Five of the faces children observed and imitated. Courtesy of UCLA
Happy people make people happy, sad people make people sad, and tense, anxious, twitchy people are nearly impossible to tolerate. These reactions stem from our knack for empathizing with people. However, individuals with autism don't have this automatic, empathetic response to emotion. A team of UCLA researchers thinks it knows why.
According to a recent paper in Nature Neuroscience, children with autism have virtually no activity in their brain's mirror neuron system, the apparatus that facilitates imitation and empathy. The researchers believe this malfunction may be the primary cause of autism.
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"I think that, unlike previous theories, a mirror neuron theory of autism does a pretty good job at accounting for all major symptoms of autism," lead author Mirella Dapretto said via e-mail.
According to coauthor Marco Iacoboni, if poor mirror neuron system development is the cause of autism, it may be possible to treat the disorder with therapies that rely on imitation, as they engage and activate the system.
"Some of the most successful interventions already out there do seem to capitalize on strategies that could bring this system 'online,'" Dapretto said. "We hope these new findings will lead to greater emphasis on these strategies in future interventions."
The researchers used functional MRI to image the brains of 20 children—10 with autism and 10 without—as the children viewed photographs of young people displaying different emotions. In the first five-minute scan, the children just observed the emotions; in the second five-minute scan, they were asked to imitate the expressions.
"Typically-developing" children showed activity in a section of the brain with mirror properties. The children with autism, on the other hand, showed no significant activity in the region, even though they could successfully imitate the expressions.
Dapretto said they also evaluated the level of impairment in the children with autism, and found a strong inverse relationship between symptom severity and activity in the mirror neuron system.
"The more impaired a child was, the less the activity in this key mirror area and, conversely, the less impaired a child was, the greater the activity we observed in this region," she said.
This, Dapretto said, lends support to the theory that failure in the mirror neuron system lies at the core of autism.
While pinpointing the cause can bring us closer to successful therapies for autism, Dapretto points out that when the disorder is diagnosed late, as often happens, some damage may be irreparable.
"The brain is very plastic," she said. "But we should keep in mind that most kids do not get diagnosed until they're two to three years old, and a lot of social learning has taken place by then—learning that would be significantly jeopardized by a dysfunctional mirror neuron system."