Visual motor processing in retino-collicular and cortico-collicular circuits

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Visual stimuli are encoded in the retina and processed in cortical and subcortical circuits to ultimately guide behaviors. A neural circuit that is central for visually guided behaviors and visual motor processing is the superior colliculus. The superior colliculus is a layered structure in the midbrain that receives afferent sensory inputs, descending top-down information from cortical neurons and that mediates behavior via its output projections to different motor structures. For example, neurons in the superficial visual layer receive inputs from retinal ganglion cells and are organized in a direction preference map for visual motion, while neurons in the deeper layers integrate inputs from the motor cortex and mediate directional saccadic eye movements. Thus, the superior colliculus serves as a critical gateway for visual processing and visually guided behaviors. However, several questions remain open in regard to the mechanisms underlying the functional organization of the superior colliculus and the neural basis of visual-motor processing in retino-collicular and cortico-collicular circuits. Here we will employ large-scale electrophysiological recordings using high-density electrodes (Neuropixels probes) in head-fixed mice and computational modeling to address the following aims: To reveal the functional organization of the retino-collicular circuit we will employ a novel method that we recently established and that allows recording retinal ganglion cells and their connected targets simultaneously in vivo. Using this method, we will (1) characterize how the retinal ganglion cell afferent input is organized in the visual layers of the superior colliculus. Moreover, we will (2) study potential developmental mechanisms that give rise to the functional maps in superior colliculus using a computational model. In parallel, we will (3) investigate how saccadic eye movements modulate sensory processing in the retina in awake mice and (4) measure the causal role of the cortico-collicular pathway in generating saccadic eye movements during navigation. Thus, our major goal is to examine the mechanisms underlying visual-motor processing in retino-collicular and cortico-collicular circuits and we will thereby reveal new insights about the role of the superior colliculus in visually guided behaviors.