this transfer indicates that language relies partially on functional and neural processes that are not language specific.

Aged↗

PubMed2003

Distinct patterns of neural modulation during the processing of conceptual and syntactic anomalies.

The aim of this study was to gain further insights into how the brain distinguishes between meaning and syntax during language comprehension. Participants read and made plausibility judgments on sentences that were plausible, morphosyntactically anomalous, or pragmatically anomalous. In an event-related potential (ERP) experiment, morphosyntactic and pragmatic violations elicited significant P600 and N400 effects, respectively, replicating previous ERP studies that have established qualitative differences in processing conceptually and syntactic anomalies. Our main focus was a functional magnetic resonance imaging (fMRI) study in which the same subjects read the same sentences presented in the same pseudorandomized sequence while performing the same task as in the ERP experiment. Rapid-presentation event-related fMRI methods allowed us to estimate the hemodynamic response at successive temporal windows as the sentences unfolded word by word, without assumptions about the shape of the underlying response function. Relative to nonviolated sentences, the pragmatic anomalies were associated with an increased hemodynamic response in left temporal and inferior frontal regions and a decreased response in the right medial parietal cortex. Relative to nonviolated sentences, the morphosyntactic anomalies were associated with an increased response in bilateral medial and lateral parietal regions and a decreased response in left temporal and inferior frontal regions. Thus, overlapping neural networks were modulated in opposite directions to the two types of anomaly. These fMRI findings document both qualitative and quantitative differences in how the brain distinguishes between these two types of anomalies. This suggests that morphosyntactic and pragmatic information can be processed in different ways but by the same neural systems.

Adult↗

PubMed2003

Effects of age and speed of processing on rCBF correlates of syntactic processing in sentence comprehension.

Positron emission tomography (PET) was used to determine the effect of age on regional cerebral blood flow (rCBF) during syntactic processing in sentence comprehension. PET activity associated with making plausibility judgments about syntactically more complex subject object (SO) sentences (e.g., The juice that the child spilled stained the rug) was compared to that associated with making judgments about synonymous syntactically simpler object subject (OS) sentences (e.g., The child spilled the juice that stained the rug). In the first study, 13 elderly (70-80-year-old) subjects showed increased rCBF in the left inferior parietal lobe. This result contrasted with previous studies, which have shown activation in Broca's area in this task in young subjects. Elderly subjects were noted to have longer reaction times than young subjects previously tested. A second study found that young subjects whose reaction times were as long as those of the elderly subjects tested in Experiment 1 activated left superior parietal, and not left inferior frontal, structures. A third experiment found that elderly subjects with reaction times as fast as previously tested young subjects activated left inferior frontal structures. The results suggest that the speed of syntactic processing, but not age per se is related to the neural location where one aspect of syntactic processing is carried out.

Adult↗

PubMed2003

On-line syntactic processing in aphasia: studies with auditory moving window presentation.

Twenty-eight aphasic patients with left hemisphere strokes and matched control subjects were tested on an auditory moving windows task in which successive phrases of a sentence were presented in response to subjects' self-paced button presses and subjects made timed judgments regarding the plausibility of each sentence. Pairs of sentences were presented that differed in syntactic complexity. Patients made more errors and/or took longer in making the plausibility judgments than controls, and were more affected than controls by the syntactic complexity of a sentence in these judgments. Normal subjects showed effects of syntactic structure in self-paced listening. On-line syntactic effects differed in patients as a function of their comprehension level. High-performing patients showed the same effects as normal control subjects; low performing patients did not show the same effects of syntactic structure. On-line syntactic effects also differed in patients as a function of their clinical diagnosis. Broca's aphasic patients' on-line performances suggested that they were not processing complex syntactic structures on-line, while fluent aphasics' performances suggested that their comprehension impairment occurred after on-line processing was accomplished. The results indicate that many aphasic patients retain their ability to process syntactic structure on-line, and that different groups of patients with syntactic comprehension disorders show different patterns of on-line syntactic processing.

Acoustic Stimulation↗

PubMed2003

Electrophysiological distinctions in processing conceptual relationships within simple sentences.

