Development of Human Visual Cortex: A Neurobiological Approach

Abstract

Human visual perception changes across the lifespan that relies on changes in synaptic plasticity in the visual cortex. Anatomical studies of the visual cortex, however, suggest human V1 develops early and remains relatively constant from childhood and on. Animal models have pin-pointed specific neurobiological mechanisms that are necessary for the development of visual plasticity and receptive field properties in the visual cortex. Very little is known, however, about how those synaptic mechanisms develop in the human visual cortex to support plasticity and perception across the lifespan. This thesis addresses this gap by providing new studies on the development of those neurobiological mechanisms in postmortem human visual cortex cases that range in age from 20 days to 79 years. The main findings from this thesis support prolonged development of plasticity mechanisms in human V1 that could be characterized in 5 stages of change across the lifespan: booting up synaptic function in infancy, high neural variability in young childhood, peaks of development in older childhood, prolonged plasticity in adulthood, and return to juvenile-like state in aging. In addition, I show a contrasting development of synaptic plasticity mechanisms in V1 and extrastriate areas that suggest higher order visual perception is processed differently. I also highlight a modernized technique for isolating synaptoneurosomes in human brain that helps quantify synaptic proteins using postmortem human tissue. Together these findings aid in the translation of neurobiological mechanisms in animal models for identifying new therapeutic targets for recovery in human visual disorders and vision loss.