How the brain responds to surprising events

When your brain needs you to pay attention to something important, one way it can do that is to send out a burst of noradrenaline, according to a new MIT study.

This neuromodulator, produced by a structure deep in the brain called the locus coeruleus, can have widespread effects throughout the brain. In a study of mice, the MIT team found that one key role of noradrenaline, also known as norepinephrine, is to help the brain learn from surprising outcomes.

“What this work shows is that the locus coeruleus encodes unexpected events, and paying attention to those surprising events is crucial for the brain to take stock of its environment,” says Mriganka Sur, the Newton Professor of Neuroscience in MIT’s Department of Brain and Cognitive Sciences, a member of MIT’s Picower Institute for Learning and Memory, and director of the Simons Center for the Social Brain.

In addition to its role in signaling surprise, the researchers also discovered that noradrenaline helps to stimulate behavior that leads to a reward, particularly in situations where there is uncertainty over whether a reward will be offered.

Sur is the senior author of the new study, which appears today in Nature. Vincent Breton-Provencher, a former MIT postdoc who is now an assistant professor at Laval University, and Gabrielle Drummond, an MIT graduate student, are the lead authors of the paper.

Modulating behavior

Noradrenaline is one of several neuromodulators that influence the brain, along with dopamine, serotonin, and acetylcholine. Unlike neurotransmitters, which enable cell-to-cell communication, neuromodulators are released over large swathes of the brain, allowing them to exert more general effects.

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