The use of resting state data to study developmental differences has many advantages (Fair et al. 2007). Data acquisition requires minimal task demands, so task-related differences between children and adults that confound many developmental functional imaging studies are not an issue (see Church et al. 2010 for a discussion). Moreover, rs-fcMRI analyses require relatively little time to acquire: 5–10 min of data are often adequate to perform these analyses. rs-fcMRI analyses can also be performed on a brain-wide scale, in contrast with connectivity measured based on functional data such as effective connectivity (Friston et al. 2003) and Granger causality (Granger 1969; Eichler 2005). It may also allow network definition that considers a broad history of co-activity across many tasks, rather than relying on relationships defined in a single task, like those used in dynamic causal modeling (Friston et al. 2003) or Granger causality (Granger 1969; Eichler 2005). Note that these comments are by no means intended to denigrate the role of task-based connectivity measures. Such measures accomplish what rs-fcMRI cannot—a measure of the relationship between regions activated in a specific
