Dynamics of within-, inter-, and cross-modal attentional modulation.

Numerous studies have demonstrated effects of spatial attention within single sensory modalities (within-modal spatial attention) and the effect of directing attention to one sense compared with the other senses (intermodal attention) on cortical neuronal activity. Furthermore, recent studies have been revealing that the effects of spatial attention directed to a certain location in a certain sense spread to the other senses at the same location in space (cross-modal spatial attention). The present study used magnetoencephalography to examine the temporal dynamics of the effects of within-modal and cross-modal spatial and intermodal attention on cortical processes responsive to visual stimuli. Visual or tactile stimuli were randomly presented on the left or right side at a random interstimulus interval and subjects directed attention to the left or right when vision or touch was a task-relevant modality. Sensor-space analysis showed that a response around the occipitotemporal region at around 150 ms after visual stimulation was significantly enhanced by within-modal, cross-modal spatial, and intermodal attention. A later response over the right frontal region at around 200 ms was enhanced by within-modal spatial and intermodal attention, but not by cross-modal spatial attention. These effects were estimated to originate from the occipitotemporal and lateral frontal areas, respectively. Thus the results suggest different spatiotemporal dynamics of neural representations of cross-modal attention and intermodal or within-modal attention.