Learning to see again: biological constraints on cortical plasticity and the implications for sight restoration technologies

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ABSTRACT The field of sight restoration has made dramatic progress over the last decade. Two types of retinal implants have been commercially approved, and several other designs are in development worldwide. In addition, two groups are actively implanting and developing cortical electronic implants. The first optogenetic clinical trial has begun, with many others likely in the next two years. Within a decade, many blind individuals are likely to be offered a wide range of options for sight restoration that depend on widely different technologies. Interactions between implant electronics and the underlying neurophysiology of the retina or cortex mean that the vision provided by most of these technologies will differ substantially from normal sight. The question of this proposal is – What role can cortical plasticity play in helping patients make use of this artificial visual input? Over the past 15 years our research group has been generating computational models, developed using a combination of physiological and psychophysical data, which can predict the percepts that patients might experience for a variety of sight recovery technologies. We propose to use these models to simulate, within visually normal participants, four critical neurophysiological distortions inherent in sight restoration technologies: Aim 1. Abnormal neuronal population responses during retinal stimulation: Simultaneous stimulation of on and off cells. Aim 2. Spatial distortions: Stimulation of retinal ganglion cell axons. Aim 3. Abnormal cortical neuronal population responses: Distortions induced by the V1 neural architecture. Aim 4. Temporal blurring due to slow optogenetic kinetics. Our goal is to use normally sighted participants, viewing distorted visual input, as ‘virtual patients’ to learn which spatiotemporal distortions can be compensated for by plasticity, and which must be compensated for in device design. This will provide device manufacturers with a more nuanced understanding of the abilities and limits of visual perceptual adaptability. Finally, this work will provide novel insights regarding the fundamental mechanisms of cortical plasticity by asking whether, in adulthood, it is possible to reconfigure the fundamental building blocks of visual perception?