Repetition suppression for spoken sentences and the effect of task demands.

We examined whether the repeated processing of spoken sentences is accompanied by reduced bold oxygenation level-dependent response (repetition suppression) in regions implicated in sentence comprehension and whether the magnitude of such suppression depends on the task under which the sentences are comprehended or on the complexity of the sentences. We found that sentence repetition was associated with repetition suppression in temporal regions, independent of whether participants judged the sensibility of the statements or listened to the statements passively. In contrast, repetition suppression in inferior frontal regions was found only in the context of the task demanding active judgment. These results suggest that repetition suppression in temporal regions reflects facilitation of sentence comprehension processing per se, whereas in frontal regions it reflects, at least in part, easier execution of specific psycholinguistic judgments.