First-hand Pain Sensitivity Influences Empathy For Others’ Pain

Pain is a painful experience associated with actual or potential tissue damage.It is a complex sensory experience which does not only simply reflect sensory information processing but also can be substantially influenced by various psychological and environmental factors.Thus,individuals have different levels of pain sensory threshold and tolerable threshold,or perceive same sensory events or clinical symptoms greatly different,which reflects the difference of individual’s sensitivity to pain.Empathy for pain implies perception and judgement of the other’s pain,as well as affective responses,that is,to empathize with the pain of others.Previous studies have shown that empathy for others’ pain also partially activates brain areas associated with first-hand pain experience,such as the insula and the anterior cingulate cortex.However,there is asynchronous sensitivity to first-hand pain and others’ pain in clinical patients.Studies have found that neural circuits required for first-hand pain and empathy for pain do not completely overlap.We aimed to investigate whether first-hand pain sensitivity influences the empathic response to others’ pain,as well as its underlying mechanisms in healthy population.It is also noticeable that most experimental studies adopted pictures or video materials to induce empathy for pain,but in the real life,empathy for pain is not only triggered by visual stimulation(such as observing pain in others),but also induced by auditory stimulation(such as the hearing painful sounds of others).Therefore,this study employed visual and auditory stimuli to induce empathy for pain,and explored the influence of first-hand pain sensitivity on the behavior and electrophysiological responses to pain in others.Study 1 adopted the picture-based paradigm,where empathy was elicited via the presentation of pictures displaying hands in painful situations,and explored the influence of first-hand pain sensitivity on the behavioral and event-related potential(ERP)responses to pain in others.We recruited participants with high pain sensitivity(HPS)and low pain sensitivity(LPS)through the pain sensitivity questionnaire,and this grouping was verified by physical pain assessment.Participants in both HPS and LPS groups completed the Pain Judgment Task and the Pain Rating Task when viewing pictures of others in painful and non-painful situations.Behavioral results showed that compared with the LPS group,participants in the HPS group exhibited greater sensitivity in discriminating others’ pain,estimated greater pain intensity experienced by others,and felt greater unpleasantness when viewing others in pain.Electrophysiological results showed that only participants in the HPS group exhibited significant pain empathic effects on event-related potential(N1 and P3)responses to others’ pain,while the LPS group showed comparable neural responses to both picture types.Further,first-hand pain sensitivity facilitates the judgment of others’ pain is due to the mediating effect of empathic N1 response.These results suggested that HPS group distinguished and respond to others’ pain more quickly at an early stage.The first-hand pain sensitivity influences the picture-based empathic responses to others’ pain,including grater affective empathy and cognitive empathy,as well as the early bottom-up process and late top-down processing of empathy for pain.Study 2 employed the voice-based paradigm,where empathy was evoked via the presentation of painful and non-painful voices of others,and explored the ERP responses to empathy for pain induced by painful voices,as well as the influence of first-hand pain sensitivity on the empathic responses to hearing others’ pain.Behavioral results showed that compared with non-painful voices,hearing others’ painful voices elicited higher pain intensity and unpleasantness score.Electrophysiological results showed that N1,N2,P3 and late positive potential(LPP)responses to painful and nonpainful auditory stimuli were significantly different.For participants in the HPS group,the N1,P3,and LPP responses to painful and non-painful auditory stimuli were significantly different,whereas the LPS group showed comparable ERP responses to both types of voices.These results suggest that first-hand pain sensitivity may influence empathic responses evoked by painful voices,including the early bottom-up process and late top-down processing of empathy for pain.In conclusion,regardless in auditory or visual modality,first-hand pain sensitivity can influence both early and late ERP components in response to others’ pain(e.g.,N1 and P3).It indicates that the observer’s first-hand pain sensitivity affects early bottomup process and late top-down processing of others’ pain.This understanding supports the “shared representation theory” of empathy(empathy for others’ pain relies on the same psychological and neural representations that underlie first-hand experience of physical pain),and provides insights into the linkage between pain and empathy.