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Many agrammatic aphasics have a specific syntactic comprehension deficit involving processing syntactic transformations. It has been proposed that this deficit is due to a dysfunction of Broca's area, an area that is thought to be critical for comprehension of complex transformed sentences. The goal of this study was to investigate the role of Broca's area in processing canonical and non-canonical sentences in healthy subjects. The sentences were presented auditorily and were controlled for task difficulty. Subjects were asked to judge the grammaticality of the sentences while their brain activity was monitored using event-related functional magnetic resonance imaging. Processing both kinds of sentences resulted in activation of language-related brain regions. Comparison of non-canonical and canonical sentences showed greater activation in bilateral temporal regions; a greater activation of Broca's area in processing antecedent-gap relations was not found. Moreover, the posterior part of Broca's area was conjointly activated by both sentence conditions. Broca's area is thus involved in general syntactic processing as required by grammaticality judgments and does not seem to have a specific role in processing syntactic transformations. (C) 2004 Wiley-Liss, Inc
The presence or absence of generalization after treatment can provide important insights into the functional relationship between cognitive processes. The aim of the present study was to investigate the relationship between the cognitive processes that underlie sentence comprehension and production in aphasia. Using data from seven participants who took part in a case-series intervention study that focused on noncanonical sentence production [Stadie et al. (2008). Unambiguous generalization effects after treatment of noncanonical sentence production in German agrammatism. Brain and Language, 104, 211-229], we identified patterns of impairments and generalization effects for the two modalities. Results showed (a) dissociations between sentence structures and modalities before treatment, (b) an absence of cross-modal generalization from production to comprehension after treatment, and (c), a co-occurrence of spared comprehension before treatment and generalization across sentence structures within production after treatment. These findings are in line with the assumption of modality-specific, but interacting, cognitive processes in sentence comprehension and production. More specifically, this interaction is assumed to be unidirectional, allowing treatment-induced improvements in production to be supported by preserved comprehension.
An important aspect of aphasia is the observation of behavioral variability between and within individual participants. Our study addresses variability in sentence comprehension in German, by testing 21 individuals with aphasia and a control group and involving (a) several constructions (declarative sentences, relative clauses and control structures with an overt pronoun or PRO), (b) three response tasks (object manipulation, sentence-picture matching with/without self-paced listening), and (c) two test phases (to investigate test-retest performance). With this systematic, large-scale study we gained insights into variability in sentence comprehension. We found that the size of syntactic effects varied both in aphasia and in control participants. Whereas variability in control participants led to systematic changes, variability in individuals with aphasia was unsystematic across test phases or response tasks. The persistent occurrence of canonicity and interference effects across response tasks and test phases, however, shows that the performance is systematically influenced by syntactic complexity.