10 June 2013. Rewards can be powerful teachers, but it’s actually the surprising moments—when an anticipated reward doesn’t come or arrives unexpectedly—that drive the brain to learn. According to a study in rats published May 26 in Nature Neuroscience, the brain chemical dopamine flags the difference between what is expected and what actually happens, providing a kind of “uh-oh” moment that alerts the brain to change course in order to get a reward. Led by Patricia Janak at the University of California, San Francisco, the study found that artificially stimulating dopamine neurons at inappropriate times could alter learning in rats.
The results highlight a role for precisely timed dopamine signals in these uh-oh moments, known as prediction errors, which seem to fuel some of schizophrenia’s symptoms. Researchers have proposed that the overactive dopamine system characteristic of schizophrenia could muck with the timing of prediction error signals in the brain. For example, an innocuous event in a person’s life could be mistakenly flagged as important, and provide grist for delusions and hallucinations. (For more details on this study, see SRF related news story.)—Michele Solis.