Electrophysiology of action representation.

We continuously act on objects, on other individuals, and on ourselves, and actions represent the only way we have to manifest our own desires and goals. In the last two decades, electrophysiological experiments have demonstrated that actions are stored in the brain according to a goal-related organization. The authors review a series of experimental data showing that this "vocabulary of motor schemata" could also be used for non-strictly motor purposes. In the first section, they present data from monkey experiments describing the functional properties of inferior premotor cortex and, in more detail, the properties of visuomotor neurons responding to objects and others' actions observation (mirror neurons). In the second section, human data are reviewed, with particular regard to electrophysiological experiments aiming to investigate how action representations are stored and addressed. The specific facilitatory effect of motor imagery, action/object observation, and speech listening on motor excitability shown by these experiments provides strong evidence that the motor system is constantly involved whenever the idea of an action is evoked.