Comments on “Loss of intranetwork and internetwork resting state functional connections with Alzheimer’s disease progression”

Neuroimaging evidence of disconnection syndrome of Alzheimer’s disease (AD) is extremely fascinating. In the study by Brier et al.,[1] they examined resting-state functional-connectivity magnetic resonance imaging (rs-fcMRI) in 5 functionally defined brain networks: default mode network (DMN), executive control network (CON), salience network (SAL), dorsal attention network (DAN), and sensory-motor network (SMN). Within a large sample size of human participants of either sex (n = 510), they divided subjects into three subgroups according to different AD severities, i.e. unaffected (clinical dementia rating, CDR 0), very mild (CDR 0.5), and mild AD (CDR 1). The major findings of this study were as follows. First, they found a loss of intra-network correlations in the DMN and other networks at CDR 0.5. Second, they found increases of intra-network correlations within the SAL between CDR 0 and CDR 0.5; however, they found reduced intra-network correlations within all networks at CDR 1. Third, they found that the three network pairs, DMNDAN, DMN-SMN, and CON-SMN were preferentially affected at certain CDR stages. Finally, they found all inter-network correlations consistently reduced with advancing CDR stage.