Neuroscientists have discovered extra synapses in the brains of children and adolescents with autism. The excess is due to a slowdown in the normal brain “pruning” process during development, they say.
Because synapses are the points where neurons connect and communicate with each other, the excessive synapses may have profound effects on how the brain functions. The study appears online in the journal Neuron.
A drug that restores normal synaptic pruning can improve autistic-like behaviors in mice, the researchers found, even when the drug is given after the behaviors appear.
“This is an important finding that could lead to a novel and much-needed therapeutic strategy for autism,” says Jeffrey Lieberman, professor and chair of psychiatry at Columbia University Medical Center (CUMC) and director of the New York State Psychiatric Institute, who was not involved in the study.
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,” says the study’s senior investigator, David Sulzer, professor of neurobiology at CUMC.
During normal brain development, a burst of synapse formation occurs in infancy, particularly in the cortex, a region involved in autistic behaviors; pruning eliminates about half of these cortical synapses by late adolescence.
Scientists know that many genes linked to autism affect synapses, and some researchers have hypothesized that people with autism may have more synapses.