An Effect of Education on Memory-Encoding Activation in Subjective Cognitive Decline

Background: Subjective cognitive decline (SCD) may be an early manifestation of pre-clinical Alzheimer's disease. Elevated amyloid-beta (A beta) is a correlate of SCD symptoms in some individuals. The underlying neural correlates of SCD symptoms and their association with A beta is unknown. SCD is a heterogeneous condition, and cognitive reserve may explain individual differences in its neural correlates. Objective: We investigated the association between brain activation during memory encoding and SCD symptoms, as well as with A beta, among older individuals. We also tested the moderating role of education (an index of cognitive reserve) on the associations. Methods: We measured brain activation during the face-name memory-encoding fMRI task and A beta deposition with Pittsburgh Compound-B (PiB)-PET among cognitively normal older individuals (n = 63, mean age 73.1 +/- 7.4 years). We tested associations between activation and SCD symptoms by self-report measures, A beta, and interactions with education. Results: Activation was not directly associated with SCD symptoms or A beta. However, education moderated the association between activation and SCD symptoms in the executive control network, salience network, and subcortical regions. Greater SCD symptoms were associated with greater activation in those with higher education, but with lower activation in those with lower education. Conclusion: SCD symptoms were associated with different patterns of brain activation in the extended memory system depending on level of cognitive reserve. Greater SCD symptoms may represent a saturation of neural compensation in individuals with greater cognitive reserve, while it may reflect diminishing neural resources in individuals with lower cognitive reserve.

Automated summary

Subjective cognitive decline (SCD) may be an early sign of pre-clinical Alzheimer's disease, with elevated amyloid-beta (Aβ) potentially correlating with SCD symptoms. This study found that education level moderates the association between brain activation during memory encoding, SCD symptoms, and Aβ, indicating different patterns of brain activation in individuals with varying levels of cognitive reserve. Individuals with greater cognitive reserve may show increased neural compensation for SCD symptoms, while those with lower cognitive reserve may exhibit diminishing neural resources.