4.2 Study E: The neural correlate of speech rhythm as evidenced by meter processing: an fmri study.

摘要: The present study investigates the neural correlates of rhythm processing in speech perception. German pseudo-sentences spoken with an exaggerated (metric) or a conversational (non-metric) rhythm were compared in an auditory fMRI experiment. The subjects had to perform either a rhythm task (explicit rhythm processing) or a prosody task (implicit rhythm processing). The study revealed bilateral activation in the supplementary motor area (SMA) extending into the cingulate gyrus and in the insulae extending into the right basal ganglia (neostriatum, NS), as well as activity in the right inferior frontal gyrus (IFG) related to the performance of the rhythm task. A direct contrast between metric and the non-metric sentences revealed differences in lateralization of activation for metric processing as a function of the explicit and implicit task. Explicit processing revealed activation in the right posterior superior temporal gyrus (pSTG), the right supramarginal gyrus (SMG) and the right parietal operculum (PaOp). Implicit processing showed activation in the left SMG, the left posterior STG, and the left PaOp. The present results indicate a function of SMA and insula beyond motor timing and speak for a role of these brain areas in the perception of temporal intervals. Secondly, the data speak for a specific task-related function of the right IFG in the processing of accent patterns. Finally, the data sustain the assumption that the right secondary auditory cortex is involved in the explicit perception of auditory cues and moreover, that activity in the right secondary auditory cortex can be modulated by top-down processing mechanisms.