Fig 3. Maturation of mean diffusivity (MD) and fractional anisotropy (FA) in white matter tracts of the genu, splenium, and left corticospinal tract (n = 47). In the genu, MD was significantly correlated with age in the central (r² = 0.2392; P = .0005) and peripheral (r² = 0.3781; P < .0001) regions. FA also was significantly correlated with age in the central (r² = 0.1810; P = .0029) and peripheral (r² = 0.4219; P < .0001) regions. Unlike other fiber tracts studied, there were no significant correlations of age with MD in the central (r² = 0.05944; P = .0986) and peripheral (r² = 0.02135; P = .3271) regions of the splenium. In the splenium, FA also was not significantly correlated with age in the central (r² = 0.000027; P = .9720) and peripheral (r² = 0.00175; P = .7800) regions. In the left corticospinal tract, MD was significantly correlated with age in the central (r² = 0.3447; P < .0001) and peripheral (r² = 0.4727; P < .0001) regions. FA was significantly correlated with age in the central (r² = 0.2363; P = .0005) and peripheral (r² = 0.1138; P < .0204) regions.