Rapid topographic reorganization in adult human primary visual cortex (V1) Restricted; Files Only
Jamal, Yaseen (Spring 2020)
Published
Abstract
Can the human primary visual cortex (V1), once wired up in development, change in adulthood? Although numerous studies in adult nonhuman animals have observed topographic reorganization in V1 following the loss of typical visual input (e.g., due to a retinal lesion), this phenomenon is far less understood in adult humans. Specifically, neurons in the deprived portion of V1 start responding to stimuli that would normally activate adjacent cortex only, and in adult nonhuman animals, such topographic reorganization has been documented after both short-term (i.e., minutes to hours) and long-term (i.e., months to years) visual cortical deprivation. However, similar changes in adult human V1 have only been reported following long-term deprivation, while some studies have even challenged the nonhuman and human findings entirely. Further, just one study in adult humans has explored the perceptual consequences of long-term topographic reorganization in V1 while none have addressed this issue in adult nonhuman animals. Finally, the mechanisms underlying topographic reorganization in adult human V1 have never been investigated. Therefore, three essential questions remain: i) Can topographic reorganization in adult human V1 also occur following short-term deprivation? ii) If so, what are the perceptual consequences of such rapid neural change? iii) What is the mechanism underlying short-term topographic reorganization in adult human V1? Here I address these questions through a series of four studies in two papers. In Paper 1, I found that topographic reorganization in adult human V1 can occur following short-term deprivation, and that the perceptual consequence of such rapid neural change is elongation of stimuli presented adjacent to the deprived region (e.g., squares are perceived as rectangles). In Paper 2, I demonstrated that short-term topographic reorganization in adult human V1 is mediated by the disinhibition of preexisting connections via a reduction in GABA. Overall, this research takes advantage of multiple methodologies (i.e., fMRI, MRS, and psychophysics) to provide converging neural and behavioral evidence that highlights the remarkable potential for plasticity in the adult human V1, thus not only advancing our understanding of fundamental cortical physiology and its relation to visual perception, but also informing potential treatments for patients with vision loss.
Table of Contents
General Introduction.....1
Evidence for topographic reorganization in adult V1.....3
Perceptual consequences of topographic reorganization in adult V1.....10
Mechanisms underlying topographic reorganization in adult V1.....12
Interim summary.....16
Paper 1: Rapid topographic reorganization in adult human primary visual cortex (V1) and consequent perceptual elongations following non-invasive and reversible deprivation
Title.....17
Abstract.....18
Introduction.....20
Results.....22
Discussion.....38
Methods.....43
Paper 2: Rapid topographic reorganization in adult human primary visual cortex (V1) and consequent perceptual elongations are mediated by GABA
Title.....49
Abstract.....50
Introduction.....51
Results.....53
Discussion.....63
Methods.....70
Supplemental Figures.....76
General Discussion.....81
References.....85
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File download under embargo until 18 May 2026 | 2020-03-08 15:14:25 -0400 | File download under embargo until 18 May 2026 |
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