contents were tested with a speeded, eye-hand coordination test. Further, longitudinal NCANDA data were used to validate the cross-sectionally observed developmental trajectories. To do so, our approach harmonized the computations of myelin content across visits by matching the intensities of the MRIs of the follow up visits to the baseline so that they agreed with respect to the low-frequency patterns. This procedure reduced the variance in myelin content across visits, which was verified on human phantom data. Of those regions with significant-age effects, permutation testing identified those whose myelin scores significantly correlated with the performance scores of an eye-hand coordinated, speeded motor task. In summary, this analysis makes three novel contributions: (1) characterizing the age-related pattern of cortical myelin content in 992 individuals aged 12 to 35 years, harmonized across two independently-collected data sets; (2) demonstrating the relation between regional developmental trajectories of myelin content and brain function in youth aged 12 to 21 years; (3) and developing longitudinally consistent analysis of myelin content thereby confirming the adolescent developmental patterns of myelin content of the cross-sectional study.
