Abstract
Evidence suggests that individual variability in lifetime exposures influences how cognitive performance changes with advancing age. Brain maintenance and cognitive reserve are theories meant to account for preserved performance despite advancing age. These theories differ in their causal mechanisms. Brain maintenance predicts more advantageous lifetime exposures will reduce age-related neural differences. Cognitive reserve predicts that lifetime exposures will not directly reduce these differences but minimize their impact on cognitive performance. The present work used moderated-mediation modeling to investigate the contributions of these mechanisms at explaining variability in cognitive performance among a group of 39 healthy younger (mean age (standard deviation) 25.9 (2.92) and 45 healthy older adults (65.2 (2.79)). Cognitive scores were computed using composite measures from three separate domains (speed of processing, fluid reasoning, and memory), while their lifetime exposures were estimated using education and verbal IQ measures. T1-weighted MR images were used to measure cortical thickness and subcortical volumes. Results suggest a stronger role for cognitive reserve mechanisms in explaining age-related cognitive variability: even with age-related reduced gray matter, individuals with greater lifetime exposures could perform better given their quantity of brain measures.
Highlights
Evidence is accumulating to support the idea that individual variability in lifetime exposures influence how cognitive performance changes with advancing age
Underlying these theories is the assumption that advancing age leads to brain changes including declines in gray matter [2] and that cognitive performance decline is the result of these neural declines
These abbreviated batteries were unrelated to participant speed, but reflected limitations due to the duration of the battery
Summary
Evidence is accumulating to support the idea that individual variability in lifetime exposures influence how cognitive performance changes with advancing age. Investigations into the mechanisms by which this occurs has led to a number of different theories, see [1] for a recent review Underlying these theories is the assumption that advancing age leads to brain changes including declines in gray matter [2] and that cognitive performance decline is the result of these neural declines (for a review see [3]). This scheme provides two locations for the effect of lifetime exposures (LE) to operate. These two roles are broadly described in the literature as the theories of brain maintenance (BM) [4] and cognitive reserve (CR) [5,6]
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