Autism is a disease that is still very much a puzzle to scientists, but progress is ongoing.
Most recently, researchers have found that children and adolescents with autism have more synapses than normal in the brain as a result of a slowdown in the brain's pruning mechanism during development.
In the study published in Neuron, researchers at Columbia University Medical Center found that these excess synapses are typically in areas where the neurons connect and communicate and they have a profound effect on how the brain functions.
Researchers also found a drug that could help restore normal pruning at these sites. Unfortunately, the current drug, rapamycin, has side effects that may affect many autistic patients. However, study authors remain optimistic.
"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 David Sulzer, senior investigator for the study.
Researchers have hypothesized that children with autism have more synapses in their brain area. In normal development, there is a surge of synaptic formation during infancy, but over the course of childhood into late adolescence, about half of these synapses are pruned.
In the study, 26 brains from children with autism who died of other causes were examined. Thirteen of the brains came from children ages 2 to 9 while the other 13 came from children ages 13-20. Researchers also examined the brains of 22 other children without autism for comparison.
The number of synapses was counted by looking for the tiny spines that branch from the cortical neurons. In the control brains, researchers found that the number of synapses dropped to about half in non-autistic cases, while the autistic cases only saw a 16 percent drop.
Study co-author Guomei Tang found that the answer to why there are so many more synapses can be found in deficiencies in the brain's autophagy degradation pathway. This pathway is used by cells to degrade their own components.
The study authors used mouse models to examine mTor, the protein responsible for the pruning defect. When the protein is overactive, the brain cells are not pruned appropriately.
When scientists administered rapamycin, the mice showed a reversal in autistic-like behaviors.
