Age-related differences in brain activity despite matched cognitive performance: A moderated-mediation analysis.

Abstract

Despite facing the same task demands, every individual experiences different levels of perceived difficulty. This complicates the interpretation of cognitively induced brain activity due to the confounding of task demands and difficulty. Within the context of aging, differences in brain activity may reflect variations in perceived difficulty or age-related divergence in the recruitment of neural resources. The current work used titrated cognitive demands during a verbal delayed match to sample task within the fMRI. Between-group comparisons of 40 younger and 39 older healthy adults identified brain regions significantly related to behavioral performance. Brain regions were identified using the "Reserve and Resilience Framework," supporting the theories of upregulation or reorganization. The two age groups in this study did not significantly differ in their titrated cognitive capacity scores. Despite all participants performing a task they found equally challenging, moderated-mediation analysis of the fMRI data showed brain activity that differed between the two age groups. Furthermore, the relationships between brain activity and cognitive capacity differed between the age groups. Results supported upregulation, reorganization, and suppression of brain activity related to both increases and decreases in cognitive capacity. Therefore, brain activity increases and decreases appear to be balanced against each other to maintain high cognitive capacity. Furthermore, current findings show a beneficial effect of suppressed brain activity. These results support the need to expand the current cognitive reserve and resilience framework to include neural suppression as a potential mechanism of healthy cognitive aging.