Pain perception in the self and observation of others: an ERP investigation

The nature of interactions between observing pain in others (other-pain) and subjective pain perception (self-pain) has been debated. To test whether other-pain and self-pain primes increase or decrease responsiveness to complementary self-pain or other-pain targets, two ERP studies were conducted. In Study 1, twenty participants (10 women, 10 men) were exposed to pictures depicting other-pain or other non-painful situations, followed by self-pain or non-nociceptive heat stimulation delivered to the forearm. Significant visual prime×sensory target interactions indicated that compared to other non-painful primes, other-pain visual primes predicted faster reaction times (RTs) and smaller P2 amplitudes in response to self-pain stimuli while responses to self-heat stimuli were not affected by priming images. However, effects of other-pain primes on elevations in intensity ratings were not specific to self-pain and extended to self-heat targets. In Study 2, self-pain and self-heat stimuli were applied to the same participants followed by other-pain and other non-painful visual targets. Similar to the pattern for Study 1, sensory prime×visual target interactions indicated that compared to self-heat primes, self-pain sensory primes predicted marginally faster RTs and smaller P3 amplitudes in response to other-pain targets while responses to other non-painful targets were unaffected by sensory priming stimuli. Again, self-pain primes predicted higher intensity ratings for both target types compared to self-heat primes. Together, findings supported the shared-representation model of pain empathy more strongly than the threat value of pain hypothesis.