Magnetic resonance imaging (MRI) methods introduced a new set of noninvasive tools for capturing brain development in humans. MRI is particularly useful in the study of children and adolescents as it provides precise, high-resolution anatomical images without the use of ionizing radiation (Kennedy et al., 2003). Although total brain size is approximately 90% of its adult size by age 6 (Casey et al., 2005), the gray and white matter subcomponents continue to undergo changes throughout adolescence (Giedd et al., 1999; Sowell et al., 2003; Gogtay et al., 2004). Specifically, there is a significant decrease in cortical gray matter by 12 years (Giedd et al., 1999) and an increase in cerebral white matter throughout childhood and young adulthood (Caviness et al., 1996). Recent data suggest that gray matter volume has an inverted U-shape pattern, with greater regional variation than white matter (Sowell et al., 1999, 2003; Gogtay et al., 2004). Particularly relevant to a review about the development of the dopamine system is evidence showing that the dopamine-rich frontal and striatal regions undergo significant maturational changes through adolescence (Giedd et al.,
