VISUAL NOISE: ITS EFFECT ON PATTERN DISCRIMINATION IN PIGEONS BEFORE AND AFTER LESIONS OF THE VISUAL SYSTEM.
Item
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Title
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VISUAL NOISE: ITS EFFECT ON PATTERN DISCRIMINATION IN PIGEONS BEFORE AND AFTER LESIONS OF THE VISUAL SYSTEM.
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Identifier
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AAI8203343
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identifier
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8203343
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Creator
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WEST, BEVERLY V.
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Contributor
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William Hodos
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Date
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1981
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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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Recent anatomical, physiological and behavioral studies of the avian visual system have indicated that like the mammalian colliculofugal visual pathway, the avian tectofugal visual pathway is important in visual function. In both birds and mammals, a number of studies have attempted to analyze the nature of the deficit; i.e., to determine whether a sensory defect or a lack of attention is responsible for the impairments of visual performance following interruption of the tectofugal pathway. A number of these experiments have reported deficits on embedded-figures tests. However, a weakness of these tests has been the paucity of quantitative data on the limits of performance of subjects with tectofugal pathway lesions. The present experiment was an attempt to use quantitative methodology based on psychophysics and information theory in order to gain further insight into the nature of the deficit. The technique used required the subjects to perform a simple visual discrimination in the presence of progressively increasing levels of visual noise. In other words, the subjects were required to perform at the limits of their ability to extract information from a noisy information channel.;Fourteen pigeons (Columba livia) were trained to discriminate two planometric patterns. Once pattern discrimination was achieved, various percentages of static visual noise were introduced in progressive increments during discrimination testing. Using a variation of the method of constant stimuli, a psychometric function of the degrading effects of added noise on the discrimination was determined. An index of the interfering effects of this noise was derived. This index (Noise Interference Index) reflected the greatest percentage of background noise which the pigeon could tolerate while maintaining a discrimination performance of no less than 75% correct. Discrimination testing was continued until five successive sessions occurred during which the noise interference index was stable.;After satisfying the stability criterion, each pigeon was anesthetized and subjected to bilateral, electrolytic lesions which were stereotaxically aimed at the ectostriatum (the telencephalic target of the tectofugal pathway), visual wulst (telencephalic target of the avian equivalent of the geniculostriate pathway) or control areas.;After postoperative recovery, testing was resumed using the same preoperative procedures.;The results revealed that pigeons with ectostriatum (tectofugal) lesions showed significantly less tolerance to visual noise than did pigeons with visual wulst (geniculostriate) lesions or control lesions. The results indicate that the deficits observed after lesions of the tectofugal pathway may be the result of an inability to suppress the irrelevant aspects of the visual environment. The results are discussed in the context of information theory, attention theory, signal detection and response inhibition. The implications of these findings for research on the mammalian visual system are also discussed.
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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
