Pain Perception In The Self And Observation Of Others:Do Congruency Effects Exist?

Empathy for pain implies perception, judgment and affective response of anothers’pain (other-pain) as if it was one’s own pain. Overlapping neural circuits labeled as the "pain matrix" have been implicated in brain responses to both subjective pain perception (self-pain) and response to other-pain. However, the nature of interactions between observing other-pain and self-pain has been debated in competing theoretical perspectives. To test whether other-pain and self-pain primes increase or decrease responsiveness to complementary self-pain or other-pain targets, behavior, eye movement (EM), and event-related potential (ERP) studies were conducted, and the mechanism underling the congruency effect of pain representations between self-pain and other-pain was explored.This thesis is organized into eight chapters. Following an overview of associated theory and research on pain and empathy for pain (Chapter1), a discussion of gaps in associated work and the research plan for this thesis are presented (Chapter2). In the five chapters that comprise the main body of the thesis, seven studies are presented to test competing models of empathy for pain. In both Chapters3and4, which employed behavior and ERP techniques, respectively, two studies were conducted to explore the effect of other-pain on self-pain and the impact of self-pain on other-pain. Chapter5employed eye-movement (EM) tracking to investigate the effect of self-pain on visual attention to other-pain. Chapters6and7explored possible mechanisms underlying the congruency effect of pain representations. In the final chapter (Chapter8), implications and limitations of these studies were discussed.The main purposes and results were as follows:In Chapter3, two studies were included. In Study1-a. self-pain and self-heat stimuli previously primed with other-pain or other non-painful pictures were applied to undergraduate students (15men,15women). Faster reaction times (RTs), and higher pain intensity/unpleasantness ratings were found in response to pain stimulation that followed other-pain priming pictures rather than other non-painful pictures. However, responses to self-heat stimuli were not influenced by visual primes. In Study1-b, the same participants completed an identical task with the exception that either self-pain or self-heat stimulation was used to prime responses to other-pain and other non-painful depictions. Once again, faster RTs were found in response to other-pain pictures following self-pain stimuli than self-heat stimuli yet responses to other non-painful pictures were not influenced by pain and heat stimuli.In Chapter4, the study design was identical with Chapter3with the exception that both behavior and cortical responses were recorded. Twenty undergraduate participants (10men,10women) were recruited. In Study2-a, compared to other non-painful primes, other-pain visual primes predicted faster RTs and smaller P2amplitudes in response to self-pain stimuli while responses to self-heat stimuli were not affected by priming images. In Study2-b, results indicated that compared to self-heat primes, self-pain sensory primes predicted marginally faster RTs and smaller P3amplitudes in response to other-pain targets while responses to other non-painful targets were unaffected by sensory priming stimuli.Study3, presented in Chapter5, used EM tracking to assess biases of visual attention to other-pain depictions following self-pain or self-heat primes in a sample of30undergraduate participants (15men,15women). Compared to self-heat primes, self-pain sensory primes predicted a longer mean first fixation duration in response to other-pain targets. No significant results were found in other EM or behavior index.In Chapter6, Study4was designed to explore effects of negative, neutral, and positive emotional priming stimuli on cortical responses to other-pain and other non-painful depictions among20undergraduate participants (10men,10women). ERP data revealed that relative to other non-painful pictures, differential P3amplitudes for other-pain were larger followed by negative primes than either neutral or positive primes. These results were not in line with the effect of self-pain on other-pain revealed in Study2-b, thus, congruency effects of pain representations could not be explained by the general affective congruency effect.As described in Chapter7, Study5found that when participants (10men,10women) were exposed to other non-painful and other-pain priming depictions which were high (stimuli applied in the same body site) or low congruent (stimuli applied in the different body site) with self-pain target stimulation. Once again, self-pain stimulation elicited decreased P2amplitude in other-pain priming condition relative to other non-painful priming condition. In addition, smaller P2amplitudes were found in response to self-pain stimulation following high congruent other-pain priming pictures than low congruent other-pain priming pictures. Thus, the similarity of body site and pain intensity may influence congruency effects of other-pain on self-pain.In summary, findings supported the shared-representation model of pain empathy and implied that congruency effects, characterized by response facilitation rather than response competition, may exist when examining effects of other-pain and self-pain experiences, respectively, on complementary behavior and brain responses to subsequent self-pain and other-pain. Although both other-pain and self-pain experiences had negative emotional valences, congruency effects of pain representations could not be explained by the affective congruency effect alone. The similarity of pain intensity and body site between self-pain and other-pain may be the reason of congruency effects.