It has been proposed that the basal ganglia and the supplementary motor area (SMA), to which much of the output of motor areas of the basal ganglia is directed, play special roles in the control of movements that are based on internally stored information. It also has been proposed that information from SMA and the postarcuate premotor cortex (APA), which is hypothesized to play an important role in movement guided by externally derived sensory signals, send information to separate neurons in the basal ganglia. To test these hypotheses, the proposed experiments will: 1) compare the activity of individual pallidal (and SMA) neurons during kinematically similar movements made under behavioral conditions that do or do not require memory of target location or sequence, 2) determine whether different groups of pallidal neurons receive input from different motor and premotor cortical areas, and 3) determine the changes produced in motor performance (and SMA neuronal activity) on internally and externally guided tasks when normal pallidal output is disrupted. These experiments will extend our understanding of the control of normal targeted limb movements and will provide information that can be used to assess, and perhaps rehabilitate, individuals with motor disabilities due to conditions such as Parkinson's disease, Huntington's chorea, slowly growing brain tumors and vascular or traumatic brain injury.
