It's human nature to sometimes regret a decision. Now scientists have identified the brain region that mediates that feeling of remorse: the medial orbitofrontal cortex.

Giorgio Coricelli of the Institute of Cognitive Sciences at the National Science Research Center in Bron, France, and his colleagues designed a functional magnetic resonance imaging (fMRI) experiment to monitor how people make decisions and feel about them after the fact. The team presented volunteers with two choices, one of which carried higher risk than the other, but had the potential for greater reward as well. After indicating their choices, the subjects were told the outcome of their decision. In some cases, however, the researchers also revealed what would have happened if they had chosen differently. Choosing the less lucrative option and learning the other one was better was strongly correlated with activity in the medial orbitofrontal cortex, which sits above the orbits of the eyes in the brain's frontal lobe. The amount of activity observed was also tied to the level of regret, which corresponded to the difference between the result of the choice made and that of the alternative outcome

When participants were assigned one of two possibilities and thus felt no control over the outcomes, this activity was not observed, suggesting a feeling of personal responsibility helps govern OFC activity in addition to feelings of regret. The findings support previous studies involving patients with damaged OFC areas who do not experience regret and are also unable to alter their behavior to avoid situations that would induce the feeling. A paper describing the results was published online yesterday by Nature Neuroscience.