Age-related changes in the topological organization of white matter structural networks across the human lifespan.

s / Int. J. Devl Neuroscience 47 (2015) 1–131 27 Fig. 1. The lifespan trajectories of the global network metrics of Wm networks. (A) Tje lifespan trajectories of global and local efficiency. (B) The lifespan trajectories of small-world parameters (Lp, Cp, normalized Lp, normalized Cp and small-worldness). The blue dots represent the adjusted values of each subject after controlling for age, gender, and brain size. The curve-fitted lines are shown in red. Significant age-related trajectories were found for all global metrics of the WM networks. Results: Most of the global network properties, including network strength, topological efficiency, and robustness, followed an inverted U-shaped trajectorywith an age peak at the fourth decade (Fig. 1). The brain areaswith themost prominent quadratic changes with age were primarily located in the prefrontal and temporal cortices and exhibited heterogeneous trajectories: several defaultmode regions displayedprolongedmaturation and aging compared to the prefrontal cortex (Fig. 2). Rich-club organizationwas evident across lifespan, whereas hub integration decreased linearly with age, especially accompanied by the loss of frontal hubs and their connections. Finally, we identified age-related quadratic changes in WM connectivity strength predominantly within and between prefrontal and temporal modules. Fig. 2. The distribution of regions with significant age related alterations and the AoPs across regions. (A) A 3D representation of brain regions illustrating age-related alterations of nodal efficiency. Two representative nodeswere selected to depict the age-related trajectory curves of nodal efficiency, one is the right MFG (upper right panel) and the other is the left MTG (lower right panel). (B) 3D representation of the AoPs across the regions with quadratic trajectories (p<0.05, uncorrected). To present the early and the late AoPs, left SFGdor and right PCG were selected to depict the trajectory curves, and the AoPs were marked with orange lines. Conclusion: These data indicated lifespan changes in the topological organization of human whole-brain WM networks, thus providing possible structural substrates underlying behavioral and cognitive changes with age. http://dx.doi.org/10.1016/j.ijdevneu.2015.04.079