Neuroimaging Studies of Human Binocular Vision and Stimulus Selection

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Normal binocular vision requires the cooperation of two frontally placed eyes. The stimulation received by each eye is never identical. Remarkably, we usually, but not always, experience a single view perceptually. The computations that achieve binocular combination depend on the stimuli shown to each eye, and distinct regimes exits. Our long-term goal is to provide a perceptual and physiological account of these binocular combination regimes that integrates with our understanding of the visual system as a whole. The objective of this application is to focus on binocular rivalry (BR) as a window onto mechanisms of binocular integration. We propose a multidisciplinary approach that combines detailed vision testing with high-resolution neuroimaging of brain activity so that we can evaluate competing theories of binocular vision, and relate our findings to current understanding of perceptual awareness. In addition to functional magnetic resonance imaging (fMRI), we have also begun to incorporate magnetoencephalography (MEG) for non-invasive human neuroimaging. This work will be further enhanced by new analysis techniques such as network modelling of functional connectivity, and emerging machine learning techniques. Specifically, we propose here to advance the characterization of the brain networks that underlie the perception of binocular rivalry, including the relationship to pattern rivalry, interocular grouping, and selective attention. Aim 1 - Compare and contrast the neural correlates of binocular and pattern rivalry, to define the sites of both monocular and binocular neural competition. Aim 2 - Determine the mechanisms of interocular grouping in binocular rivalry, to further isolate the neural substrates of binocular competition across large regions of space. Aim 3 - Relate the effects of voluntary visual attention to the effects of stimulus contrast on rivalry, to better understand the role of selective attention. Aim 4 - Apply network modelling analysis to both fMRI data and MEG data, to describe the mechanisms of communication used between networks of cortical regions. In addition, we also propose to take advantage of the robust individual differences known to exist in the normal visual brain, and behaviourally in binocular vision in particular. Direct correlation of such brain-behaviour differences can be applied to effectively address the putative neural mechanisms even more finely than in the past. Moreover, some perceptual differences will relate to genetic traits, and such cognitive neuroscience-to-molecular biology integration will likely impact our understanding of behaviour in the years to come. Finally, advancing our models of rivalry to the level of single subjects makes the eventual translation to subjects with abnormal binocular vision far more likely, and increases our impact even further.