The more our social relationships would be, the more certain structures of our brain would be developed. This is the hypothesis that has been the basis of several studies in neuroscience for several years. Researchers from Inserm and the universityLyon 1 within the Stem Cell and Brain Institute, in collaboration with the University of Pennsylvania, focused more specifically on a of macaques including is similar to that of humans.
By observing the animals in their natural state and analyzing images of their brains, they found that the number of companions of this non-human primate made it possible to predict the size of certain brain regions, particularly related to thesocial and the † The results of this study are published in the journal †
The connections between theand have been the subject of previous studies in the field of neuroscience. By for example, are already interested in the variation in the size of the amygdala of the human brain, according to the number of friends that an individual has. To complete this study and better understand the organization and functions of neural networks in humans, teams worked with an animal species with brain characteristics close to those of humans, namely rhesus.
Behavioral observations supported by scanners
In this new study, the team of researchers studied a group of thesenon-humans in their natural state and for several months before imaging their brains. Studying wildlife allowed them to grasp the social group in all its complexity. This allowed the scientists to measure the intensity of the interactions (number of interactions, cooperative or aggressive, and ) with other individuals or to identify the animal’s social hierarchical position within the group.
For example, some of the observations focused on grooming partners, who represent direct and important relationships for† In parallel with this behavioral observation work, the scientists analyzed the brains of the individuals in the group, which consisted of 103 including 68 adults and 21 juvenile macaques under the age of 6. They found that, in adults, the more the animal had a large number of companions, the more certain areas of the brain are located in the lobe. were of considerable size.
The more the animal had a significant number of companions, the larger certain brain regions in the temporal lobe were of significant size.
This is theanterior and the median portion of the superior temporal sulcus, which are considered essential to represent 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 brain structures, but rather they are put into place as they develop.
The brain evolves throughout life
Thus, according to the researchers’ observations, there would be no correlation between the size of the baby at birthand the 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 the birth of a very popular mother (who interacts a lot with the group) would have predisposed the newborn to become popular in On the contrary, our data suggests that the differences we observe in adults are strongly determined by our social environment, 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, to reveal the mechanisms at work when the brain regions identified using brain images enlarge.
Social networks increase the size of (part of) your brain!
To find out if a person has many friends, look at their Facebook profile or… their brain! Indeed, people with a large and complex social circle would have a significant increase in the volume of the tonsils.
Article by Claire Peltier, published January 4, 2011
Usedoes it mean you have a certain brain? A priori yes, according to Boston researchers. Special brain structures called are not only involved in emotions, but also necessary for the socialization of animal species. Indeed, this had been demonstrated thanks to previous studies based on comparisons of the brains of where the size of the tonsils was correlated with the mean number of individuals making up the group.
But if the amygdala therefore turns out to be important for the socialization of animals, does the size also differ between people 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 peopleand psychologically. To assess the complexity of these people’s social networks, the researchers used two variables: the first included the total number of people the volunteers had regular contact with, and the second indicated the number of different groups these contacts belonged to (family, colleagues, etc.).
An observation of the brain by MRI
The tonsils were then measured, usingobtained by imaging on magnetic ( ) then by computer reconstruction using programs developed at Harvard University (FreeSurfer). To serve as a control if a brain structure not involved in social networks, were also measured. To avoid variations due to the sizes of different the 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 age of the participant (the amygdala shrinks with age), and regardless of the amygdala considered (there is no lateralization), while the hippocampi were completely 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 involved in this increase.
Analyze better to act better
On the other hand, the measurement of otherand more particularly of the cortical thickness has made it possible to show that certain regions besides the amygdala are also correlated with the complexity of the social network. So the inferior temporal sulcus the gyrus caudally superior and the anterior subgenual cingulate are all significantly thicker than other parts of the cortex. These three regions are said to have evolved along 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 amygdala size and social network size within the same species. But in what sense does this relationship come about? Do larger tonsils favor social networks or, on the contrary, does actively visiting social networks increase the size of tonsils? The study published in the journaldon’t say it… What is certain is that the amygdala allows us, as social animals, to better understand our species, to establish strategies for better cooperation or competition.