UBC Theses and Dissertations
Explicit/implicit memory performance and memory strategies in Alzheimer patients Gallie, Karen A.
Research has shown that implicit memory can be spared in some amnesic patients, even when explicit memory is severely impaired. In contrast, results from studies with Alzheimer patients are mixed. This investigation re-explored these latter findings in a series of experiments, many that differed from those used in previous work, to find out how the performance of AD patients with different levels of functional impairment compares to that of non-institutionalized controls. The first part of this dissertation explored Alzheimer patients (AD) and age-matched controls' performance on four parallel forms of explicit and implicit memory tests employing written and spoken words, pictures, and common objects (e.g., toothbrush). For each test, subjects encoded critical targets by first identifying, and then generating a personal meaning for each item. The second part of this dissertation consists of three experiments that explored whether encoding and retrieval (i.e., test) strategies could be used to elevate the explicit memory performance of AD patients. The average age of the 20 AD patients (9 possible and 11probable using NINCDS-ADRDA criteria; 13 female, 7 male) was 70.8years (range = 50-84 years, SR = 8.2) with a mean of 12.5 years of education (range = 6-18 years, SD = 3.3). The Functional Rating Scale (Tuokko & Crockett, 1989) indicated that 6 of these functionally impaired. The average age of the 40 control subjects (27 female, 13 male) was not statistically different from that of the AD patients (67.8 years, range = 51-89 years, 2p= 9.9) although controls reported a significantly greater number of years’ of education (i.e., H = 14.83 years, range = 8-27 years, = 4.2). The overall hypothesis of part one was that differences in the memory performance of AD patients versus controls would be smaller on implicit than explicit tests. Results showed that this hypothesis was supported for tests of written and spoken words (i.e., using category completion and category cued recall tests) and for common objects in a perceptual learning condition(i.e., the same objects re-presented over two trials using a tactile identification and a tactile recognition test). In contrast, this hypothesis was not supported for tests using picture materials (i.e., using a picture fragment and a picture recognition test) or for common objects in a skill-based learning condition (i.e., different objects presented over two trials in a tactile identification and a tactile recognition test). These findings support previous reports that AD patients exhibit impaired performance on picture fragment completion tests. In contrast, these results do not support previous work which has indicated that performance on semantic priming tests is also impaired in these patients. This study extends current work by finding that implicit memory for spoken words and common objects need not be impaired in these patients. In addition, that AD patients with mild, moderate, and severe levels of functional impairment can show a similar magnitude of priming on some tests. Results from this study are discussed in terms of the influence that the encoding task, stimuli, and test form may have had on memory performance. The overall hypothesis for part two was that the explicit memory performance of AD patients would be elevated using specific encoding and retrieval conditions. This hypothesis was supported in the levels-of-processing and partially supported for the Subject Performed-Experimenter Performed (i.e., SPT-EPT) and the multisensory (i.e., See, Say, and Do) experiments. Results from this study extends previous work by showing that AD patients' explicit memory abilities can be significantly elevated when performance and meaning-generated encoding strategies are used in combination with a cued recall or recognition test retrieval condition. In addition, the ability of these encoding and retrieval strategies to raise the explicit memory performance of AD patients was found to decline as these patients' level of functional impairment increased. These findings are discussed in terms of the possible mechanisms by which these encoding and retrieval strategies influenced the memory performance of AD patients.
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