New Study Shows Autism May Be Caused by Inadequate Synaptic Pruning? How About Epilepsy?

An infant's brain is chock full of connections. The average one has many times more synapses per neuron than the typical adult's. It is with the pruning of those extra neurons that networks enabling specific functions emerge. A story in today's New York Times describes research, published Thursday in the journal Neuron,  suggesting that the brains of autistic children are failing to prune away synapses as aggressively as they should.

David Sulzer, at Columbia University Medical Center, analyzed tissue from the brains of 20 children who had died between the ages of 2 and 20. Ten of those children had autism. The other ten did not. Both groups had about the same number of synaptic connections when they were very young. By the time the non-autistic children turned 19, they had 41 percent fewer synapses than when they were infants. The children with autism had only 16 percent fewer synapses.

Sulzer and colleagues found the same trends in rat models. Administering a drug used to prevent organ transplant rejection, to rats caused their brains to restore normal levels of synaptic pruning.

From the Columbia University press release:

"Although the drug, rapamycin, has side effects that may preclude its use in people with autism, “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,” said the study’s senior investigator, David Sulzer, PhD, professor of neurobiology in the Departments of Psychiatry, Neurology, and Pharmacology at CUMC."

More than a third of kids with autism also have epilepsy, and it is thought that reduced synaptic pruning, and the neural over-excitation it may cause, could also play a key role in some forms of epilepsy. See my story about epilepsy and autism in Epilepsy USA. I'll investigate this further from the epilepsy researcher's point of view and report back soon.