Individuals at risk for Alzheimer's disease show differential patterns of ERP brain activation during odor identification

Abstract

Background: Studies suggest that older adults at risk of developing Alzheimer's disease may show olfactory processing deficits before other signs of dementia appear.

Methods: We studied 60 healthy non-demented individuals, half of whom were positive for the genetic risk factor the Apolipoprotein E ε4 allele, in three different age groups. Event-related potentials to visual and olfactory identification tasks were recorded and analyzed for latency and amplitude differences, and plotted via topographical maps.

Results: Varying patterns of brain activation were observed over the post-stimulus epoch for ε4- versus ε4+ individuals on topographical maps. Individuals with the ε4 allele demonstrated different ERP peak latencies during identification of olfactory but not visual stimuli. High correct ApoE classification rates were obtained utilizing the olfactory ERP.

Conclusions: Olfactory ERPs demonstrate functional decline in individuals at risk for Alzheimer's disease at much earlier ages than previously observed, suggesting the potential for pre-clinical detection of AD at very early stages.

Figure 1

Topographical representation of OERP amplitudes in μV across 19 electrode sites by age and ApoE groups for 700-1300 ms post-stimulus time intervals.

Figure 2

Visual and olfactory average N1, P2, N2, and P3 latencies by age and ApoE groups. Error bars represent the standard error of the mean (SEM).