Mirror neurons, neurons that fire both when an animal acts and when the animal observes the same action being performed by another, have been implicated in the understanding of intentions, empathy, language, and autism (among other things). Several pop science books and articles have raved about mirror neurons and their widespread applications to our everyday lives. In the research and neuroblogging worlds, however, the functional significance of mirror neurons is persistently being brought into question.
Here is a quick summary of the most recent controversies:
March 10: The Italian neuroscientist Giacomo Rizzolatti, who discovered mirror neurons in the brains of monkeys with his team, published a paper in Nature Reviews Neuroscience describing the functional role of mirror neurons, as understood based on findings from recent studies in monkeys and humans.
March 19-26: After the paper was released, the Talking Brains blog posted a series of critical articles in response to Rizzolatti’s paper. Talking Brains accused the paper of “self-destructing” the mirror neuron theory, and they even questioned whether it should be considered a theory at all:
"Can someone from the mirror neuron camp come forward and provide us with an example of what kind of empirical result would falsify the theory? Because if you can't falsify it, it's no longer a scientific theory, it's religion."
March 25: I criticized Louann Brizendine, author of The Male Brain, for calling the mirror neuron system the “I feel what you feel” part of the brain. (Okay, this doesn’t add much substance to my summary of events, but I decided to be an ego-maniac and include it anyway).
April 8: A study by Roy Mukamel and colleagues being published in Current Biology, supposedly identifying mirror neurons in humans by looking at single-neuron responses in epileptic patients, conveniently became available online.
April 9: BPS Research Digest blog called Mukamel’s study “what appears to be the first ever direct evidence” for mirror neurons in humans, stating that all evidence for human mirror neurons up until now came from neuroimaging studies that could not directly identify mirror neurons.
April 13: Finally, the Neurocritic has spoken. The Neurocritic argues in an elegant, witty article that Mukamel’s study does not provide direct evidence for mirror neurons in humans. Among his criticisms is the claim that mirror neurons lose their explanatory power if they are found all over the brain (they were supposedly found in the hippocampus in Mukamel’s study, whereas they were classically identified in a fronto-parietal network in monkeys).
Confusing? The mirror neuron theory is clearly not as simple as it is sometimes claimed to be, and so far skepticism has been healthy. The fate of the mirror neuron lies in the findings of future studies and the interpretations of neurobloggers alike.