VELOCITY STORAGE IN VERTICAL OPTOKINETIC AND VESTIBULAR NYSTAGMUS AND VISUAL-VESTIBULAR INTERACTION.
Item
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Title
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VELOCITY STORAGE IN VERTICAL OPTOKINETIC AND VESTIBULAR NYSTAGMUS AND VISUAL-VESTIBULAR INTERACTION.
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Identifier
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AAI8112367
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identifier
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8112367
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Creator
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MATSUO, VICTOR EIICHI.
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Contributor
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Bernard Cohen
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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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Vertical optokinetic and vestibular nystagmus were recorded in 9 monkeys. Eye movements were recorded using silver silver-chloride EOG electrodes and direct coupled amplifiers. The EOG was electronically differentiated and rectified to get slow phase velocities of nystagmus. Monkeys were tested lying on their sides. Steps of full field optokinetic and/or vestibular stimulation were given at velocities from 10 to 180 deg/sec.;Downward nystagmus was always more prominent than upward nystagmus. Downward OKN reached higher velocities than upward OKN did, and downward OKAN was more vigorous, saturating at about 45 deg/sec. Upward OKAN was weak or absent, and group mean values did not exceed 10 deg/sec. Peak velocities of vertical vestibular nystagmus induced by rotation in darkness were symmetrical, but time constants of downward nystagmus were longer than those of upward nystagmus (12 to 16 sec vs 5 to 10 sec). Exposure to a stationary surround (visual suppression) was less effective in suppressing downward vestibular nystagmus than upward nystagmus. Time constants of visual suppression of downward vestibular nystagmus were about 8 sec. This is in contrast to time constants of visual suppression of upward nystagmus which were about 3.5 sec.;The asymmetry in vertical nystagmus was also seen during visual-vestibular interactions. After rotation in light that evoked downward nystagmus, animals were halted in darkness. Downward OKAN summed with upward post rotatory nystagmus and cancelled the after response. As a result, little or no after nystagmus was seen. Rotation in the opposite direction evoked upward OKN. Since upward OKAN was weak or absent, at the end of stimulation downward post rotatory nystagmus was unopposed and was as strong as post rotatory nystagmus recorded after rotation in darkness. When the optokinetic input was altered, the after responses increased or decreased over a range that was limited only by the saturation velocities of upward and downward OKAN. The results were interpreted in terms of a model of optokinetic and vestibular nystagmus generation that includes a velocity storage integrator. The degree of velocity storage during downward nystagmus was comparable to that during horizontal nystagmus. In contrast, there was little or no evidence of velocity storage during upward nystagmus.
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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
