Rütgen, M. | bioRxiv Science

bioRxiv2020

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

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.

neuroscience↗

bioRxiv2020

Another's pain in my brain: No evidence that placebo analgesia affects the sensory-discriminative component in empathy for pain

The shared representations account of empathy suggests that sharing other peoples emotions relies on neural processes similar to those engaged when directly experiencing such emotions. Recent research corroborated this by showing that placebo analgesia resulted in reduced pain empathy and decreased activation in shared neural networks. However, those studies did not report any placebo-related variation of somatosensory engagement during pain empathy. The experimental paradigms used in these studies did not direct attention towards a specific body part in pain, which may explain the absence of effects for somatosensation. The main objective of this preregistered study was to implement a paradigm overcoming this limitation, and to investigate whether placebo analgesia may also modulate the sensory-discriminative component of empathy for pain. We induced a localized, first-hand placebo analgesia effect in the right hand of 45 participants by means of a placebo gel and conditioning techniques, and compared this to the left hand as a control condition. Participants underwent a pain task in the MRI scanner, receiving painful or non-painful electrical stimulation on their left or right hand, or witnessing another person receiving such stimulation. In contrast to a robust localized placebo analgesia effect for self-experienced pain, the empathy condition showed no differences between the two hands, neither for behavioral nor neural responses. We thus report no evidence for somatosensory sharing in empathy, while replicating previous studies showing overlapping brain activity in the affective-motivational component for first-hand and empathy for pain. Hence, in a more rigorous test aiming to overcome limitations of previous work, we again find no causal evidence for the engagement of somatosensory sharing in empathy. Our study refines the understanding of the neural underpinnings of empathy for pain, and the use of placebo analgesia in investigating such models. HighlightsO_LIInvestigated placebo modulation of somatosensory and affective components of pain C_LIO_LILocalized placebo analgesia effects for self-report and fMRI of first-hand pain C_LIO_LINo evidence for such effects in empathy for pain C_LIO_LISuggests that somatosensory sharing does not play a critical role in pain empathy C_LI

neuroscience↗