Here, we studied how the intermodal selective attention between vision and audition affects the sensory information processing in the human auditory and visual cortical areas. Specifically, we investigated whether audio-visual intermodal orientation of attention modulates neural activity in the human visual and auditory cortices. We used MEG to assess the neural activity in both the primary auditory area and the extrastriate visual areas, where visual stimulus features such as color and shape are processed, while subjects performed spatial and non-spatial discrimination tasks, as presented by either visual or auditory modality, under three attentional conditions, namely a) selective attention to vision (V), b) selective attention to audition (A), and c) divided attention between vision and audition as neutral condition (N). MEG signals were analyzed by using linearly-constrained minimum-variance (LCMV) beamformer and the differences of the estimated activities in the visual cortical areas between the conditions were statistically tested. Neural activity in the contralateral occipitotemporal area (BA18) was significantly increased under the V condition in the spatial discrimination task but not in the non-spatial (color) discrimination task. On the other hand, attention to vision significantly enhanced activity in the posterior inferotemporal area (BA19, 37). The results support the hypothesis that the intermodal selective attention between the visual and auditory modalities modulates the neural activities in the ventral visual system in the stimulusfeature specific manner at different latencies.
Keywords: Audio-visual attention, data analysis, magnetoencephalography (MEG), spatial filter, spatial visual/auditory discrimination experiment, ventral visual system.