9312878 Mangel The retina is the tissue of the eye containing the photoreceptors. In mammals these cells are of two basic types, rods and cones. The rod cells are most sensitive in dim light, while the cone cells operate best in bright light. When different light levels are maintained, the change in visual responsivness is called adaptation. At another layer in the retina lie a whole class of cells called horizontal cells, because they collect input over a fairly wide area of photoreceptors. These horizontal cells provide input to the nerve cells fof the optic nerve, called ganglion cells, which provide the output of the retina to the brain for vision. This proposal will use physiological, pharmacological and anatomical techniques to clarify the functional role of the horizontal cells in the rod and cone pathways. Different levels of light intentsity will be used to see how the rod and cone cells influence the horizontal cell activity at different levels of light adaptation. Pharmacological agents and electrophysiology will be used to determine the functional connections between horizontal cells and ganglion cells at different levels of light adaptation. These studies are important for understanding the basic property of adaptation in visual function, and will have impact on computational models of visual systems as well. ***
