A neurobiological model of adolescent development 2 that builds on rodent models 13, 14 and recent imaging studies of adolescence 6, 7, 15–20 is depicted Figure 1. This model illustrates how subcortical and prefrontal top-down control regions must be considered together as a circuit. The cartoon shows different developmental trajectories for signaling of these regions, with limbic projections developing earlier than prefrontal control regions. According to the model, the adolescent is biased by functionally mature subcortical relative to less mature cortical circuitry during adolescence (i.e., imbalance in reliance of systems), compared to children, for whom this frontolimbic circuitry is still developing; and compared to adults, for whom these systems are fully mature. With development and experience, the functional connectivity between these regions is strengthened and provides a mechanism for top down modulation of the subcortical systems 7. Thus it is the frontostriatal circuitry, along with functional strengthening of connections within this circuitry, that may provide a mechanism to explain changes in both impulsivity and risk-taking observed across development.
