BINOCULAR INTERACTIONS IN HUMANS: AN EVOKED POTENTIAL AND PSYCHOPHYSICAL STUDY.
Item
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Title
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BINOCULAR INTERACTIONS IN HUMANS: AN EVOKED POTENTIAL AND PSYCHOPHYSICAL STUDY.
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Identifier
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AAI8801748
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identifier
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8801748
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Creator
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PINKHASOV, ELIZABETH I.
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Contributor
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James Gordon
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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, Physiological
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Abstract
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In the present study visual evoked potentials (VEPs) and psychophysical techniques were used to determine the site of binocular interactions. Spekreijse and Oosting in 1970 offered a three-stage model of processing information in the visual system. In their model one linear filter precedes and another linear filter follows a static nonlinearity. To test the site of binocular interaction with respect to this nonlinearity two models of binocular interaction were examined. In one model, binocular summation occurs prior to the nonlinearity (rectification of the neural signals). In the other model binocular summation occurs after rectification.;Gratings of sinusoidal and square-wave spatial profiles were viewed dichoptically. Spatial frequencies of these gratings were 0.4-3.2 cycles per degree, and they were contrast-reversed at 2-6 Hz. The gratings presented to the two eyes were identical in spatial and temporal frequencies, but their relative temporal phase was varied parametrically: 0, 45, 90, 135, and 180 degrees. These stimuli elicited visual evoked potentials that contained a prominent component at twice the stimulus frequency (second harmonic). The amplitude and phase of this component depended on the relative temporal phase between the dichoptic stimuli. The two models make distinct predictions concerning this dependence.;The results indicate that the major contribution to the VEP arises from summation of monocular signals subsequent to the essential nonlinearity. A small but significant contribution, however, appears to originate from a binocular pathway that contains summation of monocular signals prior to the nonlinearity.;In the psychophysical part of the study, subjects used the method of adjustment to control the temporal phase of the second grating. They were instructed to bring both gratings in-phase to see it sharply, or out-of-phase to cancel the percept.;Results showed that responses depended on the fundamental temporal frequency component when the spatial frequency of the stimulus was low, but more upon the second harmonic component when the spatial frequency was high.
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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
