The good, the bad and the brain: Neural correlates of appetitive and aversive values underlying decision making.

Approaching rewards and avoiding punishments could be considered as core principles governing behavior. Experiments from behavioral economics have shown that choices involving gains and losses follow different policy rules, suggesting that appetitive and aversive processes might rely on different brain systems. Here we contrast this hypothesis with recent neuroscience studies exploring the human brain from brainstem nuclei to cortical areas. Although some circuits show rigid specialization, many others appear to process both appetitive and aversive stimuli, in a flexible manner that depends on a context-wise subjective reference point. Moreover, appetitive and aversive aspects are often integrated into net values that are signaled with enhanced activity in 'positive regions', and suppressed activity in 'negative regions'. This dichotomy might explain why drugs or lesions can produce valence-specific effects, biasing decisions towards approaching a reward or avoiding a punishment.