This project consists of a broad neurophysiological and neuroanatomical investigation of the corticocortical and corticofugal connections within the somatic sensorimotor cortex and their role in the generation and control of primate motor behavior. One of the central questions concerning both the synaptic and general organization of the cerebral cortex is how inputs to a cortial region from a variety of cortical and subcortical sources combine to contribute to its output. We have chosen to concentrate on the precentral motor cortex (MI), known to project directly to spinal motor neurons, and those cortical areas in close functional association with MI, the supplementary motor cortex (MII); area 3a (a transitional region between MI and the postcentral somatic sensory cortex), and the premotor cortex (area 6). Three related approaches have been adopted for this project: (1) an analysis of the organization of peripheral inputs to MI, MII, and area 3a; (2) single unit studies of cortical areas which supply inputs to MI; and (3) an analysis of MI output neurons whose targets (e.g., spinal cord, basal ganglia, cortex) have been identified.