Cognitive reserve modulates the neurophysiological complexity of the aging brain

Normal aging experiences a general decrement in physiological function and cognitive abilities, and the age-related neurocognitive declines is highly variable within the aged population. Previous studies have suggested that Cognitive Reserve (CR) factor such as education could cope with the neurocognitive impairments emerging as a consequence of age-associated brain damage or pathology. Given that age-related and individual differences in neurocognitive function are associated with dynamic processes of the functional brain networks, we hypothesized that CR may involve facilitating age-related changes in flexibility and efficiency of neural networks and individual variations in educational level would be associated with altered functional brain complexity of the aging brain.  In this resting-state functional magnetic resonance imaging (rs-fMRI) study, we applied multiscale entropy, cross-sample entropy, and neuropsychological approaches to examine whether and how educational level impacts the complexity of brain function, intrinsic networks, and cognitive ability in healthy aging. The rs-fMRI results showed that, compared with the healthy elder with lower CR, the healthy elder with higher CR presented better performance of executive function, youthful brain entropy and increased efficiency of networks in fronto-parietal (FPN), cingulo-opercular (CON), and default mode network (DMN). These findings provide neurobiological evidence of CR and suggest that CR may facilitate and scaffold neural networks of the aging brain to act as a protective mechanism.