Peripheral visual localization is degraded by globally incongruent auditory-spatial attention cues.

Global auditory-spatial orienting cues help the detection of weak visual stimuli, but it is not clear whether crossmodal attention cues also enhance the resolution of visuospatial discrimination. Here, we hypothesized that if anywhere, crossmodal modulations of visual localization should emerge in the periphery where the receptive fields are large. Subjects were presented with trials where a Visual Target, defined by a cluster of low-luminance dots, was shown for 220 ms at 25°-35° eccentricity in either the left or right hemifield. The Visual Target was either Uncued or it was presented 250 ms after a crossmodal Auditory Cue that was simulated either from the same or the opposite hemifield than the Visual Target location. After a whole-screen visual mask displayed for 800 ms, a pair of vertical Reference Bars was presented ipsilateral to the Visual Target. In a two-alternative forced choice task, subjects were asked to determine which of these two bars was closer to the center of the Visual Target. When the Auditory Cue and Visual Target were hemispatially incongruent, the speed and accuracy of visual localization performance was significantly impaired. However, hemispatially congruent Auditory Cues did not improve the localization of Visual Targets when compared to the Uncued condition. Further analyses suggested that the crossmodal Auditory Cues decreased the sensitivity (d') of the Visual Target localization without affecting post-perceptual decision biases. Our results suggest that in the visual periphery, the detrimental effect of hemispatially incongruent Auditory Cues is far greater than the benefit produced by hemispatially congruent cues. Our working hypothesis for future studies is that auditory-spatial attention cues suppress irrelevant visual locations in a global fashion, without modulating the local visual precision at relevant sites.