Metabolism Modulates Global Synchrony in the Aging Brain

Shown is the probability distribution of synchrony (s) vs. Λ, viewed from the top down. Aging from younger (yellow) to older (red) induces a sharp reconfiguration in the distribution of synchrony. Here, the plotted triangles correspond to the Λ values (from Cam-CAN) centered at ages 25 (younger) and 81 (older).

Brain aging is associated with hypometabolism and global changes in functional connectivity. Using functional MRI (fMRI), we show that network synchrony, a collective property of brain activity, decreases with age. Applying quantitative methods from statistical physics, we provide a generative (Ising) model for these changes as a function of the average communication strength between brain regions. We find that older brains are closer to a critical point of this communication strength, in which even small changes in metabolism lead to abrupt changes in network synchrony. Finally, by experimentally modulating metabolic activity in younger adults, we show how metabolism alone—independent of other changes associated with aging—can provide a plausible candidate mechanism for marked reorganization of brain network topology.

Λ controls the balance between segregated (low s) and integrated (high s) networks. (A and B) FC (averaged over all Cam-CAN subjects) during low (A) and high (B) synchrony, visualized using the BrainNet Viewer showing the top five percentages of connections. (A) Low synchrony (s = 0) reflects segregation (Seg). (B) High synchrony ( | s | > 1/2) reflects integration (Int). (C) The fraction of time each subject (each data point and the specific value of Λ) spends in integrated (P Int ; orange) and segregated (P Seg ; blue) networks. Λ < 0 corresponds to large P Seg and small P Int , while Λ > 0 corresponds to the opposite. The cross-over in C occurs at the critical point, Λ = 0.

For more information, see:

Weistuch et al. Metabolism Modulates Global Synchrony in the Aging Brain. Supplementary Information