Social deficits attract so much attention in the study of autism spectrum disorder, it’s easy to forget there are motor learning deficits during early childhood as well. For kids hoping to throw a ball around the schoolyard and connect with classmates, these physical skill differences can isolate a child further.
In a new study published today in Nature Neuroscience, researchers have closed in on the neurological underpinnings of the motor delay. Dr. Simon Chen’s lab used a mouse model of autism to demonstrate a shortage in the amount of the neurotransmitter noradrenaline being released into the brain’s primary motor cortex. The problem seems to originate some distance away in an area of the hindbrain called the locus coeruleus, which is known as a centre of motivation, alertness and attention.
The experiments hinged on a running task that the 16p11.2 deletion (autism model) mice as well as wild-type mice had to learn.
“Mice like to run. It’s hard for them to sit still. Instead of a running wheel, we measured how long it took them to learn how to run on a rotating disk,” says Dr. Chen, assistant professor in the Department of Cellular and Molecular Medicine and Canada Research Chair in Neural Circuits in Behaviour.
The 16p11.2 deletion mice were slower to learn, but the researchers were able to remedy that difference by activating the locus coeruleus’ signals to the motor cortex, boosting the amount of noradrenaline received in the area responsible for movement.
Another pattern emerged that could help explain the learning problem. While lots of connections were strengthened during the learning phase in the motor cortex of 16p11.2 deletion mice, not as many were then winnowed away to refine the memory due to the abnormally high neuronal activity. Dr. Chen says that forgetting unnecessary information is crucial to forming a usable memory.
“If I go and play a round of golf in the fog and don’t have a clear sense of where the ball goes when I swing, I’ll be much slower to differentiate the right movement and develop a good golf swing,” says Dr. Chen.
The next question Dr. Chen’s team will address will be whether the difference is down to something happening in the locus coeruleus, or a problem with the motor cortex itself. Meanwhile, they keep their eyes fixed squarely on the eventual goal of the research, which is to help autistic children learn motor skills faster to compensate for some of their social deficits.
“We already know that other kids with slower motor skill learning avoid participating in gym class,” says Dr. Chen. “The take-home message is that kids with autism tend to show this delay in motor learning, and when it seems like they don’t want to play with neurotypical kids, many doctors are saying it could be due to slower learning of these physical skills.”
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