Older, non-demented apolipoprotein ε(4) carrier males show hyperactivation and structural differences in odor memory regions: a blood-oxygen-level-dependent and structural magnetic resonance imaging study

The current study sought to examine the interaction of sex and Apolipoprotein ε(4) status on olfactory recognition memory within non-demented, older individuals. We separated 39 participants into groups based on ε(4) status and sex. Each participant completed an olfactory memory recognition task during 2 functional magnetic resonance imaging scans and 1 structural scan. The ε(4) carriers had greater functional recruitment of memory regions during false positives relative to ε(4) non-carriers. During hits, the male ε(4) carriers showed greater functional recruitment compared to female ε(4) carriers. The ε(4) carriers had larger bilateral putamen volumes relative to ε(4) non-carriers. Neuroimaging data were significantly associated with Dementia Rating Scale scores solely in males. Results suggest differential olfactory memory processing in relation to sex and ε(4) status. Male ε(4) carriers in particular, demonstrated hyperactivation during recognition memory, which we suspect reflects neuronal compensation to maintain functional performance. Future studies should consider examining underlying mechanisms that contribute to these sex differences within ε(4) carriers.