Regulating visual awareness during binocular rivalry

The brain has a limited processing capacity, which means that we can only be aware of a limited amount of information hitting the retina at any given moment in time. Not surprisingly, we very often experience failures in updates to our conscious experience of the world, for instance failures to notice changes within a scene, especially if our attention is engaged elsewhere. Binocular rivalry, which occurs when perception alternates between conflicting monocular inputs, provides a way to study updates in consciousness in a unique way since changes in awareness are not the result of a change in what the eyes see, but rather to changes in what the brain has made accessible to awareness. The research contained within this thesis seeks to better understand updates more generally through a probe-mediated version of binocular rivalry in which briefly presented task-irrelevant probes modulate reversals in a way that provides a degree of experimental control over an otherwise highly stochastic process. The following questions are asked: Why do probes accelerate/decelerate reversals? Which ERP components are associated with the reversal? Which are associated with the probe? What mechanisms do the probes interact with, and at what level of processing? Chapter 2 suggests that P3b activity is associated with reversal-related activity. Specifically, that P3b activity indexes the immediacy/intensity of updates to consciousness during binocular rivalry. Sensory evoked data (i.e. P1/N1 ERP activity) reported in Chapters 2 and 4 suggest that P1 and/or N1 amplitude index probe-related processes, but may also index the depth of neural suppression (i.e. dominant percept inhibitory strength) during binocular rivalry. Across three experiments (Chapters 3 and 4) on-object differences in percept duration between suppressed- and dominant-eye probes were larger relative to off-object probes, suggestive of an object-based mechanism. However, and equally present across the three experiments, suppressed-eye off-object probes were associated with shorter reversal latencies relative to dominant-eye off object probes, suggestive of an eye-based mechanism. Finally, N2 data suggests that on-object probes differentially generate a perceptual conflict signal relative to off-object probes, which then may be followed by a reorienting of attention