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Autism spectrum disorder research looks at monkeys as possible models

Autism spectrum disorder research looks at monkeys as possible models

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Summary: The study builds on growing evidence suggesting 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 growing evidence demonstrating the importance of rhesus macaque monkeys (Macaca mulatta) as a model for the core social impairments seen in autism spectrum disorder (ASD).

ASD is an early-onset neurodevelopmental condition characterized by persistent impairments in social communication and interaction. Despite its prevalence and societal costs, its underlying disease mechanisms remain poorly understood in part due to an overreliance on rodent models that lack the complex social and cognitive skills critical to modeling behavioral symptoms associated with human ASD.

Like humans, rhesus monkeys have complex cognitive abilities and show robust and distinct individual differences in social functioning, making them a promising model for better understanding the biological and behavioral mechanisms underlying social impairments.

“Rhesus monkey sociality is stable over time and is associated with variation in the initiation but not the adoption of prosocial behavior,” a study by Assistant Professor Catherine F. Talbot, Ph.D., in the School of Psychology at Florida Tech, and researchers from Stanford University and the University of California, Davis 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 monkeys housed at the California National Primate Research Center in large outdoor social groups in semi-naturalistic habitats, the team first classified the monkeys based on their natural social behavior.

For example, they looked at whether the monkeys engaged in activities such as grooming, a behavior that facilitates social bonding in non-human primates, or whether they were in close proximity or contact with other individuals, or if they were just hanging out alone with no one else around .

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. The researchers then assessed the differences between the social communication profiles of these two groups of monkeys.

The team found that the high-social monkeys initiated more prosocial behavior, which included behaviors such as sitting in contact with others and grooming, compared to the low-social monkeys. However, there was no difference between how often low-social monkeys and high-social monkeys received prosocial behavior.

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

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

This hypothesis suggests that individuals with ASD tend to have deficits in social reward processing, which causes reduced social initiative and difficulties in promoting and maintaining social relationships. 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, neither in initiating nor receiving threats. This was contrary to their hypothesis, which suggested that if low-social monkeys did not communicate effectively with their peers, they would be more likely to be bullied and suffer traumatic injuries, something they had found in previous research.

Like humans, rhesus monkeys have complex cognitive abilities and show robust and distinct individual differences in social functioning, making them a promising model for better understanding the biological and behavioral mechanisms underlying social impairments. Credit: Kathy West

Findings from 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 individuals with ASD.

“There really hasn’t been a lot of work done looking at rhesus macaques as a model of ASD,” Talbot said.

“What we are modeling are natural social deficits. So, in humans, autism spectrum disorder is just that—a spectrum—and you see these traits that are prevalent throughout the human population, not just the clinical population. People who may not be classified as on the spectrum will also exhibit some of these traits.

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

Tracking eye gaze and understanding what another person is looking at is another component of theory of mind. Impaired ability to track eye gaze is often one of the first behavioral signs to appear in children with ASD.

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 gaze of peers, how well they interact with peers, how well identify faces and how this compares to their performance in the non-social domain, such as how well they identify objects.

About this autism research news

Author: Press office
source: Florida Institute of Technology
Contact: Press Office – Florida Institute of Technology
Image: Image credited to Katy West

Original Research: Closed access.
Rhesus monkey sociality is stable over time and is associated with variation in initiation but not acquisition of prosocial behavior” by Catherine F. Talbot et al. American Journal of Primatology


Summary

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Autism spectrum disorder research looks at monkeys as possible models

Rhesus monkey sociality is stable over time and is associated with variation in initiation but not acquisition of prosocial behavior

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

Naturally occurring low sociability in rhesus monkeys may be a promising construct by which to model social impairments associated with autism spectrum disorder (ASD), particularly if low sociability is found 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 the social behavior of n= 95 male rhesus macaques (Mulatto macaque), housed in large groups outdoors.

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

To assess group differences in social communication profiles, in Study 2 we quantified the frequency of transient social communication cues and whether these social cues were initiated by or directed at the focal subject.

Finally, in Study 3, we assessed the intraindividual stability of sociality in a subgroup of monkeys (n= 11 low social, n= 11 highly social) two years after our initial observations.

Frequency of antisocial behavior 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 the groups did not differ in receiving prosocial behavior, nor did they differ in threat behavior.

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

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


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