in cortical and subcortical fiber tracts (Asato et al., 2010; Benes et al., 1994; Paus et al., 2001; Paus et al., 1999), resulting from increased myelination, axon caliber, or both (Paus, 2010). Changes in the patterns of connectivity also occur during adolescence. For example, axonal sprouting and growth have been observed in circuits connecting the amygdala to cortical targets (Cunningham et al., 2002), and increasing measures of white matter are observed between the PFC and striatum and other areas (Asato et al., 2010; Giedd, 2004; Gogtay et al., 2004; Liston et al., 2006; Paus et al., 2001; Sowell et al., 1999).
