This model is consistent with previous ones 21–24 in that it provides a basis for nonlinear inflections observed in behavior from childhood to adulthood, due to earlier maturation of subcortical projections relative to less mature top down prefrontal ones. Specifically, the triadic model 21 proposes that motivated behavior has three distinct neural circuits (approach, avoidance and regulatory). The approach system is largely controlled by the ventral striatum, avoidance system by the amygdala and lastly, the regulatory system by the prefrontal cortex 25. The current model differs largely from others in that it is grounded in empirical evidence for brain changes not only in the transition from adolescence to adulthood, but rather the transition into adolescence from childhood and later out of adolescence into adulthood. Moreover, the model does not suggest that the striatum and amygdala are specific to approach and avoidant behavior given recent studies showing valence independence of these structures 26, but rather are systems that are important in detecting motivationally and emotionally relevant cues in the environment that can bias behavior. In this review, we describe the most
