Functional specialization of foveal visual cortex

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PROJECT SUMMARY Despite decades of research studying primate primary visual cortex (V1), remarkably little is known about cortical processing in the region representing the central few degrees of the visual field: the fovea. This is particularly notable given that a disproportionately large fraction of V1 is dedicated to foveal processing, and the “central” role of the fovea in both human visual perception and behavior. Studies of foveal V1 function have been greatly limited by the inability to track an animal's eye position with sufficient accuracy to reconstruct the position of the visual stimulus on the retina. We have recently developed a model-based eye tracking method to address this problem, which can continuously infer eye position with sufficient accuracy to study foveal V1 processing. We thus propose to perform the first detailed studies of stimulus processing in foveal V1. Simply put, it is not known whether the enormous body of work studying V1 outside the fovea is applicable to foveal V1, and whether there are critical elements of cortical function that only might be observed in the fovea. Due to the different dynamics of visual input to the fovea that are driven by eye movements, the different composition of retinal inputs, and the distinct functional roles the fovea plays in visual perception, we expect to identify fundamental differences in foveal V1 function. We will perform multi-electrode recordings across eccentricity in awake macaque, and target analyses to three aspects of visual processing expected to be different: (1) tuning for spatiotemporal elements of vision; (2) tuning to binocular disparity; and (3) color processing. We expect that this proposed study will reveal substantial differences in the stimulus processing of foveal neurons, potentially transforming our current understanding of visual processing in the cortex. Health Relevance. Understanding the unique functional role of foveal V1 in visual processing will provide critical insight into how human visual perception is constructed, and will likewise inform our understanding of the effects of many disorders that impact central vision. For example, age-related macular degeneration (AMD) is a leading cause of vision loss of Americans 60 and older. Patients with advanced AMD retain their peripheral vision, but lose vision in the fovea, resulting in severe difficulties with a wide range of important tasks requiring high-acuity vision, including reading, writing, driving, and object/facial recognition. Likewise, a range of disorders such as nystagmus can disrupt normal eye movements and fixations, thereby disproportionally affecting foveal vision. A better understanding of neural function subserving foveal vision could yield insights into their effects on visual perception and potentially facilitate the development of novel therapeutic strategies.