Social Behavior: How Does Your Brain Determine How Many People Are Comfortable for You?

Some people are really comfortable hanging out in large groups of people where everyone knows everyone else. They have a lot of friends and impressive social connections. And some people know two or three people and feel comfortable with them, even if their names are Tyler Durden and Marla Singer. But why do we choose a specific circle of acquaintances, and how is social behavior tied to brain biology?

It just so happens that the once “subtle” or “divine” aspects of our personality turned out to be conditioned by nothing more than neurohormonal balance or hard work. Knowledge, skills and abilities can be developed and improved. And if you choose the right fuel, then doing this is incredibly effective. Read more about learning methods, the work of the brain and consciousness – tell community materials. Subscribe to stay up to date with new articles!

Neural connections and social behavior

Scientists have focused on studying the brain connections that enable spiny mice to live in large groups. Current Biology published work led by researchers at Emory University, the study shows how connections between the anterior cingulate cortex and the lateral septum mediate the tendency of spiny mice (A comys) to form large groups.

To our knowledge, this is the first study to identify the neural network that mediates group size preferences in mammals. We hope that our work will pave the way for new insights into complex social behavior in a range of mammals, including humans. Especially since a colony of spiny mice is not just one big family. It’s like a miniature society.

Aubrey Kelly, the study's senior author, is an associate professor of psychology at Emory.

Unlike rats and mice, which are commonly used in lab research, spiny mice have evolved to live in large, mixed groups in the wild. They even allow unrelated newcomers to join their “community.”

Social behavior in mammals and the difficulties of studying it

It was challenging but fun to design experiments and test our methods in a species new to social neuroscience. I really enjoyed working with spiny mice. They have a very different temperament than other lab rodents I've worked with. They don't show as much fear or aggression toward each other or even toward people.

Brandon Fricker, the study's first author, is a postdoctoral fellow at Harvard University.

Despite the prevalence of communal living in the animal kingdom—from ants to birds to humans—methods for studying the neural mechanisms that underlie group living are lacking.

One of the main limitations is that the species of rats and mice commonly used in laboratory research do not do well in large mixed groups. In the wild, for example, the classical laboratory rat Rattus norvegicus domestica Lives mostly in groups of one male and several females. When males get together, they tend to fight.

Steppe vole — a small, mouse-like rodent that mates with a partner for life. In recent decades, the species has become an excellent laboratory model for studying the neurobiology of pair bonding. However, although they are notable for their lifelong family bonds, wild prairie voles live in small groups and are quite aggressive toward strangers.

Where to look for animals whose social behavior is similar to humans?

Aubrey Kelly, a PhD candidate in evolutionary biology, was investigating the neural evolution of flocking behavior in birds using several species of finches, ranging from solitary to highly social. She wanted to study group-living in mammals, but was faced with a lack of suitable animal models.

It is important to consider how an animal behaves in the real world before trying to understand how its brain works. You need to find an animal equivalent to your query.

Aubrey Kelly, the study's senior author, is an associate professor of psychology at Emory.

Kelly first heard about spiny mice from a casual conversation with Ashley Seifert, a biology professor at the University of Kentucky and a co-author of the study.

The spiny mouse and prosocial behavior

More than a decade ago, scientists learned that the spiny mouse, which lives in arid regions of Africa, the Middle East, and South Asia, has remarkable wound-healing abilities, including the ability to regenerate large swaths of tissue. If a predator grabs a spiny mouse, its skin will rip or peel off, allowing the mouse to escape. The mouse then regenerates its skin, growing a coat of stiff, spiny hairs.

Research has also shown that the spiny mouse has unique adaptive responses to damage to the heart, kidneys, and spinal cord. Similar lability is also evident in the mice's social behavior.

Ashley Seifert is among a growing number of scientists using spiny mice as a biomedical model for regeneration research. Spiny mice have also recently emerged as a model for type 2 diabetes research. And several labs have published work on the prosocial behavior and developmental features of spiny mice.

Adaptability to regeneration and adaptability to socialization

Brandon Fricker came to Emory as a graduate student five years ago, shortly after Kelly launched her lab's spiny mouse program. As a graduate student, he was intrigued by the new approach.

