When faced with an unexpected event, the neurotransmitter produced by the central and peripheral nervous system helps the brain to focus its attention and learn from the experience.

In a study on mice, which appeared in “Nature”, a team of neuroscientists from MIT discovered the key role played by norepinephrine, a substance produced by locus coeruleusa small area of ​​the brain that codes for unexpected events, facilitating the subject’s immediate reaction.

Norepinephrine is one of several neuromodulators that affect the brain, along with dopamine, serotonin, and acetylcholine. According to one of the authors, Mriganka Sur, of the Department of Brain and Cognitive Sciences at MIT, these substances amplify the excitatory or inhibitory stimulus that neurons undergo and appear to perform brain functions important for survival and brain state regulation.

In the new study, neuroscientists delved into the role of locus coeruleus in reinforcement learning, or trial and error learning. To do this, they trained the mice to push a lever only when they heard a high-frequency tone, giving them water as a reward.

Mice also learned to push the lever harder when the tones were higher. At lower frequencies, the animals were more uncertain whether they should push or not. When the researchers inhibited the activity of the locus coeruleusthe mice have become much more reluctant to push the lever in the face of lower tones, suggesting that norepinephrine prompts action in situations where the gain is uncertain.

Confirming this, neurons appear to release norepinephrine into the motor cortex, which offers further evidence that this signal stimulates animals to act. Neuroscientists also found that when the mice received the intended reward, the spread of the substance was limited. On the other hand, if a mouse received a punishment (a puff of air) in place of the expected reward, the locus coeruleus released a large amount of norepinephrine.

In subsequent tests, the rat that had been punished was more uncertain and hardly pushed the lever. According to Sur, the conclusion is that the animal is constantly adapting its behavior based on what it has just done.

The same situation occurred when the mice received an unexpected reward. Norepinephrine spread to many parts of the brain, including the prefrontal cortex, where planning and other higher cognitive functions occur.

The researchers now intend to explore the possible synergy between norepinephrine and other neuromodulators, particularly dopamine, which itself responds to unexpected rewards. They also hope to learn more about how the prefrontal cortex stabilizes short-term memory of input from the locus coeruleus to help animals improve their performance in future trials.

Image: Wikimedia Commons

Image by JL G from Pixabay

(rp)

The post Noradrenalina, the wake-up call of the brain first appeared on Technology Review Italia.

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