The aim of this study was to determine whether or not the brain distinguishes between two types of conceptual relationships between noun-phrases (NPs) and verbs during online processing of simple, unambiguous English sentences. A total of 15 participants read and made plausibility judgments on sentences that were presented word-by-word. Event-related potentials elicited by critical verbs were measured. In all cases, the critical verb assigned a thematic role of 'agent' to its subject NP. In non-violated sentences (e.g. "For breakfast the boys would only eat em leader"), the preceding NP was animate ("boys") and was a likely agent for a given verb ("eat") given its preceding context ("For breakfast"). In both types of conceptually violated sentences, the NPs were unlikely agents for the verbs given their preceding contexts. In 'thematic role animacy violations' (e.g. "For breakfast the eggs would only eat em leader"), the NP was inanimate ("eggs") and was therefore more likely to occupy the role of 'theme' than 'agent', i.e. eggs, being inanimate, cannot eat but they can be eaten. In 'non-thematic role pragmatic violations' (e.g. "For breakfast the boys would only bury em leader"), the thematic role of agent assigned by the verb ("bury") to its preceding NP ("boys") is inherently acceptable (boys can bury), but the sentence is still pragmatically incongruous given the preceding context ("At breakfast"). As expected, the non-thematic role pragmatic violations elicited a significant N400 effect. The thematic role animacy violations elicited a smaller N400 effect that only approached significance across all participants. The thematic role animacy violations, however, elicited a significant P600 effect-an ERP component that is most commonly associated with processing syntactic information during language comprehension. We discuss the possibility that the P600 was elicited by the thematic role animacy violations (but not by the non-thematic role pragmatic violations) because, in the former but not the latter, there was an online attempt to structurally repair and make sense of the sentences by reassigning the thematic role of the NP that preceded the critical verb from 'agent' to 'theme'. Our findings suggest a qualitative neural distinction in processing these two types of conceptual anomalies within simple, unambiguous sentences.

Adolescent↗

PubMed2003

Individual differences in rCBF correlates of syntactic processing in sentence comprehension: effects of working memory and speed of processing.

Positron emission tomography (PET) was used to determine the effect of working memory and speed of sentence processing on regional cerebral blood flow (rCBF) during syntactic processing in sentence comprehension. PET activity associated with making plausibility judgments about syntactically more complex subject-object (SO) sentences (e.g., The juice that the child spilled stained the rug) was compared to that associated with making judgments about synonymous syntactically simpler object-subject (OS) sentences (e.g., The child spilled the juice that stained the rug). Two groups of nine subjects differing in working memory and matched for speed of sentence processing both showed increases in rCBF in lateral posteroinferior frontal lobe bilaterally. The subjects were reclassified to form two groups of eight subjects who were matched for working memory but who differed in speed of sentence processing. Fast-performing subjects activated lateral posteroinferior frontal lobe bilaterally and slow-performing subjects showed activation of left superior temporal lobe. The results indicate that rCBF responses to syntactic comprehension tasks vary as a function of speed of sentence processing but not as a function of working memory.

Adult↗

PubMed2003

On-line syntactic processing under concurrent memory load.

Thirty-six university students were tested in a plausibility judgment task using a self-paced listening paradigm under no-interference and two-digit load conditions. Listening times were longer at syntactically more complex portions of syntactically more complex sentences, and greater loads led to increased listening times. However, listening times at syntactically more complex positions in syntactically more complex sentences did not increase more than listening times at comparable positions in syntactically simple sentences under digit load conditions. The results indicate that a concurrent memory load does not reduce the availability of working memory resources used for on-line syntactic processing and, thus, provide evidence that the working memory system used for assigning syntactic structure is separate from that measured by standard working memory tasks.

Adolescent↗

PubMed2002

Face encoding and psychometric testing in healthy dextrals with right hemisphere language.

OBJECTIVE: To document how right hemisphere language dominance in neurologically normal right-handed individuals affects lateralization of face encoding and level of performance in neuropsychological tests. METHODS: Three healthy right-handed adults with predominantly right hemisphere language activation during single-word or sentence-level processing were identified from 210 consecutive right-handed subjects studied using blood oxygenation level-dependent contrast fMRI. These three study subjects (S1 to S3) underwent a second scanning session where they performed word and face encoding. Their functional scans were contrasted with those obtained from six healthy control subjects (C1 to C6) with left hemisphere language dominance. Psychometric tests were performed on the study subjects. RESULTS: Right hemisphere-dominant language activation was reproduced in the second scanning session in the three study subjects. The extent to which the lateralization of face encoding was reversed varied. Right hemisphere language was associated with lower (but within normal) verbal IQ compared with performance IQ in two of three volunteers. Verbal and nonverbal memory scores were normal and did not differ appreciably. CONCLUSION: Right hemisphere-dominant language in healthy dextrals exists but is rare. The extent to which face encoding is reversed in these individuals is variable. Cognitive function does not appear to be significantly compromised even though some psychometric test scores are asymmetric in favor of nonverbal performance when the reversal of lateralization of face and word memory is not complete.

