The objective of this research is to contributed to a better understanding of the neural mechanisms subserving the cerebellar control of eye movements. The significance of the cerebellum as a part of oculomotor control system has long been suggested from the clinical observations and the results of animal experiments. However, the precise location of the oculomotor area in the vermis was inconclusive in the literature until recently a small area in the posterior vermis was found to evoke saccades with very weak currents in the monkey. We now know that the Purkinje cells in this cerebellar cortex project almost exclusively to an ellipsoidal region in the caudodorsal portion of the fastigial nucleus and that oculomotor signals from the cortical area are transmitted to the brainstem through this region. The specific objectives of this research focus on the determination of the pathways for the oculomotor signals beyond the ellipsoidal fastigial region in the monkey. Anterogradely HRP-labeled axons of the fastigial neurons will be traced into the brainstem nuclei after injecting wheat germ-agglutinin conjugated horseradish peroxidase (WGA/HRP) into the ellipsoidal region which is identified by recording saccade-related units and confirming that these units are inhibited by vermal stimulation. The single-unit studies focus on the analyses of the variety and distribution of signals concerning saccadic directions within the ellipsoidal region and within the projection areas of the fastigial region that will be identified by tracing HRP-labeled axons of fastigial neurons. The saccade-related discharges of the fastigial neurons will be analyzed in relation to each of the horizontal and vertical components of the saccade. When projection areas of the ellipsoidal region are determined, their roles in transmitting oculomotor signals will be studied by analyzing discharges of neurons during saccades. In order to confirm that the neurons are anatomically connected to the ellipsoidal region, such neurons will be searched for that are inhibited during stimulations of the oculomotor vermis. The determination of the cerebello-oculomotor projections from the ellipsoidal region in the fastigial nucleus and the analyses of neuronal correlates of oblique eye movements, both in the cerebellum and in the brainstem, will provide important new information concerning the functional significance of the cerebellum in the oculomotor system.
Showing the most recent 10 out of 34 publications
