Abstract
Healthy aging is associated with structural and functional changes in the brain even in individuals who are free of neurodegenerative diseases. Using resting state functional magnetic resonance imaging data from a carefully selected cohort of participants, we examined cross sectional changes in the functional organization of several large-scale brain networks over the adult lifespan and its potential association with general cognitive performance. Converging results from multiple analyses at the voxel, node, and network levels showed widespread reorganization of functional brain networks with increasing age. Specifically, the primary processing (visual and sensorimotor) and visuospatial (dorsal attention) networks showed diminished network integrity, while the so-called core neurocognitive (executive control, salience, and default mode) and basal ganglia networks exhibited relatively preserved between-network connections. The visuospatial and precuneus networks also showed significantly more widespread increased connectivity with other networks. Graph analysis suggested that this reorganization progressed towards a more integrated network topology. General cognitive performance, assessed by Addenbrooke’s Cognitive Examination-Revised total score, was positively correlated with between-network connectivity among the core neurocognitive and basal ganglia networks and the integrity of the primary processing and visuospatial networks. Mediation analyses further indicated that the observed association between aging and relative decline in cognitive performance could be mediated by changes in relevant functional connectivity measures. Overall, these findings provided further evidence supporting widespread age-related brain network reorganization and its potential association with general cognitive performance during healthy aging.
Highlights
The structural and functional changes the brain undergoes due to the aging process have been studied for many years
The list of all clusters showing significant (p < 0.05 corrected for multiple comparisons using family-wise error correction) relationship with age for each resting state networks (RSNs) is given in Supplementary Table S1
Www.nature.com/scientificreports compared with reference connectivity maps derived from the mean RSNs of the young adult subgroup, all canonical RSNs except the left and right executive control and dorsal default mode networks had similarity measures that negatively correlated with age; and (3) network measures estimated using graph theory showed progression towards a more integrated network topology as indicated by a decreasing shortest path length and an increasing global efficiency with age
Summary
The structural and functional changes the brain undergoes due to the aging process have been studied for many years. Segregation in brain systems, which reflects dense within-system but parser between-system connectivity and quantified using network measures such as modularity and participation coefficient (a measure of the extent a given node connects to nodes in other systems), has been shown to decrease across the adult lifespan[29], opposite findings have been reported[34] Overall, these studies have provided insights into how the brain’s functional organization is altered during healthy aging. By doing this multi-level analysis approach, we aimed to comprehensively investigate age-related network changes and to identify global connectivity measures that may be associated with general cognitive performance
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