Social networks and brain size are linked

The more our social relationships would be, the more certain structures of our brain would be developed. This is the hypothesis at the heart of several research works in neuroscience for several years. Researchers from Inserm and the university Claude Bernard Lyon 1 within the Stem Cell and Brain Institute, in collaboration with the University of Pennsylvania, focused more specifically on a species of macaques including brain architecture is comparable to that of humans.

By observing the animals in their natural state and analyzing images of their brains, they discovered that the number of companions of this non-human primate made it possible to predict the size of certain areas of its brain, which are notably associated with the cognition social and theempathy. The results of this study are published in the journal Science Advances.

The links between the social network and brain size have been the subject of previous studies in the field of neuroscience. From scientists have for example already been interested in the variation in the size of the amygdala of the human brain, according to the number of friends Facebook that an individual has. To complete this research and try to better understand the organization and functions of neural networks in humans, teams have worked with an animal species with brain characteristics close to those of humans, namely macaques rhesus.

Behavioral observations supported by scanners

In this new study, the team of researchers studied a group of these primates non-humans in their natural state and for several months before imaging their brains. The fact of studying animals in the wild allowed them to apprehend the social group in all its complexity. The scientists were thus able to measure the intensity of the interactions (number of interactions, cooperative or aggressive, and duration) with other individuals or to identify the social hierarchical position of the animal within the group.

Part of the observations focused, for example, on grooming partners, which represent direct and important relationships for macaques. In parallel with this behavioral observation work, the scientists analyzed the scanners brains of the individuals in the group, which consisted of 103 rhesus macaques including 68 adults and 21 young macaques under 6 years old. They discovered that, in adults, the more the animal had a large number of companions, the more certain regions of its brain located in the lobe temporal were of significant size.

This is theisland anterior and the median part of the superior temporal sulcus which are regions considered essential to represent the emotions and the perception of the behavior of others. To better understand how this phenomenon takes place, the scientists were also able to collect the brain scans of 21 young newborn macaques. The work has shown that they are not born with these differences in the size of the cerebral structures but that they are put in place during their development.

The brain evolves throughout life

According to the researchers’ observations, there would therefore be no correlation at birth between the size of the social network and the volume of the brain. These results suggest that exposure to the social environment during life contributes to the maturation of brain networks.

“This aspect is interesting, because if we had observed the same correlation in young macaques, it could have meant that being born to a very popular mother (having a lot of interaction with the group), could have predisposed the newborn to become popular in turn. On the contrary, our data suggest that the differences we observe in adults would be strongly determined by our social environments, perhaps more than our innate predisposition.” explains Jérôme Sallet, research director at Inserm.

As a result of this study, the researchers now want to study anatomical changes at the cellular level, in order to reveal the mechanisms at work when the brain areas identified using brain imaging increase in size.

Social networks increase the size of (part of) your brain!

To find out if a person has a lot of friends, look at their Facebook profile or… their brain! People with a large and complex social circle would indeed have a significant increase in the volume of the tonsils.

Article by Claire Peltier, published on January 4, 2011

Utilize Facebook does it imply having a particular brain? A priori yes, according to researchers from Boston. Particular brain structures named tonsils, in addition to being involved in emotions, are also required for the socialization of animal species. Indeed, this had been shown thanks to previous studies based on comparisons of the brains of non-human primates where the size of the tonsils was correlated with the average number of individuals making up the group.

But if the amygdala therefore appears to be important for animal socialization, does its size also differ among humans depending on their social network? Researchers from the Northeastern University in Boston were interested in the question and chose to answer it by observing the size of the tonsils of 58 healthy adult people physical and psychological. To assess the complexity of the social networks of these people, the researchers used two variables: the first comprising the overall number of people with whom the volunteers had regular contact, and the second indicating the number of different groups to which these contacts belonged ( family, colleagues, etc.).

An observation of the brain by MRI

The tonsils were then measured, using brain pictures obtained by imaging at resonance magnetic (MRI) then by computer reconstruction using programs developed at Harvard University (FreeSurfer). To serve as a control as a brain structure not involved in social networks, the seahorses were also measured. To avoid variations due to the sizes of different cranial boxesthe measured volume of the structures was related to the total brain volume.

Linear regression analyzes showed that people with larger and more complex social networks had greater amygdala volume. This finding could be established regardless of the participant’s age (the tonsils shrink with age), and regardless of the amygdala considered (there is no lateralization), while the hippocampi were totally independent. the complexity of the social network.

Conversely, amygdala size was not related to other parameters such as life satisfaction, or perceived social support, indicating that the happiness of having friends is not implicated in this increase. tonsil volume.

Analyze better to act better

On the other hand, the measurement of other brain areas and more particularly of the cortical thickness has made it possible to show that certain regions in addition to the amygdala are also correlated with the complexity of the social network. Thus, the inferior temporal sulcus caudalthe gyrus frontal caudal superior and the cortex anterior subgenual cingulate are all three significantly thicker than other parts of the cortex. These three regions would have evolved together with the amygdala to ensure the management of a complex social network.

According to the authors, this would be the first demonstration of a correlation between the size of the amygdala and the size of the social network within the same species. But in what sense is this relationship established? Do bigger tonsils favor social networks or, on the contrary, does the active frequentation of social networks increase the size of the tonsils? The study published in the journal Nature Neuroscience does not say it… What is certain is that the amygdala allow us, as social animals, to better understand our congeners, in order to establish strategies for better cooperating or entering into competition.