Person-Based Similarity Index for Cognition and Its Neural Correlates in Late Adulthood: Implications for Cognitive Reserve

Abstract

Healthy aging is typically associated with some level of cognitive decline, but there is substantial variation in such decline among older adults. The mechanisms behind such heterogeneity remain unclear but some have suggested a role for cognitive reserve. In this work, we propose the “person-based similarity index” for cognition (PBSI-Cog) as a proxy for cognitive reserve in older adults, and use the metric to quantify similarity between the cognitive profiles of healthy older and younger participants. In the current study, we computed this metric in 237 healthy older adults (55–88 years) using a reference group of 156 younger adults (18–39 years) taken from the Cambridge Center for Ageing and Neuroscience dataset. Our key findings revealed that PBSI-Cog scores in older adults were: 1) negatively associated with age (rho = −0.25, P = 10−4) and positively associated with higher education (t = 2.4, P = 0.02), 2) largely explained by fluid intelligence and executive function, and 3) predicted more by functional connectivity between lower- and higher-order resting-state networks than brain structural morphometry or education. Particularly, we found that higher segregation between the sensorimotor and executive networks predicted higher PBSI-Cog scores. Our results support the notion that brain network functional organization may underly variability in cognitive reserve in late adulthood.

When Age Tips the Balance: a Dual Mechanism Affecting Hemispheric Specialization for Language

“…We chose language-related measures because of their effectiveness in assessing diverse language-related aspects, encompassing word production, lexical access, and word retrieval (evaluated via picture naming accuracy and the tip-of-the-tongue ratio), as well as the understanding of semantics and syntax (measured through accuracy and reaction time). Further comprehensive descriptions of these behavioral variables are available in the supplementary materials provided by West and colleagues (West et al, 2022).…”

“…For all 728 participants, we checked the Mini Mental State Examination (MMSE) scores to ensure that the general cognitive functioning of our sample remained within the expected range The behavioral tests assess various cognitive functions associated with language: word production, lexical access/retrieval abilities (picture Naming accuracy and Tip of the tongue ratio), and semantic and syntactic comprehension abilities (Accuracy and Reaction Time). A description of the behavioral variables is available as supplementary material in the article by West and colleagues (West et al, 2022). Reaction Time and Tip of the tongue performance were inverted, so all scores close to 0 represent worse performances.…”