The Filtering of Cortical and Basal Ganglia Outputs

Asdourian, David

Abstract

The long-term objective of the proposed research is to determine the relative contributions of the basal ganglia and the cortex to motor control. A large experimental literature deals with the effects of various interventions (electrical stimulation, electrolytic and cytotoxic lesions, injection of pharmacological agents) of the basal ganglia on motor coordination. These studies are of interest because of the light they shed on basal ganglia mechanisms that control normal behavior, and the information they provide about malfunctions of these mechanisms that underlie disorders such as Parkinson's Disease, tardive dyskinesia, and Huntington's Chorea. Many of these studies have been done with rats, and in rats the caudate, putamen and globus pallidus are replete with cortifugal fibers of passage. This cohabitation of basal ganglia neurons with cortial fibers of passage makes it difficult to interpret the results of studies that have utilized electrical stimulation or electrocoagulation of these structures. In the proposed research the electrical activity of specific muscles of the neck and shoulder of anesthetized rats will be recorded bilaterally in response to unilateral electrical stimulation of the cortex, caudate nucleus and globus pallidus. Large aspiration lesions of the cortex will be made leading to degeneration of the cortical fibers of passage. Electrical stimulation of a given nucleus of the basal ganglia following degeneration of the cortical fibers will provide information about the effect of the output of that nucleus on muscle activity in the absence of cortical output. Cytotoxic lesions of a given nucleus of the basal ganglia will leave cortical fibers of passage intact. Electrical stimulation of the cortex following degeneration of neurons in a given nucleus of the basal ganglia will reveal the characteristics of motor activity driven by the cortex in the absence of output from that nucleus.