Viewer perspective in the mirroring of actions.

A remarkable capability of the brain's action representation system is that neurons with 'mirroring' properties respond both when an agent (human or monkey) executes an action and also when the agent observes a similar action performed by someone else. Curiously, however, observed actions involve numerous viewer perspectives, whereas execution of actions occur with respect to 'self' coordinate space, and the mapping between viewer perspectives is not a known property of the so-called mirror neuron system (MNS). Toward a resolution of this paradox, we demonstrate in humans striking new evidence that key areas defined as part of the MNS of the frontal lobe, directly encode viewer perspective during action observation (Exps 1, 2). What is more, this property applies only to observation of embodied actions and not when disembodied movements of objects are observed (Exp 3). These findings raise the intriguing possibility that the MNS plays a critical role in the formation of action memories.