The mammlian retina contains at least 3 major classes of output cells, X-Y-, and W-cells. These differ in receptive field properties, morphology, axon conduction velocity, and central destination of their axons. In the cat, the various subdivisions of the thalamic relay complex of the retina, the lateral geniculate nucleus (LGN), differ both in the proportions of X-, Y-, and W-cells the visual cortex. The manner in which the outputs of these subdivisions interact at the visual cortex is not understood. I propose to investigate the differential roles of the LGN subdivisions in areas 17 and 18 of the cat visual cortex. This will be done by reversibly blocking activity of a discrete portion of a particular subdivision with microinjections of either the local anesthetic lidocaine or cobalt chloride. Before, during, and after recovery from the block, response properties of individual neurons in the region of area 17 or 18 receiving input from the anesthetized area will be quantitatively assessed. By knowing how cortical neurons behave with and without these inputs, I hope to deduce the contributions of the individual subdivisions to cortical function.