Cortical feedback and the integration of signals across the visual field.
Item
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Title
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Cortical feedback and the integration of signals across the visual field.
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Identifier
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AAI3187369
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identifier
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3187369
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Creator
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Cantone, Gina.
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Contributor
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Advisers: Jonathan B. Levitt | Richard L. Chappell
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Date
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2005
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Neuroscience
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Abstract
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Mammalian cerebral cortex is comprised of many anatomically and physiologically distinct areas. Anatomical connections among these areas are a fundamental aspect of cortical architecture, yet many aspects of their organization and functional relevance remain poorly understood. We have studied the fine topographic organization of cortical feedback inputs to primary visual cortex (area 17) of the ferret (Mustela putorius furo). We made restricted injections of the anatomical tracer CTb into area 17, and mapped the distribution of retrogradely labeled cells throughout cerebral cortex. We found dense cell label in areas 18, 19, 21 and suprasylvian cortex (Ssy), and sparser connections from visual areas in lateral temporal and posterior parietal cortex. We then related the distribution of labeled cells to the map of visual space in each area, determined by electrophysiologically mapping receptive fields throughout cortex. In areas 18, 19, and 21 receptive fields of cells in the region containing labeled neurons overlapped those at the injection site, but spanned a greater distance in visual space than the receptive fields at the injection site. In electrophysiological experiments, we studied the physiological properties of single neurons in area 17. We directly measured the extent of visual space over which neuronal responses in the near-central representation of area 17 could be elicited or modified. We find for a proportion of cells that visual stimuli can evoke or modify responses over a region in visual space extending at least 35° in diameter. This distance exceeds that spanned by monosynaptic connections within area 17, but is commensurate with the extent of feedback connections. We consistently found substantial feedback projections to area 17 arising from Ssy. Therefore we established the retinotopic organization in Ssy as a step in confirming the retinotopic precision of feedback connections arising from this area. Based on the retinotopic organization and receptive field size that it is likely that larger visuotopic extents converge onto less extensive regions of visual space in area 17 through feedback connections. These data are thus consistent with the suggestion that feedback connections in visual cerebral cortex contribute to response modulation by stimuli beyond the classical receptive field.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
