Two subadult Rhesus macaques on Cayo Santiago in distance. They share a strong relationship bond. Credit: Dr. Lauren JN Brent
Scientists from Penn, Inserm, and elsewhere observed that the number of grooming partners an individual animal had anticipated the size of brain areas related to social decision-making and empathy.
Whats the link in between social life and brain structure? Scientists from the University of Pennsylvania, the Stem Cell and Brain Research Institute at Inserm, and in other places are now one action closer to comprehending this connection for rhesus macaques.
In work released in Science Advances today (April 13, 2022), the team discovered that for these nonhuman primates the number of social connections anticipated the size of key nodes in parts of the brain responsible for social decision-making and empathy. Particularly, the researchers determined that, for macaques with more grooming partners, the mid– superior temporal sulcus (STS) and ventral-dysgranular insula grew larger. They found no such link between brain structure and other variables like social status.
” For the very first time, were able to relate the complexity of social lives of a group of living primates with brain structure,” says Camille Testard, a fourth-year doctoral student in the Platt Labs at Penn and lead author of the paper.
Previous research on human social media networks has actually hinted at this relationship, says Michael Platt, the James S. Riepe Penn Integrates Knowledge University Professor. “The literature, for example, ties variation in the size of the amygdala to the variety of Facebook friends that you have. But its hard to get granular information on human social interactions since we cant follow individuals around all day,” he says.
With the rhesus macaques living on Cayo Santiago, an island off the coast of Puerto Rico, nevertheless, its a various story. Platt and colleagues have studied this group of free-ranging nonhuman primates for more than a decade. Part of that research study has concentrated on grooming partners, which represent crucial and direct relationships for the macaques, along with taking a look at the animals broader social networks, representing individuals they connect with indirectly.
After Hurricane Maria struck the island, for example, the researchers examined whether the macaques grew or shrunk their socials media in the face of more restricted resources. Testard, who signed up with the laboratory in 2018, led the analysis for that research study, which discovered that the animals ended up being more social and more accepting of one another, forming brand-new relationships in addition to those they already had.
Structure on that and on previous work from partner Jérôme Sallet of Inserm, Testard likewise designed the existing research study. Here, the team taped the in-depth interactions of a social group of 68 adult rhesus macaques on Cayo Santiago, then examined 5 elements: social status, number of grooming partners, physical range with other monkeys, connectedness to popular monkeys in the network, and what the scientists called “betweenness,” or the ability to serve as a bridge in between detached parts of the social network. They also collected brain scans for each person in the social group, including 35 juvenile and infant macaques.
Analyzing the adult data, Testard and colleagues found that the more grooming partners individuals had, the bigger their mid-STS and ventral-dysgranular insula were. “It was very intriguing to discover these regions, as their significance is understood for social cognition in human beings,” Sallet says. “We also identified the mid-STS area in another study showing that activity in this area is regulated by the predictability of others habits.”
One unforeseen finding centered around the infants. According to Testard and colleagues, the work showed that young macaques werent born with these distinctions in brain structure however, rather, the differences emerged with development.
You d think it would be composed into your brain when youre born, however it seems more likely to emerge from the patterns and interactions that you have,” Platt states. “Perhaps that suggests that if your mom is social and youve got the capability to be social, your brain can grow in the way that looks like the findings weve uncovered.
This negative result is telling, Sallet says. “If we had seen the same connection, it might indicate that if you are born from a popular mother then somehow you have a brain that predisposes you to become more popular later on in life. Rather, what I believe it suggests is that the modulation we observe is highly driven by our social environments, maybe more than by our innate predisposition.”
Though all these findings relate specifically to free-ranging rhesus macaques, they have possible implications for human behavior, in particular to understanding neurodevelopmental disorders like autism, according to Platt.
Such connections, nevertheless, are still in the distance. For now, the group is moving ahead with additional research study studying Cayo Santiagos population of macaques, looking at aspects like whether a natural catastrophe such as Hurricane Maria impacts the animals brain structure and how social connectedness affects long-term survival. Theyll continue to dive deeper into their latest findings, too.
This is genuine life, the genuine world,” Platt says. Its really exhilarating and rewarding that this work done in the field is synergizing work weve been doing in the lab for a long time.”
Recommendation: “Social connections forecast brain structure in a multidimensional free-ranging primate society” 13 April 2022, Science Advances.DOI: 10.1126/ sciadv.abl5794.
Funding for this research study came from the National Institutes of Health (grants R01MH118203, U01MH121260, R00AG051764, r01ag060931, and r01mh096875), the National Science Foundation (Grant 1800558), the Royal Society (Grant RGS/R1/191182), the National Center for Research Resources and the Office of Research Infrastructure Programs (Grant P40OD012217-25), the Blavatnik Family foundation, an IDEXLYON “IMPULSION 2020” grant (IDEX/ IMP/2020/14), and the Wellcome Centre for Integrative Neuroimaging (grants 203139/Z/16/ Z and WT101092MA).
Michael Platt is the James S. Riepe Penn Integrates Knowledge University Professor with visits in the Perelman School of Medicine, School of Arts & & Sciences, and Wharton School at the University of Pennsylvania.
Jérôme Sallet is a member of the Neurobiology of Executive Function team in the Stem Cell and Brain Research Institute at Inserm and a research study lecturer at the University of Oxford.
Camille Testard is a fourth-year doctoral student in the Neuroscience Graduate Group in the Perelman School of Medicine, a member of the Platt Labs at the University of Pennsylvania, and a Blavatnik Family Fellow.
In work released in Science Advances today (April 13, 2022), the team found that for these nonhuman primates the number of social connections forecasted the size of crucial nodes in parts of the brain responsible for social decision-making and empathy. Here, the group tape-recorded the in-depth interactions of a social group of 68 adult rhesus macaques on Cayo Santiago, then took a look at five elements: social status, number of grooming partners, physical distance with other monkeys, connectedness to popular monkeys in the network, and what the researchers called “betweenness,” or the ability to act as a bridge in between disconnected parts of the social network. They also collected brain scans for every person in the social group, including 35 infant and juvenile macaques.
“Perhaps that implies that if your mom is social and youve got the capability to be social, your brain can mature in the way that looks like the findings weve uncovered. For now, the group is moving ahead with extra research studying Cayo Santiagos population of macaques, looking at aspects like whether a natural disaster such as Hurricane Maria affects the animals brain structure and how social connectedness influences long-lasting survival.