Social brain: the neurons that decide which wins and which yields

Summary: The researchers have identified specific brain cells which control the way in which animals react to social defeat, thus offering a new overview of the biology of domination and submission. In male mice, it has been found that the neurons of the dorsomedial striatum, called cholinergic interneurons, regulate “the effect of the loser”, where past defeats lower the future social rank of an individual.

When these neurons were withdrawn, the mice stopped presenting submission behaviors after losing, even if their “winning effect” remained intact. The results reveal that separate brain circuits determine winning and losers behavior and could help explain the flexible social dynamics in humans.

Key facts:

• Neuronal basis of loss: The abolition of cholinergic interneurons blocked “the losing effect” in mice.
• Distinct circuits: Distinct brain roads govern the domination acquired between victory and defeat.
• Human parallels: Similar brain structures suggest that these discoveries could shed light on human social behavior.

Source: Oist

Social hierarchies are omnipresent: think of high school dramas, where athletes are presented as the most popular, or large companies, where the CEO makes important decisions.

Such hierarchies are not limited to humans, but extend to the whole animal kingdom, dominant individuals benefiting from faster access to food, a higher coupling priority and larger or larger territories.

Even if we have long thought that winning or losing could influence the position of an individual in a social hierarchy, the brain mechanisms at the origin of these social dynamics remain a mystery.

In iscienceResearchers from the Institute of Sciences and Technologies of Okinawa (OIST) study the neurological bases of the social hierarchy in male mice, by identifying the neurons they believe crucial to determine the dynamics of this social hierarchy.

“You may think that being dominant in the animal kingdom is a question of physical attributes, such as size. But it is interesting to note that we have found that this seems to be a choice, based on previous experience,” said Professor Jeffery Wickens, chief of the research unit in neurobiology at the OIST and co-author of this study.

“The brain circuits involved in these decisions are well preserved between mice and humans, there are therefore probably useful parallels to establish.”

Determination of social hierarchy in mice

The researchers used tube dominance tests to determine social structures within mouse groups. In these tests, mice are placed at the opposite ends of a tube and stand against each other, the most dominant mouse having priority.

Thanks to repeated tests over several days, they identified which mice were dominant and which were at the bottom of their social order in their cage, on the basis of victories or constant defeats in dominance tests.

They then twinned the mice, with dominant mice in different cages in competition against each other, as well as mice subordinate in competition against each other. Depending on the results of these competitions, the social status of mice in their cages changed.

“This is due to the effects of the winner and the loser,” said Dr. Mao-Ting Hsu, the main author of this article.

“Those who have the experience of winning become more dominant in future competitions, and those who lose become less dominant. In this study, we discovered that” the losing effect “can be attributed to the activity of certain brain cells, called cholinergic interneurons.”

The neuroscience of loss

Central gray nuclei is an area of ​​the best known brain in the context of the mechanisms and the treatment of Parkinson’s disease. But it also participates in the regulation of behavioral flexibility. This means that this influences the way we adapt to specific scenarios and the decisions we make in different conditions.

The central gray nuclei are divided into several components and inside one of them, the dorsomedial striatum, we find a group of brain cells called cholinergic interneurons, which have already been linked to this flexible decision.

To understand how these brain cells are involved in social hierarchies, researchers selectively removed these mice neurons and repeated dominance tests.

Surprisingly, the researchers discovered differences between the brain circuits to win and lose. The abolition of cholinergic interneurons disturbed “the effect of the loser”: the dominance of the mice has not decreased due to their past experiences of loss. But no change has been observed in the winning effect, which suggests that different brain circuits are involved in these social behaviors.

These results also suggest that the winning effect will probably be a learning process based on the reward, while the losing effect will probably be a decision -making process when animals are faced with different contexts or environments.

Human social dynamics

Although this study is limited to male mice, the results could shed light on human social behavior.

“Human social dynamics are obviously much more complex. The boss of a household can be at the bottom of the social classification at work, and the dominance behavior will change according to the situation,” noted Dr. Hsu.

“There is little evidence of the cerebral circuits involved in these flexible social behaviors in humans. However, similarities in the structure of the brain between mice and humans mean that these types of studies could help us to unlock future information on human social dynamics.”

Key questions answered:

About this research news in social neuroscience

Author: Tomomi Okubo
Source: Oist
Contact: Tomomi Okubo – Oist
Picture: The image is credited with Neuroscience News

Original search: Free access.
“The cholinergic interneurons of the dorsomedial striatum is dumbfiding the effects winning-perceiving on the dynamics of the social hierarchy in male mice” by Jeff Wickens et al. iscience

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Abstract

The cholinergic interneurons of the dorsomedial striatum dies of the winning-perdant effects on the dynamics of the social hierarchy in male mice

The establishment of a new social hierarchy involves flexible behavior to decide to be a winner or losing during competitions.

Neuronal circuits underlying such flexible behavior must still be fully understood, but previous research indicates that the cholinergic interneurons of the dorsomedial striatum play a role in behavioral flexibility.

We discovered, thanks to a series of dominance tests in tube, that losing (when dominant mice were defeated by mice of the same rank from another cage) led to a decrease in social rank in their original cage. Conversely, victory – by initially subordinate mice – led to an increased classification in the social hierarchy of domestic cages.

The losing effect on subsequent behavior in dominant mice was reduced after selective lesions of the cholinergic interneurons of the dorsomedial striatum.

We suggest that the loss produces these effects by modifying the activity of cholinergic interneurons and thus modulating synaptic plasticity in the neural circuits involved in flexible decision -making and positive strengthening.