Project Summary/Abstract How visual information is processed and transformed in the nervous system is a fundamental question in vision research. Given its clear importance in visually-guided behaviors and the available genetic tools, the mouse superior colliculus (SC) holds great promise for understanding visual processing and its neural mechanisms. The SC is a midbrain structure important for multimodal integration and sensorimotor transformation. Its superficial layers are purely visual and receive direct inputs from the retina. In this proposal, the investigators will study motion processing in a visual layer of the SC, the SGS, with a particular focus on its modulation by stimulus context, locomotion state, and self-generated visual flow. First, in vivo whole cell recording will be performed to determine the synaptic inputs that individual SGS neurons receive from the region surrounding their receptive fields. These experiments will reveal the local connectivity of excitatory and inhibitory neurons that mediates the bidirectional encoding of motion contrast between the visual stimulus and its context. Second, two-photon calcium imaging will be performed in awake mice to determine whether and how locomotion affects visual responses in the SGS. These experiments will be done across the depth of the SGS and in a cell- type-specific manner. Finally, the investigators will study whether and how self-generated visual flow affects the responses of SGS neurons. Two-photon imaging and physiological recording will be performed in head- restrained mice running in a virtual reality system. These experiments will be conducted across different retinotopic locations in the SGS, in order to reveal whether a region-specific organization exists in the SGS in the context of encoding self-generated motion. Together, these experiments will generate important data needed for a complete understanding of visual processing in the brain. Because normal visual processing is compromised in a number of neurological and psychiatric disorders, such as dyslexia, schizophrenia, and autism spectrum disorders, these studies will provide novel insights for the understanding and treatment of these disorders.