This project will investigate the neural mechanism that mediates a fundamental visual function - motion detection. Although computational theories have been developed to explain how neurons can detect moving objects and patterns, it has been very difficult to investigate how (or if) the models are implemented in the visual cortex. I will examine controversial aspects of current theories. With innovative methods, I will characterize neurons connected in a motion detection circuit for the first time, as well as study how they function after a critical component in the circuit is shut off. The research will lead to better understanding of how visual experience is created by the brain and will have implications in computer vision and bionics.