New
research in mice has identified neurons in the brain that influence competitive
interactions between individuals and that play a critical role in shaping the social
behavior of groups. Published in Nature by a team led by
investigators at Massachusetts General Hospital (MGH), the findings will be
useful not only for scientists interested in human interactions but also for
those who study neurocognitive conditions such as autism spectrum disorder and
schizophrenia that are characterized by altered social behavior.
"Social interactions in humans and animals occur most
commonly in large groups, and these group interactions play a prominent role in
sociology, ecology, psychology, economics and political science," says
lead author S. William Li, an MD/PhD student at MGH. "What processes in
the brain drive the complex dynamic behavior of social groups remains poorly
understood, in part because most neuroscience research thus far has focused on
the behaviors of pairs of individuals interacting alone. Here, we were able to
study the behavior of groups by developing a paradigm in which large cohorts of
mice were wirelessly tracked across thousands of unique competitive group
interactions."
Li and his colleagues found that the animals' social ranking in
the group was closely linked to the results of competition, and by examining
recordings from neurons in the brains of mice in real time, the team discovered
that neurons in the anterior cingulate region of the brain store this social
ranking information to inform upcoming decisions.
"Collectively, these neurons held remarkably detailed
representations of the group's behavior and their dynamics as the animals
competed together for food, in addition to information about the resources
available and the outcome of their past interactions," explains senior
author Ziv M. Williams, MD, a neurosurgical oncologist at MGH. "Together,
these neurons could even predict the animal's own future success well before
competition onset, meaning that they likely drove the animals' competitive
behavior based on whom they interacted with."
Manipulating the activity of these neurons, on the other hand,
could artificially increase or decrease an animal's competitive effort and
therefore control their ability to successfully compete against others.
"In other words, we could tune up and down the animal's competitive drive
and do so selectively without affecting other aspects of their behavior such as
simple speed or motivation," says Williams.
The findings indicate that competitive success is not simply a
product of an animal's physical fitness or strength, but rather, is strongly
influenced by signals in the brain that affect competitive drive. "These
unique neurons are able to integrate information about the individual's
environment, social group settings, and reward resources to calculate how to
best behave under specific conditions," says Li.
In addition to providing insights into group behavior and competition
in different sociologic or economic situations and other settings, identifying
the neurons that control these characteristics may help scientists design
experiments to better understand scenarios in which the brain is wired
differently. "Many conditions manifest in aberrant social behavior that
spans many dimensions, including one's ability to understand social norms and
to display actions that may fit the dynamical structure of social groups,"
says Williams. "Developing an understanding of group behavior and
competition holds relevance to these neurocognitive disorders, but until now,
how this happens in the brain has largely remained unexplored."
Additional co-authors include Omer Zeliger, Leah Strahs,
Raymundo Báez-Mendoza, Lance M. Johnson, and Adian McDonald Wojciechowski.
Funding for this research was provided by the National
Institutes of Health, the Autism Science Foundation, an MGH-ECOR Fund for
Medical Discovery Fellowship, and a NARSAD Young Investigator Grant from the
Brain & Behavior Research Foundation.
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Source:
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In mice, social ranking in a group was linked to the
results of competition, and certain neurons in the brain stored this social
ranking information to inform decisions. Manipulating the activity of these
neurons could increase or decrease an animal's competitive effort and therefore
control their ability to successfully compete against others.