Thesis defense Artem Platonov (Donders Series 161)

30 June 2014

Promotor: Prof.dr. A.J. van Opstal, copromotor: dr. H.H.L.M. Goossens

Mechanisms of binocular motion rivalry

The visual system is confronted with the task to create coherent and reliable percept out of low-resolution, two-dimensional and incomplete image on the retina. Studying how the brain deals with inherent ambiguity of a visual input is far from trivial. In the 4 studies described in this thesis, we approach this problem by studying perceptual alternations in binocular motion direction rivalry. Binocular rivalry is a phenomenon which occurs when our eyes receive a pair of stereo-incompatible inputs at the same retinal location. Even though both stimuli are constantly present, one generally perceives only one image at a time, with switches between the two percepts occurring every few seconds. The fact that under most circumstances the two stimuli are never seen together (e.g., transparently or as a summed image), points to a central role for inhibition. However, the exact mechanisms underlying binocular rivalry are not fully understood. Our research presented in this thesis systematically supports the notion of binocular rivalry as resulting from an interplay between mutual inhibition and slow adaptation of the competing percepts. We further show that dominance and suppression alternations in two populations during binocular rivalry do not automatically entail changes in awareness states. We present convincing evidence that ocular dominance rivalry does not require visual awareness, suggesting that the neuronal mechanisms of binocular rivalry are at least partly different from those which support conscious perception. Finally, we show that integration of multisensory information in binocular rivalry can be described as a Bayesian process of perceptual decision-making based on an optimal cue-integration.