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| Home > Publications database > Functional network reorganization in older adults : structural relations and its impact on sex and cognitive performance |
| Dissertation / PhD Thesis | FZJ-2022-03777 |
2022
RWTH Aachen University
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Please use a persistent id in citations: http://hdl.handle.net/2128/32106 doi:10.18154/RWTH-2022-03308
Abstract: The normal aging process is accompanied by a progressive decrease of cognitive abilities which is highly variable across individuals. Sources of heterogeneity are far from being fully understood, but seem to be associated with multiple neurobiological substrates. The present work aimed at contributing to this highly important issue of identifying potential neurobiological sources for the inter-individual variability in higher age. Therefore, the whole brain’s resting-state functional connectivity (RSFC), its association with age, sex, cognitive performance as well as its relation to structural connectivity (SC) was investigated. The first studies’ results based on 772 older adults (55-87 years) indicate aging to be accompanied by a shift from rather specialized and segregated functional networks towards a higher network integration. These results not only underpin previous findings based on lifespan samples, but additionally expand the current state of research by showing that this trend also persists into older age. Moreover, as compared to lifespan studies, different networks were found to be affected in older adults: While predominantly higher-order networks change across the lifespan, in older adults particularly the primary processing networks seem to be age sensitive. Furthermore, they were found to influence the cognitive performance differences in aging, i.e. lower RSFC of the visual and sensorimotor network (SMN) being associated with lower cognitive performance. With regards to sex, RSFC differences were found between males and females, potentially facilitating sex-related behavioral functioning and emphasizing the need for sex-stratified analyses in studies with older subjects. Building upon the results of the first study, the second study aimed at unveiling potential origins for the depicted RSFC differences by relating age-related RSFC differences to SC differences (n=636, 55-85 years). Although SC is the underlying construct for brain regions to exchange information, RSFC cannot yet be directly linked to SC. Using a multivariate statistical approach, whole-brain region-wise RSFC and SC estimates were used to predict the older adults age and to thereby unveil RSFC and SC differences that are together age-characteristic. Results indicate that while for RSFC regions of the SMN are particularly indicative for older peoples’ chronological age to, SC of the frontal lobes seems be age-characteristic. Additionally, the results point at two differential age progressions: If age-related differences in SC only affect the frontal lobe, RSFC of the SMN is relatively preserved. In contrast, if age-related decreases in SC pertain to the whole brain, the SMN shows overall RSFC decreases, which with regards to results of the first study potentially hint at a more accelerated aging process. In conclusion, the age-related RSFC reorganization in older adults particularly affects the SMN. Here, differences are not only related to cognitive performance decline, but also dependent on whole-brain SC differences underpinning the necessity to integrate multiple modalities for a comprehensive understanding of the cognitive aging in older adults.
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