DEVELOPMENT OF BINOCULAR CONNECTIONS IN PRIMATE

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The goal of the proposed research is to study the development of binocular connections that mediate sensitivity for the direction of stimulus motion, and to correlate the emergency of specific connections with the onset of stereopsis and symmetric motion processing. the project is based on the well established notion that stereoscopic vision is dependent on the normal development of direction selective neurons that are tuned for binocular disparity. The central hypothesis is derived from observations that pursuit eye movements in infant monkeys are biased for temporal-to-nasal directions of motion and that objects moving in nasal-to-temporal directions are ignored. Our hypothesis predicts that connections dominated by inputs from the nasal retina develop in advance of those that are dominated by inputs from the temporal retina. To test this prediction infant macaque monkeys will first be examined behaviorally for visual acuity, stereopsis and pursuit eye movements. Subsequently, animals will be used in anatomical tracing experiments for determining: 1) the segregation of lateral geniculate afferents into ocular dominance columns within layer 4Ca of the striate cortex, 2) the development of local connections from left and right eye columns within layer 4B of striate cortex, and 3) the development of striate cortical projections from layer 4B of left and right eye columns to thick stripes of V2 and MT. This experimental design will allow us to evaluate the development of relevant connections at several different levels of the motion processing pathway. Documenting the timing of the emergence of these connections in normal animals is important not only for understanding the neuroanatomic co-development of stereopsis and motion sensitivity, but also because it will provide a framework for understanding the cause of deficits in strabismic monkey and human.