Although Bjork and colleagues have more recently replicated these findings in a doubled sample size and using an improved headcoil (Bjork et al., in preparation, personal communication), numerous papers have reported the opposite results (May et al., 2004; Ernst et al., 2005; Galván et al., 2006; van Leijenhorst et al., 2009). These studies have shown that, relative to other age groups, adolescents show greater activation in the ventral striatum in response to reward. For instance, in our work, children, adolescents and adults were asked to perform a simple, youth-friendly task in the scanner in which different reward values were delivered following correct responses (Galván et al., 2006). Relative to children and adults, the adolescent group showed heightened ventral striatal activation in anticipation of reward. In another example, Ernst et al. (2005) used a probabilistic monetary reward task to show that 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
