Calculating consequences: brain systems that encode the causal effects of actions.

The capacity to accurately evaluate the causal effectiveness of our actions is key to successfully adapting to changing environments. Here we scanned subjects using functional magnetic resonance imaging while they pressed a button to earn money as the response-reward relationship changed over time. Subjects' judgments about the causal efficacy of their actions reflected the objective contingency between the rate of button pressing and the amount of money they earned. Neural responses in medial orbitofrontal cortex and dorsomedial striatum were modulated as a function of contingency, by increasing in activity during sessions when actions were highly causal compared with when they were not. Moreover, medial prefrontal cortex tracked local changes in action-outcome correlations, implicating this region in the on-line computation of contingency. These results reveal the involvement of distinct brain regions in the computational processes that establish the causal efficacy of actions, providing insight into the neural mechanisms underlying the adaptive control of behavior.