Familiarity deficits in cognitively normal aging individuals with APOE ε4: A follow-up investigation of medial temporal lobe structural correlates

INTRODUCTION: The apolipoprotein E ε4 (APOE ε4) allele is a well-documented risk factor for Alzheimer's disease (AD). Accordingly, aging individuals carrying one or more ε4 alleles are at considerably greater risk of developing AD over time. In an effort to characterize early cognitive manifestations of AD, we previously outlined selective deficits in familiarity-based recognition in otherwise asymptomatic carriers of the APOE ε4 allele (Schoemaker et al., 2016). In this follow-up report, we aimed to explore the neural correlates of this selective cognitive impairment. METHODS: For this purpose, within the same population and using high-resolution structural neuroimaging, we explored relationships between volumes of the hippocampus, entorhinal, and perirhinal cortices and performance in recollection and familiarity. RESULTS: Overall, our results revealed significant positive relationships between familiarity performance and volumes of the perirhinal and entorhinal cortices in aging individuals with APOE ε4. In APOE ε4 carriers, a positive correlation between recollection performance and hippocampal volume was also found. In contrast, no correlation reached statistical significance in the group of noncarriers. CONCLUSION: These findings suggest that familiarity performance might be a useful marker of the integrity of the rhinal cortex, especially in populations at risk of AD.