Odor memory in normal aging and Alzheimer's disease

The ability in normal elderly to verbally recall previously presented odors and to learn this task across trials was studied by applying a design which compared performance on the California Verbal Learning Test (CVLT) with an analogous odor test, Results suggest that both immediate and delayed recall of odors, both free and cued, as well as the ability to learn across trials is impaired in normal aging, perhaps more so for olfaction than for audition, which can be referred to poor use of semantic-clustering strategies and poor identification. Olfactory decline in memory in normal aging is, however, far from as affected as in Alzheimer's disease (AD). Two studies of persons with questionable AD demonstrated significant deficits in both recognition memory and identification of odors. Although further research is required, the findings from these 'preclinical' cases imply that performance on olfactory-mediated tasks may contribute to early diagnosis of AD.