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Extra Synapses Found in Brains of Children with Autism

Date Published: 
August 25, 2014

Researchers have discovered an excessive number of synapses in the brains of some children and teens with autism, which they believe may help explain the disorder.

In studying the brains of people with autism who died, the scientists found that their brains did not "prune" excess synapses as much as did the brains of typically-developing people, resulting in too many synapses. Synapses on nerve cells enable the cells to pass signals to, or communicate with, other cells. Typically, as a child grows up, some of these synapses become unnecessary and disappear. But in the people with autism, that pruning of unnecessary synapses did not occur to the same degree that it did in people who didn't have autism.1

The study by scientists at Columbia University Medical Center was published online in the journal Neuron this month.2

The study said that a drug, rapamycin, can improve the pruning process, along with autistic behaviors, in mice. However, that drug has serious side effects that may prevent its use in people with autism spectrum disorder (ASD). Despite that, “the fact that we can see changes in behavior suggests that autism may still be treatable after a child is diagnosed, if we can find a better drug,” senior investigator David Sulzer, Ph.D., professor of neurobiology in the Departments of Psychiatry, Neurology, and Pharmacology at CUMC, said in a press release by CUMC.1

Many genes that have been linked to autism also can affect synapses, which has caused some scientists to believe that synapses play a role in autism.1 The researchers examined the brains of 26 people with autism from ages two to 20 who had died, and compared them to the brains of 22 children who did not have autism. Brain tissue came from the Harvard Brain Bank and the National Institute of Child Health and Human Development Brain and Tissue Bank in Maryland.

The researchers also studied mice with particular defects used to imitate autism. Mice with an overactive protein called mTOR were less able to prune away unnecessary synapses in their brains. In the future, researchers may be able to develop treatments that improve the pruning process in people with autism.1

This study received support from the Simons Foundation, the U.S. government, the Parkinson’s Disease Foundation, JPB Foundation and the American Heart Association.