Neurophysiological markers of empathy for pain

Empathy, a defining feature of human interpersonal interaction, is a complex psychological construct ranging from low-level mechanisms such as contagion to higherorder processes such as perspective taking and mentalizing. Empathy is crucial for sharing and comprehending another person's feelings and intentions and may ultimately shape our pro-social behaviour. Studies indicate that imagining or seeing other individuals in pain may trigger an empathic mapping of the others’ physical and emotional state.At least two forms of empathy for pain have been postulated.The first one, possibly based on affective resonance, deals with emotional sharing and with the evaluation of social bonds and interpersonal relations. The second, based on somatomotor resonance, may be primarily concerned with mapping external stimuli onto one’s own body. Here we report a series of transcranial magnetic stimulation studies investigating the sensorimotor side of empathy for pain.We report that healthy individuals observing needles penetrating hands or feet of a human model present a consistent amplitude reduction of motor-evoked potentials, which is specific to observation of the pricked muscle.This inhibition correlated with the observer’s subjective rating of the sensory qualities of the pain attributed to the model. Notably, however, the onlooker cortico-spinal reactivity to the pain of others was very much reduced when the model belonged to a different ethnic group.This result indicates that stereotypes and racial bias may influence also basic aspects of empathic reactivity.