Effects of eye position on event-related potentials during auditory selective attention

Event-related potentials (ERPs) were recorded from normal subjects who received random sequences of tone pips from loudspeakers located to the left and right of a central point. The task was to detect occasional higher pitched tones (targets) from one designated speaker. The negative difference (Nd) wave between ERPs for relevant and irrelevant tones was largest when subjects fixated on the relevant speaker, smallest when subjects fixated on the irrelevant speaker, and intermediate in a central fixation. In addition, the Nd modulation for the left tones was produced by the more negative (or less positive) shift of irrelevant-stimulus ERPs and the less negative shift of relevant-stimulus ERPs associated with fixating away from the relevant speaker. These findings suggest the possibility of both facilitatory and inhibitory effects of eye position on auditory spatial attention. The substantial modulation of ERPs due to eye position also indicated the necessity of fixation control in auditory attention ERP research.