Two separate frontal components in the N1 wave of the human auditory evoked response

Scalp current density analysis of the auditory evoked response to 1‐kHz tone bursts delivered at various interstimulus intervals (ISIs) (from 1 s to 2 min in separate runs) shows that two different frontal components can be observed and functionally dissociated in the N1 time range: one is elicited for all ISIs, peaks at about 95 ms poststimulus, and has a full recovery time below 8 s; the second is elicited only by infrequent stimuli (ISIs > 4 s), peaks around 140 ms, and significantly increases in amplitude with increasing ISIs. The first component can be considered a new obligatory component in N1 elicited simultaneously with the responses in auditory cortex; the later component could correspond to the orienting Component III of Näätänen and Picton (1987).