Tonic interocular suppression by a dark adapted eye upon spatial vision in the contralateral eye.
Item
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Title
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Tonic interocular suppression by a dark adapted eye upon spatial vision in the contralateral eye.
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Identifier
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AAI9218231
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identifier
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9218231
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Creator
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Denny, Noreen M.
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Contributor
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Adviser: Thomas E. Frumkes
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Date
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1992
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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 | Psychology, Physiological | Health Sciences, Ophthalmology
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Abstract
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Monocular contrast sensitivity functions (contrast sensitivity to sinusoidal gratings as a function of their spatial frequency) were determined while the adapted state of the contralateral eye was systematically altered. Three observers were used.;1. In general, grating contrast sensitivity was least if the contralateral eye was totally dark adapted, and increased if it was light adapted. With gratings viewed foveally, this effect was observed for all spatial frequencies {dollar}\ge{dollar}2 cycles per degree (cpd), as long as the overall dimensions of the test grating were {dollar}\ge{dollar}1{dollar}\sp\circ{dollar}. This effect increased with parafoveal displacement, but was absent when 0.5{dollar}\sp\circ{dollar} foveal gratings were used. These interocular effects could not be mimicked by direct adaptation of the "test eye," or by binocular adaptation.;2. This interocular adaptation effect occurs over the entire range of grating luminance (0.01-10.0 cd/m{dollar}\sp2{dollar}) examined. This effect was obtained with 2-5 cpd gratings using any interocular background luminance {dollar}>{dollar}10 {dollar}\times{dollar} 10{dollar}\sp{lcub}-4{rcub}{dollar} cd/m{dollar}\sp2{dollar}. For frequencies from 10-20 cpd, this effect was obtained with interocular background luminance {dollar}>{dollar}0.1 cd/m{dollar}\sp2{dollar}. Dark adaptation experiments showed that grating sensitivity in the "test eye" decreased as the rods in the contralateral "adapting eye" progressively changed to being dark adapted. Both rod- and cone-mediated spatial sensitivity in the contralateral eye are influenced by the adapted state of rods.;3. Pressure blinding and light adapting one eye produce similar improvement in grating visibility in the contralateral eye. Therefore, dark adapted rods in one eye exert a tonic interocular suppression (TIS) upon spatial vision in the contralateral eye.;4. In the fovea, binocular presentation and interocular adaptation produce nearly identical grating sensitivity. In the periphery, binocular presentation produces greater sensitivity than interocular adaptation. However, both viewing conditions often improve grating visibility {dollar}>{dollar}0.3 log{dollar}\sb{10}{dollar}, the maximum amount consistent with binocular summation. Therefore, the improvement in sensitivity resulting from binocular viewing may be due to a removal of TIS rather than to "binocular summation.".
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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.
