THE EFFECTS OF LONG TERM AND SHORT TERM ADAPTATION ON CONE-MEDIATED SPATIAL VISION.
Item
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Title
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THE EFFECTS OF LONG TERM AND SHORT TERM ADAPTATION ON CONE-MEDIATED SPATIAL VISION.
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Identifier
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AAI8801743
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identifier
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8801743
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Creator
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NAARENDORP, FRANKLIN.
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Contributor
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Thomas E. Frumkes
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Date
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1987
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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, Experimental
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Abstract
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Part One of the present study concerns the influence of selective long term rod adaptation on cone-mediated spatial acuity. On-off squarewave gratings of 6{dollar}\sp\circ{dollar} diameter and 600 ms duration were presented to the parafovea by means of a projection system. Threshold Grating Luminance (TGL) was the index of spatial acuity. TGL was determined as a function of background luminance. With fine gratings, TGL decreased (acuity increased) as background luminance increased up to {dollar}-{dollar}2 log cd/m{dollar}\sp2{dollar}. This effect was small for coarse gratings, but increased with spatial frequency up to one log unit for a 21 cycle per degree (cpd) grating. Action spectra established that enhancement of acuity was due to an influence by rods.;During the rod recovery stage of long term dark adaptation, TGL increased. This effect was small with coarse gratings but increased with spatial frequency. The results suggest that dark adapted rods tonically inhibit cone-mediated spatial acuity.;Part Two concerns the influence of short term adaptation of both rods and cones upon cone-mediated spatial acuity. A test stimulus of 54{dollar}\sp\prime{dollar} diameter, 10 ms duration and concentric adapting flash (AF) of 20{dollar}\sp\circ{dollar} diameter, 500 ms duration, variable in illuminance were presented in Maxwellian view to either the fovea or parafovea. The test was either a homogeneous flash (TF) or an 18 cpd grating. TF threshold and Threshold Grating Illuminance (TGI) were determined as a function of Stimulus Onset Asynchrony (SOA). Results obtained with a homogeneous TF resembled Crawford's (1947) early light and dark adaptation data, but TGI results were much different. AFs too dim to influence cones decreased TGI. This effect gradually reached a maximum at an SOA of 250 ms and then remained steady. Following offset of bright AFs, TGI decreased below control values. TGI was minimal at an SOA of 900 ms, but returned to control level by an SOA of 5000 ms. Action spectra show that: (1) the influence of dim and bright AFs were attributable to rods and cones, respectively; (2) TGI is always cone-mediated; (3) enhancement of grating acuity involves an increase in sensitivity at the red end of the spectrum.
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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
