Together, the studies described support a view of adolescent brain development as characterized by a tension between early emerging “bottom-up” systems that express exaggerated reactivity to motivational stimuli and later maturing “top-down” cognitive control regions. This bottom-up system which is associated with sensation- seeking and risk-taking behavior gradually loses its competitive edge with the progressive emergence of “top-down” regulation (e.g., 2, 7, 15, 23, 64, 121–123). This imbalance between these developing systems during adolescence may lead to heightened vulnerability to risk-taking behaviors and increased susceptibility to the motivational properties of substances of abuse.
