adolescents recruited significantly greater left NAcc activity than adults during winning trials. These findings directly contrast the Bjork paper and lend support for the hypothesis that disproportionately increased activation of the ventral striatal motivational circuit characterizes adolescent neurodevelopment and behavior (Chambers et al., 2003). A recent paper by van Leijenhorst et al. (2009) supports the hyper-responsive view as well. In contrast to the majority of similar work, they used an fMRI paradigm that was not dependent on behavior. That is, participants passively viewed stimuli that either certainly or uncertainly predicted subsequent reward. This approach is particularly important because previous studies may have been confounded by the behavioral component of the tasks. Their main finding is that adolescents show greater striatal activation than children or adults in response to reward receipt (van Leijenhorst et al., 2009), suggesting that even when reward is not contingent on behavior and thus there are no differences in motivation, adolescents show a hyper-active striatal response to reward.
