summary: The study builds on growing evidence that rhesus monkeys may be a good model for studying the social deficits associated with autism spectrum disorder.
Source: Florida Institute of Technology
New research builds on mounting evidence demonstrating the importance of rhesus macaques (Macaca mulatta) as a model for the underlying social impairments observed in autism spectrum disorder (ASD).
ASD is an early-onset neurodevelopmental condition characterized by persistent social contact and poor interaction. Despite its prevalence and societal cost, the underlying disease mechanisms remain poorly understood due in part to an over-reliance on rodent models, which lack the complex social and cognitive skills critical to modeling behavioral symptoms relevant to human autism.
Like humans, rhesus monkeys have complex cognitive abilities and display stable and pronounced individual differences in social functioning, making them a promising model to better understand the biological and behavioral mechanisms underlying social impairments.
“The social life of a Rhesus monkey is stable across time and associated with variability in initiating but not receiving prosocial behavior,” a study led by Associate Professor Catherine F. Talbot, Ph.D., in the School of Psychology at Florida Tech and researchers from Stanford University and the University of California, National Primate Research Center in Davis in California, showed that many aspects of social functioning differ between monkeys rated as low social compared to monkeys rated as highly social.
Analyzing three years of data from 95 male rhesus monkeys at the California National Primate Research Center in large outdoor social groups in semi-natural habitats, the team first classified the monkeys based on their normal social behaviour.
For example, they looked at whether the monkeys engaged in activities such as grooming, a behavior that facilitates social bonding in non-human primates, if they were in close proximity to or in contact with other individuals, or whether they were just lounging by themselves with no distractions. another person.
The monkeys that spent the most time alone were rated as low social, while the monkeys that spent the least time alone were rated as highly social. Next, the researchers evaluated the differences between the social communication profiles of these two groups of monkeys.
The team found that highly social monkeys initiate more prosocial behavior, which includes behaviors such as sitting in contact with others and grooming, compared to low social monkeys. However, there was no difference between the number of times low social and low social monkeys received prosocial behaviour.
“This suggests that there is this underlying social motivation factor, that we are experiencing higher social motivation as highly social monkeys, which doesn’t sound like rocket science, but supports the autistic social drive hypothesis, and provides insight into how this might be affected by underlying biology,” he said. Talbot.
“There are many theories or ideas about the causes of the social impairments observed in autism, and one of these theories is that individuals with autism have less social drive.”
This hypothesis suggests that people with autism spectrum disorder tend to have deficits in processing social rewards, which results in diminished social engagement and difficulty in promoting and maintaining social bonds. In other words, social interactions are not inherently rewarding.
The team also found that there was no difference in threat behavior between low social and social monkeys, both in initiating and receiving threats. This was contrary to their hypothesis, as they discovered that if low social monkeys did not communicate effectively with their peers, they were more likely to be bullied and suffer traumatic injuries, something they had discovered in previous research.
The results of the current study better describe this naturally low-occurring social phenotype and could help researchers gain mechanistic insight into the social stimulation deficits observed in people with autism.
“There hasn’t been a lot of work done to look at rhesus macaques as a model of ASD,” Talbot said.
“What we model is a naturally occurring social deficit. So, in humans, autism spectrum disorder is just a spectrum — and you see these traits distributed across all humans, not just the clinical population. People who might not be classified as being on the spectrum will also exhibit some of these traits.” “.
Individuals with autism spectrum disorder may also have deficits in other social cognitive skills such as theory of mind, which is recognizing that personal beliefs and knowledge are different from others.
Following eye gaze and understanding what another person is looking at is another component of theory of mind. An impaired ability to follow eye gaze is often one of the first behavioral signs seen in children with autism.
The team is also working on research looking at the basic biology of low social and high social monkeys and how this might relate to their performance on other social cognitive tasks, including how well the monkeys follow the gazes of their peers, and how well they do so. They interact with their peers, how well they recognize faces and how that compares to their performance in the non-social domain, such as how well they recognize objects.
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“The social life of rhesus monkeys is stable over time and is associated with variability in the initiation of social behaviour, but not its receptionWritten by Catherine F. Talbot et al. American Journal of Primatology
The social life of rhesus monkeys is stable over time and is associated with variability in the initiation of social behaviour, but not its reception
Rhesus monkeys and humans are highly social primates, yet both species display marked variability in social functioning, spanning a social spectrum.
The naturally occurring low social engagement in rhesus monkeys may be a promising construct with which to model social impairments relevant to human autism spectrum disorder (ASD), especially if a low social level is found to be stable across time and associated with diminished social motivation.
Thus, to better characterize the variance in sociability and sociability profiles, we performed quantitative assessments of social behavior on n= 95 male rhesus macaques (Macaca mulatta) in large outdoor groups.
In Study 1, we determined our subjects’ social rating by ranking their overall frequency of antisocial behaviour. Monkeys with a higher frequency of antisocial behavior were classified as having low social behavior (n= 20) and the monkeys with the lowest frequency of antisocial behavior were rated as highly social (n= 21).
To assess group differences in social communication profiles, in Study 2 we quantified rates of transient social communication cues, and whether these social cues were initiated or directed toward the focal subject.
Finally, in Study 3, we assessed the intra-individual stability of social communication in a subgroup of monkeys (n= 11 low social, n= 11 social high) two years after our initial observations.
The frequency of antisocial behavior correlated significantly across the two time points (Studies 1 and 3). Similarly, low versus high social rating accurately predicted rating two years later.
The low social monkeys initiated less positive social behavior than the high social monkeys, but the groups did not differ in receiving positive social behaviour, nor did they differ in threat behaviour.
These results indicate that sociality is a stable trait-like characteristic and that low sociality is associated with decreased initiation of prosocial behavior in rhesus macaques.
This evidence also suggests that low social contact may be a useful construct for gaining mechanistic insight into social motivational deficiencies often observed in people with autism.