THE EFFECT OF ROD ADAPTATION ON CONE-MEDIATED FLICKER SENSITIVITY.
Item
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Title
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THE EFFECT OF ROD ADAPTATION ON CONE-MEDIATED FLICKER SENSITIVITY.
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Identifier
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AAI8401933
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identifier
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8401933
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Creator
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GOLDBERG, STUART HENRY.
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Contributor
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Thomas E Frumkes
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Date
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1983
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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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Psychology, Physiological
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Abstract
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The present study is concerned with the influence of selective rod adaptation on the sensitivity of the human observer to cone-mediated flicker. A five-channel Maxwellian view optical system was used to present an LED generated, sinusoidally flickering test stimulus of 2 20' in diameter at 7 from fixation to the right eye of three observers. In general, this stimulus was red and had a greater influence on cones than on rods, but similar results were also obtained with flickering stimuli of other spectral compositions. In particular, red and green flicker of equal modulation depth and scotopic illuminance (but for which the photopic illuminance of the red flicker was 1.6 log units greater) were sometimes presented in counterphase, resulting in a nonflickering stimulus for rods but a flickering stimulus to cones. Sensitivity to flicker was measured during the time course of dark adaptation, or in the presence of an adapting field of variable illuminance which due to its spectral properties and illuminance respectively was shown to exert its influence on rod light adaptation. Sensitivity to flicker was usually assessed by having the observer adjust the illuminance of a flickering stimulus of constant modulation depth (87%) and frequency until flicker could just be perceived, but conclusions were verified by means of modulation thresholds.;Cone-mediated flicker sensitivity decreases throughout the rod recovery stage of dark adaptation. This effect is relatively small (0.3 log units) for flicker frequencies up to 5 Hz, but increases to about a log unit for flicker frequencies exceeding 15 Hz. Similarly, cone-mediated flicker sensitivity increases as the illuminance of a rod-stimulating adapting field increases. By varying both the size and the shape of the rod-stimulating adapting field, this influence was shown to involve a retinal area of about 1 mm (3 20') in diameter.;The present results were discussed in terms of findings reported by other laboratories including psychophysical data from normal observers, color deficient subjects, and ophthalmological patients, as well as electrophysiological data in subhuman species. The combined findings suggest that unstimulated, dark adapted rods initiate a tonic inhibition of cone-mediated flicker signals. Several possible retinal pathways were suggested which could underly this influence.
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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.
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Program
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Psychology
