Attending to visual or auditory motion affects perception within and across modalities: an event-related potential study.

The present event-related potential (ERP) study examined the role of dynamic features in multisensory binding. It was tested whether endogenous attention to the direction of motion affects processing of visual and auditory stimuli within and across modalities. Human participants perceived horizontally moving dot patterns and sounds that were presented either continuously (standards) or briefly interrupted (infrequent deviants). Their task was to detect deviants moving in a particular direction within a primary modality, but to detect all deviants irrespective of their motion direction within the secondary modality. Attending to the direction of visual motion resulted in a broad selection negativity (SN) starting at about 200 ms post-stimulus onset, and attending to the direction of auditory motion resulted in a positive difference wave at 150 ms that was followed by a broad negativity starting at about 200 ms (unimodal effects). Moreover, dot patterns moving in a direction that was attended within audition were detected faster and more accurately than oppositely moving stimuli and elicited a cross-modal SN wave. Corresponding cross-modal behavioural and ERP results were obtained for sounds moving in a direction that was attended within vision. Unimodal and cross-modal ERP attention effects partially differed in their scalp topography. The present study shows that dynamic features (direction of motion) may be used to link input across modalities and demonstrates for the first time that these multisensory interactions take place as early as about 200 ms after stimulus onset.