THE TRANSMISSION OF VISUAL INFORMATION TO THE BRAIN VIA DIRECT AND INTERHEMISPHERIC PATHWAYS.
Item
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Title
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THE TRANSMISSION OF VISUAL INFORMATION TO THE BRAIN VIA DIRECT AND INTERHEMISPHERIC PATHWAYS.
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Identifier
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AAI8401940
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identifier
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8401940
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Creator
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LADENHEIM, BARBARA DALE.
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Contributor
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James Gordon
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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, Psychobiology
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Abstract
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The apparent delay in the transmission of information to the brain as a function of locus of visual stimulation was measured using the visually evoked potential (VEP). Pathways from the left hemiretinas outside of the foveal area lead only to the left cerebral hemisphere and vice versa. Stimuli were presented at .5 degrees of visual angle lateral to the point of central fixation to assure that stimulation of the central area of the fovea (which has projections to both hemispheres) was avoided. Stimuli consisted of sinusoidally modulated checkerboard patterns (1.5 cycles per degree) contrast reversed at eight different temporal frequencies (3.5, 4.25, 5, 5.75, 6.5, 7.25, 8 and 8.75 Hz) which were presented monocularly to either a right or left hemiretina.;Steady state visually evoked cortical potentials were measured bilaterally over five electrode sites. An electrode was located at Oz, two electrodes at 3.5 cm intervals lateral and to the right of Oz and two electrodes at 3.5 cm intervals lateral and to the left of Oz. All electrodes were referenced to Cz and the two electrodes closest to Oz were also referenced to Oz.;Fourier analyses were performed on the data. By examining the phase of the second harmonic response the relative latency of response at different recording sites was determined. Within the frequency range tested, phase changed as a linear function of frequency. The slopes of the phase by frequency functions were used to determine the apparent latency of response.;Response latencies recorded from over the directly stimulated hemisphere were shorter than those from over the non-directly stimulated hemisphere (receiving input via the corpus callosum). This may be interpreted as evidence of a delay in transmission of information to the nondirectly stimulated hemisphere. No differences in response latencies were found as a result of stimulus presentation through the eye ipsilateral or contralateral to the directly stimulated hemisphere. Consistent differences in the pattern of the VER recorded from over the directly compared with the nondirectly stimulated hemispheres were also observed; a simple delay due to either neural transmission time or volume conduction cannot account for these differences.
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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
