The capacity for cortical reorganization following brain injury in adult primates will be examined using modern neurophysiological and behavioral training techniques. The overall objectives of this study are to examine functional reorganization in primary motor cortex of adult primates following focal vascular infarct, and to examine the interactive effects of physical use of affected muscle(s) on the areal extent and time course of reorganization. To determine whether lesions within cortical area 4 (primary motor cortex) alter the organizational details of motor and sensory representations, physiological maps will be compared before and a few months after infarct. To determine whether intensive use of affected muscles can alter the extent of lesion-induced changes, maps will be compared before and a few months after infarct in animals that have undergone intensive pre-lesion or post-lesion behavioral training. To determine the time course of behavioral recovery from ischemic infarct, and the correlation with functional reorganization in motor cortex, lesion-induced changes in representational maps will be tracked in animals undergoing behavioral assessment of motor abilities both before and after infarct. In each of these experiments, detailed maps of both sensory and motor topography will be derived in adult squirrel monkeys using standard intracortical microstimulation and multi-unit recording, combined with chronic electromyographic recording techniques. Detailed analyses of videotaped motor behavior, as well as operant training techniques will be used to assess spontaneous recovery of motor abilities following cortical infarct, and to provide motor exercise (i.e., physical therapy) before and/or after cortical infarct. The possible generalization of adaptive processes to motor cortex has broad theoretical and clinical implications. It is important to advance these studies to determine whether the many experimental manipulations demonstrating functional plasticity in somatosensory cortex, especially cortical injury, result in significant changes in functional topography in motor cortex. These studies have the potential of providing a simple model of the neurophysiological bases for recovery of motor function following brain damage. While limited recovery of voluntary movement often occurs following injury to motor cortex, few detailed electrophysiological mapping studies have examined cortical reorganization as a possible correlate of functional recovery. Any understanding of the dynamics of cortical motor map establishment, maintenance and alterability, bears significance not only for the normal development of sensorimotor skills under cortical control, but also for the impact of physical therapy on recovery of lost motor skills following injury.
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