Magnetoencephalographic study of the cortical activity elicited by human voice.

In an attempt to identify voice-specific neural activities in auditory cortex in humans, we recorded cortical magnetic responses. Volunteers were instructed to listen to vocal and instrumental sounds matched in fundamental-frequency, duration, temporal envelope and average root mean square power. The stimuli were sounds produced by four singers and four musical instruments at each of two fundamental frequencies: 220 Hz (musical note A3) and 261.9 Hz (C3). Two components of the evoked responses were analyzed, one at approximately 100 ms (N1m) and the other 400 ms after the stimulus onset (sustained field, SF). The source locations of equivalent current dipoles for both components were estimated around the Heschl's gyrus in both hemispheres. Compared with the instrumental sound, the source strength of the SF component for the voice was significantly larger.