This review provides behavioral, clinical and neurobiological evidence for dissociating these subcortico-cortico systems developmentally. Behavior data from laboratory tasks and self -report ratings administered to children, adolescents and adults (e.g., 18, 20, 37, 42) suggest curvilinear development of sensation-seeking with a peak inflection roughly between 13 and 17 years, while impulsivity decreases across development in a linear fashion from childhood to young adulthood. Human imaging studies show patterns of activity in subcortical brain regions sensitive to reward (ventral striatum) that parallel the behavioral data. Specifically, they show a curvilinear pattern of development in these regions and the magnitude of their response is associated with risk-taking behaviors. In contrast, prefrontal regions, important in top down regulation of behavior, show a linear pattern of development that parallels those seen in behavioral studies of impulsivity. Moreover, clinical disorders with impulse control problems show less prefrontal activity, further linking neurobiological substrates with the phenotypic construct of impulsivity.
