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Carrie R Bailey, Steven L Prime; TMS over the right parietal cortex disrupts audiovisual binding in the line motion illusion. Journal of Vision 2014;14(10):1096. doi: 10.1167/14.10.1096.
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In the line motion illusion (LMI), a static bar presented all at once is perceived to shoot out from one end where a preceding cue was presented (Hikosaka et al., 1993). The LMI can be induced by either a visual or auditory cue (Shimojo et al., 1997). Though the LMI with visual cues has been widely studied, little is known about the processes that underlie the audiovisual binding when auditory cues are used to induce illusory visual motion. Here, we used transcranial magnetic stimulation (TMS) to investigate the cortical mechanisms of multisensory integration between auditory and visual stimuli in the LMI. Ten subjects were presented with an auditory cue at one of eleven times around the presentation of the bar starting at 500ms before to 500ms after the bar, separated by 100ms intervals. Presenting the cue at a range of timings allowed us to obtain information of the timing of the crossmodal interaction between the auditory cue and bar. At the beginning of each trial, we applied triple-pulse TMS (20Hz at 60% intensity) over the right or left intraparietal sulcus (IPS), an area implicated in attention-related multisensory interactions (Klemen & Chambers, 2012), immediately before stimulus presentation. Subjects had to report the direction the bar appeared to move, either toward or away from the cue. Subjects were also tested in a similar visual cue version of the task. We found that the LMI was only disrupted when TMS was applied to the right IPS with auditory cues, but not with visual cues. No effect was found when TMS was applied to the left IPS with either cue modality. These results show the right IPS plays a crucial role in the audiovisual interactions in the line motion illusion and further clarify the role the parietal attention system plays in binding audiovisual events.
Meeting abstract presented at VSS 2014
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