How the brain encodes social rank and ‘winning mindset’: In mice, one area of the brain is constantly tuned in to whether nearby animals are higher or lower in social hierarchy

If you’re reaching for the last piece of pizza at a party and at the same time see the other hand go for it, your next step probably depends on how you feel and whose hand it is. Your little sister – you can go ahead and have pizza. Your Boss – You’re probably more likely to back off and leave the piece. But if you’re hungry and feeling particularly confident, you can go for it.

Now, Salk researchers have entered the understanding of how the mammalian brain encodes social rank and uses this information to shape behavior – such as whether to fight for the last pizza slice. In rats engaged in a competition, the team found, patterns of brain activity varied depending on the social rank of the opposing animal. In addition, scientists could use brain readouts to accurately predict which animal would win a food reward—the winner was not always the more socially dominant animal, but engaged in a “winning mindset.” Conclusion. were published in Nature On 16 March 2022.

“Most social species organize themselves into hierarchies that guide each individual’s behavior,” says senior author Kay Tye, a professor at the Salk Systems Neurobiology Laboratory and a Howard Hughes Medical Institute Investigator. “Understanding how the brain mediates this can help us understand the interplay between social rank, isolation, and psychiatric diseases such as depression, anxiety, or even substance abuse.”

Researchers already knew that an area of ​​the brain called the medial prefrontal cortex (mPFC) was responsible for representing social rank in mammals; Changes in the mouse’s mPFC alter the dominance behavior of the animal. But it was unknown how the mPFC represented this information and which neurons (if any) were involved in changing dominance behavior.

In the new study, Ty and his team let groups of four rats share a cage, allowing a social hierarchy to develop naturally—some animals became more dominant and others more subordinate. Then, the researchers selected pairs of rats to compete for food prizes in a “round robin” tournament style structure.

To capture the brain activity of the animals, as well as the slight, difficult to measure differences in their behavior as they competed, led researchers to a number of new techniques. They used new wireless devices to record brain activity in free-roaming animals and developed a multi-animal artificial intelligence tracking device to follow the mice’s movements over time, even if the two animals looked alike. In the end, he turned to new modeling approaches to analyze the data.

As the rats were paired, the scientists found, the activity of neurons in their mPFC could predict — with 90 percent certainty — the rank of their opponent.

“We expected that animals could only indicate rank when they heard a beep to start a competition,” says co-first author Nancy Padilla-Coreno, an assistant professor at the University of Florida who worked while being a postdoctoral student. Companion at Salk. “But it turns out that animals are walking around with this representation of social rank in their brains all the time.”

When the researchers further asked whether the activity of mPFC neurons was associated with behavior, they found something surprising. Brain activity patterns were associated with minor changes in behavior, such as how fast the mouse moves, and they could also predict – 30 seconds before the start of the competition – which mouse would win the food reward.

While the more dominant mouse was usually predicted to win, sometimes the model accurately predicted that the subordinate animal would win. The model, the team says, was capturing competitive success, or what some might call a “winning mindset.”

Just as you may sometimes be in a more competitive mood and more likely to snag that pizza slice in front of your boss, a subordinate mouse may be in a more “winning mindset” than a more dominant animal. And may win in the end.

The regions of the mPFC associated with social rank and competitive success are closely related, the researchers discovered, and highly connected. Hints on social rank, they say, influence the state of the brain involved in competitive success. In other words, a subordinate animal’s confidence and “winning mindset” may be partially diminished when confronted with an alpha mouse.

“This is the first time we have been able to capture these internal states that link social rank to behavior,” says Kanha Batra, a graduate student in the TIE lab and a co-author of the paper. “At any given time, we can use these internal states to predict an animal’s next move from brain activity.”

The researchers also showed that changes in brain activity occurred when the animals were in competition when they were collecting rewards alone. However, the social rank of a surviving group of animals can still be decoded from brain activity, even when the animals are solitary.

“There is further evidence to suggest that we are in different brain states when we are alone than when we are with others,” says Tye, holder of the Wylie Vale Chair. “Regardless of who you are with, if you are aware of other people around you, your brain is using different neurons.”

Next, the scientists will investigate how and when animal representations of social rank first develop in the brain, as well as how other types of behavior are affected.

Other authors include Mackenzie Patrino, Sebastian B. Hausman, Risha Patel, Srishti Mishra, Darin O. Leduc, Jasmine Revanna, Hao Lee, Matilde Borio, Rachel Palmintuan, Anish Bal, Laurel R Keys, Avram Liebster, Romi Wichman, Fergil Mills. , Felix H. Tashbach and Gillian A. Matthews of Salk; Zhexin Chen, Hao-Shu Feng and Sewu Lu of Shanghai Jiao Tong University; Rachel R. Rock, Ruihan Zhang, Xavier C. Weddington and El R of Massachusetts Institute of Technology. fiat; Yu Eva Zhang of the University of California San Diego; and the University of Texas at Austin’s James P. Curly.

The work was supported by the Howard Hughes Medical Institute, the National Institutes of Health (R01-MH115920, Pioneer Awards DP1-AT009925 and K99 MH124435-01), the JPB Foundation, the Dolby Family Fund, the Kavli Foundation, the Simmons Center for the Social Brain and the Social Sciences. , Ford Foundation, L’Oreal for Women in Science, Burroughs Wellcome Fund, AI Institute, SJTU, Shanghai Qi Zi Institute and Meta Technology Group.

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