The research projects proposed in this application are a continuation of our somatotopic mapping of climbing fiber (CF) responses elicited by cutaneous stimulation in the cerebellar cortex of cats and monkeys. Extracellular recordings with tungsten microelectrodes will be made of the CF responses in lobules IV and VI and the paramedian lobule (HVIIB + HVIIA) of cats and in lobule VI of monkeys anesthetized with sodium pentobarbital. In monkeys prepared for chronic extracellular recordings, the location, size and threshold of somatic receptive fields in lobule VI will also be studied in an awakerestrained condition and during sodium pentobrabital anesthetic in the same animal. The CF responses will be elicited by low threshold cutaneous stimulation presented by a computer-control electromechanical device. The fine grain mapping of CF input will reveal the spatial organization of the skin surfaces in the cerebellar cortex, the degree of cortical representation of different body areas, whether various cortical areas for different species are homologous, and the differences in receptive field characteristics between anesthetized and awake states. These proposed studies will provide the first complete description of the receptive field characteristics for the CF system. Such information is essential in order to understand how multiple representation of various body surfaces to different longitudinal zones and/or lobules produce a unique pattern of input within each zone or lubule. Thus, the underlying concept of the proposed studies is that the fine-grain somatotopic organization of CF cutaneous input is a valuable indicator of functional specialization of different areas of the cerebellar cortex. The porposed studies will make a major contribution to the formulation of new theories pertaining to CF and cerebellar function.