One of the fastest ways to learn how to execute a given action is by watching someone else performing it first. Learning how to dance, how to play tennis and how to fix your tie are good examples of tasks that are best learned if we watch closely the movements of our teacher. How does the nervous system process someone else's actions? Is there something about the brain that makes it easier for us to imitate others? Only a few studies have addressed this question but a remarkable answer has begun to emerge from them: the primate brain possesses a 'mirror' system — neurons that are active both during the execution of an action and during the observation of the same action made by another subject. A recent study published in the European Journal of Neuroscience has obtained new evidence for the existence of a mirror system in the human brain by showing that, much like the motor system itself, the mirror system is organized in a somatotopic manner.

Buccino et al. carried out an imaging study in which subjects were required simply to watch clips of people performing motor actions with different parts of their bodies — mouth, hand and foot. The authors found that watching the movements of another person led to the bilateral activation of the premotor cortex. Moreover, the pattern of activation resembled the motor homunculus — watching someone chewing led to activation of the ventral premotor cortex, watching the movement of a foot elicited activation of the dorsal premotor area and watching someone move a hand caused the activation of an intermediate premotor region.

Another remarkable finding from this study was that the pattern of brain activation differed depending on whether the motor action involved the actual manipulation of an object. In other words, it was not the same to watch someone grabbing a ball as it was to watch a person merely mimicking this action. In the case of object-related movements, some parts of the parietal cortex — Brodmann's areas 39 and 40 — were also activated. As parts of area 40 are active during object manipulation and the parietal lobe has been implicated in action-orientated object description, it is likely that a similar 'pragmatic' analysis takes place when passively watching an object-related action.

How does the existence of this mirror system affect the execution of our own movements? How does it function when observing complicated movement sequences? Does a system like this really help us to improve our backhand or our serve? We don't have rigorous answers for these questions yet, but this should not stop the existence of a mirror system from becoming a new incentive for people like me, who are hopeless during tennis lessons.