Probe-evoked potential correlates of hemispheric asymmetries during a speech shadowing task

Evoked potentials (EPs) to a monaurally presented probe stimulus were recorded from the vertex in subjects engaged in shadowing a word list presented simultaneously to the contralateral ear. Greater attenuation of the N1-P2 and baseline-P2 amplitude of the probe EPs was observed when the probe stimulus was presented to the right ear and the verbal material presented to the left ear than when the opposite stimulation arrangement was used. The baseline-N1 amplitude, however, was equally attenuated during the two stimulation arrangements. The implication of these findings for the issue of differential, task-specific attenuation of probe EPs are discussed.