Adult↗

PubMed2002

Vascular responses to syntactic processing: event-related fMRI study of relative clauses.

Event-related functional magnetic resonance imaging was used to investigate the localization of syntactic processing in sentence comprehension. Matched pairs of sentences containing identical lexical items were compared. One member of the pair consisted of a syntactically simpler sentence, containing a subject relativized clause. The second member of the pair consisted of a syntactically more complex sentence, containing an object relativized clause. Ten subjects made plausibility judgments about the sentences, which were presented one word at a time on a computer screen. There was an increase in BOLD hemodynamic signal in response to the presentation of all sentences compared to fixation in both right and left occipital cortex, the left perisylvian cortex, and the left premotor and motor areas. BOLD signal increased in the left angular gyrus when subjects processed the complex portion of syntactically more complex sentences. This study shows that a hemodynamic response associated with processing the syntactically complex portions of a sentence can be localized to one part of the dominant perisylvian association cortex.

Adolescent↗

PubMed2002

Frequency of concrete words modulates prefrontal activation during semantic judgments.

The effect of word frequency on semantic processing was characterized by studying two groups of right-handed participants using fMRI. Stimuli were presented in blocks of either high frequency or low frequency word triplets where a sample word appeared above a pair of test words. One group (n = 8) made semantic judgments by selecting the word from the test pair that was more closely associated with the sample. Stimulus triplets were designed such that relatedness between sample and "correct" items was obvious. The other group (n = 8) read the words silently without making any semantic decision and pressed a button on completing the reading of each triplet. Semantic judgments while no less accurate, were associated with greater left prefrontal BOLD signal change when they involved low frequency words, whereas there was no reliable effect of word frequency in the reading condition. These findings suggest that retrieval effort modulates left prefrontal activity when deliberate access to semantics is required.

Adult↗

PubMed2002

Working memory and online syntactic processing in Alzheimer's disease: studies with auditory moving window presentation.

Twenty patients with dementia of the Alzheimer's type (DAT) and 20 controls were tested on six tests of working memory and a test of online auditory sentence comprehension in which listening times for each phrase in the sentence, as well as the time required for an end-of-sentence plausibility judgment, were measured. The sentences differed in syntactic complexity. Patients had lower working memory scores than controls and performed more poorly on the plausibility judgments. However, patients were not more affected than controls by the syntactic complexity of a sentence in these judgments, and both groups showed similar effects of syntactic structure in the listening-time data. The increase in listening times at syntactically capacity-demanding points in complex sentences, compared with comparable points in matched simpler sentences, did not correlate with measures of working memory. The results indicate that early-stage DAT patients are not impaired in their ability to assign syntactic structure and to use it to determine aspects of sentence meaning, despite their reduced working memories. This provides evidence for a specialization within working memory for syntactic processing.

Aged↗

PubMedDate not supplied

Effects of acoustic degradation on syntactic processing: implications for the nature of the resource system used in language processing.

This study investigated the effect of noise masking on on-line syntactic processing. Ninety college students were tested on measures of working memory and on-line sentence comprehension. Subjects were divided equally into three listening conditions: no noise masking, -3 dB signal-to-noise ratio (S:N), -4.5 dB S:N. The auditory moving windows (AMW) paradigm was used to measure on-line sentence processing. In the AMW paradigm, subjects pressed a button for the successive presentation of each phrase in two types of sentences (syntactically simple and complex), and listening times were recorded for each phrase. Previous studies have shown that the verb in the more complex sentence type is the most capacity demanding portion of the sentence. Listening times were longer overall with increased noise masking, and listening times were longer overall at the verb of the harder sentence type. However, the increase at the verb was not larger with increased noise masking. All three groups showed similar effects of syntactic structure in the on-line data. The on-line syntactic effects were not due to problems in word recognition. Correlational analyses did not indicate a relationship between the increase in processing time at the capacity demanding region of the harder sentence types and any of the measures of working memory capacity in any of the three listening conditions. Results indicate that on-line sentence processing is not affected by noise masking if lexical access (e.g., word recognition) remains intact.

Adolescent↗