Preserved Medial Temporal Lobe Flexibility Predicts Memory Generalization Only in the Context of Good Sleep Quality among Older African Americans
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Objectives
Poor sleep quality is a risk factor for Alzheimer’s disease (AD). Older African Americans experience disproportionately high rates of sleep disturbance and AD. Medial temporal lobe (MTL) flexibility reflects dynamic neural reorganization and may be a marker of generalization performance. This study examined whether sleep quality moderates the association between MTL flexibility and memory generalization.
Methods
Fifty older African Americans (MeanAge=69.7±6.21 years; 80% women) underwent rs-fMRI to quantify MTL flexibility, Rutgers Acquired Equivalence Task for memory generalization, and Pittsburgh Sleep Quality Index for sleep quality.
Results
Greater MTL flexibility was associated with better generalization (r=0.367, p=.017). Good sleepers showed higher MTL flexibility (F (1,44) =8.11, ηp 2 =.156, p=.007) and superior generalization (F (1,46) = 12.33, ηp 2 =.211, p=.001). Sleep quality significantly moderated the MTL flexibility–generalization relationship (β=−1.519, p=.012).
Conclusions
Preserved MTL flexibility may confer generalization only in good sleepers, suggesting that sleep disturbance may disrupt the MTL neural resilience among older African Americans.
WHAT WAS KNOWN
Prior research has established that poor sleep quality is associated with increased Alzheimer’s disease (AD) risk, hippocampal dysfunction, and impaired memory. Studies also show that medial temporal lobe (MTL) network dynamics, including flexibility, support key features of cognition including memory generalization. However, limited work has examined how sleep quality interacts with neural flexibility to influence cognition, particularly in older African Americans, a population at elevated risk for both sleep disturbance and AD.
WHAT THIS STUDY ADDS
This study demonstrates that sleep quality significantly moderates the relationship between MTL flexibility and memory generalization. While greater MTL flexibility is associated with better generalization, this benefit is evident only among individuals with good sleep quality. These findings suggest that sleep disruption may impair the functional expression of neural resilience mechanisms, even when underlying network flexibility is preserved.
