Precuneus activity during retrieval is positively associated with amyloid burden in cognitively normal older APOE4 carriers

Abstract

The precuneus is an early site of amyloid-beta (A{beta}) accumulation. Previous cross-sectional studies reported increased precuneus fMRI activity in older adults with mild cognitive deficits or elevated A{beta}. However, longitudinal studies in early Alzheimers disease (AD) risk stages are lacking and the interaction with Apolipoprotein-E (APOE) genotype is unclear. In the PREVENT-AD cohort, we assessed how precuneus activity during successful memory retrieval at baseline and over time relates to future A{beta} and tau burden and to change in memory performance. We further studied the moderation by APOE4 genotype. We included 165 older adults (age: 62.8{+/-}4.4 years; 113 female; 66 APOE4 carriers) who were cognitively normal at baseline and had a family history of AD. All participants performed task-fMRI at baseline and underwent 18F-flortaucipir-PET and 18F-NAV4694-A{beta}-PET on average 5 years later. We found that higher baseline activity and greater longitudinal change in activity in precuneus were associated with higher subsequent A{beta} in APOE4 carriers but not non-carriers. There were no effects of precuneus activity on tau burden. Finally, APOE4 non-carriers with low baseline activity in the precuneus exhibited better longitudinal performance in an independent memory test compared to APOE4 non-carriers with high baseline activity and APOE4 carriers. Our findings suggest that higher task-related precuneus activity at baseline and over time are associated with subsequent A{beta} burden in cognitively normal APOE4 carriers. Our results further indicate that the absence of hyperactivation and the absence of the APOE4 allele is related with the best future cognitive outcome in cognitively normal older adults at risk for AD. Significance StatementThe precuneus is a brain region involved in episodic memory function and is an early site of amyloid-beta (A{beta}) accumulation. Alterations in task-related activity occur in the precuneus with ageing as well as with Alzheimers disease (AD) pathology even in the absence of cognitive symptoms; however, their course and implications are not well understood. We demonstrate that higher precuneus activity at baseline and its change over time during successful memory retrieval is associated with higher A{beta} burden on average 5 years after baseline in Apolipoprotein-E4 (APOE4) carriers. Lower precuneus baseline activation was related to better memory performance over time in APOE4 non-carriers. Our findings provide novel longitudinal evidence that increased activity in posterior midline regions is linked to early AD pathology in dependence of APOE4 genotype.