Social Brain, Body and Action Lab, Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, Ontario, Canada.
J Neurophysiol. 2021 Feb 1;125(2):599-605. doi: 10.1152/jn.00600.2020. Epub 2020 Dec 30.
Previous transcranial magnetic stimulation (TMS) studies have reported a decrease in motor cortical output during pain observation. In contrast, recent behavioral studies have shown that response times are faster after pain observation. This suggests that there is a mismatch between motor activity "during" versus "after" pain observation. We propose that these opposing effects of pain observation on motor activity may be explained by task constraints, as participants in TMS studies are instructed to keep still and relax their hands, whereas participants in behavioral studies maintain a state of readiness to respond. Task and methodological differences make it difficult to compare the results from TMS and behavioral paradigms examining the motor consequences of pain observation. As such, the aim of the current study is to directly test whether task instructions affect motor activity in TMS and behavioral measures of motor activity in the context of pain observation, within a single experiment. Participants watched videos of hands in painful versus nonpainful scenarios while TMS-induced motor evoked potentials were recorded. In the "active" block, participants responded to a cue that appeared immediately after each video; in the "passive" block, they relaxed their hand. Contrary to expectations, participants showed enhanced motor cortical output during pain observation (vs. no-pain) in "both" blocks. We discuss these results in relation to the wider literature on the social neuroscience of empathy. The current study provides novel results showing an increase motor cortical output, measured via transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs), during empathic pain observation regardless of motor preparation state. Interestingly, this finding runs counter to the empathy for pain literature, which often finds a decrease in motor cortical output during empathic pain observation. We discuss potential explanations for this discrepancy and relate these results to the wider empathy for pain literature.
先前的经颅磁刺激 (TMS) 研究报告称，在观察疼痛时运动皮质的输出减少。相比之下，最近的行为研究表明，观察疼痛后反应时间更快。这表明在观察疼痛时与观察后之间的运动活动存在不匹配。我们提出，观察疼痛对运动活动的这些相反影响可能是由任务约束来解释的，因为 TMS 研究中的参与者被指示保持静止并放松手部，而行为研究中的参与者则保持准备响应的状态。任务和方法学上的差异使得比较 TMS 和行为范式研究观察疼痛对运动活动的影响结果变得困难。因此，本研究的目的是在单个实验中直接测试任务指令是否会影响 TMS 和行为测量在观察疼痛时的运动活动。参与者观看手在疼痛与非疼痛场景中的视频，同时记录 TMS 诱导的运动诱发电位。在“主动”块中，参与者对出现在每个视频之后的提示做出反应；在“被动”块中，他们放松手部。出乎意料的是，参与者在“两个”块中均显示出在观察疼痛时（与无疼痛时相比）运动皮质输出增强。我们将这些结果与同理心的社会神经科学的更广泛文献进行了讨论。本研究提供了新的结果，表明在共情疼痛观察期间，无论运动准备状态如何，通过经颅磁刺激 (TMS) 诱导的运动诱发电位 (MEPs) 测量的运动皮质输出增加。有趣的是，这一发现与同理心疼痛文献的结果相反，后者经常发现共情疼痛观察时运动皮质输出减少。我们讨论了这种差异的潜在解释，并将这些结果与更广泛的同理心疼痛文献联系起来。
