Binocular rivalry occurs when dissimilar images are presented to each eye. Rather than a combined picture being perceived, each monocular image competes for perceptual dominance, becoming visible for a few seconds while the other is suppressed. Stable visual input thus leads to alternations in conscious perception, dissociating stimulation from awareness. This makes rivalry particularly useful for elucidating the neural processes underlying consciousness . Retinotopic visual cortex  and lateral geniculate nucleus  activity are modulated by such alternating perception, implying an early locus for rivaling neural representations. However, higher cortical regions, including right superior parietal cortex, exhibit activity that is time-locked to perceptual transitions . Though this implies the involvement of top-down processes in rivalry, the correlational nature of neuroimaging precludes the attribution of a causal role to such activity, which may instead simply reflect orientating attention to the transition. Here we distinguish these two hypotheses by showing that repetitive transcranial magnetic stimulation (rTMS) over right superior parietal cortex shortened binocular rivalry dominance durations. This suggests that right parietal cortex maintains the current perceptual state during rivalry.
Copyright © 2010 Elsevier Ltd. All rights reserved.