Research On The Mechanism Of Empathy For Pain Based On MRI And TMS

Empathy for Pain refers to a typical form of empathy in which individuals perceive,understand,judge and evaluate the pain experience of others without confusing themselves with others.It not only helps individuals to identify potential dangerous situations and improve survival chances,but also helps individuals to understand the plight of others,so as to produce timely prosocial behaviors and promote the harmonious development of society.People who show less empathy for pain,as well as those who are too sensitive to others' pain,may not be socially well-adapted.Therefore,it has always been an important topic of social cognitive neuroscience research.Using Magnetic Resonance Imaging(MRI)and Transcranial Magnetic Stimulation(TMS),a series of studies have been conducted on the mechanisms of empathy for pain.1.Based on structural and functional Magnetic Resonance Imaging,exploring the mechanism of empathy for pain.The first study: healthy adult participants performed an empathy for pain rating task combined with psychometric measurements of trait empathy(using the Chinese version of Davis' Interpersonal Reactivity Index).Results found that the task mainly activated the anterior insula cortex(AIC),middle cingulate cortex(MCC),inferior frontal gyrus(IFG),inferior parietal lobule(IPL)and other important brain functional areas.(1)The bilateral AIC shows a pronounced asymmetry in its involvement with empathy for pain.The gray matter volume and brain activity of the right AIC were significantly correlated with affective trait empathy,while that of the left AIC were significantly correlated with cognitive trait empathy.(2)Seed-based functional connectivity analysis showed that the right AIC showed significant functional connectivity with the frontal lobe,and the strength of functional connection was significantly correlated with trait empathy;the left AIC showed significant functional connectivity with the right AIC,the right IFG and the left IPL,and the strength of functional connection was significantly correlated with trait empathy.In addition,the left AIC also affected participants' pain rating through its functional connection with MCC,suggesting that the left AIC had a stronger advantage in connectivity with other related brain regions in empathy for pain than the right AIC.(3)The AIC and MCC showed extensive resting state functional connectivity with the default mode network,and this functional connectivity was related to affective trait empathy rather than cognitive trait empathy.These results suggest that the resting state functional connection patterns between AIC/MCC and the default mode network may be the basis of affective trait empathy.The second study: in order to further explore the functions of the IFG and IPL,healthy participants performed a pain-related empathy-judgment task.The results showed that:(1)The process of empathy for pain based on objective sensory cues significantly activated the right IFG.The right IFG showed significant functional connectivity with the MCC and the cerebellum,and the strength of these functional connections was significantly correlated with trait empathy.(2)The pain-related empathy judgment based on objective sensory cues significantly activated the bilateral IPL,and the activation intensity of the left IPL was significantly higher than that of the right IPL.2.Online TMS demonstrated that the inferior frontal gyrus and the inferior parietal lobule are important brain regions in pain related empathy.The third study: the previous study found that the right IFG was significantly activated when participants completed the pain-related empathy-judgment task.In order to verify the causal relationship between the activity of this region and behavior,the study used a 2(Stimulation Site)× 2(Picture Valence)× 2(Task)design.The stimulation site(the right IFG vs.the control Vertex site)and picture valence(painful stimuli vs.neutral stimuli)were within-subject factors,and the Task(pain-related empathy-judgment task,TP vs.task of body identification,TB)was the between-subject factor.During the performance of the task,online repetitive TMS was delivered at 10 Hz in trains of three pulses at the right IFG and the control Vertex site.We observed prolonged reaction times during TMS delivery to the right IFG under the painful condition,as compared with the control site in TP task.Moreover,the present TMS experiment found a significant negative relationship between the behavioral results and the trait empathy scores.These results suggest that the right IFG is a key brain region in pain related empathy judgment based on objective sensory cues.The forth study: the previous study found that IPL(especially left IPL)were significantly activated(the activation intensity of the left IPL was higher than the right IPL)when healthy participants performed a pain-related empathy-judgment task based on objective sensory cues.In order to verify the causal relationship between the activity of this region and behavior,the study used a 3(Stimulation Site)× 2(Picture Valence)× 2(Task)design.The stimulation site(the left IPL vs.the right IPL vs.the control Vertex site)and picture valence(painful stimuli vs.neutral stimuli)were within-subject factors,and the Task(pain-related empathy-judgment task,TP vs.task of body identification,TB)was the between-subject factor.During the performance of the task,online repetitive TMS was delivered at 10 Hz in trains of three pulses at the site of stimulation.The results showed that compared with the Vertex intervention,TMS intervention on the left IPL was more likely to interfere with participants' accuracy in judging others' pain based on objective sensory cues than that on the right IPL.Individual trait empathy scores did not predict this interference.These results suggest that bilateral IPL(especially left IPL)is an important brain region in pain related empathy judgment.To sum up,this dissertation revealed a widely distributed brain area for empathy for pain including the insula cortex,cingulate cortex,frontal lobe,parietal lobe,etc,using MRI,TMS and psychometric measurements of trait empathy.The AIC and MCC are the core regions in which other brain regions work together to support pain-related empathy.