The relationship between cortical motor representations and motor abilities in adult primates will be examined using modern neurophysiological and behavioral training techniques. The overall objective of these proposed studies is to determine whether idiosyncrasies in motor representations in primary motor cortex are related to specific behavioral traits, and whether these representations can be altered through use. In order to determine whether idiosyncrasies in map detail have functional correlates, we will examine asymmetries in motor representations between the two hemispheres of the same individuals, and the relationship of these asymmetries to lateralized motor skills, i.e., handedness. In order to determine whether functional maps in motor cortex are static or, as in somatosensory cortex, are subject to use-dependent alterations throughout life, we will compare motor and sensory map topography before and after operant conditioning of specific sets of muscles and/or movements. In each of these experiments, detailed maps of the cortical motor topography will be derived using standard intracortical microstimulation and multi-unit recording methods, combined with chronic electromyographic recording techniques. The possible generalization of adaptive processes to motor cortex ha far-reaching theoretical implications. The relationship of individual variation in motor maps and the specialization of motor skills may provide a basis for interpreting fundamental relationships between neuroanatomical structure and neurophysiological mechanisms operating in central motor systems. These studies may lead to a better understanding of the neural mechanisms underlying handedness and, more generally, may yield insight into the neural bases for motor learning. From a clinical perspective, these studies have the potential of providing a simple model of the neurophysiological processes underlying recovery of function following central or peripheral nervous system injury.