  Altered functional brain networks have been a typical manifestation that
distinguishes major depressive disorder (MDD) patients from healthy control
(HC) subjects in functional magnetic resonance imaging (fMRI) studies.
Recently, rich club and diverse club metrics have been proposed for network or
network neuroscience analyses. The rich club defines a set of nodes that tend
to be the hubs of specific communities, and the diverse club defines the nodes
that span more communities and have edges diversely distributed across
different communities. Considering the heterogeneity of rich clubs and diverse
clubs, combining them and on the basis to derive a novel indicator may reveal
new evidence of brain functional integration and separation, which might
provide new insights into MDD. This study for the first time discussed the
differences between MDD and HC using both rich club and diverse club metrics
and found the complementarity of them in analyzing brain networks. Besides, a
novel index, termed "active index", has been proposed in this study. The active
index defines a group of nodes that tend to be diversely distributed across
communities while avoiding being a hub of a community. Experimental results
demonstrate the superiority of active index in analyzing MDD brain mechanisms.
