gray matter volume peaked at 10.5 years in girls and 14.5 years in boys. Cortical frontal gray matter volume of girls peaks about a year before that of boys (10.5 compared with 11.5 years of age). This sex-related difference in volume peak was slightly earlier than those reported in an earlier study from the same research group based on fewer adolescents for whom the peaks were at 11 years of age for girls and 12.1 years for boys (Giedd et al., 1999). Shaw et al. (Shaw et al., 2008) reported on 375 youth and adults of the NIH-CHPB cohort, age 3.5 to 33 years, and a total of 764 MRIs collected longitudinally at 2-year intervals. Age of peak cortical thickness of different frontal regions ranged between 9.6 years for precentral cortex to 13.8 years for the cingulate cortex. Cortical brain regions have characteristically different cell types and structures and followed different growth trajectories, for example, cubic for neo (iso) cortex and linear for allocortex. Our increased “temporal” resolution of image acquisition was sensitive enough to detect a 2% decline in anterior cortical volume. The implication of this ability suggests that narrowing the retest interval should increase accuracy in timing of
