Placebo analgesia does not reduce empathy for naturalistic depictions of others' pain in a somatosensory specific way

Abstract

Empathy for pain involves the affective-motivational and sensory-discriminative pain network. The shared representations account postulates that sharing anothers pain recruits underlying brain functions also engaged during first-hand pain. Critically, causal evidence for this has only been shown for affective pain processing, while the specific contribution of ones own somatosensory system to empathy remains controversial. Experimental paradigms used in previous studies did not a) direct attention towards a specific body part or b) employed naturalistic depictions of others pain, which could explain the absence of somatosensory effects. In this preregistered fMRI study, we thus aimed to test whether a causal manipulation of first-hand pain affects processing of empathy in a somatotopically- matched manner. Forty-five participants underwent a placebo analgesia induction in the right hand and observed pictures of right vs. left hands in pain. We found neither behavioral nor neural evidence for laterality-specific modulation of empathy for pain. However, exploratory analyses revealed a general effect of the placebo on empathy, and higher brain activity in bilateral anterior insula when viewing others hands in pain corresponding to ones own placebo hand. These results refine our knowledge regarding the mechanisms underlying empathy for pain by specifying the influence of first-hand pain on empathic responding.