The effects exerted on movement by different portions of the globus pallidus will be examined and compared to those of the cerebello-thalamo-cortical system using electrophysiological stimulation and recording techniques in awake monkeys performing arm movements in reaction time tasks. We will test the hypothesis, pertinent to the movement disorders seen in patients with Parkinson's and Huntington's disease, that portions of the pallidum receiving input from sensorimotor regions of the cerebral cortex and the thalamic neurons to which they project are important in scaling the amplitude of muscle activity and, thus, the speed of movement, but are not important in controlling the initiation of movement. Other portions of the globus pallidus, which anatomical studies shown are connected with prefrontal, cingulate, and posterior portions of the cerebral cortex, may have more profound effects on motor programming and reaction times, as does cerebellar output from the dentate nucleus. This project will be the first in which thalamic neurons in the pallidothalamocortical and cerebellothalamocortical systems are identified and their activity is compared in the same animal doing the same motor task. In addition, we will begin and extensive anatomical and electrophysiological investigation of the pedunculopontine region, which is known to be reciprocally connected with the globus pallidus and to receive input from other motor-related areas such as the red nucleus and the precentral motor cortex.
