Electrophysiological evidence of an attentional bias in crossmodal inhibition of return.

Inhibition of return (IOR) refers to a delay in responding to targets when they appear at recently attended locations, relative to unattended locations. Within the visual modality, this attentional bias has been associated with a reduction in the N2pc event-related potential (ERP) component at previously attended locations. The present study examined whether a similar attentional bias was observed in crossmodal audio-visual IOR. Our results demonstrate that for visual targets, the attentional component of IOR behaves similarly for both unimodal and crossmodal target pairs, as indexed by a reduction in the N2pc component for targets appearing at previously attended locations. Further, similar IOR-related modulations on the auditory-evoked N2ac indicated that an attentional bias can be observed for auditory targets as well. Finally, we identified two additional ERP components - the ACOP and VCAN - that appear to reflect biasing of attention in the currently unattended sensory modality. These results suggest that the inhibitory attentional bias that underlies the IOR effect may be supramodal and bias attention away from previously attended locations regardless of sensory modality.