Assessing corollary discharge in humans using noninvasive neurophysiological methods.

In this paper, we present a vocal production protocol for studying the neurophysiological action of the corollary discharge, a mechanism that allows animals to ignore sensations resulting from their own actions, and tag them as 'self'. Electroencephalograms are recorded while subjects say 'ah' about 100 times with minimal throat, jaw and tongue movements (Talk condition). This sequence of sounds is recorded and played back during the Listen condition. Event-related potentials are synchronized to the onset of speech sounds during the Talk and Listen conditions. Neural responses from the auditory cortex to the spoken sound as it is being spoken during the Talk condition are compared with neural responses to the same sounds when played back during the Listen condition. The successful action of the corollary discharge is seen when the response of the auditory cortex is suppressed during the Talk compared with the Listen condition. The protocol takes about 5 min to complete.