PRESTIMULUS EEG ALPHA-PHASE SYNCHRONICITY INFLUENCES N100 AMPLITUDE AND REACTION-TIME

The influence of the level of prestimulus alpha phase synchronicity on the N100 component and reaction time (RT) was examined, in target aud itory oddball data from 25 normal subjects. Alpha phase synchronicity is a new measure consisting (for a given stimulus presentation) of the angular or circular variance of the alpha phase at stimulus onset acr oss the parieto-occipital sites. The lower the angular variance, the h igher the phase synchronicity (the more closely in phase the alpha act ivity across these sites) and vice versa. Subaveraged event-related po tentials (ERPs) were formed for high and low prestimulus alpha phase s ynchronicity stimulus presentations. N100 amplitude was significantly greater in the high than the low phase synchronicity subaverages. In a ddition, RT was significantly reduced in the high prestimulus alpha ph ase synchronicity cases. Alpha phase synchronicity reflects an aspect of brain state that influences subsequent stimulus processing.