No abstract

The aging brain undergoes alterations of both Structural Connectivity (SC) and timeaveraged Functional Connectivity in the resting state (rs FC). Here, we show by means of functional MRI (fMRI) human brain imaging that aging also profoundly impacts on the spontaneous temporal reconfiguration of this rs FC. Analyzing time-dependent correlations between human rs fMRI blood oxygen level dependent (BOLD) time series, we describe Functional Connectivity Dynamics (FCD) as a switching between epochs of meta-stable FC and transients of fast network reconfiguration. We find that the flux of FCD markedly slows down and becomes more "viscous" across the adult lifespan (18-80 yrs), also accounting for the wide inter-subject variability of performance observed in cognitive screening tasks. Such remodeling of FCD discloses qualitatively novel effects of aging that cannot be captured by variations of SC or of static FC, opening the way to improved imaging-based characterizations of the functional mechanisms underlying cognitive aging.