New lessons: A three-year old autistic child touches a dolphin’s fin during a therapy session in Antalya , Turkey

Do you ever feel a twitch in your arm as you watch a baseball player wallop the ball? When others cry, do your eyes tear up as well? Do you tense as a TV surgeon slices into an incision?

Those are your “mirror neurons” at work. Just over a decade ago, Italian neuroscientists studying monkeys were amazed to discover that the brain has a system of neurons, or nerve cells, that specialise in a sort of “walking in another’s shoes” function.

Some of the same neurons, they found, become active when a monkey actually makes a movement and when it is only watching another monkey, or even a human, make that same movement. It is as if the monkey is imitating ? or mirroring ? the other’s movement in its mind.

The discovery of mirror neurons was important for basic brain science, but now it is also proving medically relevant: Researchers are reporting in the January issue of the journal, Nature Neuroscience, that malfunctioning mirror neurons appear to play a central role in the social isolation of autistic children.

“We found that, lo and behold, the kids that had the most severe symptoms were the ones that had the least amount of activity” in certain mirror neurons, said lead author Mirella Dapretto of the University of California at Los Angeles.

Dapretto’s team used an MRI to scan the brains of 10 autistic and 10 non-autistic children to see how their mirror neurons reacted as they saw and imitated pictures of faces expressing anger, happiness or other emotion. The study, the first to look at the mirror neuron system in autistic children, found that the system was generally less active in the autistic children than in the non-autistic ones.

The findings add to a body of work in adults suggesting that problems with mirror neurons contribute to the trouble that autistic people have connecting with others. Autistic children often seem unable to read emotions and intentions, and unable to develop a “theory of mind” ? the idea that other people think and feel as they do.

In the non-autistic children, Dapretto writes in the paper, which has already been released online, the mirror-neuron activity “further indicates that this mirroring mechanism may underlie the remarkable ability to read others’ emotional states from a mere glance at their faces”.

Indeed, scientists believe that the mirror neurons may help form the biological basis of empathy, and the penchant for imitation ? the baby responding to a smile with a smile, the toddler clapping as a teacher claps ? that is at the very foundation of so much of learning.

The mirror neuron system seems to be involved not in the rational sort of empathy involved in purposely imagining yourself in another’s place, Dapretto said, but in the deep, automatic empathy of “really feeling what another person is feeling”.

Overall, said Marco Iacoboni, a leading mirror-neuron researcher who is at UCLA with Dapretto, “we’ve made really huge progress in the last 10 years in understanding what these neurons do” . Mirror neurons are simply motor neurons ? the brain cells that control movements. But they show signs of activity not only when a person moves, but when a person only observes someone else making that movement. In monkeys, the patterns can be picked up by using hair-thin needles to record the activity of single neurons in the brain; in humans, researchers can track them using less invasive methods like brain scans.

Earlier this year, Iacoboni published work suggesting that the mirror neurons respond not merely to another person’s action but to the intention behind that action. He found that the mirror neurons did not fire much when study subjects looked at a simple image of a hand picking up a coffee cup. But, when the cup was part of a social situation ? a table set for a party or a messy table that needed clearing ? their mirror neurons became much more active.

So when we see another person act, maybe the mirror neurons “are not just encoding the actions, but going deeper”, he said. They seem to respond to emotions or intentions, as well.

Fascinating, but can the growing understanding of mirror neurons somehow help autistic children? “That’s the $64 million question, and it’s unclear,” said Kimberly Montgomery, a mirror-neuron researcher at Princeton University. “If the deficits in autism are linked to low activity in the mirror neuron system, then the hope would be that if you diagnose someone with autism early”, you might be able to fix their mirror neurons, she said.

Another possibility, she said, is that other parts of the brain may be able to compensate for mirror-neuron malfunctions, and therapies could focus on strengthening those other areas.

Also, previous research has found mirror neurons are more active when a professional dancer watches familiar ballet movements, for instance, than unfamiliar martial-arts movements. So in autistic children, current therapies that help them become more familiar with emotions might work by bolstering mirror neurons, Montgomery said.

It is unclear if a drug could target specifically the mirror neurons because we know practically nothing about the pharmacology of the mirror cells.