Spatial attention and crossmodal interactions between vision and touch.

In the present paper, we review several functional imaging studies investigating crossmodal interactions between vision and touch relating to spatial attention. We asked how the spatial unity of a multimodal event in the external world might be represented in the brain, where signals from different modalities are initially processed in distinct brain regions. The results highlight several links between visual and tactile spatial representations. First, we found that activity in the anterior part of the intraparietal sulcus was influenced by stimulus position independently of the modality of the stimulation. This is consistent with crossmodal interactions via sensory convergence from early modality-specific spatial maps to higher-order multimodal regions. Second, we found that stimulation in, or attention to, one modality could affect activity in areas dedicated to a different modality, in a spatially-specific manner. These spatial crossmodal effects in unimodal regions demonstrate congruous activity in anatomically distant brain areas that represent similar external locations, implicating a distributed network of spatial representations in crossmodal integration. Finally, the results suggest that the temporo-parietal junction may be involved in aspects of controlling spatial attention, for both vision and touch. A multimodal attentional system may influence activity in distinct brain areas representing common regions of space for different modalities, thus suggesting a link between spatial attention and crossmodal integration.