Auditory-motor integration during fast repetition: The neuronal correlates of shadowing

Shadowing multiple speakers compared to a single speaker elicited increased bilateral activation predominantly in the superior temporal sulci. These regions may mediate acoustic-phonetic speaker normalization in preparation of a translation of perceptual into motor information. Additional activation in Broca's area and the thalamus may reflect motor effects of the adaptation to multiple speaker models. Item-wise correlational analyses of response latencies with BOLD signal changes indicated that longer latencies were associated with increased activation in the left parietal operculum, suggesting that this area plays a central role in the actual transfer of auditory-verbal information to speech motor representations. A multiple regression of behavioral with imaging data showed activation in a right inferior parietal area near the temporo-parietal boundary which correlated positively with the degree of speech rate imitation and negatively with response latency. This activation may be attributable to attentional and/or paralinguistic processes.