The ability to assay relationships between brain regions was greatly advanced by the recent introduction of techniques such as MRI tractography and functional connectivity MRI (fcMRI), which measure macroscopic brain relationships at the level of voxels (cubes of several mms). These techniques have enabled the first relatively comprehensive, if coarse, measurements of structural and functional brain networks in humans. Although initial studies were largely carried out in adult populations, recent studies have examined networks in infants, children, and adolescents. Elsewhere in this volume, Giedd and colleagues review the literature on the development of structural brain networks. Here, we review developmental studies on functional brain networks, as measured by resting-state functional connectivity MRI (rs-fcMRI).
