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Patricia A. Neil, Aman Chawla, Joydeep Bhattacharya, Shinsuke Shimojo; Significant audio-visual interaction for spatially congruent stimuli. Journal of Vision 2004;4(8):702. doi: 10.1167/4.8.702.
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Studies on auditory and visual interactions encompass a wide range of tasks and methodologies. Direct comparison of different studies is often difficult when the stimuli, tasks, and analytical approach differ. Animal studies have shown that spatially and temporally congruent visual and auditory stimuli produce an enhanced neural response in multisensory neurons of the superior colliculus, whereas incongruent stimuli produce either a suppressed or unchanged response. A similar behavioral response has been found in humans; congruent visual and auditory stimuli produce reduced response latencies in target localization. Most audiovisual research has focused on temporal properties and arbitrary or learned connections. We investigated the role of spatial congruency in multisensory interaction in adult human subjects (n=11) using both behavioral and multi-channel EEG signal recordings. Subjects were asked to saccade toward a target presented at +/− 25 or 45 deg, while their eye movements and cortical activity were recorded. The target was either a vertical red line (V), a short burst of white noise (A), or both at congruent (AVc) or incongruent (AVi) locations. Interaction was studied by comparing the response latencies and event-related potential (ERP) responses toward A and V targets with their AV counterparts. The results revealed strong audio-visual interaction with earliest onset latency of 150 ms for spatially congruent stimuli with a correspondingly shorter response latency, but were inconsistent for spatially incongruent stimuli. Although many cortical regions showed temporally sustained interaction, the earliest effect was found in anterior frontal regions, perhaps influencing sensory-specific areas through feedback projections. These results demonstrate that spatial coincidence can significantly modulate the neuronal information processing in the modality-specific regions, thus mediating multisensory interaction and the overt behavioral response.
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