A quarterly publication of the Autism Research Institute

The Autism Research Review International is quarterly publication of the Autism Research Institute

Spring, 2021 | Number 2, Volume 35

Study offers insights into motor delays in children with ASD

Children with autism spectrum disorders (ASD) exhibit delays in learning motor skills, and a new study points to one possible cause of this problem. 

Xuming Yin and colleagues studied mice missing one copy of a chromosome region called 16p11.2. This deletion is also seen in many individuals with autism. (See related article on page 4.) 

The researchers put normal mice and mice with the 16p11.2 deletion through two tests of motor learning. In one, the mice had to balance on the top of a rotating rod. In the other, they had to spin a disk with their feet. 

The researchers found that both groups of mice eventually mastered the tasks, but it took the 16p11.2 mice significantly longer. In addition, they found that in mice with the deletion, reduced amounts of the neurotransmitter noradrenaline were released into the primary motor cortex of the brain during learning. 

The researchers determined that the deficit in noradrenaline originated in a separate region of the brain called the locus coeruleus. Examining the brains of the mice, they found that compared to control mice, the 16p11.2 mice had fewer axons extending from the locus coeruleus into the motor cortex. 

Senior study author Simon Chen says, “The locus coeruleus is the area in the brain that releases noradrenaline—or adrenaline—which makes you more alert. In the mouse model of autism, we found that in the motor cortex there is a lack of adrenaline’s innervation to the area which caused them to have delayed motor learning.” 

Chen says, “The implication is similar for kids with autism. They normally behave the same whether reaching to grab something or playing ball or catch—they learn at a slower pace compared to kids of the same age, which could cause them to feel more distant and perhaps prefer not to play with them.” 

He adds, “With autistic kids, we sometimes think that an aspect of this delayed motor learning is a result of social deficits and dysfunction: that they simply don’t want to play with the other kids. But it might be because they’re learning how to play these games slower than the other kids, which is why they’re distancing themselves from them.” 

The researchers also found that neurons in the motor cortex of the 16p11.2 mice were more active during the initial stages of learning, and that there was a delay in removing unnecessary synapses in the motor cortex while forming new ones. Chen says, “When you are not removing the unnecessary synapses (old memories) you have higher noise, and we think the brain doesn’t know what signal to process because of its delay of removing the unnecessary synapses.” 

He adds, “Think of it as you and I go play golf and we hit the ball many times. With a good signal-to-noise ratio in the brain, I will remember the movement when I hit the ball far. But if I have high noise and low signal-to-noise ratio, I’ll hit the ball many times without knowing which movement is good for me, meaning it will take me longer to differentiate what’s the right movement for a good golf swing.” 

The researchers also found that boosting noradrenaline in the motor cortex successfully reestablished motor learning in the mice. This finding, Chen suggests, could possibly lead someday to treatments to help children with ASD learn motor skills more easily.

Chen and colleagues found that in mice with the 16p11.2 deletion, significantly less noradrenaline was released into the primary motor cortex during learning

Citations

“Delayed motor learning in a 16p11.2 deletion mouse model of autism is rescued by locus coeruleus activation,” Xuming Yin, Nathaniel Jones, Jungwoo Yang, Nabil Asraoui, Marie-Eve Mathieu, Liwen Cai, and Simon X. Chen, Nature Neuroscience, March 22, 2021 (online). Address: Simon Chen, [email protected]

—and— 

“Researchers close in on root of slow motor learning in autism,” news release, University of Ottawa, March 22, 2021. 

—and— 

“Circuit flaw underlies motor learning issues in autism mouse model,” Peter Hess, Spectrum News, April 12, 2021.