Autism spectrum disorder research looks at monkeys as possible models

Overview: Study builds on mounting evidence suggesting rhesus macaques may be a good model to study social deficits associated with autism spectrum disorder.

Source: Florida Institute of Technology

New research builds on growing evidence showing the importance of rhesus macaques (Macaca mulatta) as a model for key social impairments seen in autism spectrum disorder (ASD).

ASD is an early-onset neurodevelopmental disorder characterized by persistent social communication and interaction disorders. Despite the prevalence and societal costs, the fundamental disease mechanisms remain poorly understood, in part because of the over-reliance on rodent models, which lack the complex social and cognitive skills critical for modeling behavioral symptoms relevant to human ASD.

Like humans, rhesus macaques have complex cognitive abilities and show stable and marked individual differences in social functioning, making them a promising model to better understand the biological and behavioral mechanisms underlying social impairments.

“Rhesus sociality is stable over time and linked to variation in the initiation but not the reception of prosocial behaviors,” a study by assistant professor Catherine F. Talbot, Ph.D., in the School of Psychology at Florida Tech and researchers at Stanford University and University of California, Davis’ California National Primate Research Center found that several aspects of social functioning differed between monkeys classified as low social compared to monkeys classified as high social.

Analyzing three years of data from 95 male rhesus macaques housed in large social outdoor groups in semi-naturalistic habitats at the California National Primate Research Center, the team first classified monkeys based on their natural social behavior.

For example, they looked at whether the monkeys participated in activities such as grooming, a behavior that promotes social bonding in non-human primates, or whether they were near or in contact with other individuals, or whether they were used to hanging out alone with no one else in sight. the neighbourhood.

Monkeys that spent the most time alone were classified as low social, while monkeys that spent the least time alone were classified 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 behaviors, which include behaviors such as socializing and grooming, compared to low social monkeys. However, there was no difference between how often low-social monkeys and high-social monkeys showed prosocial behavior.

“This suggests that there is an underlying social motivation factor, that we see higher social motivation as highly social monkeys, which doesn’t sound like rocket science, but it does support the social motivation hypothesis of ASD and provides insight into how this may be influenced by the underlying biology,” Talbot said.

“There are multiple theories or ideas about the causes of social impairments seen in autism and one of them is that individuals with ASD have lower social motivation.”

This hypothesis suggests that individuals with ASD tend to have deficits in social reward processing, leading to impaired social initiation and difficulties in nurturing 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 high-social monkeys, both in initiating and receiving threats. That ran counter to their hypothesis, in which they thought that if low-social monkeys don’t communicate effectively with their peers, they would be more likely to be bullied and sustain traumatic injuries, something they’ve found in previous research.

This shows rhesus monkeys
Like humans, rhesus macaques have complex cognitive abilities and show stable and marked individual differences in social functioning, making them a promising model to better understand the biological and behavioral mechanisms underlying social impairments. Credits: Kathy West

The findings of the current study better characterize this naturally occurring, low-social phenotype and may help researchers gain mechanistic insight into the social motivation deficits observed in people with ASD.

“There really hasn’t been much work looking at rhesus macaques as an ASD model,” Talbot said.

“What we model are naturally occurring social deficits. So in humans, autism spectrum disorder is just that — a spectrum — and you see these traits spread across the entire human population, not just the clinical population. People who may not be classified as being on the spectrum will exhibit some of these traits as well.

Individuals with ASD may also experience deficits in other social-cognitive skills, such as theory of mind, meaning that one’s own personal beliefs and knowledge are different from those of others.

Eye-catching and understanding what another person is looking at is another part of the theory of the mind. A reduced ability to follow gaze is often one of the first behavioral signs to emerge in children with ASD.

The team is also working to investigate the underlying biology of low-social and high-social monkeys and how this relates to their performance on other social-cognitive tasks, including how well the monkeys follow their peers’ gazes, how well they communicate with their peers, how well they identify faces and how that relates to their performance in the non-social domain, such as how well they identify objects.

About this autism research news

Writer: Press Office
Source: Florida Institute of Technology
Contact: Press Service – Florida Institute of Technology
Image: The image is credited to Kathy West

Original research: Closed access.
“Rhesus macaque sociality is stable over time and linked to variation in the initiation but not the reception of prosocial behaviors” by Catherine F. Talbot et al. American Journal of Primatology


Abstract

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Rhesus macaque sociality is stable over time and is associated with variation in the initiation, but not the reception, of prosocial behavior

Rhesus macaques and humans are highly social primates, but both species show marked variation in social functioning, spanning a spectrum of sociality.

Naturally occurring low sociality in rhesus macaques may be a promising construct to model social disorders relevant to human autism spectrum disorder (ASD), especially if low sociality appears to be stable over time and associated with reduced social motivation.

Thus, to better characterize variation in sociality and social communication profiles, we performed quantitative assessments of social behavior N= 95 male rhesus monkeys (Mulatto macaque) housed in large outdoor groups.

In Study 1, we determined the social classification of our subjects by ranking their overall frequency of non-social behavior. Monkeys with the greatest frequency of nonsocial behavior were classified as low social (n= 20) and monkeys with the lowest frequency of non-social behavior were classified as highly social (n= 21).

To assess group differences in social communication profiles, in study 2 we quantified the speed of transient social communication cues and whether these social cues were initiated by or directed to the central subject.

Finally, in study 3, we assessed the internal individual stability of sociality in a subgroup of monkeys (n= 11 low-social, n= 11 highly social) two years after our first observations.

Frequency of non-social behavior was significantly correlated between the two time points (Studies 1 and 3). Similarly, low-social versus high-social classification accurately predicted classification two years later.

Low-social monkeys initiated less prosocial behavior than high-social monkeys, but groups did not differ in reception of prosocial behavior, nor did they differ in threat behavior.

These findings indicate that sociality is a stable trait-like trait and that low sociality is associated with reduced initiation of prosocial behavior in rhesus macaques.

This evidence also suggests that low sociality may be a useful construct to gain mechanistic insight into the social motivation deficits commonly observed in individuals with ASD.

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