PROJECT SUMMARY/ABSTRACT Vision is an important driver of our evolution and adaptation to different environments. It is a complex process that begins with photoreceptor signal transduction in retinal circuitry before transmitting to central brain targets to drive a range of image-forming visual functions, from color discrimination to navigation. Canonically, studies on image forming vision in the retina and cortex have largely focused on rod and cone inputs that encode pattered visual images. However, additional inputs that contribute to complex retinal and cortical computations from melanopsin-expressing intrinsically photosensitive retinal ganglion cells (iPRGCs) or sleep are largely unexplored. Therefore, there is a need to understand how multiplexed photoreceptor inputs mediate retinal and cortical processes and how such responses are altered with sleep. I hypothesize that multiplexing of rod, cone, and melanopsin input will allow cortical neurons to respond to visual stimuli with a large range of irradiance under complex visual features like natural scenes, and that these processes will be modulated by sleep. My objectives are to measure melanopsin-specific retinal and cortical responses, use that information to build a predictive computational model of the early visual system that incorporates multiplexed photoreceptor inputs, and determine how sleep alters cortical computations for visual processing. I will begin by isolating and measuring melanopsin-specific responses in the retina and cortex under natural scenes in Aim 1. Then, I will record responses in the visual cortex under natural scenes at different points of circadian time-of-day and sleep deprivation in Aim 2. By understanding a detailed quantitative description of how visual experience is represented in the retina and visual cortex, we will better understand how and why vision loss occurs in diseases and disorders that affect the early visual system. Furthermore, my work will contribute to the de