Environmentally-induced plasticity of hippocampal dentate gyrus evoked potentials in freely behaving rats.
Item
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Title
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Environmentally-induced plasticity of hippocampal dentate gyrus evoked potentials in freely behaving rats.
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Identifier
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AAI9417455
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identifier
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9417455
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Creator
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Croll, Susan Debora.
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Contributor
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Adviser: M. Elizabeth Bostock
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Date
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1994
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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 | Biology, Neuroscience
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Abstract
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Short-term exploratory modulation (STEM) is a recently described form of environmentally-induced hippocampal physiological plasticity. STEM is characterized by a rapidly-occurring increase in field EPSP magnitude accompanied by a decrease in population spike magnitude which occur after an animal is transferred into a different environment. The increase in EPSP magnitude and change in spike magnitude observed in STEM are also observed in a much better characterized form of hippocampal plasticity, long-term potentiation (LTP). This dissertation contains five experiments used to more fully characterize STEM by comparing it to LTP. The first experiment confirms that an NMDA receptor antagonist, MK-801, interferes with the induction of LTP in freely behaving rats. The second experiment demonstrates that MK-801 also interferes with STEM induction, suggesting that both phenomena are NMDA receptor-dependent. The third experiment demonstrates that EPSP to spike relationship shifts are observed after LTP in freely behaving rats, and that MK-801 interferes with, and even reverses, this shift. The shift is characterized by smaller EPSPs being associated with larger spikes. The fourth experiment shows that an EPSP to spike relationship shift also occurs during STEM, and that MK-801 interferes with the shift. Unlike the shift observed in LTP, the shift during STEM is characterized by larger EPSPs being associated with smaller spikes. The final experiment shows that STEM occurs with transfers to both simple and complex environments, and that the EPSP enhancements decrease with repeated exposures to an environment. These experiments demonstrate that STEM and LTP share some common characteristics, such as reduction by MK-801 and alterations in EPSP to spike relationships, but are also different in many ways. In addition, they suggest that STEM occurs regardless of the nature of the environment into which an animal is transferred, but that the EPSP magnitude may depend on the animal's familiarity with the environment. This work suggests that while both LTP and STEM may reflect mechanisms underlying the hippocampus' response to stimulation (artificial or environmental), they are likely to represent two unique processes which may work together or separately to contribute to this response.
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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.
