In addition to fMRI activation studies, the relatively new and increasingly utilized method of resting state functional connectivity MRI (rs-fcMRI) allows for a complementary examination of the functional relationships between regions across development. Resting state fcMRI is based on the discovery that spontaneous low-frequency (<∼0.1 Hz) blood oxygen level dependent (BOLD) signal fluctuations in sometimes distant, but functionally-related grey matter regions, show strong correlations at rest [11]. These low frequency BOLD fluctuations appear to relate to spontaneous neural activity [11]–[13]. In effect, rs-fcMRI evaluates regional interactions that occur when a subject is not performing an explicit task (i.e., subjects are “at rest”) [11], [12], [14]–[23]. To date, rs-fcMRI has been used in several domains to examine systems-level organization of motor [11], memory [24],[25], attention [26], and task control systems [21],[22],[27].
