We will study the transmission of visual information through the lateral geniculate nucleus of the thalamus (LGN). Geniculate neurons have been studied extensively for the past 30 to 40 years with simple stimuli and with fixed gaze, but we still have only a dim understanding of geniculate activity during natural vision: when an alert animal scans a complex scene. Studies in both the anesthetized and the alert animal will provide a two pronged attack on this problem. Basic problems in geniculate physiology and information processing will be addressed first in the anesthetized animal, because visual stimuli are easier to control than in the alert animal and histology can be used to assign neurons in the magnocellular parvocellular or intercalated layers. In the alert animal, will be able to study how eye movements affect visual responses in each of the three geniculate divisions. In both sets of experiments, we will characterize receptive fields with the reduced stimuli typically employed in visual physiology, as well as with more natural stimuli. In later projects, multi-e4lectrode recording will be used to analyze the activity of the ensemble, rather than of individual neurons. Beyond this grant period, the long-term goal of this research program is to use our studies in the LGN as a foundation for the study of visual cortical physiology during perception. Much of visual physiology, in striate and especially extra striate cortex-is now being performed in the alert primate. We nevertheless have an imperfect understanding of the thalamic inputs to visual cortex when the eyes move. A more complete analysis of the interplay of vision and eye movements in the LGN will help put this emerging field on a more secure footing. This basic research on information processing in the visual thalamus-and on the relations between thalamus and cortex-should further our knowledge of general mechanisms of thalamocortical function. Only by exploring the normal activity of multiple thalamic inputs to cortical neurons can we begin to understand functional disorders of this pathway, such as in certain forms of epilepsy.