Esquizofrenia

SPECIAL SECTION: NEUROSCIENCE

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MIRRORS THE MIND
A special class of brain cells reflects the outside world, revealing a new avenue for human understanding, connecting and learning
By Giacomo Rizzolatti, Leonardo Fogassi and Vittorio Gallese
ACTION PERFORMED by one person can activate motor pathways in another’s brain responsible for performing the same action. The second understandsviscerally what the first is doing because this mirror mechanism lets her experience it in own her mind.
C A R Y W O L I N S K Y ( p h o t o g r a p h) ; J E N C H R I S T I A N S E N ( p h o t o i l l u s t r a t i o n)

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ohn watches Mary, who is grasping a flower. John knows what Mary is doing— she is picking up the flower— and he also knows why she is doing it. Mary is smiling at John,and he guesses that she will give him the flower as a present. The simple scene lasts just moments, and John’s grasp of what is happening is nearly instantaneous. But how exactly does he understand Mary’s action, as well as her intention, so effortlessly? A decade ago most neuroscientists and psychologists would have attributed an individual’s understanding of someone else’s actions and, especially,intentions to a rapid reasoning process not unlike that used to solve a logical problem: some sophisticated cognitive apparatus in John’s brain elaborated on the information his senses took in and compared it with similar previously stored experiences, allowing John to arrive at a conclusion about what Mary was up to and why. Although such complex deductive operations probably do occur in somesituations, particularly when someone’s behavior is difficult to decipher, the ease and speed with which we typically understand simple actions suggest a much more straightforward explanation. In the early 1990s our research group at the University of Parma in Italy, which at the time included Luciano

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Fadiga, found that answer somewhat accidentally in a surprising class of neurons in the monkey brain that fire when an individual performs simple goal-directed motor actions, such as grasping a piece of fruit. The surprising part was that these same neurons also fire when the individual seessomeone else perform the same act. Because this newly discovered subset of cells seemed to directly reflect acts performed by another in the observer’s brain, we named them mirror neurons. Much as circuits of neurons are believed to store specific memories within the brain, sets of mirror neurons appear to encode templates for specific actions. This property may allow an individual not only toperform basic motor procedures without thinking about them but

Instant Recognition

ou r r e se a rc h grou p was not seeking to support or refute one philosophical position or another when we first noticed mirror neurons. We were studying the brain’s motor cortex, particularly an area called F5 associated with hand and mouth movements, to learn how commands to perform certain actions are encodedby the firing patterns of neurons. For this purpose, we were recording the activity of individual neurons in the brains of macaques. Our laboratory contained a rich repertoire of stimuli for the monkeys, and as they performed various actions, such as grasping for a toy or a piece of food, we could see that distinct sets of neurons discharged during the execution of specific motor acts.

Thepattern of activity was a true representation in the brain of the act itself, regardless of who was performing it.
also to comprehend those acts when they are observed, without any need for explicit reasoning about them. John grasps Mary’s action because even as it is happening before his eyes, it is also happening, in effect, inside his head. It is interesting to note that philosophers in the...