The human brain has a particularly protracted maturation, with different tissue types, brain structures, and neural circuits having distinct developmental trajectories undergoing dynamic changes throughout life. Longitudinal MR scans of typically developing children and adolescents demonstrate increasing white matter (WM) volumes and inverted U shaped trajectories of gray matter (GM) volumes with peak sizes occurring at different times in different regions. Figure 1 shows age by size trajectories from a longitudinal study comprising 829 scans from 387 subjects, ages 3–27 years (see Figure 1 and Supplemental Experimental Procedures).
