In vivo evidence for post-adolescent brain maturation in frontal and striatal regions was studied using high-resolution MRI and voxel-based morphometry. The study found that brain maturation between adolescence and young adulthood was localized to dorsal, medial, and orbital frontal cortex and lenticular nuclei, with relatively little change in other regions. This pattern agrees with post-mortem studies of brain development and the continued development of cognitive functions attributed to frontal structures. The results showed that frontal lobe maturation occurs later than previously expected, with significant reductions in gray-matter density in frontal and striatal regions between adolescence and adulthood. These findings are consistent with post-mortem, electrophysiological, and neuropsychological studies indicating delayed frontal maturation. The study also found that striatal changes, primarily in the putamen and globus pallidus, may result from regressive events, myelination, and iron deposition. The results highlight the potential importance of frontal/striatal maturation to adult cognition. A longitudinal MRI study of brain development in children and adolescents confirmed linear increases in white matter and nonlinear changes in cortical gray matter, with peaks in frontal and parietal lobes around age 12 and temporal lobes around age 16. Cortical gray matter continued to increase in the occipital lobe through age 20. The study found no significant sex differences in age, Tanner stage, ethnicity, socioeconomic status, height, weight, or handedness. The results suggest that brain development is regionally specific and that the frontal and striatal regions are particularly important for cognitive development. The study used a combination of cross-sectional and longitudinal data to assess developmental changes and found that the volume of white matter increased linearly with age, while cortical gray matter volume showed nonlinear changes. These findings provide important insights into the timing and regional patterns of brain maturation during childhood and adolescence.In vivo evidence for post-adolescent brain maturation in frontal and striatal regions was studied using high-resolution MRI and voxel-based morphometry. The study found that brain maturation between adolescence and young adulthood was localized to dorsal, medial, and orbital frontal cortex and lenticular nuclei, with relatively little change in other regions. This pattern agrees with post-mortem studies of brain development and the continued development of cognitive functions attributed to frontal structures. The results showed that frontal lobe maturation occurs later than previously expected, with significant reductions in gray-matter density in frontal and striatal regions between adolescence and adulthood. These findings are consistent with post-mortem, electrophysiological, and neuropsychological studies indicating delayed frontal maturation. The study also found that striatal changes, primarily in the putamen and globus pallidus, may result from regressive events, myelination, and iron deposition. The results highlight the potential importance of frontal/striatal maturation to adult cognition. A longitudinal MRI study of brain development in children and adolescents confirmed linear increases in white matter and nonlinear changes in cortical gray matter, with peaks in frontal and parietal lobes around age 12 and temporal lobes around age 16. Cortical gray matter continued to increase in the occipital lobe through age 20. The study found no significant sex differences in age, Tanner stage, ethnicity, socioeconomic status, height, weight, or handedness. The results suggest that brain development is regionally specific and that the frontal and striatal regions are particularly important for cognitive development. The study used a combination of cross-sectional and longitudinal data to assess developmental changes and found that the volume of white matter increased linearly with age, while cortical gray matter volume showed nonlinear changes. These findings provide important insights into the timing and regional patterns of brain maturation during childhood and adolescence.