The main goal of the proposed studies is to elucidate the anatomical organization of three major components of the motor control system in a non-human primate, namely the nigro-, pallido-, and cerebellothalamocortical pathways. Injections of WGA-HRP and, in some instances, of tritiated amino acids will be made in discrete thalamic regions that comprise the projection zones of the nigral, pallidal, or cerebellar efferents. The anterograde and retrograde labeling pattern resulting from these injections will be plotted and analyzed. The proposed studies are focused on analysis of the organization, topography, and relationship of the cortical projections originating from thalamic territories occupied by nigral, pallidal, and cerebella afferents. Additionally, the data will be obtained on the sources and topography of other afferents to these thalamic regions. The data currently available in regard to the extent and topography of the cortical targets of the nigral, pallidal, and cerebellar output systems in monkey are incomplete, controversial, and based mostly on retrograde tracing from selected cortical areas. The proposed studies will utilize anterograde tracers injected in the thalamus and, therefore, will provide a comprehensive overview of the organization and anatomical relationships of nigro-, pallido-, and cerebellothalamocortical pathways. This information is of fundamental importance for understanding the mechanisms of voluntary movements in normal and diseased states (i.e. dyskinetic disorders). The techniques to be used include histochemistry of anterogradely and retrogradely transported HRP, autoradiography of anterogradely transported tritiated amino acids, histological stains for cyto- and myeloarchitectonics, computer-assisted image analysis with three-dimensional reconstructions, and highly accurate stereotactic technique that is based on contrast ventriculography and an intracerebral coordinate system for the injection of tracers into subcortical structures. The use of this surgical technique together with a recently constructed stereotactic atlas of monkey brain that also utilizes the intracerebral coordinate system ensures the success of the proposed experiments.
