2 AUDITORY COMPONENTS IN THE 130-230-MS RANGE DISCLOSED BY THEIR STIMULUS FREQUENCY-DEPENDENCE

THE auditory P2 wave has been studied by means of scalp potential and scalp current density (SCD) mapping. Two components were described. On e, peaking around 150 ms, probably reflects a major activity in both s upra temporal planes as revealed by SCD maps (P150). The other is a bi lateral temporo-parietal component peaking around 220 ms (P220). These two components were functionally disclosed by their stimulus frequenc y dependence. The P150 potential and SCD amplitudes significantly decr ease with increasing frequencies. Whereas this could be interpreted as a modulation of the neural activity, it may also be related to a tono topical organization of the underlying generators distinct from that p reviously found for the N100. No frequency effect was found on P220.