Age-dependent changes in the dynamic functional organization of the brain at rest – a cross-cultural replication approach

Abstract

Age-associated changes in brain function play an important role in the development of neurodegenerative diseases. Although previous work has examined age-related changes in static functional connectivity (FC), accumulating evidence suggests that advancing age is especially associated with alterations in the dynamic interactions and transitions between different brain states, which hitherto has received less attention. Moreover, conclusions of previous studies in this domain are limited by suboptimal replicability of resting state fMRI and culturally homogenous cohorts. Here, we investigate the robustness of age-associated changes in dynamic functional connectivity (dFC) by capitalizing on the availability of fMRI cohorts from two cultures (Western European and Chinese). In both cohorts we consistently identify two distinct connectivity states: a more frequent segregated within-network connectivity state (state I) and a less frequent integrated between-network connectivity state (state II). In both cohorts, older (55-80 years) compared to younger participants (20-35 years) exhibited lower occurrence of and spent less time in state I. Moreover, older participants tended to exhibit more transitions between networks and greater variance in global efficiency. Overall, our cross-cultural replication of age-associated changes in key dFC metrics implies that advancing age is robustly associated with a reorganization of dynamic brain activation that favors the use of less functionally-specific networks.

Test-Retest Reliability of Dynamic Functional Connectivity Parameters for a Two-State Model

“…Furthermore, the structure of the two states based on the not-centered data is visually consistent with dynamic two-state patterns in the whole brain at rest for not only healthy people (Choe et al, 2017) with eyes opened/closed (Weng et al, 2020) and different ages (young as 20-35 years old and older as 55-80 years old)(X. Yang et al, 2022), but also clinic patients of Parkinson's disease (Fiorenzato et al, 2019;Kim et al, 2017), major depressive disorder (Zheng et al, 2022) and dementia with Lewy bodies (Ma et al, 2019). This consistency in state structure between studies is encouraging because, if the structure had varied, statements about brain organization would have lacked a common ground for comparison.…”