Areas of the brain affected in the early stages of
Alzheimer's disease are also areas heavily involved in
the processing of olfactory information. Olfactory event-related
potentials (OERPs) and auditory ERPs were recorded from the
Fz, Cz, and Pz electrode sites in 12 Alzheimer's disease
(AD) patients and 12 age and gender matched normal controls
(NC) in a single-stimulus paradigm with a 45 s inter-trial
interval, using amyl acetate as the olfactory stimulus, and
in a separate session a 500 Hz tone as the auditory stimulus.
Odor identification (ID) was also used to assess ability to
identify odors. The results indicate that (1) OERP P2 and P3
latencies were significantly longer in AD patients than normal
controls; (2) olfactory ERP latency measures correlated
significantly with dementia status as measured by the Dementia
Rating Scale (DRS), indicating that as participants performed
more poorly on the DRS, reflecting increased dementia, OERP
latencies increased; (3) olfactory ERP latency measures better
differentiated AD patients from normal controls than auditory
ERP latency measures; (4) olfactory ERP measures alone correctly
classified up to 92% of participants; (5) odor ID measures,
namely the UPSIT and San Diego-Odor-ID tests also classified
participants at a high rate. Combining scores for odor
identification with olfactory P3 latency measures resulted in
a correct classification rate of 100%. The results strongly
support the use of olfactory measures in the assessment of AD.
(JINS, 2002, 8, 753–763.)
