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Impaired ability to remember what has gone before is one of the most distressing aspects of the aging process. Odor recognition memory is particularly vulnerable to the effects of aging, yet the underlying neural substrate is unknown. This study investigated the neural substrate of cross-modal olfactory recognition memory in young and older adults using fMRI. Participants were presented with 16 familiar odors immediately before entering the scanner, and were then tested for retrieval with words, either names of odors previously presented (targets) or names of new odors (foils), while being scanned at 3 T. Activation was reduced in the old subjects, both in regions involved in episodic memory retrieval and in regions involved in olfactory processing. Greater activation in the cerebellum of older adults was observed, suggesting increased response to attentional demands or compensatory mechanisms. Unlike in a number of studies in other sensory modalities, no increase in activation in frontal areas in older adults was observed during retrieval.

Olfactory function is affected by aging and deficits often result in decreasing quality of life, health and safety. The present study investigated the cortical substrate of olfactory deficits related to aging with functional Magnetic Resonance Imaging (fMRI), with a retronasal olfactory stimulation protocol using flavored aqueous solutions presented to the mouth. Activation was found in young subjects in the piriform/amygdalar region and in the orbitofrontal cortex and in other areas previously found activated in neuroimaging studies using odorized air, including insula and cerebellum. Activation was seen in similar areas in old subjects but the degree of activation was significantly lower in regions receiving primary olfactory projections (piriform cortex, entorhinal cortex, and amygdala). This result supports the hypothesis of dysfunction and/or degeneration in areas critical to olfactory processing as a major cause of olfactory deficits in the older population.