How the brain responds to unexpected events, according to MIT scientists

When the brain needs us to pay attention to something important, one way to do that is by transmitting norepinephrine blastto me New study From Massachusetts Institute of Technology (MIT, for its English abbreviation), which was published in the scientific journal temper nature.

east nervous rateproduced by a structure deep in the brain called Ceruleus place, It can have widespread effects throughout the brain. In a study conducted on mice, a team at Massachusetts Institute of Technology Find out The main function of norepinephrine, also known as norepinephrine, is to help the brain learn from surprising results.

What this work shows is that coeruleus site encodes unexpected events, Watch out for these amazing events It is critical for the brain to evaluate its environment“, He says Southern MarijankaProfessor of Neuroscience at Department of Brain and Cognitive Sciences at the Massachusetts Institute of Technology, Member of the MIT Picower Institute for Learning and Memory and manager Simmons Center for the Social Brain.

In addition to its role in sending sudden signals, researchers have also found that Norepinephrine helps motivate behavior that leads to reward, particularly in situations where there is uncertainty about whether a reward will be offered.

Behavior Modification

The norepinephrine he is One of several neuromodulators that affect the brain, together with dopamineThe serotonin and the acetylcholine. Unlike neurotransmitters, which allow cell-to-cell communication, neuromodulators They are released into large parts of the brain, allowing them to exert more general effects.

“he thinks that Neuromodulators narrate large areas of the brain Thus, they alter the excitatory or inhibitory impulse that neurons receive in a more punctual manner,” he explains. South. “This indicates that They must have very important brain functions that are important for survival and regulation of the state of the brain. “

Although scholars have learned a lot about it The role of dopamine in motivation and reward seeking, Little is known about other neuromodulators, including norepinephrine. It has been linked to agitation and increased alertness, but excessive norepinephrine can lead to anxiety.

Previous studies of Ceruleus place, The main source of norepinephrine From the brain, they have shown it It receives information from many parts of the brain and sends its signals everywhere. In the new study, a team at Massachusetts Institute of Technology I set out to study its role in a particular type of learning called Reinforcement learning, or learning by trial and error.

For this study, researchers Mice trained to push a lever when they heard a high-frequency tone, But not when they heard a low-frequency tone. When the mice responded correctly to the high tone, they got water, but if I hit the lever when they heard a low tone, they got a nasty puff of air.

mice They also learned to push the lever harder when the tones are higher. When the sound was lower, they were more hesitant about whether to push or not. yes , When the researchers blocked the blue locus’ activity, the mice were more reluctant to push the lever When they heard low tones, suggesting so Norepinephrine enhances the possibility of obtaining a reward in situations where the reward is uncertain.

“The animal pays because it wants a reward, and the blue locus provides important cues to say, ‘Pay now, because the reward is coming,'” Sur says.

The researchers also found that the neurons that generate this norepinephrine signal send most of their output to the motor cortex, providing further evidence that this signal motivates the animals to act.

surprise banners

While this initial rush of norepinephrine appears to motivate the mice to act out, the researchers found that too A second burst often occurs after the test is complete. When the mice received an expected reward, these bursts were small. However, when the test result was a surprise, the eruptions were much larger. for examplewhen the rat received a gasp of air instead of the expected reward, the blue locus sent out a large boost of norepinephrine.

In the Articles LaterThat was the mouse Less likely to push the lever when he wasn’t sure he would get a bonus. “The animal is constantly adjusting its behavior,” he explains. South. “Although you have already learned the task, He’s adjusting his behavior based on what he just did.”

As shown by mice Norepinephrine bursts At rehearsals when they received an unexpected reward. These are bursts They appear to release norepinephrine to many parts of the brain, including the prefrontal cortex, where planning and other higher cognitive functions occur. Blue position snap coding function It appears to be more prevalent in the brain, And that can make sense because everything we do is supervised Surprise,” adds the expert.

Researchers are now planning Exploring the potential synergy between norepinephrine and other neuromodulators, especially dopamine, Which also respond to unexpected rewards. They also hope to learn more about how the prefrontal cortex stores short-term memory inputs from the blue locus to help the animals improve their performance in future experiments.

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