Selective priming of syntactic processing by event-related transcranial magnetic stimulation of Broca's area.

It remains controversial whether Broca's aphasia is an articulatory deficit, a lexical-access problem, or agrammatism. In spite of recent neuroimaging studies, the causal link between cortical activity and linguistic subcomponents has not been elucidated. Here we report an experiment with event-related transcranial magnetic stimulation (TMS) to clarify the role of Broca's area, more specifically, the left inferior frontal gyrus (F3op/F3t), in syntactic processing. An experimental paradigm contrasted sentences requiring syntactic decisions with those requiring semantic decisions. We found selective priming effects on syntactic decisions when TMS was administered to the left F3op/F3t at a specific timing, but not to the left middle frontal gyrus (F2). Our results provide direct evidence of the involvement of the left F3op/F3t in syntactic processing.