New Research on Mirror Neurons
Serendipity brought us the big bang theory, penicillin and Velcro. If not for the chance observation of, respectively, cosmic noise, an odd fungal growth in a petri dish, and burrs stuck to wool trousers, who knows where we'd be today? To this disparate list of fortuitous discoveries, we can add mirror neurons. Located in the brain, these nerve cells may help explain autism and are now believed to be linked to everything from empathy, language and culture to why sports fans enjoy the big game and others like porn. Some researchers have tied them to violent television and aggressive behaviour. And Giacomo Rizzolatti, a physiology professor at the University of Parma in Italy, accidentally discovered them while studying monkeys.
At a conference in Germany in the early 1990s, Rizzolatti sat down to lunch with colleagues, including Mel Goodale, a professor of physiology and pharmacology at the University of Western Ontario. Mirror neurons weren't on the agenda, but Rizzolatti gave his fellow scientists a sneak peek at a rather curious video. On the tape, monkeys with electrodes implanted in their brains were shown picking up various objects. When an animal moved, monitoring equipment recorded its motor neurons firing as a staccato burst of static noise. Amazingly, the same crackling could be heard when a monkey simply witnessed a lab technician lift an object - the animal's motor neurons, in effect, mirrored the technician's movement, firing as if the animal had performed the task itself. "It was a stunning demonstration," recalls Goodale."I hadn't seen it before, and I don't think anyone else in the room had either."
Mirror neurons are motor neurons that fire whether an action is observed or performed. They lend new meaning to feeling someone else's pain. For instance, a certain part of the brain is activated when we feel sad, but the same area lights up, albeit to a lesser extent, when we see someone else in distress. Likewise, mirror neurons are stimulated when we watch athletes in competition or porn stars in the bedroom, just as they'd be had we performed the acts ourselves. When we act, instead of observe, they fire at higher levels.
Mirror neurons may also play a role in cultural conditioning because much of how we behave is based on imitation. A child will stick out her tongue if she sees her father do likewise. The nerve cells aid in language, teaching the brain how to properly signal the mouth and tongue. And they help interpret another person's intentions; as such, they are important for survival.
"Mirror neurons will do for psychology what DNA did for biology," writes Vilayanur Ramachandran, director of the Center for Brain and Cognition at the University of California, San Diego. "They will ... help explain a host of mental abilities that have hitherto remained mysterious and inaccessible to experiments." Using an electroencephalogram, Ramachandran has observed children with mild autism perform simple physical tasks; their neurons fired normally. But as they watched another child perform the same action, there was no mirror-neuron activity. "When you have damage to mirror neurons, you'd expect loss of empathy, difficulty in miming skilled acts, difficulty in knowing what somebody else is up to," says Ramachandran. This is just what we observe in autistic children.
Recent research suggests violent TV activates mirror neurons, as well as parts of the brain linked to aggressive behaviour. But Hugo Théoret, a psychology professor at the University of Montreal, dismisses the notion that these single-celled neurons can drive us to lash out. "I think the mirror system just gives you the tools to understand what you are seeing," he says. "The rest then depends on other brain mechanisms - personality traits, education, or your emotional state." But the work of Rizzolatti and others has tied the study of motor behaviour to our attempts to understand sensory processing and vision. "Our perception of the world," Goodale says, "is intimately related to how we act in that world." Little wonder that, in the early days, scientists referred to the mirror-neuron phenomenon as "monkey see, monkey do."
See also NEUROSCIENCE.
Maclean's March 6, 2006