Updating Mechanisms Using an Olfactory Cue Were Not Successful in Improving Memory in a Rodent Model of Cognitive Aging or in Older Adults

As the number of adults over 65 years of age is steadily rising, it is increasingly important to identify strategies to either maintain or improve cognition to positively impact quality of life and potentially inform treatment strategies for age-related cognitive disorders. There is evidence to suggest that olfactory cues can aid recall (Rihm, Diekelmann, Born, & Rasch, 2014). It is still unknown whether olfactory cues can cause recalled information to enter a labile state, allowing it to be updated with new information. The current study investigated whether administration of a contextual olfactory cue would improve learning and memory dependent on frontal lobes and the hippocampus respectively in both a rat model of cognitive aging (two-vessel occlusion [2-VO]) and in nondemented older adult humans. Specifically, rats and humans were trained on their respective versions of a elemental visual discrimination task while an olfactory stimulus was presented. Following training, rats and humans were reexposed to the contextual olfactory cue and their performance was tested on a reversal learning (frontal-dependent) and the transverse patterning (hippocampus-dependent) tasks that were constructed from visual stimuli presented during the elemental task. In rats, we found 2-VO related decrements in frontal-dependent memory performance and age-related decrements in hippocampus-dependent task performance in humans. For both rats and humans, we found no rescue of memory through olfactory contextual cueing. Overall, our results suggest that mechanisms underlying olfactory contextual cueing may not be sufficient to enhance declining memory performance with age.