Olfaction in Aging and Alzheimer's Disease Event-related Potentials to a Cross-modalOdor-Recognition Memory Task Discriminate ApoEs4~+and ApoEIndividuals

摘要

Alzheimer's disease (AD) is a devastating neurodegenerative condition that affects morethan 5 million Americans. Currently, a definitive and unequivocal diagnosis of AD canonly be confirmed histopathogically via postmortem autopsy, demonstrating the needfor objective measures of cognitive functioning for those at risk for AD. The singlemost important genetic risk factor of AD is the apolipoprotein E (ApoE) 64 allele. Thepresent study investigated olfactory and cognitive processing deficits in ApoE 64+ indi-viduals using a cross-modal recognition memory task and an objective electrophysio-logical measure, the event-related potential (ERP). Ten e4+ individuals (5 M, 5 F, mean[M] = 75.1 years) and 10 age- and gender-matched 64- individuals (5 M, 5 F, M = 71 years)sequentially encoded a set of 16 olfactory stimuli and were subsequently shown namesof odors previously presented (targets) or not (foils). EEG activity was recorded from 19electrodes as participants distinguished targets from foils using a two-button mouse.P3 latencies were significantly longer in 64+ individuals, and intraclass correlationsdemonstrated differential activity between the two groups. These findings are consis-tent with a compensatory hypothesis, which posits that nondemented 64+ individualswill expend greater effort in cognitive processing or engage in alternative strategiesand therefore require greater activation of neural tissue or recruitment of different neu-ral populations. The findings also suggest that cross-modal ERP studies of recognitionmemory discriminate early neurocognitive changes in ApoE 64+ and ApoE 64- indi-viduals and may contribute to identifying the phenotype of persons who will developAlzheimer's disease.