疼痛共情的神经机制

Neural Mechanisms Underlying Empathy for Pain

疼痛是一种多维度的体验。情感成分和感觉成分是疼痛体验的主要成分,二者有着不同的神经机制。疼痛共情是痛觉"共鸣"的情绪反应,其神经机制的研究也围绕疼痛的情感成分和感觉成分展开。疼痛共情的情感成分的相关脑区主要有前扣带皮层和脑岛等脑区,与自身疼痛时相比,它们的激活位点及所处的神经网络存在差异;疼痛共情的感觉成分主要与初级感觉皮层以及一些其它的躯体感觉皮层有关,对它们的激活情况的研究受技术手段和实验范式的影响较大。未来的研究应从技术手段、分析方法及实验操作上予以关注。

Pain, an unpleasant sensory and emotional experience caused by real or possible tissue damage, includes two primary aspects： affective and sensory components. The two components have different neural bases. Pain stimuli are processed in several brain areas including the thalamus, contra lateral primary somatosensory cortex （51） , secondary somatosensory cortices （52） , insula （IC） , anterior cingulate cortex （ACC） , as well as some prefrontal areas. The neural processes involved in the experience of empathy for pain, the understanding of pain in other persons, are not well understood. Studies on the neural basis of empathy for pain are also concerned about the sensory aspect and the affective aspect. Current evidences show that the perception of pain in others relies partly on the neural systems activated by noxious stimuli and involved in pain experiences ; perception of pain in others taps the affective component of pain processing, notably through the activation of the ACC and anterior IC. Most of the neuroimaging studies so far indicate that only the affective component of the pain matrix is called into play during empathy for pain. But the affective component of pain processing may have different neural bases. Peaks of activations in the ACC and IC reported in different neuroimaging studies were plotted together to examine possible distinctions between activity changes reported for pain in the self and perception of pain in others. The results indicate that activation sites in the ACC follow a clear caudo-rostral organization based on the target of the pain ： one＇s own or other＇s . Significant activation for the statistical conjunction of pain effects felt and seen was present both at the group level and the individual subject levels, although each subject showed distinct felt and seen pain areas in the cingulate, and a conjunction between these activations was not found in every individual. Researchers isolated overlapping regions for one＇s and others＇ pain in the ACC and AI and then used them as seed regions for two kinds of functional connectivity analyses. Their analyses identified clusters in the midbrain and periaqueductal gray with greater connectivity to the AI during one＇s own pain as opposed to other pain. The opposite pattern was found in the dorsal medial prefrontal cortex that showed greater connectivity to the ACC and AI during other pain than during self pain. This demonstrated that regions showing similar activity during one＇s and other＇s pain may nonetheless be part of distinct functional networks ; these networks could not have been detected in prior work that examined overlaps between one＇s and other＇s pain in terms of average activity, but not connectivity. Empathy, however, is a complex construct consisting not only of emotional but also of cognitive and somatomotor components. The sensory dimension of pain is mainly coded in parietal sensorimotor neural structures, including the somatosensory cortices. Thus, it is entirely possible that empathy may also rely on basic resonant mechanisms that allow mapping others＇ sensation onto one＇ s own sensorimotor system. Single-pulse TM5 may provide indirect information about the sensorimotor structures involved in this mapping. The primary somatosensory cortex （S1） is involved in pain and touch shared representations by recording somatosensory-evoked potentials during the direct observation of painful and nonpainful stimuli delivered to a human model＇ s hand. This paper reviews the research advance in the field of the neural bases of empathy for pain from the perspective of the affective aspect and the sensory aspect respectively. Future studies should pay more attention to the research technologies, analysis methods and experimental manipulation.