WallStreet Journal
How Your Brain Allows You to Walk In Another's Shoes
Friday August 17, 2007 1:37 pm ET
By Robert Lee Hotz

In subtle patterns of brain cells, researchers are exploring empathy -- an essential intuition that helps us understand our fellow human beings.

These unusual brain circuits are mirrors in the mind that reflect the actions and intentions of others as if they were our own, new research has revealed. Scientists call them mirror neurons. They allow us to feel a loved one's pain, or suffer the pangs of appetite when we hear someone crunch into an apple. They are a reason we are moved by the images of art and can feel the appeal of characters in a book. They supply the voyeuristic thrill of pornography, a German brain-scanning team documented. They also are a hidden persuader in advertising, UCLA researchers said.

And if researchers in Europe and the U.S. are correct, these cells are subconscious seeds of social behavior that also can be manipulated to boost sales, generate fads or influence political beliefs.

"The mirror system gives us some kind of open-mindedness, a propensity to understand others and other cultures," said neuroscientist Marco Iacoboni at the University of California, Los Angeles, who is pioneering the study of these cells in human brains. In a way researchers are only beginning to understand, the cells physically embody what University of Chicago psychologist Jean Decety called "the sense of similarity."

Located in the brain's motor cortex, which orchestrates movement and muscle control, the cells fire when we perform an action and also when we watch someone else do the same thing. When someone smiles or wrinkles her nose in distaste, motor cells in your own brain associated with those expressions resonate in response like a tuning fork, triggering a hint of the feeling itself.

"The more empathetic you are, the stronger your mirror neuron response," said Dr. Iacoboni, whose book on the phenomenon, "Mirroring People," is scheduled for publication next year.

"We see that the mirror system is really a system of trying to make connections," said neuroscientist Istvan Molnar-Szakacs at UCLA's Center for the Biology of Creativity.

Among those diagnosed with autism, this mirror of neurons may be broken, independent research groups at the University of Montreal and the University of California, San Diego, recently reported. The more severely the mirror networks are disrupted, the more pronounced the symptoms of autism, which impairs language, behavioral and social skills, UCLA researchers reported in May.

"We don't really know if it is the mirror system itself that is dysfunctional or whether the data that it is getting is the problem," said Dr. Lindsay Oberman at Harvard's Beth Israel Deaconess Medical Center. "It's really a puzzle."

Physically, these mirror cells may be no different from any other neuron in the motor cortex, experts said. Their abilities arise from their links to other regions of the brain. On average, each human neuron has connections to thousands of other cells, creating intricate constellations of relationships.

"There is not one mirror system," said computational biologist Michael Arbib at the University of Southern California. "There are mirror neurons for the hands. There are mirror neurons for the face and presumably for other parts of the body."

Until now, though, the only direct evidence of such brain cells came from laboratory monkeys, in which researchers could record the behavior of an individual neuron responding to the actions of others. That's how they were discovered in animal experiments at the University of Parma in Italy more than a decade ago. With human subjects, scientists so far have relied on noninvasive, medical-imaging devices, which can't detect single neurons.

But preliminary data from unpublished experiments this spring suggest that researchers at UCLA, probing the exposed brain tissue of patients undergoing neurosurgery, for the first time have isolated individual human brain cells that act as mirror neurons, Dr. Iacoboni said.

These mirrors also are attuned to cultural experience and ethnic identity, Dr. Iacoboni and Dr. Molnar-Szakacs reported in the journal PloS One last month. (Read the journal article.) They determined that this involuntary sense of empathy responds differently depending on whether we are looking at someone who shares our culture or someone who doesn't.

Already, Dr. Iacoboni is assessing how mirror neurons react to commercial advertising, effectively turning brain circuits into focus groups. Later this summer, he plans to study how mirror neurons in the brains of independent voters react to campaign speeches by Republican and Democratic candidates.

It will be his second foray into the neurobiology of politics. During the last presidential election, he tried and failed to detect the activity of mirror neurons among loyalists of both parties as they watched political ads.

"Frankly, the campaign was so nasty," he said, "that the empathetic response had completely disappeared."

Email me at ScienceJournal@wsj.com.

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