subnetwork (Figure 2D). Epilepsy may be a paradigmatic example of a disease resulting from such a process (Bettus et al., 2008), while recent work suggests that such alterations in the strength of connectivity between different brain regions are also critical in depression and schizophrenia. A shift in the topology of network connectivity (for example, a decrease in long-distance connections with increases in local connectivity; Figure 2E) could affect the efficiency of information processing in the brain. Studies have suggested that such network topology changes might be occurring in autism (Barttfeld et al., 2011). Finally, another possibility is that network connectivity is unchanged, but the operations carried out by different subnetworks are somehow altered. It is worth emphasizing that studies focused only on anatomic pathologies (ie. structural MRI) may not detect any abnormalities in diseases with preserved structural connectivity but altered functional connectivity (such as in figure 2D), emphasizing the critical need for further studies investigating brain connectivity networks.
