Structure-function relationships in elderly resting-state-networks : influence of age and cognitive performance

The aim of this work was to investigate the structure-function relationship in cognitive resting state networks in a large population-based elderly sample. The first study characterized the functional connectivity in four cognitive resting state networks with respect to age, gender and cognitive performance: Default Mode Network (DMN), executive, and left and right frontoparietal resting state networks. The second study assessed the structural correlates of the functional reorganization of the DMN during aging, using local gyrification index.Small age-related increases in functional connectivity were present for the executive, left and right frontoparietal resting state networks, but not for the DMN. Men and women were found to differ across all resting state networks of interest. Performance in working memory was negatively associated with functional connectivity within the left frontoparietal resting state network. Elderly seem to exhibit compensatory mechanisms as an attempt to maintain cognitive performance. However, the negative correlation between resting state functional connectivity and cognitive performance emphasizes limits in cognitive reserve in the elderly. Interestingly, men and women seem to show differences in cognitive strategies, which might be related to differences in performance of various cognitive domains. Thus, the current results provide a basis for further research with a particular focus on the functional organization of the elderly brain. Structurally, age-related decreases in gyrification were present for the right anterior DMN and the medial posterior DMN bilaterally. Relations of gyrification to cognitive performance were found for all right hemispheric parts of the DMN and the left medial posterior DMN. The more pronounced vulnerability of the posterior DMN as well as the right hemispheric parts of the DMN in relation to age and cognitive performance provide the structural underpinning of functional theories of aging, i.e. posterior to anterior shift in aging and the right-hemi aging theory. Thus, gyrification decreases within the DMN may functionally lead to an insufficient DMN in the current elderly sample