Galang Carl Michael, Naish Katherine R, Arbabi Keon, Obhi Sukhvinder S
Social Brain, Body and Action Lab, Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, Canada.
Exp Brain Res. 2017 Nov;235(11):3469-3477. doi: 10.1007/s00221-017-5070-9. Epub 2017 Aug 24.
Excitability in the motor cortex is modulated when we observe other people receiving a painful stimulus (Avenanti et al., Nat Neurosci 8(7):955-960, 2005). However, the task dependency of this modulation is not well understood, as different paradigms have yielded seemingly different results. Previous neurophysiological work employing transcranial magnetic stimulation (TMS) suggests that watching another person's hand being pierced by a needle leads to a muscle specific inhibition, assessed via motor evoked potentials. Results from previous behavioural studies suggest that overt behavioural responses are facilitated due to pain observation (Morrison et al., Cereb Cortex 17:2214-2222, 2007b; Morrison et al., Cognition 104:407-416, 2007a). There are several paradigmatic differences both between typical TMS studies and behavioural studies, and within behavioural studies themselves, that limit our overall understanding of how pain observation affects the motor system. In the current study, we combine elements of typical TMS experimental designs in a behavioural assessment of how pain observation affects overt behavioural responding. Specifically, we examined the muscle specificity, timing, and direction of modulation of motor responses due to pain observation. To assess muscle specificity, we employed pain and non-pain videos from previous TMS studies in a Go/No-Go task in which participants responded by either pressing a key with their index finger or with their foot. To assess timing, we examined response times for Go signals presented at 0 or 500 ms after the video. Results indicate that observation of another individual receiving a painful stimulus leads to a non-effector specific, temporally extended response facilitation (e.g., finger and foot facilitation present at 0 and 500 ms delays), compared to observation of non-pain videos. This behavioural facilitation effect differs from the typical motor inhibition seen in TMS studies, and we argue that the effects of pain observation on the motor system are state-dependent, with different states induced via task instructions. We discuss our results in light of previous work on motor responses to pain observation.
当我们观察他人受到疼痛刺激时，运动皮层的兴奋性会受到调节（阿韦南蒂等人，《自然神经科学》8(7):955 - 960，2005年）。然而，这种调节的任务依赖性尚未得到很好的理解，因为不同的范式产生了看似不同的结果。先前采用经颅磁刺激（TMS）的神经生理学研究表明，观看他人的手被针刺会导致特定肌肉的抑制，这是通过运动诱发电位来评估的。先前行为学研究的结果表明，由于疼痛观察，明显的行为反应会得到促进（莫里森等人，《大脑皮层》17:2214 - 2222，2007年b；莫里森等人，《认知》104:407 - 416，2007年a）。在典型的TMS研究和行为学研究之间，以及行为学研究本身内部，存在着几个范式上的差异，这些差异限制了我们对疼痛观察如何影响运动系统的整体理解。在当前的研究中，我们将典型TMS实验设计的要素结合到一项行为评估中，以研究疼痛观察如何影响明显的行为反应。具体而言，我们研究了由于疼痛观察导致的运动反应的肌肉特异性、时间和调节方向。为了评估肌肉特异性，我们在一个“是/否”任务中使用了先前TMS研究中的疼痛和非疼痛视频，参与者通过用食指或脚按键来做出反应。为了评估时间，我们检查了在视频后0或500毫秒呈现“是”信号时的反应时间。结果表明，与观看非疼痛视频相比，观察他人受到疼痛刺激会导致非效应器特异性的、时间上延长的反应促进（例如，在0和500毫秒延迟时手指和脚的促进）。这种行为促进效应不同于TMS研究中常见的运动抑制，我们认为疼痛观察对运动系统的影响是依赖状态的，不同的状态是通过任务指令诱导的。我们根据先前关于对疼痛观察的运动反应的研究来讨论我们的结果。
