鈥淲HEN you鈥檙e smilin鈥�, the whole world smiles with you,鈥� sang Louis Armstrong. He could have been referring to what some consider one of the greatest recent discoveries of neuroscience: mirror neurons.
Discovered in macaques in the 1990s, these cells were spotted when researchers made recordings from microelectrodes placed in the animals鈥� brains as they performed various tasks. While many neurons fired when the animal performed an action, a subset also fired when the animals saw the researcher perform the same action, with different groups of mirror neurons for different actions.
Neuroscientists have speculated that in people, mirror neurons could represent the neural basis of empathy. They could also contribute to imitation and learning, and perhaps even language acquisition.
Advertisement
It has been hard to find out if people have mirror neurons, but MRI scans have shown that certain areas of the brain 鈥� dubbed mirror systems 鈥� 鈥渓ight up鈥� when we perform and watch the same action. Numerous studies have shown that people with more activity in their mirror systems seem to be better at understanding other people鈥檚 emotions. Conversely, less activity in mirror systems has been linked to autism and also with psychopathy 鈥� different conditions that are both noted for low levels of empathy. Nina Bien鈥檚 team at Maastricht University in the Netherlands recently identified inhibition mechanisms that hint at how we can mentally imitate an action without actually performing it (Cerebral Cortex, vol 19, p 2338).
Nevertheless, some researchers question whether mirror systems can take sole responsibility for empathy. 鈥淯nderstanding someone else鈥檚 actions and empathy are huge cognitive achievements,鈥� says Cecilia Heyes, a psychologist at the University of Oxford. 鈥淪o to suggest that there鈥檚 one discrete neural system responsible for it doesn鈥檛 make sense.鈥�
However, , a neuroscientist at the University of California, Los Angeles, claims to have seen individual brain cells behaving like mirror neurons in people. He made his observations when someone with epilepsy was undergoing exploratory brain surgery to investigate the cause of their seizures. The results are due to be published this month in Current Biology.
Read the answer to the next question: How many ways can we be conscious?
or return to this special feature鈥檚 main page: Picking our brains: Nine neural frontiers
