Odor identification in normal aging and early Alzheimer's disease: effects of retrieval support.

Odor sensitivity and identification were examined in normal aging and early Alzheimer's disease (AD). The aims were to investigate AD as associated with lower odor sensitivity, odor identification as a function of retrieval support, and the relationship between global cognitive functioning (Mini-Mental State Exam [MMSE]; M. F. Folstein, S. E. Folstein, & P. R. McHugh, 1975) and olfactory performance. Results indicated intact odor sensitivity but deficient odor identification in AD. Both groups benefited from cues in identification, and the size of the gains was equally large in AD patients and controls. The finding of no selective benefit from retrieval support in AD suggests that a degradation of olfactory knowledge contributes to the odor identification deficits in these patients. MMSE and identification were positively related, whereas MMSE and olfactory sensitivity were unrelated. These findings suggest that the AD-related olfactory impairment stems from lesions in cortical rather than peripheral structures.