Recent studies confirm that the primate Frontal Eye Fields (FEF) have animportant role in the generation of voluntary saccadic eye movements and that unit activity in the FEF is, contrary to earlier reports, well-suited for such a role. The proposed experiments will further investigate the role of the FEF in the generation of voluntary eye movements. A FEF region that appears to be related to smooth pursuit eye movements will be studied using single neuron recordings, microstimulation, anatomical tracing, and oculomotor testing following lesions. Because FEF neural activity suggests a role in predictive aspects of voluntary eye movements, this lesion study will also test for deficits in utilizing predictive aspects of target movements. Since clinical cases suggest a loss of voluntary control of eye movements with frontal lobe pathology, the ability to make voluntary saccades not directly guided by visual targets will be tested. Some FEF units respond to auditory stimuli; the proposed research explores the hypothesis that these responses function to direct saccadic eye movements towards sound sources. Experiments include mapping auditory receptive fields, testing the effects of direction of gaze upon auditory responses, and testing for an enhancement of responses as a function of behavioral significance of the stimuli. Physioilogical studies have indicated the FEF to be a discrete cortical zone with a systematic representation of saccade metrics and a subdivision concerned with smooth pursuit. The radioactive 2-deoxy-D-glucose method of measuring metabolic activity will be used to examine the overall functional organization of the FEF. Metabolism in the FEF and other structures during different oculomotor behaviors will be analyzed; the proposed cases are designed to contrast the loci of saccadic and smooth pursuit regions and map the topography of the metrics of both types of eye movements. The results of these studies should illuminate the involvement of frontal cortex in mediating complex oculomotor behavior in normal individuals and may have clinical value for the large heterogeneous population of neurological patients with eye movement disorders.
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