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December 10, 2012

Mirror Neurons: The Most Hyped Concept in Neuroscience?

by Christian Jarrett, Ph.D in Brain Myths

Mirror neurons are fascinating but they arent the answer to what makes us human.

Back in the 1990s neuroscientists at the University of Parma identified cells inthe premotor cortex of monkeys that had an unusual response pattern. They wereactivated when the monkeys performed a given action and, mirror-like, when theysaw another individual perform that same movement. Since then, the precise function and influence of these neurons has become perhaps the most hyped topic in neuroscience.

The hype

In 2000, Vilayanur Ramachandran, the charismatic neuroscientist, made a bold prediction: mirror neurons will do for psychology what DNA did for biology. He's at the forefront of a frenzy of excitement that has followed these cells ever sincetheir discovery. For many, they have come to represent all that makes us human.

Perhaps, in those early heady years, Ramachandran was just getting a little carried away? Not at all. For his 2011 book, The Tell-Tale Brain, Ramachandran tookhis claims further. In the chapter The neurons that shaped civilisation, he arguesthat mirror neurons underlie empathy, allow us to imitate other people, that they accelerated the evolution of the brain, that they help explain the origin oflanguage, and most impressively of all, that they prompted the great leap forward in human culture that happened about 60,000 years ago.

We could say mirror neurons served the same role in early hominin evolution as the Internet, Wikipedia, and blogging do today, he concludes. Once the cascade was set in motion, there was no turning back from the path to humanity.

Ramachandran is not alone. Writing for The Times (London) in 2009 about our inte

rest in the lives of celebrities, the eminent philosopher AC Grayling traced itall back to those mirror neurons. We have a great gift for empathy, he wrote. Thisis a biologically evolved capacity, as shown by the function of mirror neurons. Inthe same newspaper this year, Eva Simpson wrote on why people were so moved whenTennis champ Andy Murray broke down in tears. Crying is like yawning, she said, blame mirror neurons, brain cells that make us react in the same way as someone were watching (emphasis added). In a New York Times article in 2007, about one mans heroic actions to save another, those cells featured again: people have mirror neurons, Cara Buckley wrote, which make them feel what someone else is experiencing (emphasis added).

If mirror neurons grant us the ability to empathise with others, it follows thatattention should be drawn to these cells in attempts to explain why certain peo

ple struggle to take the perspective of others such as can happen in autism. Loand behold the broken mirror hypothesis of autism.

The reality

The ubiquitous idea that mirror neurons cause us to feel other peoples emotions canbe traced back to the original context in which they were discovered the motorcells in the monkey brain that responded to the sight of another person performing an action. This led to the suggestion that mirror neurons play a causal rolein allowing us to understand the goals behind other peoples actions. By represent

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ing other peoples actions in the movement-pathways of our own brain, so the reasoning goes, these cells provide us with an instant simulation of their intentions a highly effective foundation for empathy.

Its a simple and seductive idea. What the newspaper reporters (and over-enthusiastic neuroscientists) dont tell you is just how controversial it is. The biggest and most obvious problem for anyone advocating the idea that mirror neurons playa central role in our ability to understand other peoples actions, is that we arequite clearly capable of understanding actions that we are unable to perform.

A non-player tennis fan whos never held a racket doesnt sit baffled as Roger Federer swings his way to another victory. They understand fully what his aims are, even though they cant simulate his actions with their own racket-swinging motor cells. Similarly, we understand flying, slithering, coiling and any number of other creaturely movements, even if we dont have the necessary motor cells to simulate them. From the medical literature there are also numerous examples of comprehension surviving after damage to motor networks people who can understand speech,though they cant produce it; others who recognise facial expressions, though their own facial movements are compromised. Perhaps most awkward of all, theres evidence that mirror neuron activity is greater when we view actions that are less familiar such as a meaningless gesture as compared with gestures that are imbuedwith cultural meaning, such as the victory sign.

Mirror neuron fans generally accept that action understanding is possible withou

t corresponding mirror neuron activity, but they say mirror neurons bring an extra depth to understanding. In a journal debate published this year in Perspectives in Psychological Science, Marco Iacoboni insists mirror neurons are importantfor action understanding, and he quotes others saying how they allow an understanding from within. Critics in the field believe otherwise. Gregory Hickok at theUniversity of California Irvine thinks the function of mirror neurons is not about understanding others actions per se, but about using others actions in the process of making our own choice of how to act. Seen this way, mirror neuron activity is just as likely a consequence of action understanding, as a cause.

What about the grand claims that mirror neurons played a central role in accelerating human social and cultural evolution by making us empathise with each other? Troublesome findings here include the fact that mirror neurons appear to acqui

re their properties through experience. Research by Cecelia Heyes and others hasshown that learning experiences can reverse, nullify or exaggerate mirror-likeproperties in motor cells. It cant reasonably be claimed that mirror neurons madeus imitate and empathise with each other, if the way we choose to behave instead dictates the way our mirror neurons work. On their role in cultural evolution,Heyes says mirror neurons are affected by cultural practices, such as dancing and music, just as much they influenced them.

Finally, what about the suggestion that mirror neurons play a role in autism? Itshere that the hype is probably the least justified. There are numerous findingsshowing that people with autism have no problem understanding other peoples actions (contrary to the broken mirror hypothesis) and that they show normal imitation abilities and reflexes. For a new review paper, Antonia Hamilton assessed the

results from 25 relevant studies, concluding: there is little evidence for a global dysfunction of the mirror system in autism.

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Motor cells that respond to the sight of other people moving are intriguing, theres no doubt. Its likely they play a role in important social cognitions. But to claim that they make us empathic, and to raise them up as neurosciences holy grail, as the ultimate brain-based root of humanity, is ridiculous. The evidence Ive mentioned is admittedly somewhat biased, designed to counteract the hype and show

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just how much debate and doubt persists. In fact, the very existence of mirrorneurons in the human brain is still disputed by some. Thats where were at with thestudy of these cells. Were still trying to find out whether they exist in humans, where they are, and what exactly it is they do. Mirror neurons are fascinatingbut they arent the answer to what makes us human.

http://www.psychologytoday.com/blog/brain-myths/201212/mirror-neurons-the-most-hyped-concept-in-neuroscience