I'm really interested in the neuroscience of social behavior. How do neurons respond to stimuli from other individuals that we encounter and then signal how we should respond? Understanding this is important for both our survival and our emotional well-being. It's like the first day of school, when you're under a lot of pressure to make friends. Misinterpreting what's happening is not ideal.

Brandon Fricker, the study's first author, is a postdoctoral fellow at Harvard University.

In the next step, the researchers characterized the social behavior of spiny mice in a laboratory setting. They found that, regardless of familiarity, spiny mice quickly bond with peers, demonstrating high social boldness. They are much more prosocial with each other than aggressive. At the same time, spiny mice also prefer to be in large groups rather than small ones.

Neural Circuitry of Prosocial Behavior

In the current work, the above-mentioned scientists set out to identify the neural circuitry underlying the spiny mouse's drive to organize into large groups.

In one experiment, the researchers allowed mice to organize themselves into large and small groups. The scientists then scanned the subjects’ brains to detect expression of a protein called Fos, a product of neuronal activation. This neuroscience technique showed that activity in the lateral septum (LS) region of the brain was higher in spiny mice that were in large groups and exhibited social behavior. The LS is active = the individual likes large groups and is comfortable in them.

The lateral septum is well known to be involved in various forms of social behavior. In previous studies, Kelly found that this brain region is associated with flocking behavior in zebra finches.

This area of ​​the brain can be involved in a variety of different things, from aggression to pack behavior, depending on how it interacts with other areas. As technology advances, neuroscience is moving beyond studying individual areas of the brain and is beginning to study the connections between different areas.

Aubrey Kelly, the study's senior author, is an associate professor of psychology at Emory.

Delving into Brain Function and Social Behavior

To identify the neural pathways responsible for the tendency to choose large groups, the researchers repeated the previous experiment by adding neural tracers to the subjects. These chemical probes, similar to those used in the study serotonin expression in depressiondisplay the source of the signal and the direction in which it is propagating.

The results showed a stronger signal from the anterior cingulate cortex (ACC) to the lateral cortex (LC) in spiny mice, which prefer to live in larger groups. Previous work has linked ACC activity to consolation and other social behaviors in prairie mice. In humans, the ACC is involved in attentional control, decision making, and emotional control.

The researchers then conducted experiments using chemogenetic tools that allowed them to temporarily disable the PPC-to-LC circuit. The results showed that when this circuit was disabled, female spiny mice did not care about group size, but males changed their preferences and became sigma-hican mice. Choosing the proud path of loners, minimizing social behavior.

I was surprised to see how much of a change in behavior was caused by disabling this circuit. This shows that the ACC-LS circuit has a large influence on group size preferences.

Brandon Fricker, the study's first author, is a postdoctoral fellow at Harvard University.

Detailing social behavior and working with the shutdown of neural networks in the brain

Co-author Malvika Murugan, an associate professor in Emory University's Department of Biology and an expert in viral chemogenetic methods for neuroscience, helped edit the study of social behavior in spiny mice.

The researchers used inanimate objects in the form of rubber ducks to test whether the ACC-LC connection promotes specific social preferences or simply a tendency to choose large groups of any objects. While all spiny mice prefer to be among large groups of rubber ducks, manipulating this brain circuit had no effect on preference for rubber ducks.

This indeed showed that the neural circuit we identified modulates preferences for social group size rather than abstract sets of objects.

Brandon Fricker, the study's first author, is a postdoctoral fellow at Harvard University.

Based on this, scientists are preparing a wide range of studies on the social behavior of mammals, using the spiny mouse model as a basis.

We aim to collect more behaviorally rich data sets by allowing spiny mice to interact freely with each other in large groups and analyze their brain activity. This will give us a better understanding of how neural activity manifests itself in complex, dynamic, social behavior.

Aubrey Kelly, the study's senior author, is an associate professor of psychology at Emory.

Among the questions she wants to study are what factors promote group cohesion and what are the critical environmental points that lead to group breakdown and selfish behavior.

Studying the evolution of the social brain can provide insight into how our own brains facilitate socializing in groups. What brain circuitry is involved in welcoming a newcomer, or cooperating and sharing food when resources are depleted?

Aubrey Kelly, the study's senior author, is an associate professor of psychology at Emory.

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