Hemispheric asymmetry: Looking for a novel signature of the modulation of spatial attention in multisensory processing

The extent to which attention modulates multisensory processing in a top-down fashion is still a subject of debate amongst researchers. Typically, cognitive psychologists interested in this question have manipulated the participants’ attention in terms of single/dual tasking or focal/divided attention between sensory modalities. Here, we suggest an alternative approach, one that builds on the extensive older literature highlighting hemispheric asymmetries in the distribution of spatial attention. Specifically, spatial attention in vision, audition, and touch is typically biased preferentially toward the right hemispace, especially under conditions of high perceptual load. Here, we review the evidence demonstrating such an attentional bias toward the right in extinction patients and healthy adults, and the evidence of such rightward-biased attention in multisensory experimental settings. We then evaluate those studies that have either demonstrated a more pronounced multisensory effect in the right than left hemispace, or else demonstrated similar effects in the two hemispaces. The results suggest that the influence of rightward-biased attention is more likely to be observed when the crossmodal signals interact at the later stages of information processing and under conditions of higher perceptual load – the conditions where attention is perhaps a compulsory enhancer in information processing. We therefore suggest that the spatial asymmetry in attention may provide a useful signature of top-down attentional modulation in multisensory processing