Processing of multisensory spatial congruency can be dissociated from working memory and visuo-spatial attention

Tactile stimuli at the same location as a visual target can increase activity in the contralateral occipital cortex compared with spatially incongruent bimodal stimulation. Does this cross-modal congruency effect in the visual cortex depend on available cognitive resources? Visual attention and working memory can modulate responses to visual stimuli in the occipital cortex, with attenuation in conditions of high-attentional or low-memory load. Here, we asked if these two cognitive factors affect multisensory processing in the visual cortex. Using functional magnetic resonance imaging in humans, we manipulated the load of working memory or visuo-spatial attention. Concurrently with these primary tasks we presented same-side (congruent) or opposite-side (incongruent) visuo-tactile stimuli. Both experiments revealed enhancement of brain activity for congruent vs incongruent bimodal stimulation in the contralateral occipital cortex. Critically, these cross-modal effects occurred irrespective of the level of load. We conclude that processing of visuo-tactile spatial congruency in the visual cortex does not depend on available visuo-spatial and memory resources.