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Contribution of somatosensory input to mechanisms of movement suppression during action observation

体感输入对动作观察过程中运动抑制机制的贡献

基本信息

批准号：
BB/P006027/1
负责人：
Alexander Kraskov
金额：
$ 63.44万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FP006027%2F1
关键词：
Contribution somatosensory input mechanisms movement

项目摘要

Execution of everyday movements as for example grasping of an object appears and feels effortless but requires a sophisticated mechanical machinery of muscles and joints and a complex control system including spinal cord and brain circuits. There is accumulating evidence that large part of this control system is active during movement observation. More than twenty years ago Prof Rizzolatti and colleagues discovered single neurons in area F5 of macaque monkeys brain responding not only to monkey grasping but also to observation of the same grasp performed by human experimenter. These neurons were called "mirror neurons". Our group made a major contribution to the field of mirror neurons by discovering that in area F5 and in primary motor cortex even neurons directly connected to the spinal motor neurons can be modulated just by observation of an action. This apparent paradox of the motor system being active during action observation without production of any movement challenges our understanding of how movements are generated and prompts research to identify what separate movement execution from action observation.An obvious candidate is somatosensory system that responds to changes to the surface or internal state of the body. Somatosensory input is clearly very different between observation of a grasp when hand is at rest and grasp execution when hand is moving and touching an object. This difference might be an important contributing factor to why movements do not occur during action observation despite mirror neuronal activity present in motor areas. A dramatic examples of how powerful the somatosensory input is for perception is the "rubber hand" illusion: light stroking of subject hand combined with observation of synchronous stroking of an artificial hand forces subjects to believe that an artificial rubber hand is their own and that they can control it. To understand the possible contribution of somatosensory input to the mechanisms of movement suppression during action observation, we suggest to investigate the somatosensory properties of the mirror neuron system (MNS). This includes responses of single mirror neurons to light touch, hair brushing and passive hand movement. Some neurons in area F5, where mirror neurons where discovered, have been shown to respond to such stimulation but it was not so far tested for mirror neurons. And more specifically we will investigate differences in somatosensory properties of facilitation and suppression mirror neurons discovered in our laboratory. It is well established that during movement we are less sensitive to the sensory input, eg touch. This reduced sensitivity manifests itself in a smaller neuronal signal in response to electrical stimulation of the nerve in comparison to the response at rest. This phenomenon is called sensory attenuation but it was not tested for mirror neurons. Non-invasive studies aiming at revealing sensory attenuation during action observation are contradictory. Some studies report attenuation while others enhancement. To resolve this controversy it is critical to investigate sensory attenuation on the level of local neuronal signals.In classical studies of the MNS, subjects just passively observe the actors' movements. In real life, it is quite often an active observation. While we execute an action we simultaneously observe a similar action, e.g. in a shared motor task such as two surgeons working together. Here action observation happens in the presence of somatosensory input, which resembles somatosensory input of an actor. What happens to the MNS simultaneously driven by action execution and action observation? To answer this question we will combine invasive neurophysiological investigation of non-human primates with non-invasive transcranial magnetic stimulation (TMS) studies of human volunteers.

执行日常动作（例如抓取物体）看起来和感觉起来毫不费力，但需要复杂的肌肉和关节机械装置以及包括脊髓和大脑回路的复杂控制系统。越来越多的证据表明，该控制系统的大部分在运动观察期间处于活动状态。二十多年前，Rizzolatti 教授及其同事发现，猕猴大脑 F5 区的单个神经元不仅对猴子的抓握做出反应，而且对人类实验者进行的相同抓握动作的观察也做出反应。这些神经元被称为“镜像神经元”。我们的小组对镜像神经元领域做出了重大贡献，他们发现在 F5 区域和初级运动皮层中，甚至直接连接到脊髓运动神经元的神经元也可以通过观察动作来调节。这种明显的悖论是，运动系统在动作观察过程中处于活跃状态，但不产生任何运动，这挑战了我们对运动如何产生的理解，并促使我们研究确定运动执行与动作观察之间的区别。一个明显的候选者是体感系统，它对身体表面或内部状态的变化做出反应。手静止时观察抓取与手移动并触摸物体时抓取执行之间的体感输入显然有很大不同。这种差异可能是为什么尽管运动区域存在镜像神经元活动但在动作观察期间不发生运动的一个重要因素。体感输入对于感知的强大作用的一个戏剧性例子是“橡胶手”错觉：轻轻抚摸受试者的手，再加上观察人造手的同步抚摸，迫使受试者相信人造橡胶手是他们自己的，并且他们可以控制它。为了了解体感输入对动作观察过程中运动抑制机制的可能贡献，我们建议研究镜像神经元系统（MNS）的体感特性。这包括单个镜像神经元对轻触、梳理头发和被动手部运动的反应。发现镜像神经元的 F5 区域的一些神经元已被证明对这种刺激有反应，但迄今为止尚未测试镜像神经元。更具体地说，我们将研究我们实验室发现的促进和抑制镜像神经元的体感特性差异。众所周知，在运动过程中，我们对感官输入（例如触摸）不太敏感。与休息时的反应相比，这种敏感性降低表现为对神经电刺激的神经元信号较小。这种现象称为感觉衰减，但尚未针对镜像神经元进行测试。旨在揭示动作观察过程中感觉衰减的非侵入性研究是矛盾的。一些研究报告减弱，而另一些研究报告增强。为了解决这一争议，研究局部神经元信号水平的感觉衰减至关重要。在 MNS 的经典研究中，受试者只是被动地观察演员的动作。在现实生活中，这通常是一种主动观察。当我们执行一个动作时，我们同时观察到一个类似的动作，例如在共同的运动任务中，例如两名外科医生一起工作。这里的动作观察是在存在体感输入的情况下发生的，这类似于演员的体感输入。由动作执行和动作观察同时驱动的 MNS 会发生什么？为了回答这个问题，我们将对非人类灵长类动物的侵入性神经生理学研究与对人类志愿者的非侵入性经颅磁刺激（TMS）研究结合起来。