Parietal disruption alters audiovisual binding in the sound-induced flash illusion

Abstract

Selective attention and multisensory integration are fundamental to perception, but little is known about whether, or under what circumstances, these processes interact to shape conscious awareness. Here, we used transcranial magnetic stimulation (TMS) to investigate the causal role of attention-related brain networks in multisensory integration between visual and auditory stimuli in the sound-induced flash illusion. The flash illusion is a widely studied multisensory phenomenon in which a single flash of light is falsely perceived as multiple flashes in the presence of irrelevant sounds. We investigated the hypothesis that extrastriate regions involved in selective attention, specifically within the right parietal cortex, exert an influence on the multisensory integrative processes that cause the flash illusion. W e found that disruption of the right angular gyrus, but not of the adjacent supramarginal gyrus or of a sensory control site, enhanced participants' veridical perception of the multisensory events, thereby reducing their susceptibility to the illusion. Our findings suggest that the same parietal networks that normally act to enhance perception of attended events also play a role in the binding of auditory and visual stimuli in the sound-induced flash illusion.

The Role of the Parietal Cortex in Multisensory and Response Integration: Evidence from Transcranial Direct Current Stimulation (tDCS)

“…2). This finding is consistent with previous observations showing that TMS over the right PPC reduces binding errors ('illusory conjunction ' -Esterman et al, 2007) as well as disrupts synes thesia (Muggleton e ta i, 2007) and audio-visual binding in the sound-induced flash illusion (Kamke et al, 2012). Moreover, the link between multisensory integration and the right PPC was also apparent in studies with patients suffer ing bilateral PPC lesions (Friedman-Hill etal., 1995) and other tDCS studies where anodal stimulation improved visual search (Bolognini etal., 2010a) and enhanced audio-visual interactions (Bolognini et al, 2010b).…”

Dissecting neural circuits for multisensory integration and crossmodal processing

“…B 370: 20140203 shifts across and within modalities. Because TMS targeting the right AG also impairs the temporal binding of auditory and visual stimulation [10], multisensory PPC circuits may be involved in attentional control over space and time. Although PPC may function as a general filter and integrator of sensory information within and across modalities, different PPC subregions residing in the inferior parietal lobule and intraparietal sulcus (IPS) probably subserve attention functions for particular modalities over others [11].…”

Where are multisensory signals combined for perceptual decision-making?

“…This issue cannot be addressed with behavioural neurophysiology or neuroimaging alone and requires neural manipulation to establish the causal effects of perturbing multisensory integration [7]. So far, causal contributions of both sensory and higher order areas to multisensory integration have been shown in humans [39][40][41] and other animals [26,[42][43][44]. However few studies have tested the role of cortical regions in multisensory perceptual decision-making tasks.…”