Neural bases of sensorimotor adaptation in the vocal motor system

The present study used event-related potential (ERP) recordings to investigate the neural mechanisms of sensorimotor adaptation in response to altered auditory feedback (AAF) during vocal production. 12 healthy speakers were tested under a vocal motor adaptation paradigm in which the fundamental frequency (F0) of their voice auditory feedback was pitch-shifted downward by one semi-tone (- 100 cents) during vowel vocalizations. Behavioral results revealed that subjects adapted to AAF by producing opposing (upward) responses to pitch-shift stimuli, and this adaptive behavior persisted after feedback alteration was removed (washout). We found that adaptation to AAF was accompanied by a significant increase in the amplitude of a parietal ERP activity elicited after the onset of vocalization. However, no such effect was observed for pre-motor ERPs elicited before vocalization onset. Moreover, we found that adaptive vocal responses were negatively correlated with ERPs over the parietal and positively correlated with those over the fronto-central areas after vocalization onset. These findings suggest that vocal motor adaptation is mediated by sensorimotor reprogramming of feedforward motor commands through incorporating auditory feedback, which is indexed by modulation of behavioral and ERP responses to AAF. We suggest that modulation of neural activities in the parietal cortex highlights its significance as a neural interface for sensorimotor integration and indicates its critical role in vocal motor adaptation. Our findings support the notion that the parietal mechanisms are involved in driving adaptive motor behavior to cope with unexpected changes in the sensory environment to accomplish communication goals during vocal production and motor control.