rs-fcMRI is an increasingly popular fMRI technique that measures spontaneous, high-amplitude, low-frequency (<0.1 Hz) BOLD signal fluctuations in subjects at rest (i.e., performing no explicit task). Numerous studies have documented the presence of correlated rs-fcMRI signal in distributed but functionally related brain regions in adults, beginning with somatomotor cortex in 1995 (Biswal et al., 1995), but now including visual cortex (Lowe et al., 1998), auditory cortex (Cordes et al., 2001), the default mode network (Fox et al., 2005; Greicius et al., 2003), and several other so-called resting state networks (RSNs) (Damoiseaux et al., 2006). This signal is present in light sleep (Larson-Prior et al., 2009), under anesthesia (Kiviniemi et al., 2000), and is similar across scanners and subjects (Biswal et al., 2010). Additionally, 7–10 minutes of data appear to be adequate for basic analyses (Van Dijk et al., 2010), and task compliance is not required, making this an especially attractive tool for measuring functional networks in pediatric subjects (Fair et al., 2007b).
