Children ages 9–12 years face increasing social and academic expectations that require
mastery of their thoughts, emotions, and behavior. Little is known about the development
of neural pathways integral to these improving capacities during the transition from
childhood to adolescence. Among 234 healthy, inner-city male and female youth (species
Homo sapiens ) 9–12 years of age followed by the Columbia Center for Children's Environmental
Health, we acquired diffusion tensor imaging, multiplanar chemical shift imaging,
and cognitive measures requiring self-regulation. We found that increasing age was
associated with increased fractional anisotropy and decreased apparent diffusion coefficient,
most prominently in the frontal and cingulate cortices, striatum, thalamus, deep white
matter, and cerebellum. Additionally, we found increasing age was associated with
increased N -acetyl- l -aspartate (NAA) in the anterior cingulate and insular cortices,
and decreased NAA in posterior cingulate and parietal cortices. Age-associated changes
in microstructure and neurometabolite concentrations partially mediated age-related
improvements in performance on executive function tests. Together, these findings
suggest that maturation of key regions within cortico-striatal-thalamo-cortical circuits
subserve the emergence of improved self-regulatory capacities during the transition
from childhood to adolescence. SIGNIFICANCE STATEMENT Few imaging studies of normal
brain development have focused on a population of inner-city, racial/ethnic minority
youth during the transition from childhood to adolescence, a period when self-regulatory
capacities rapidly improve. We used DTI and MPCSI to provide unique windows into brain
maturation during this developmental epoch, assessing its mediating influences on
age-related improvement in performance on self-regulatory tasks. Our findings suggest
that rapid maturation of cortico-striato-thalamo-cortical circuits, represented as
progressive white-matter maturation (increasing FA and increasing NAA, Ch, Cr concentrations
accompanying advancing age) in frontal regions and related subcortical projections
and synaptic pruning (decreasing NAA, Ch, Cr, Glx) in posterior regions, support age-related
improvements in executive functioning and self-regulatory capacities in youth 9–12
years of age.