Abstract
Several previous studies have shown that spatial attention not only affects perception within the attended modality (unimodal), but also within task-irrelevant modalities (crossmodal). The present event-related potential (ERP) study examined whether dynamic features such as the direction of motion are also important in multisensory binding. Participants perceived horizontally moving dot patterns and sounds which were presented either continuously (standards) or were 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 motion direction of visual stimuli resulted in enhanced visual ERPs over parietal sites starting at about 200 ms post stimulus onset. Attending to the motion direction of sounds elicited a positive difference (Pd) wave at 150 ms that was followed by a broad negativity (Nd) starting at about 200 ms in auditory ERPs. Moreover, attention to motion within one modality also affected processing of moving stimuli within another modality (crossmodal effects). Dot patterns moving in a direction that was relevant within audition were detected faster and elicited stronger visual ERPs than dot patterns moving in the opposite direction. Similarly, sounds moving in a direction that was relevant within vision were detected faster and were associated with larger auditory ERPs than oppositely moving sounds. These crossmodal effects were smaller than unimodal effects. Their scalp distribution partially differed from the topographies of their unimodal counterparts. The present results suggest that motion is an important feature in order to link auditory and visual input as, for instance, within multisensory integration.
This study was funded by a grant (Ro 1226/4-1, 4-2, 4-3 to B. R.) of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG). The study was conducted at the Philipps-University Marburg, Department of Psychology, Marburg, Germany.