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From thought to language

Communicating in Words

Help Link : Broadcast segment on the discovery and significance of mirror neurons Link : Do You See What I'm Saying? The Role of Gestures in Learning Link : De la réplication du bâillement
Link : Yearning to yawn: the neural basis of contagious yawning

Eight Problems with Mirror Neurons

The premotor cortex, located directly forward of the motor cortex in the brain’s frontal lobes, activates certain neurons that cause certain muscle groups in the body to contract to produce a given action. We now know that the mirror neurons in the premotor cortex that are activated to produce such an action are also activated in a person who is simply watching someone else perform this same action.

For example, when a baby sees her father stick out his tongue, the mirror neurons corresponding to this movement in her premotor cortex are activated. The result is a priming effect that is strong enough for these same neurons to be activated more readily a moment later. These neurons then in turn activate specific neurons in the primary motor cortex, which trigger the muscles that cause the baby to stick out her own tongue.


For a baby to stick out its tongue is no easy task. But if you stick out your tongue in front of a baby, chances are very good that the baby will successfully imitate you spontaneously. A similar phenomenon can be seen in adults as well: watch how often, when one person yawns, the person next to them irresistibly winds up yawning too.

The underlying cause of these imitation phenomena might well be a population of neurons known as “mirror neurons” (see sidebar). In the early 1990s, researchers working with monkeys identified a group of neurons in their frontal cortex that were activated when the monkeys made a particular motion with their hand or mouth. There was nothing surprising in that, since these neurons were located in what is considered a “motor” portion of the brain. What was surprising, though, was that this same group of neurons were also activated in monkeys who were not performing the motion themselves, but rather watching other monkeys perform it. Hence these neurons were given the name “mirror neurons”.

The part of the brain where these mirror neurons are found in monkeys corresponds to the part of the human brain known as Broca’s area, which since the 19th century has been known to play an important role in language. In addition to their being located in a brain area associated with language, two other things about mirror neurons have led many researchers to suggest that they may play a role in the evolution and learning of language: these neurons tell us about the intentions of the people around us, and they help us to imitate the movements of other people’s lips and tongues.

Though we may associate language more with sounds than with movements, speech is first and foremost a motor activity. When we watch small children speaking their first words by imitating an adult, we see that they are not just copying sounds, like a parrot. Instead, they rely much more on the “gestural” aspect of speech—the way the adult’s mouth moves as it pronounces the words, rather than the acoustic features of the sounds coming out of it.

To some researchers, it seems increasingly apparent that it is this motor aspect of new words that makes it so easy for babies to imitate them, and that these “imitation circuits” in Broca’s area operate through the mirror neurons located there. Mirror neurons have several other amazing characteristics as well.

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