Children with autism 'have too many synapses in their brain'

A new study by researchers from the Columbia University Medical Center in New York, NY, finds that children and adolescents with autism have too many synapses in their brain, which can affect their brain function. Furthermore, the team believes it may be possible to reduce this excess synapse formation with a drug, paving the way for a novel autism treatment strategy.

Around 1 in 68 children in the US have autism - a developmental condition characterized by behavioral, social and communication problems.

Exactly what causes autism is unclear, but researchers believe that it is triggered by abnormalities in the structure of the brain that stop it from functioning properly.

In this latest study, published in the journal Neuron, co-author Guomei Tang, PhD, assistant professor of neurology at Columbia University Medical Center (CUMC), analyzed 26 brains of children and adolescents with autism who had died from other causes, alongside 22 brains of children without autism.

Of the brains from those with autism, 13 came from children aged 2-9 years, while the remaining 13 came from teenagers aged 13-20 years.

Dr. Tang then assessed synapse density in each of the brains by counting how many tiny "spines" extended from them. The researchers note that synapses are where brain cells connect and communicate with each other. Each of the spines connects with a brain cell through a synapse.
Brain cells unable to 'eat' unwanted components

She found that in the brains of individuals without autism, the number of spines had reduced by almost 50% by late childhood. However, the number of spines in the brains of those with autism had only reduced by 16% by late childhood.

Further investigation revealed that the brains of children with autism possessed neurons that consisted of old and damaged components, and showed deficiency in a pathway known as autophagy - a route that cells use to "eat" their own parts.

This may explain why the brains of autistic children had higher spine density - unwanted synapse connections had not been degraded.

Commenting on this finding, senior study investigator Dr. David Sulzer, professor of neurobiology in the Departments of Psychiatry, Neurology and Pharmacology at CUMC, says:

"It's the first time that anyone has looked for, and seen, a lack of pruning during development of children with autism, although lower numbers of synapses in some brain areas have been detected in brains from older patients and in mice with autistic-like behaviors." Rapamycin restored autophagy, reversed autism symptoms in mice

The research team then analyzed mouse models of autism and found that the lack of "pruning" is down to overactivity in a protein called mTOR.