Some autistic children appear to have fewer "mirror neuron" cells in the brain, according to a new study. These neurons control learning and empathy through observation, French news agency AFP reports.

A new study from Children's Hospital of Philadelphia relied on a diffusion tensor imaging technique to track water molecules in the brains of autistic children.

Researchers found that the inability of children with autism to relate to people and real-life situations may be the result of an abnormally functioning mirror neuron system.

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The study also found autistic children often have increased gray matter in their brains, which usually means higher intelligence. However, this is not the case with autistic children, said Dr. Manzar Ashtari of the Children's Hospital of Philadelphia.

"In the autistic brain, increased gray matter does not correspond to IQ, because this gray matter is not functioning properly," he said at a meeting of the Radiological Society of North America (RSNA).