Beyond sharing unpleasant affect - evidence for pain-specific opioidergic modulation of empathy for pain

Abstract

The neural mechanisms underpinning empathy for pain are still a matter of debate. One of the major questions is whether empathy-related pain responses indicate domain-general vs. pain-specific affective responses. Using fMRI and psychopharmacological experiments, we investigated if placebo analgesia reduces first-hand and empathic experiences of affective touch, and compared them to the effects on pain. Placebo analgesia also affected the first-hand and empathic experience of unpleasant touch, implicating domain-general effects. However, and in contrast to pain and pain empathy, administering an opioid antagonist did not block these effects. Moreover, placebo analgesia reduced neural activity related to both modalities in the bilateral insular cortex, while it specifically modulated activity in the anterior midcingulate cortex for pain and pain empathy. These findings provide causal evidence that one of the major neurochemical systems for pain regulation is involved in pain empathy, and crucially substantiate the role of shared representations in empathy.