The neural mechanism behind the stimulation

When a rat presses a lever to receive a reward, different groups of neurons in its brain are activated; Those depend on the specifics of the goal the mouse has in mind. Credit: Friedrich Mischer Institute for Biomedical Research

Our actions are driven by the goals we want to achieve. However, little is known about the mechanism in our brains that allows us to make the right decisions to reach our goals. Researchers in Lüthi’s lab have now determined the sequence of events that occur in the rat’s brain when the rat behaves a certain way to obtain a reward, and how it can adapt its behavior when the reward is not the expected reward.

Imagine that you go to a bakery every day to buy just a certain piece of bread. Then you discover that your favorite bread will not be sold there. I will stop going to this bakery. This is called goal-directed behavior, and the amygdala — the small almond-shaped emotion processing center in the brain — is known to be involved in controlling it.

So far, the role of the amygdala in mice has been investigated in so-called cue-guided behavior, when a visual or auditory cue (such as a sound) is an indication that something is going to happen (for example, the mouse will receive some sugar) and make the mouse behave in a certain way ( For example he will go to a place in the cage where he receives sugar). However, how the amygdala is involved in goal-directed behavior — when mice do something without cues, and at their own pace to achieve the goal — has been unclear.

In a study published in ScienceJulian Curtin, a postdoctoral researcher in Andreas Luthy’s group, trained mice on a goal-directed task: Over the course of several days, the animals learned that when they pushed one lever, they received a drop of sucrose, and when they pushed another lever, they received a drop of milk. Once the animals became expert at performing these tasks, Curtin adapted the experimental setup: He gave the mice the reward without having to press the lever; or having them hit the lever without reward; Or let the mice stuff themselves with a treat. During all of these different actions by the mice, Curtin recorded their brain activity in the amygdala and, in collaboration with Yael Petermann, a computational neuroscientist in Lüthi’s lab, developed new analytical methods to decode the underlying neurons.

prediction machine

Courtin and Petermann, co-first authors of the study, identified distinct groups (clusters) of neurons in the amygdala that are involved in different aspects of this goal-directed behavior. For example, they showed that a particular group of neurons was active when a mouse pressed lever 1 to anticipate reward 1. But once lever 1 was no longer associated with the reward, that group of neurons lost their activity. “The number of neurons was not active because the rat squeezed the lever, but because the lever was related to reward anticipation,” Courtin says. “When the mouse learned not to expect a reward anymore, these populations disappeared,” he adds.

Significantly, the results show that not only the type of reward, its magnitude and probability is represented in the amygdala, but also its value – a flexible parameter that depends on many factors (eg how hungry a mouse is). The amygdala sends all this information to other areas of the brain, which then use it to make appropriate decisions and adapt behavior according to potential rewards.

Andreas Lüthi explains: “By simply looking at the amygdala, Julian and Yale were able to get a detailed picture of the reward that the mouse expected, and what had to be done to get it. The amygdala makes predictions—if I did, I would understand—which is to adapt those predictions to changes.” No other brain structure can accurately predict what will happen.”

The importance of the human being

The researchers’ findings can easily be linked to human behavior. Every day we perform hundreds of procedures with certain expectations in mind. If expectations are not met, we adapt our behavior – do something different, or do it less or more. It is the same neural mechanisms in the amygdala that this study of mice highlights that underlie our behaviours.

The ability to adapt our behaviors based on expectations is essential for us as humans, but sometimes these processes are negatively affected, for example in addiction, depression, obsessive-compulsive disorder (OCD) or Parkinson’s disease. “In such circumstances, the behavioral sequences in the brain that we’ve demonstrated may not be regulated correctly,” Courtin says. “This could become a vehicle for clinical research, and the challenge is: How do we interfere with a process that has gone awry in the brain when it occurs in such a short period of time?”


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more information:
Courtin et al., A Neural Mechanism for Incentive Control of Behavior, Science (2022). DOI: 10.1126 / science.abg7277

Submitted by the Friedrich Mischer Institute for Biomedical Research

the quote: The Neural Mechanism Behind Stimulation (2022, January 7) Retrieved on January 13, 2022 from https://phys.org/news/2022-01-neuronal-mechanism.html

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