We begin with an introductory review of several studies conducted in very young children. These studies highlight the presence of correlated rs-fcMRI signal in infants, but also demonstrate some limitations of traditional methods used to explore correlation patterns in rs-fcMRI data. We then examine studies in older children, which have often focused on functional connectivity within the default mode network (DMN), a collection of brain regions that deactivate during performance of many tasks in adults (Raichle et al., 2001; Shulman et al., 1997). We note that discrepant pictures of DMN connectivity emerge from different studies, making the presence and extent of coherent rs-fcMRI activity in the DMN across development unclear. We then introduce a useful paradigm for studying networks, called graph theory, which can overcome some of the limitations previously noted. We describe how this mathematical approach has informed developmental studies of rs-fcMRI networks, and reexamine functional connectivity in the DMN in light of some of the lessons learned from graph theoretic approaches to networks. We conclude with a discussion of limitations and caveats to graph theoretic approaches, and with comments on future directions for study.
