Apolipoprotein E epsilon4 positive individuals demonstrate delayed olfactory event-related potentials

Apolipoprotein E epsilon4 positive individuals have deficits in the ability to identify and remember odors, as demonstrated by psychophysical measures of olfactory function. The purpose of the present study was to identify olfactory deficits in this population using an objective electrophysiological measure: the olfactory event-related potential (OERP). Olfactory and auditory ERPs were recorded from the Fz, Cz, and Pz electrode sites in 10 epsilon4 positive individuals and 10 age and gender-matched epsilon4 negative individuals in a single-stimulus paradigm. The results indicate: (1) individuals who are positive for the apolipoprotein E epsilon4 allele demonstrated delays (of approximately 100 ms) in the processing of olfactory information compared to those who are epsilon4 negative; (2) OERP latency is more sensitive than psychophysical measures of olfactory function; (3) delays in the cognitive P3 component of the OERP are associated with deficits in the ability to identify an odor; and (4) unlike the moderate ranges found in auditory ERP, OERP latency showed high sensitivity and specificity in classifying epsilon4 positive and negative individuals.