The Effect Of Pain On Attention Bias To Emotional Face

Pain-related information as a threat cue would quickly capture human attention.Previous behavioral experiments suggest that chronic pain patients show stronger attention to pain-related information than normal individuals.In addition to response time indicators,the N2 pc component has also recently been used to detect attention allocation in anxious individuals and is thought to have a “threat-prior” hypothesis.Nevertheless,N2 pc has not been applied to chronic pain patients to detect their attention bias towards pain information.Also,previous studies have found that laboratory pain could enhance individuals' attention to pain information.However,the past laboratory pains were mostly transient,and the attention biases related to pain information were not investigated when individuals were in a state of long-lasting dynamic pain.Therefore,the following studies were utilized to investigate the bias of pain on individuals' attention to pain-related information.Study1 In order to explore whether there is a “threat-prior” hypothesis of N2 pc component,this study conducts a meta-analysis of past research on N2 pc.13 studies featuring the assessment of N2 pc amplitudes during exposure to angry-neutral and/or happy-neutral facial expression arrays were included for meta-analysis.Moderating effects of study design features and sample characteristics on effect size variability were also assessed.N2 pc amplitudes elicited by affectively-valenced expressions(angry,happy)were larger than those evoked by neutral expressions.However,the mean effect size difference between angry and happy expressions was not significant.N2 pc effect sizes were moderated by sample age,number of trials,and nature of facial images used(schematic versus real)with larger effect sizes observed within comparatively younger samples,greater number of trails and studies that used schematic face arrays.N2 pc results did not support anger superiority hypothesis.Instead,attentional resources allocated to angry versus happy facial expressions are similar in early stages of processing.As such,possible adaptive advantages of biases in orienting toward both anger and happy expressions warrant consideration in revisions of related theory.Study2 To explore whether there is an early attentional bias to pain-related information in patients with chronic pain,this study evaluated the N2 pc component of adult chronic pain patients(N = 70)and pain-free controls(N = 70)during a probetask comprising painful-neutral(P-N)and happy-neutral(H-N)facial expression image pairs.The results showed that(1)the N2 pc effect induced by painful and happy faces was stronger compared to neutral faces;(2)the N2 pc responses of painful and happy faces was stronger in chronic patients than in the control group;and(3)there was no significant intergroup difference in N2 pc latency.The results of this study suggest that patients with chronic pain tend to devote more attention to emotional faces in early attention allocation,and that there is not an attention bias specific to pain faces.Study3 To explore how dynamic long-lasting pain affect attention bias to painrelated information in normal individuals,this study adopted a mixed experimental design of 2(Group: Pain Group vs.Control Group)× 2(Image Pair Type: P-N vs.H-N)× 2(Consistency: Congruent vs.Incongruent),and Group was a within-subject factor,Image Pair Type and Consistency were between-subject factors.The results indicated that compared with pain-free sample,bias scores of pain individuals were more positive,which means pain individuals show an attention bias to emotional face,while not just for pain-related information.Although study1 did not find that N2 pc component support the threat priority hypothesis,emotional face could induce significant N2 pc effect.Study2 utilized the N2 pc component as an indicator and found that chronic pain patient tends to allocate more attention to emotional face in early attention allocation,nevertheless,there was no specific attention bias for pain information.Study3,a behavioral experiment utilized capsaicin as a pain stimulus,found that individuals with pain showed an attention bias to emotional face.The above researches indicated that chronic pain would increase individuals' attention to emotional faces in the early stage of attention,and laboratory pain that uses capsaicin pain as a pain stimulus would promote individuals' attention to emotional face.In conclusion,pain would enhance individuals' attention allocation to emotional face,and did not show a particular attention allocation to painful face.