Vision In Alzheimers Disease PDF Download

Semantic memory has been shown to deteriorate in patients with Alzheimer's disease (AD), presumably due to damage to the neocortical structures, specifically the association cortices of the temporal lobes (Terry & Katzman, 1983). Patients with Huntington's disease (HD), however, do not show the same pattern of semantic memory deficits, possibly since the greatest brain damage is found in the striatum. AD and HD patients show deficits on a variety of olfactory tasks, but their pattern of performance differs somewhat, especially for odor memory. Given that AD patients show impaired semantic memory and olfactory functioning, it was hypothesized that semantic memory for olfaction would be compromised. While olfactory functioning is also impaired in HD, semantic memory is relatively intact, suggesting less impairment of semantic memory for olfaction in HD than AD. The striate cortex is relatively spared from changes in both AD and HD patients, thus it was hypothesized that the associative networks for colors would be relatively intact in both groups. Using triadic comparison tasks, similarity judgments were obtained for odors and for colors from 12 AD, 12 HD, and 24 age-matched normal controls (12 for each patient group). Using multidimensional scaling (MDS) analyses, the results revealed that AD patients showed a more disorganized MDS map for odors, but not for colors, than the HD and control groups. Semantic memory deficits for odors were further assessed using two multiple choice odor identification tasks: one in which the distractor choices were categorically related, and another in which the choices were categorically unrelated to the odors to be identified. Also, two types of questions, one probing for detailed (contextual) knowledge and the other for category knowledge, were asked about each odor. Results revealed that, while AD patients performed similarly in both odor identification conditions (p>.05), HD and controls made fewer errors in the categorically unrelated condition (p .05). Also, whereas AD patients made fewer errors answering category compared to detailed questions about odors (p