Triadic model of the neurobiology of motivated behavior in adolescence

Background: Risk-taking behavior is a major cause of morbidity and mortality in adolescence. In the context of decision theory and motivated (goal-directed) behavior, risk-taking reflects a pattern of decision-making that favors the selection of courses of action with uncertain and possibly harmful consequences. We present a triadic, neuroscience systems based model of adolescent decision-making. Method: We review the functional role and neurodevelopmental findings of three key structures in the control of motivated behavior, i.e., amygdala, nucleus accumbens and medial/ventral prefrontal cortex. We adopt a cognitive neuroscience approach to motivated behavior that uses a temporal fragmentation of a generic motivated action. Predictions about the relative contributions of the triadic nodes to the three stages of a motivated action during adolescence are proposed. Results: The propensity during adolescence for reward-novelty seeking in the face of uncertainty or potential harm might be explained by a strong reward system (nucleus accumbens), a weak harm avoidant system (amygdala) and/or an inefficient supervisory system (medial/ventral prefrontal cortex). Perturbations in these systems may contribute to the expression of psychopathology, illustrated here with depression and anxiety. Conclusions: A triadic model, integrated in a temporally organized map of motivated behavior, can provide a helpful framework that suggests specific hypotheses of neural bases of typical and atypical adolescent behavior.