PROJECT SUMMARY Vision is a dynamic process, constantly encoding visual stimuli that depend on both one's self motion and the ever changing visual scene. Past studies have suggested that locomotion modulates visual processing in numerous brain regions, contributing to modulations of gain, spatial resolution processing, and potentially attentional state, to name a few. The caveat of many of these investigations is that they were performed in restrained experimental conditions that limited animals to head-fixation and limited locomotion on a spherical treadmill. Therefore, the impact of natural, freely moving locomotion on visual processing remains unknown. We have developed methods to record visual responses during free movement. We will apply this to investigate how two key visual brain regions, primary visual cortex (V1) and superior colliculus (SC) are modulated by natural locomotion, and compare two distinct experimental in vivo electrophysiology conditions: head-fixed and natural locomotion. In Aim 1, I will use in vivo electrophysiology in V1 to analyze visual responses in both experimental conditions as well as specifically analyzing the impact of locomotion on suppressed-by-contrast cells. In Aim 2, I will use in vivo electrophysiology in SC to analyze visual responses in both experimental conditions and compare the locomotor modulation of narrow-field vertical neurons and wide- field vertical neurons. Together, these aims will determine the impact of natural locomotion on visual processing in V1 and SC on a global level and at a cell type specific level. The proposed experiments will also inform future studies aimed at dissecting the neural circuits underlying natural vision and provide experimental paradigms that may be utilized to study free moving visual neuroscience in a variety of tasks.