Visual Form Perception Produced by Electrically Stimulating Human Visual Cortex

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Project Summary/Abstract Blindness disables millions of people across the world. In most cases, incurable blindness is caused by damage or dysfunction of the eye, retina, or optic nerve, but the visual cortex is undamaged and potentially functional. Electrical stimulation of visual cortex, even in blind patients, produces a percept of a distinct spots of light known as phosphenes. There has long been interest in developing a prosthetic device that employs direct activation of the intact visual cortex to restore vision to the blind. It has been speculated that phosphenes could serve as the building blocks for visual restoration in the blind; but unlike pixels in a video display, multiple phosphenes are not readily combined into a percept of a coherent form. We propose a novel stimulation paradigm, termed "dynamic current steering," that can dramatically enhance the ability of visual cortical prosthetics (VCPs) to produce useful percepts of visual forms. Because there are imminent plans for clinical trials of several VCPs within the next few years, now is a currently particularly important time to develop improved methods for stimulation of visual cortex. To assess and refine dynamic current steering as a methodology for a VCP, we will measure percepts produced with this novel paradigm in pre-clinical testing in human epilepsy patients with implanted intracranial electrodes. In Aim 1, we will test dynamic current steering as a novel method for producing percepts of visual forms. In Aim 2, we will optimize the components of dynamic current steering to promote perception of coherent forms. Together, these aims will result in a novel paradigm for producing useful percepts of coherent visual forms by stimulation visual cortex that will be immediately translatable in forthcoming clinical trials of the next generation of VCPs.