I feel your pain in my motor system

How do we empathize with others pain? According to mirror-matching resonance models of empathy, the observation of others motor, sensory or affective states automatically activates corresponding representations in the observer (Preston, de Waal, 2002, Behav. Brain. Sci., 25, 1-72). A recent fMRI study has reported that anterior insular and cingulate cortex, that are part of the affective division of the pain network, were activated not only during pain perception but also during imagery of others pain (Singer et al., 2004, Science, 303, 1157-62). Using Transcranial Magnetic Stimulation we explored changes of cortico-spinal motor representations of hand muscles during the mere observation of needles entering hands, feets or non-corporeal objects. We found a highly specific inhibition of motor evoked potentials recorded from the pricked hand muscle similar to what reported during actual delivery of nociceptive stimuli (Valeriani et al., 2001, Exp. Brain Res., 139, 168-72). Moreover, the inhibition was related to the sensory but not to the affective qualities of the empathized pain. In agreement with simulation theories of empathy, these findings indicate the somatotopic organisation of the motor counterpart of a neural system supposedly recruited during perception of and empathy for sensorial aspects of pain suffered by others. Thus, different features of empathy for pain are mapped in different neural structures. Remarkably, empathy for pain appears more embodied in the motor system than in affective nodes of the pain matrix.