“…Unfortunately, it is hard to reveal informative patterns by a direct comparison of the fMRI time series between different subjects, since the fMRI signals are arbitrarily scaled and have no unit (Jenkinson and Chappell, 2018 ). In contrast, brain functional network (BFN), as a measure of the relative relationship between the fMRI time series, can provide a more reliable way of exploring the inherent organization of the brain (Liu et al, 2015 ; Yu et al, 2019 ), and has been used in identifying neurological or psychiatric disorders (Stam, 2014 ), including autism spectrum disorder (Weikai et al, 2017 ), major depressive disorder (Greicius et al, 2007 ), obsessive compulsive disorder (Admon et al, 2012 ), Alzheimer's disease (AD) (Jin et al, 2010 ; Shi et al, 2017 ), and its early stage, namely mild cognitive impairment (MCI) (Yu et al, 2017 ; Li et al, 2019b ), to name a few.…”