Frontiers in Systems Neuroscience Systems Neuroscience

Abstract

groups of nodes with many intra-modular links to each other but few inter-modular links to external groups (Newman and Girvan, 2004). Graph theoretical work has shown that human brain functional modules are hierarchically organized (Meunier et al., 2009b; Bassett et al., 2010), that their structure is altered in normal aging (Meunier et al., 2009a) and in adolescence (Fair et al., 2009), and that their structure is relatively consistent for fMRI and diffusion spectrum imaging (DSI) of the same subjects (Hagmann et al., 2008). The brain, at least the healthy brain, is a modular system. Here we test the hypothesis that the normal modular community structure of functional brain networks might be somehow disrupted in neuropsychiatric disease, specifically in schizophrenia. There are theoretical reasons to posit that the brain's modularity is crucial in terms of its evolution and healthy neurodevelopment. Modularity may allow the brain to adapt to multiple, distinct selection criteria over time (Kashtan and Alon, 2005). Modules may also represent stable subcomponents of the brain, which facilitate the construction of a complex system from simple building blocks (Simon, 1962). In the context of the recent focus on the