Fig. 1.

Schematic illustration of a rich club, adapted from Sporns (11). This network structure indicates the tendency of nodes with high centrality (yellow) to form a tightly interconnected community. Members of the rich club can act as brokers between nodes that belong to different communities (white). Rich clubs are found in diverse systems, including the network of scientific collaborations between academic institutions studied by Ma et al. (7). In this case, the rich club implies a close circle of elite institutions that have increased power to control the access to information or to funding opportunities.