Organized Dynamics of Neonatal Visual Structures in the Absence of Retinal Input

This dissertation features my Ph.D work, under the supervision of Dr. Michael Crair, on spontaneous brain dynamics in the neonatal visual system. Early in mammalian development, spontaneous correlated bursts of activity in the retina, called retinal waves, dominate the visual pathway. Because diverse features of visual circuits are present by eye-opening, a leading hypothesis states that retinal waves are key for the establishment of these circuits. Given the robustness of retinal input, and the immaturity of most cortical and long-range networks, the field has maintained a retina-centric perspective on the development of the visual system. However, whether non-retina-driven activity is reflected in neonatal visual cortex is unknown. In this work, I first review the literature on visual structures, their development, and known consequences that removing retinal drive has on them. Second, I experimentally uncover and characterize non-retinal activity in neonatal visual cortex. Because visual processing is the result of local computations as well as long-range interactions, I leverage mesoscale calcium imaging to simultaneously capture non-retinal activity within and across visual structures. These experiments reveal a topographic organization and the emergence of strong long-range correlations in the absence of retinal drive. I then use genetic and pharmacological manipulations to test the dependence of these dynamics on specific brain structures. My doctoral work unveils the existence of organized visual cortex activity not originating from the retina and excludes three visual structures as potential driving sources