The primary objective of the experiments outlined in this proposal is to obtain further information on the central representation of the modalities associated with small diameter fibers, especially those projections related to cutaneous temperature sensations. It is anticipated that quantitative stimulus response data will be collected from temperature sensitive neurons in the spinal cord and thalamus of primates. This data will be compared with previous recordings of temperature sensitive neurons in the thalamus and periphery in order to assess the specificity and transformations of small afferent fiber projections. The locations of the isolated neurons will be correlated with anatomical studies of the origin and course of the spinothalamic system for pain and temperature. An additional study will attempt to alter the temperature response function of spinal cord neurons in order to elucidate the mechanisms of stimulus alteration that exist for these inputs to the spinal cord.