Circuits for active vision : parallel tectothalamocortical visual pathways in the mouse.

Abstract

Vision is a critical sensation for the interaction between humans and their surrounding environment. The eyes connect with the brain via retinal ganglion cell axons, which transmit visual sensory information from the periphery into the central nervous system for further processing, eventually leading to visual perception and the visual guidance of movement. Two main targets of retinal axons are the superior colliculus (SC) and the dorsal thalamus. From the SC, visual information is conveyed to the dorsal thalamus, and from the dorsal thalamus visual information is conveyed to the cortex, striatum and amygdala. This dissertation is focused on the functional properties of two parallel pathways from the SC to the dorsal thalamus: a pathway from the SC to the retinorecipient dorsolateral geniculate nucleus (dLGN) to the cortex, and a pathway from the SC to the pulvinar nucleus to the cortex. The experiments described in this dissertation used viral vector injections, tract tracing, in vitro whole cell patch clamp, optogenetics, electron and confocal microscopy, transgenic mouse lines and immunohistochemical staining techniques to elucidate the roles of the SC-dLGN-cortex pathway and SC-pulvinar-cortex pathway in visual coding. The first series of experiments revealed that SC and retinal inputs converge to innervate the proximal dendrites of cells in the dorsolateral shell of the dLGN that project to layer I of the striate cortex. The second series of experiments revealed the organization of subdivisions of the pulvinar nucleus in relation to inputs from the SC. The final series of experiments revealed the distribution and ultrastructure of pulvinocortical terminals, and identified the cell types activated by pulvinocortical synapses. Major targets of pulvinocortical terminals were identified as corticostriatal cells, suggesting that pulvinar acts as a hub connecting the SC, cortex and striatum