Early neurophysiological correlates of vocal versus non-vocal sound processing in adults.

Electrophysiological correlates of voice processing were studied in twenty adults by comparing auditory evoked potentials in response to voice and environmental sounds in passive condition. Both categories of stimuli elicited similar cortical auditory responses (i.e. N1, P2, N2 peaks); however these peaks were overlapped by two components specifically elicited by voice. The first component was evidenced as a positive deflection recorded over the fronto-temporal sites, and lateralized on the right hemiscalp. This fronto-temporal positivity to voice (FTPV) may constitute the electrophysiological counterpart of the activation of the temporal voice areas previously described in neuroimaging studies. The second component was recorded at occipito-temporo-parietal sites. This occipito-temporo-parietal negativity to voice might correspond to visual mental imagery of the vocal sounds or to some form of mental simulation of the action sounds (e.g. coughing). Both components began as early as 70 ms post-stimulus onset indicating a rapid discrimination of voice in our auditory environment, which might be the basis of communication functions in humans.