Hemifield asymmetry in the potency of exogenous auditory and visual cues.

Neurologically normal subjects misperceive the midpoints of lines (PSE) as reliably leftward of veridical center, a phenomenon known as pseudoneglect. This leftward bias reflects the dominance of the right cerebral hemisphere in deploying spatial attention. Transient visual cues, delivered to either the left or right endpoints of lines, modulate PSE such that leftward biases are increased by leftward cues, and are decreased by rightward cues, relative to a no-cue control condition. We ask whether lateralized auditory cues can similarly influence PSE in a tachistoscopic visual line bisection task, and describe how visual and auditory cues, in spatially synergistic or antagonistic combinations, jointly influence PSE. Our results demonstrate that whereas auditory and visual cues both modulate PSE, visual cues are overall more potent than auditory cues. Visual and auditory cues are weighted such that visual cues are significantly more potent than auditory cues when visual cues are delivered to left hemispace. Visual and auditory cues are equipotent when visual cues are delivered to right hemispace. These results are consistent with the existence of independent lateralized networks governing the deployment of visuospatial and audiospatial attention. An analysis of the weighting of unisensory visual and auditory cues which optimally predicts PSE in multisensory cue conditions shows that cues combine additively. There was no evidence for a superadditive multisensory cue combination.