Researchers identify the neurons responsible for encoding the results of our activities


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Thanks to an experiment carried out on mice, neuroscientists at MIT have managed to identify the neurons responsible for encoding the result of activities. These neurons, located in the striatum, an area of ​​the brain that notably regulates inspiration and impulsiveness, seem involved in the evaluation of the risks and benefits of an activity, thus contributing to decision-making. This discovery could lead to a new form of treatment for certain neuropsychiatric disorders.

Learning about the positive and negative results of activities, which necessarily influences behavior, is essential for the survival of individuals. Scientists know that the striatum is involved in these learning mechanisms, allowing individuals to adapt their behavior in changing environments which. opinion? Specific neurons, called striatal projection neurons, encode the different organisms between activities and results. How these organizations are formed is not fully understood, however, particularly when the results have both positive and negative characteristics (making decision-making more difficult).

A team from MIT became interested in the subject. Sober confronting mice with a foraging task, based on the one-armed bandit problem (the mice having to maximize their food intake while minimizing the punishment), they highlighted the brain cells that participated in this decision-making: a group of neurons in the striatum encoded the potential outcomes of each of the decisions; in particular, they noticed that these neurons were activated all the more when the result was different from that expected by rodents, which confirms that the brain is able to adapt to different circumstances.

Neurons coding once for a reward and a punishment

It sometimes we find ourselves in circumstances requiring complex sober decision-making: we then have to estimate the risk attributed to each of the possible choices, which amounts to a quick analysis of the risk-benefit amounts involved. Individuals with sobriety with certain neuropsychiatric issues, such as anxiety and depression, become sober unable to make such sobriety decisions. Thanks to MIT research, we now know which neurons allow us to carry out this type of analysis: according to the researchers, disturbances in the activity of these neurons could be the source of impulsive decisions or, on the contrary, a blockage of indecision.

The team took a particular interest in the way the brain makes decisions, when these have both beneficial and negative consequences. To do this, they trained mice to turn a wheel to the left or to the right. each visit, the animals received a combination of reward (sweet water) and punishment (a tiny puff of air) among four possibilities: reward+no punishment, punishment+no reward, reward+punishment and no reward+no step of punishment. As the mice performed the task, they learned to maximize rewards and minimize punishments. each result, the mice had to adjust their sober behavior permanently. In parallel, the team recorded the cerebral activity of the striosomes the groups of neurons of the striatum. Previous work has shown that striosomes send data to many other functions of the brain, including dopamine-producing regions, the neurotransmitter largely involved in pleasure, inspiration and risk-taking, and regions involved in movement planning; this data is situated for decision-making and subsequent rewards.

Increased activity to record the errors

The researchers were able to observe, as expected, that neuronal activity varied according to the results obtained by the mice packaged in the sober execution of their task : Neurons encoded data on the potential outcomes of different decisions, which allowed sober animals to know which emotion considered beneficial should be repeated, and which actions should instead not be reproduced.

But above all, they observed that many neurons also encoded a relationship between activities (turning a wheel right or left) and the two types of outcomes. We found that action-result organisms for reward and punishment were required in parallel in partially overlapping sony ericsson populations. Single neurons could, after activity, program valence outcomes are at odds of , explain the researchers in Character Marketing communications.

The team also noted that the activity on these neurons was more intense when the mice were surprised by the result, which is all in all logical, an expected result that does not induce learning. What we see is that it has a fortification encoding both unexpected rewards and unexpected negative results, explains Bernard Bloem, a former postdoctoral fellow at MIT and one of the main authors of the study. Scientists thus refer to the multiplexing of action-result contingencies by neurons. This phenomenon seems to cause the brain to change strategy as soon as necessary.

In a regular human brain, the striatum knows why such decisions are beneficial and what are the more or less harmful consequences sober each. Thus, the activity of striatal neurons reflects more the potential outcome of a decision than the likelihood of it being made, Bloem explains. In individuals suffering from mental problems (depression, schizophrenia, post-traumatic stress, etc.), the problem is that this variation between good and bad decision no longer works correctly, resulting in impaired judgment and impulsive behaviors. Behavioral therapy targeting the stage where data about potential outcomes is encoded in the brain could help people who suffer from these disorders, conclude the researchers.

Supply :B. Bloem et al., Character Marketing communications