Sentence processing in aphasia : single case treatment studies
This study presents three single case investigations of sentence processing disorders in aphasia. Assessment of the subjects was guided by models of normal sentence production and comprehension, and involved several new tests which were developed to investigate particular aspects of processing. The assessment phase generated hypotheses about where the processing system was breaking down for each patient. Although all three subjects showed disordered verb retrieval and use, different processing impairments were identified. The first subject had a deficit in the connections between verbs' semantic and phonological representations. The second subject had a hypothesised deficit in the early message level processes. The third subject had a semantic verb deficit which particularly impaired access to verbs' thematic information. Therapies were developed in the light of these hypotheses. Post therapy evaluation showed that all subjects made significant gains, although the nature and extent of their gains varied. These treatment responses are interpreted against the presumed cognitive models. The concluding discussion addresses a number of theoretical questions about the nature of the language processing system and how therapy may influence the workings of that system. Possible future directions for research are proposed.