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Poster B28, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

Impoverished Remote Semantic Memory in Mild Cognitive Impairment

Nathaniel B. Klooster1,2, Arun Pilania1, David A. Wolk1, Anjan Chatterjee1,2;1University of Pennsylvania, 2Moss Rehabilitation Research Institute

Alzheimer’s Disease (AD) is an enormous public health issue and promising interventions are under development attempting to treat it. Many of these interventions focus on both pre-symptomatic and prodromal stages of disease. Thus, cognitive assessments that are sensitive to the earliest manifestations of Alzheimer’s pathology are critical for screening and as outcome measures for therapeutic studies. Mild Cognitive Impairment (MCI) is a heterogenous clinical category frequently associated with prodromal AD and a common target group for such studies. More granular assessment of cognitive changes specific to underlying AD-related pathophysiology may be of particular value in this group. In most cases of MCI, previously acquired knowledge of word meanings and facts about the world is considered to be intact and largely indistinguishable from that of healthy participants. While MCI patients may have subtle impairments in language abilities, impairments in semantic memory are not regarded as prominent and have not been the main focus of previous research. Here, we test the hypothesis that people with MCI have semantic memory impairments. To test this hypothesis, we apply sensitive measures of depth and richness of semantic knowledge from the language learning and psycholinguistic literatures, measures that previously revealed impairments in patients with focal (and stable) hippocampal damage, impairments not captured by standard neuropsychological assessments. The Word Associates Test (WAT) is a receptive measure of depth of vocabulary used in first and second-language learning research. Consisting of 40 questions, each item has a target word with eight possible associates. Participants choose four correctly matching synonyms or collocates from among the eight possibilities for each target. The number of senses a word can take (e.g. bar: to prevent from entering, a place to drink alcohol, the legal profession, a piece of candy, a metal rod) is a widely studied measure of semantic richness. The Senses-listing task presents participants with 20 target words from normed databases and gives them one minute to list as many different senses of each target word as possible. Compared to demographically matched healthy comparison participants, MCI patients performed significantly worse on the WAT and showed a trend toward producing fewer senses to polysemous target words. These deficits, on both productive and receptive measures of semantic richness and depth of vocabulary knowledge suggest that semantic memory is impoverished in patients with MCI. Future work will examine the degree to which these experimental measures are more sensitive to MCI status than standardized measures, the degree to which they are linked to MTL integrity by determining their relationship with structural MRI, and their specificity for prodromal AD in MCI as measured by the presence of cerebral amyloid as revealed by PET imaging, a marker of AD pathology.

Topic Area: Language Disorders

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