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Abstract:
Early-stage Alzheimer disease (AD) produces deficits in
visuospatial attention in: (1) shifting covert attention from a
cued location; (2) changing the spatial scale of attention.
Qualitatively similar but smaller effects are seen in nondemented
elderly over 75. We examined whether these changes in advanced
aging arise from inclusion of carriers of the e4 allele of the
apolipoprotein E (apoE) gene, a major AD risk factor. Covert
attention and cued-visual search tasks were administered
double-blind to nondemented individuals typed for apoE. (1)
Costs-plus-benefits of location cue validity on discrimination were
greater (p<.05), and (2) the effect of precue precision on
visual search reduced (p<.04) in individuals possessing at least
one e4 allele compared to those with none. E4 carriers showed: a
positive relation between age and costs-plus-benefits of cue
validity (p<.05); reduction with age in effect of cue precision
(NS). We previously reported similar findings in persons with
diagnosed AD. In contrast, in non-e4 carriers cue precision effects
increased with age, shown previously in elderly under age 75. Thus
elderly at greater risk of AD deploy visuospatial attention
similarly to diagnosed AD patients. In contrast, elderly at reduced
risk of AD exhibit a pattern of intact shifting of covert attention
and increased effects of cue precision on the spatial scale of
attention during search. (AG12387, AG07569)
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