Phase Aspects and Localization Analysis of the Auditory N100 Component

The structure of the sources underlying surface recordings of brain activity is very complex. We have developed an iterative procedure based on independent component analysis to obtain single-trial estimates of the auditory N100 component recorded in normal subjects using a pure tone, binaural stimulation task and a wholehead, 256-channel recording system. For each channel, the processed single trials were separated into two groups, one with trials in which the N100 component had the same phase as the average response and another one with trials having the opposite phase. Our results show that the proposed method can effectively extract only the activity related to the experimental task, while removing artifacts and background activity, and that the sources of the N100 component that are typically localized on the floor of the Sylvian fissure are primarily due to in-phase responses. Keywords—Independent component analysis, Source localization, Component phase, Evoked potentials.