Entropy reduction in human cortical spontaneous activity marks healthy aging

Entropy trajectories remain unclear for the aging process of human brain system. We employed the open data from an accelerated longitudinal cohort (PREVENT-AD) including 24 healthy aging participants followed by 4 years with 5 visits per participant to establish the brain entropy aging curves and distinguish with the age and cohort effects. This reveals that global cortical entropy decreased with aging while a significant cohort effect was detectable that people who were born earlier showed higher entropy. Such entropy reduction were also evident for the large-scale networks although with different speeds for different networks: the primary and intermediate networks reduce their entropy faster than the higher-order transmodal networks. We conclude two specific brain entropy features with aging: the shift of the complexity hierarchy of networks and the diversity of complexity increases among networks.