Neuroscientists have discovered what makes our brain wonder and how it helps in learning

(ORDO NEWS) — Researchers at the Massachusetts Institute of Technology have studied in detail how the brain reacts to unexpected events, how decisions are made, how the sense of surprise helps in learning, and what role norepinephrine plays in all of this.

Norepinephrine (or norepinephrine) is one of the main neuromodulators that affects neurons in many areas of the brain, but is produced mainly deep in its depths, in the cells of the blue spot (a bluish color area in the brain stem).

It is involved in a variety of brain functions, including arousal, alertness, memory, learning, and anxiety.

Dysfunction of the locus coeruleus, degeneration of the production or recognition system of norepinephrine are considered signs of such neurodegenerative diseases as Alzheimer’s, Parkinson’s and Huntington’s diseases.

Neuroscientists have discovered what makes our brain wonder and how it helps in learning 2 1
Most of the norepinephrine in the brain is produced by the two nuclei of the locus coeruleus (one in each hemisphere). Coeruleus neurons are labeled with green fluorescent protein

In a new study, a team from the Massachusetts Institute of Technology (USA) decided to study the role of the blue spot in a specific type of learning – reinforcement learning, or trial and error.

To do this, the authors trained mice to press the lever when they heard a high-frequency sound signal, and do nothing in the case of a low-frequency signal.

When the rodents responded correctly to a high-frequency signal, they received water, but if they pressed the lever when they heard a low-frequency sound, they received an unpleasant trickle of air.

In addition, the animals were trained to push the lever harder and more decisively (in fact, faster) when the high-pitched sounds got louder. When their signal volume was lower, the mice were less sure whether they should click or not, which was reflected in an increase in decision time.

To test the role of the blue spot in learning and decision-making, the researchers suppressed its activity in trained individuals. As a result, the period of time required to decide to press the lever was significantly increased in these mice.

This suggests that the release of norepinephrine by the blue spot helps to take risks for rewards even in situations where winning is not guaranteed.

The researchers also found that the neurons that generate this norepinephrine signal appear to send most of the neuromodulator to the motor cortex to spur the animal into action.

Neuroscientists have discovered what makes our brain wonder and how it helps in learning 3
Detailed scheme of the experiment (a, b) and the results of the study

Although the initial surge in noradrenaline production appears to spur the mice into action, the scientists found that there is often a second surge that occurs after the training and trial are complete. When subjects received the expected reward at the end, these spikes were small.

However, when the result was unexpected (for example, if the mouse received an unpleasant puff of air instead of the expected well-deserved reward), the bursts of neuromodulator production turned out to be much larger.

“In subsequent trials, such a mouse is much less likely to pull the lever if it is not sure that it will receive a reward. The animal is constantly adjusting its behavior,” explained Mriganka Sur, a professor of neuroscience in the MIT Brain and Cognition Department and lead author of the study.

“Although the mouse has already learned the task, it adjusts its behavior based on what it just did.”

Subjects also showed spikes in norepinephrine production in the trials when they received a surprise reward.

These bursts appeared to distribute noradrenaline to many parts of the brain, including the prefrontal cortex responsible for complex behavior planning, decision making, and other higher cognitive functions.

Such a reaction to unexpected events made it possible to adjust the learning outcomes and better perform the task at subsequent stages of the study.

In the future, the authors of the work plan to study the possible interaction of norepinephrine with other neuromodulators, especially dopamine, which, as is known, also responds to unexpected rewards.

In addition, the scientists hope to learn more about how the prefrontal cortex stores information about locus coeruleus signals to help animals improve their performance in future trials.


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