Sixty one people with aphasia were tested on ten tests of short term memory (STM) and for the ability to use syntactic structure to determine the meanings of eleven types of sentences in three tasks – object manipulation, picture matching and picture matching with self-paced listening. Multilevel models showed relationships between measures of the ability to retain and manipulate item and order information in STM and accuracy and RT, and a greater relationship between these STM measures and accuracy and RT for several more complex sentence types in individual tasks. There were no effects of measures of STM that reflect the use of phonological codes or rehearsal on comprehension. There was only one effect of STM measures on self-paced listening times. There were double dissociations between performance on STM and individual comprehension tasks, indicating that normal STM is not necessary to perform normally on these tasks. The results are most easily related to the view that STM plays a facilitatory role in supporting the use of the products of the comprehension process to accomplish operations related to tasks.
Sixty-one people with aphasia (pwa) and 41 matched controls were tested for the ability to understand sentences that required the ability to process particular syntactic elements and assign particular syntactic structures. Participants paced themselves word-by-word through 20 examples of 11 spoken sentence types and indicated which of two pictures corresponded to the meaning of each sentence. Sentences were developed in pairs such that comprehension of the experimental version of a pair required an aspect of syntactic processing not required in the corresponding baseline sentence. The need for the syntactic operations required only in the experimental version was triggered at a "critical word" in the experimental sentence. Listening times for critical words in experimental sentences were compared to those for corresponding words in the corresponding baseline sentences. The results were consistent with several models of syntactic comprehension deficits in pwa: resource reduction, slowed lexical and/or syntactic processing, abnormal susceptibility to interference from thematic roles generated non-syntactically. They suggest that a previously unidentified disturbance limiting the duration of parsing and interpretation may lead to these deficits, and that this mechanism may lead to structure-specific deficits in pwa. The results thus point to more than one mechanism underlying syntactic comprehension disorders both across and within pwa.
Sixty one pwa were tested on syntactic comprehension in three tasks: sentence-picture matching, sentence-picture matching with auditory moving window presentation, and object manipulation. There were significant correlations of performances on sentences across tasks. First factors in unrotated factor analyses accounted for most of the variance on which all sentence types loaded in each task. Dissociations in performance between sentence types that differed minimally in their syntactic structures were not consistent across tasks. These results replicate previous results with smaller samples and provide important validation of basic aspects of aphasic performance in this area of language processing. They point to the role of a reduction in processing resources and of the interaction of task demands and parsing and interpretive abilities in the genesis of patient performance.
The effects of lesions on syntactic comprehension were studied in thirty one people with aphasia (PWA). Participants were tested for the ability to parse and interpret four types of syntactic structures and elements -- passives, object extracted relative clauses, reflexives and pronouns – in three tasks – object manipulation, sentence picture matching with full sentence presentation and sentence picture matching with self-paced listening presentation. Accuracy, end-of-sentence RT and self-paced listening times for each word were measured. MR scans were obtained and analyzed for total lesion volume and for lesion size in 48 cortical areas. Lesion size in several areas of the left hemisphere was related to accuracy in particular sentence types in particular tasks and to self-paced listening times for critical words in particular sentence types. The results support a model of brain organization that includes areas that are specialized for the combination of particular syntactic and interpretive operations and the use of the meanings produced by those operations to accomplish task-related operations.
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