How the Brain Reacts to Unexpected Events and the Role of Norepinephrine

Date:20 June 2022 Author: Juandre

Unexpected events cause noradrenaline to be released, which aids in the brain’s ability to concentrate and learn from the experience.

A recent MIT study found that your brain can send a burst of noradrenaline when it requires you to pay attention to something crucial.

The locus coeruleus, a deep brain region, is the source of this neuromodulator, which has broad effects on the entire brain. The MIT team discovered that one important function of noradrenaline, commonly known as norepinephrine, is to assist the brain in learning from unexpected results.

Some nerve cells and the adrenal gland produce norepinephrine, commonly known as noradrenaline. It can act as a hormone as well as a neurotransmitter (a chemical messenger used by nerve cells) (a chemical that travels in the blood and controls the actions of other cells or organs). The adrenal gland releases norepinephrine in reaction to stress and low blood pressure.

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, says, “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.”

The researchers also found that noradrenaline has a role in the stimulation of behavior that results in a reward, particularly in circumstances where it is uncertain if a reward would be provided.

The new study’s senior author is Sur, and it was released in the journal Nature on June 1, 2022. The paper’s lead authors are Gabrielle Drummond, a graduate student at MIT, and Vincent Breton-Provencher, a former postdoc at MIT who is now an assistant professor at Laval University.


Altering behavior

Along with dopamine, serotonin, and acetylcholine, noradrenaline is one of many neuromodulators that affect the brain. Neuromodulators are released over wide areas of the brain, allowing them to have more widespread effects than neurotransmitters, which allow cell-to-cell contact.

The excitatory or inhibitory drive that neurons are getting is thought to be altered in a more point-to-point manner by neuromodulatory chemicals, according to Sur. This implies that they must possess highly significant brain-wide processes that are necessary for both survival and the control of brain state.

Less is known about the other neuromodulators, such as noradrenaline, despite the fact that dopamine has been extensively studied for its function in motivation and reward seeking. Noradrenaline has been connected to arousal and enhancing alertness, but too much of it can cause anxiety.

The principal noradrenergic organ of the brain, the locus coeruleus, has previously been shown to accept input from numerous brain regions and to transmit signals widely. The goal of the current study by the MIT team was to investigate its function in reinforcement learning, also known as learning via mistake.

In order to conduct this study, the researchers trained mice to press a lever in response to a high-frequency tone but not a low-frequency tone. When the mice pulled the lever in response to the high-frequency tone correctly, they got water; if they did so when they heard the low-frequency tone, they got an unpleasant puff of air.

The mice discovered that louder tones caused them to press the lever more forcefully. They were less convinced whether they should push or not when the volume was lower. Additionally, the mice were substantially less likely to press the lever when they heard low volume tones when the researchers blocked locus coeruleus activity, showing that noradrenaline encourages taking a chance on receiving a reward in some circumstances.

According to Sur, “The animal is pushing because it expects a reward, and the locus coeruleus gives crucial signals to say, push now because the reward will arrive.

More evidence that this signal prompts the animals to behave comes from the discovery by the researchers that the neurons that produce this noradrenaline signal seem to direct the majority of their output toward the motor cortex.

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