Giummarra Melita J, Fitzgibbon Bernadette M, Georgiou-Karistianis Nellie, Nicholls Michael E R, Gibson Stephen J, Bradshaw John L
Experimental Neuropsychology Research Unit, School of Psychology and Psychiatry, Monash University, Wellington Road, Clayton, VIC 3800, Australia.
Perception. 2010;39(10):1396-407. doi: 10.1068/p6582.
Pain synaesthetes experience pain in a presensitised region when observing or imagining another person in pain. We conducted an upper-limb embodiment study using a modified rubber-hand illusion in which lower-limb amputees originally participated as control subjects for the upper-limb amputees. While we found all subjects experienced topographic illusory sensations, we also serendipitously found that lower-limb amputee pain synaesthetes experienced pain or a motor response in their phantom leg when the embodied hand was threatened (e.g., with a retractable knife, mousetrap, or syringe) or submitted to high-frequency stimulation (e.g., vibration). Embodiment illusions were brought about by touching, manipulating, or threatening a rubber or real hand which was observed through a mirror so that it was superimposed upon the target hand (phantom hand for upper-limb amputees, or real hand in others). Participants included eight pain synaesthetes (six lower-limb amputees, one upper-limb amputee, and one nonamputee), and thirty-one controls (eight lower-limb amputees, twelve upper-limb amputees, and eleven nonamputees). We documented participant's subjective reports, together with quantitative measures including the Questionnaire Measure of Emotional Empathy. We found no association between pain synaesthesia and empathy scores. On the basis of related literature we suggest that pain synaesthetes likely experienced phantom-leg pain because (a) the motor system was already engaged during visual capture; (b) threatening stimuli, to which they are hyper-vigilant, triggered avoidance or 'escape' motor schemata; and (c) there could be no feedback confirming that initiated motor schemata for the phantom limb were successfully performed. Ultimately, we have further defined this new condition, synaesthesia for pain, as not only having a sensory pain component, but also a key motor component, manifesting itself in avoidance, contraction, and withdrawal 'actions'.
疼痛联觉者在观察或想象他人处于疼痛状态时，会在预先敏感化的区域体验到疼痛。我们进行了一项上肢具身化研究，采用了改良的橡皮手错觉实验，其中下肢截肢者最初作为上肢截肢者的对照受试者参与实验。虽然我们发现所有受试者都经历了地形错觉感觉，但我们也意外地发现，当具身化的手受到威胁（例如，用可伸缩刀、捕鼠器或注射器）或接受高频刺激（例如，振动）时，下肢截肢疼痛联觉者会在其幻肢中体验到疼痛或产生运动反应。具身化错觉是通过触摸、操纵或威胁一面镜子中观察到的橡皮手或真实的手而产生的，这样它就叠加在目标手上（上肢截肢者的幻手，或其他人的真实手）。参与者包括八名疼痛联觉者（六名下肢截肢者、一名上肢截肢者和一名非截肢者），以及三十一名对照组（八名下肢截肢者、十二名上肢截肢者和十一名非截肢者）。我们记录了参与者的主观报告，以及包括情感同理心问卷测量在内的定量测量结果。我们发现疼痛联觉与同理心得分之间没有关联。基于相关文献，我们认为疼痛联觉者可能经历幻肢痛是因为：（a）运动系统在视觉捕捉过程中已经被激活；（b）他们对威胁性刺激高度警觉，触发了回避或“逃避”运动模式；（c）没有反馈来确认针对幻肢启动的运动模式是否成功执行。最终，我们进一步将这种新情况，即疼痛联觉，定义为不仅具有感觉疼痛成分，而且还具有关键的运动成分，表现为回避、收缩和退缩“动作”。
