Rewards, as suggested above, can enhance as well as diminish goal-directed behavior. The observation that adolescents take more risks when appetitive cues are present versus absent during gambling tasks makes this point (e.g., 37). In a recent imaging study 20, Somerville et al. identified the neural substrates of down-regulation of control regions with appetitive cues. Somerville et al. tested child, adolescent, and adult participants while they performed a go nogo task with appetitive social cues (happy faces) and neutral cues. Task performance to neutral cues showed steady improvement with age on this impulse control task. However, on trials for which the individual had to resist approaching appetitive cues, adolescents failed to show the expected age-dependent improvement. This performance decrement during adolescence was paralleled by enhanced activity in the striatum. Conversely, activation in the inferior frontal gyrus was associated with overall accuracy and showed a linear pattern of change with age for the nogo versus go trials. Taken together, these findings implicate exaggerated ventral striatal representation of appetitive cues in adolescents in the absence of a mature cognitive control response.
