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Abstract:
Despite the commonly held view that semantic impairment
accompanies Alzheimer's Disease (AD), there is considerable
variability in AD performance on different semantic memory tasks.
Deficits in other abilities required to perform these tasks may
contribute to the variability. We hypothesized that AD impairs
selection ability, which would differentially affect performance on
those semantic tasks involving selection between competing semantic
alternatives. To investigate this we compared the performance of 21
AD subjects with 28 matched control subjects on three selection
tasks. The Verb Generation task involves generating a verb related
to a noun. High Selection items have no clear dominant response;
Low Selection items have a clear dominant response. The Comparison
task involves comparing a target word to several probe words and
selecting the most similar. Comparisons are based on specific
attributes in the High Selection condition and on global similarity
in the Low Selection condition. The lexical fluency task involves
generating words to the letters F, A, and S (High Selection), and
to the letters Fl, Ap, and St (Low Selection). The AD group was
disproportionately impaired on the high selection conditions of the
Comparison task and the lexical fluency task. There was no
differential impairment in performance on the High Selection
condition of the Verb Generation task. These results provide
support for the hypothesis that AD may cause deficits in selection
abilities.
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