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Brian Metzger, Kathy Low, Edward Maclin, Gabriele Gratton, Monica Fabiani, Diane Beck; The role of parietal cortex during probe-accelerated binocular rivalry. Journal of Vision 2016;16(12):1205. doi: 10.1167/16.12.1205.
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© 2017 Association for Research in Vision and Ophthalmology.
Binocular rivalry occurs when dissimilar images are presented simultaneously but separately to corresponding retinal locations of each eye. Perception alternates between the two images such that one image dominates awareness while the other is suppressed. Prior research has shown that probes presented to the suppressed eye accelerate reversals. We've shown that these reversals are mediated by P1 amplitude (Metzger et al., VSS 2014; CNS 2015) such that P1 amplitude increases monotonically as a function of reversal latency (from probe onset), that P3b activity tracks reversal-related activity such that P3b peak latency coincides with reversal latency (Metzger et al., SPR 2015), and that activity in left and right superior parietal lobules precede the button response (i.e beginning of the reversal; Metzger et al., SfN 2015). However, the role and timing of parietal cortex relative to the transition from one percept to the other remains unclear (c.f Frassle et al., 2014; Brascamp et al., 2015). One possibility is that parietal cortex becomes active as a consequence of a change in perception. Another possibility is that parietal cortex initiates and/or facilitates changes in perception, becoming active prior to the reversal. Here, we used fast-optical imaging (EROS) to determine the timing of parietal activation relative to reversals. Percept-specific changes in cortical activity (i.e. OFA/LOC and collateral sulcus for face and texture percepts respectively) suggest that reversals begin ~384 ms prior to button release. Furthermore, these percept-specific areas oscillate in-phase with parietal activity. Critically, however, Granger causality analyses suggest that activity in rSPL precedes activity in percept-specific areas by about 75 ms, with a second peak in lSPL and rSPL during or soon after the reversal. Taken together, our data suggest that in the case of probe-accelerated reversals, parietal areas become active either to initiate, or to facilitate changes in perception during binocular rivalry.
Meeting abstract presented at VSS 2016
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