Correspondence

Nature 455, 589 (2 October 2008) | doi:10.1038/455589b; Published online 1 October 2008

Further reflections on how we interpret the actions of others

Giacomo Rizzolatti1 & Corrado Sinigaglia2

  1. Dipartimento di Neuroscienze, Università di Parma, Via Volturno 39, 43100 Parma, Italy
    Email: giacomo.rizzolatti@unipr.it
  2. Dipartimento di Filosofia, Università degli Studi di Milano, Via Festa del Perdono 7, 20122 Milano, Italy

Sir

Further reflections on how we interpret the actions of others

D. PARKINS

In their Essay 'Behind the looking-glass' (Nature 454, 167–168; 2008), Antonio Damasio and Kaspar Meyer suggest how mirror neurons might work. But they need to reflect on other aspects of the mirror phenomenon to complete the picture.

Mirror neurons are known for their intriguing property of discharging when a particular motor act is either being performed or being observed. Damasio and Meyer describe them as neural ensembles in higher-order association areas called CDZs (for 'convergence–divergence zones') that collect information from specific sensory areas and signal back to those areas. Action understanding (as in the authors' example of hearing a peanut being cracked) depends on activation of this network.

The CDZ model attempts to explain the mechanism underlying action understanding. But it overlooks a fundamental feature of the mirror mechanism: that is, the capacity to transform sensory information into a motor format — why should we have a copy of the actions of others in our motor system?

We can certainly recognize biological actions using sensory information and performing the kind of processing suggested by the CDZ model. But mirror neurons indicate that we must also have another mechanism for understanding another's actions. That mechanism directly maps sensory information on cortical motor neurons, providing the observer with an immediate representation of the motor acts being performed by others. There is no need for a higher-order association, as the CDZ model requires.

This, of course, does not imply that mirror neurons alone 'understand' the actions of others. Such an interpretation of the mirror system would go against all we know about the complexity of cortical organization. The point at issue is the specific contribution of mirror neurons to action understanding. Because of their motor nature, these neurons add a new, personal dimension to our capacity for understanding others that is based on our own motor knowledge and experience.

So, in spite of its heuristic value, the CDZ model underestimates the motor aspect of the mirror mechanism. It was this mechanism that prompted the description of action understanding as "the result of a 'first-person' process where the self feels like an actor, rather than a spectator" (M. Jeannerod The Cognitive Neuroscience of Action, Blackwell, 1997).