Is this a breakthrough in the search for a cure for autism?
During normal brain development there is a burst of formation of synapses in infancy but these are later "pruned", halving the number by late adolescence. In children with autism this doesn't happen and so they are left with a surplus.
While there is a drug, rapamycin, that restores normal pruning – and, the researchers found, improved autistic-like behaviour in mice – it has side effects that mean it cannot be used in people with autism.
But that gives hope that a treatment might be found.
"The fact that we can see changes in behaviour suggests that autism may still be treatable after a child is diagnosed, if we can find a better drug," the study's senior investigator, David Sulzer, professor of neurobiology in the Departments of Psychiatry, Neurology, and Pharmacology at Columbia University Medical Center said.
The report's co-author Guomei Tang, assistant professor of neurology at CUMC, examined brains from children with autism who had died from other causes – 13 brains came from children ages two to nine, and 13 from children ages 13 to 20. Tang examined 22 brains from children for comparison.
By late childhood synapse density had dropped by about half in the control brains, but by only 16% in the brains from autism patients.
The study is published in the journal Neuron.