Behavioral, but not reward, risk modulates activation of prefrontal, parietal, and insular cortices

Risky decisions may involve uncertainty about possible outcomes (i.e., reward risk) or uncertainty about which action should be taken (i.e., behavioral risk). Determining whether different forms of risk have distinct neural correlates is a central goal of neuroeconomic research. In two functional magnetic resonance imaging experiments, subjects viewed shapes that had well-learned response-reward contingencies. Magnitude of a monetary reward was held constant within one experiment, whereas expected value was held constant within the other. Response selection, in the absence of behavioral risk, evoked activation within a broad set of brain regions, as had been found in prior studies. However, behavioral risk additionally modulated activation in prefrontal, parietal, and insular regions,within which no effect of reward risk was observed. Reward delivery, in comparison with omission, evoked increased activity in the ventromedial prefrontal cortex and the nucleus accumbens. We conclude that distinct brain systems are recruited for the resolution of different forms of risk.