The long-term objective of our research is to understand the rules that govern the normal and abnormal development of binocular functions in primates. The proposed experiments focus on how binocular conflicting signals early in life disrupt the development of functional binocular connections in the primate visual cortex. The proposed research builds on our previous work that has documented both the normal maturation of binocular connections in the primary visual cortex (V1) and the manner in which early discordant vision alters the development of binocular signal interactions. We will create models of strabismus in infant rhesus monkeys (Macaca mulatta), many of which will have their monocular and binocular vision tested behaviorally prior to the neurophysiological experiments. Quantitative, single-unit recording techniques will be employed as our primary tool to explore the functional status of the visual cortex in anesthetized and paralyzed animals. Histochemical methods and optical imaging techniques will complement our standard neurophysiological experiments. The specific goals of the new research are to: 1) determine how the onset age of early strabismus affects the nature and severity of binocular deficits. 2) shed light on the neural mechanisms that underlie the high prevalence of binocular suppression in V1 in animals reared with strabismus. 3) investigate the hypothesis that sustained cortical suppression early in life may be a critical factor in the later emergence of amblyopia. 4) determine if V1 units in strabismic monkeys show a temporal-to- nasal bias in motion signal processing and if early binocular suppression in V1 plays a role in this asymmetry. Together, the proposed research will provide new insight into abnormal cortical events brought about by early discordant binocular visual experience. In humans, early onset strabismus severely disrupts vision development in a substantial proportion of infants in this country. Some of the experiments here are designed to test several new hypotheses that have been formulated based on our preliminary studies in monkeys and existing clinical data on binocular vision anomalies in strabismic humans. The results from the proposed research will hopefully have an impact on the development of effective strategies for the prevention and treatments of binocular vision disorders.
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