The goal of this research is to understanding how the retina contributes to motion processing in the dorsal visual pathway. The neural circuitry within the retina extracts visual information and sends that information through the axons of retinal ganglion cells to the visual thalamus and, subsequently, to the cortex. Much is known about the neural pathways that perform motion computations in the cortex, but far less is known about how the retina contributes to this pathway. The proposed research will further our understanding of how the retina contributes to motion processing and the mechanisms that contribute to this neural computation. Our first aim will directly determine whether motion detection occurs in the retina and the neural mechanisms that mediate these computations. Our second aim will reveal the types of motion computations occurring in the retina and how excitatory and inhibitory synaptic circuitries shape these computations. Our third aim will directly test our mechanistic understanding of the circuitry of the inner retina by evaluating the ability of synaptic models, generated from direct measurement, to accurately predict responses to natural motion. If successful, this research will provide several significant contributions. First, it will increase our understanding about how ethologically relevant information is encoded in parallel neural circuits - a fundamental goal of systems neuroscience. Second, it will explain how excitatory and inhibitory neural networks differentially shape information flow and contribute to neural computations. Finally, these findings will be applicable immediately to ongoing development of retinal prostheses and other techniques designed to restore visual function in blind humans.