Implicit and explicit cognitive functioning in hippocampal amnesia.
Item
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Title
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Implicit and explicit cognitive functioning in hippocampal amnesia.
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Identifier
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AAI9605682
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identifier
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9605682
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Creator
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Winter, William.
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Contributor
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Adviser: Arthur S. Reber
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Date
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1995
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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, Experimental
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Abstract
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The research reported here constitutes a cognitive neuropsychological profile of an adult male (M.S.) who became severely amnesic following a major hypoxic episode occurring at the age of eight. Recent MRI studies have confirmed the presence of a bilateral atrophy of the hippocampal formation which does not involve surrounding cortical tissue. Across ten evaluations, this subject demonstrated a general preservation of implicit cognitive functioning despite clear explicit deficits. This assessment was complicated, however, by anomalous results on certain evaluations. For example, M.S. showed relatively slow acquisition of a "perceptual/motor skill" task (the computer game Tetris). In another series of evaluations, M.S. showed evidence of an unexpectedly low rate of priming in word-stem completion, but showed a robust effect on another task ("fame-priming") which does not involve responses to partial letter sequences. This result, when combined with several other sources of evidence described herein suggest the possibility of an "acquired dyslexic" condition which may be a consequence of his hypoxic injury. The slowed rate of learning on Tetris is viewed as a function of depressed motoric response, and to subtle but significant demands upon long-term explicit memory through repeated testings. It was also concluded, based upon the results of several of these evaluations and related observations, that M.S. possesses a significant residual ability to form memories of the explicit or declarative type, but that these memories can only formed after repeated exposures to target material. Moreover, it is suggested that the amnesia suffered by this subject is less severe than that of the noted case H.M., whose mid-temporal lobe neuropathology is more extensive, and includes structures whose importance to memory are not yet fully understood. Other evaluations reported here include artificial grammar learning, an assessment of release from proactive interference, vocabulary acquisition, an evaluation of source memory, and the Tower of Hanoi puzzle. Results are discussed in terms of current theories related to the implicit and explicit, semantic and episodic, and declarative versus nondeclarative classification systems.
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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.
