Department of Psychology & NeuroMI - Milan Centre for Neuroscience, University of Milano-Bicocca, Milan, Italy; Ph.D. program in Neuroscience, School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
Department of Psychology & NeuroMI - Milan Centre for Neuroscience, University of Milano-Bicocca, Milan, Italy.
Brain Stimul. 2020 May-Jun;13(3):627-636. doi: 10.1016/j.brs.2020.01.017. Epub 2020 Feb 5.
Associative plasticity, the neurophysiological bases of Hebbian learning, has been implied in the formation of the association between sensory and motor representations of actions in the Mirror Neuron System; however, such inductor role still needs empirical support.
OBJECTIVE/HYPOTHESIS: We have assessed whether Paired Associative Stimulation (PAS), known to activate Hebbian associative plasticity, can induce the formation of atypical (absent in normal conditions), visuo-motor associations, reshaping motor resonance.
Healthy participants underwent a novel PAS protocol (mirror-PAS, m-PAS), during which they were exposed to repeated pairings of transcranial magnetic stimulation (TMS) applied over the right primary motor cortex (M1), time-locked with the view of index-finger movements of the right (ipsilateral) hand. In a first experiment, the inter-stimulus interval (ISI) between visual-action stimuli and TMS pulses was varied. Before and after each m-PAS session, motor resonance was assessed by recording Motor Evoked Potentials induced by single-pulse TMS applied to the right M1, during the observation of both contralateral (left) and ipsilateral (right) index-finger movements. In the second experiment, the specificity of the m-PAS was assessed by presenting a visual stimulus depicting a non-biological movement.
Before m-PAS, the facilitation of corticospinal excitability occurred only during the view of contralateral (with respect to the TMS side) index-finger movements. The m-PAS induced new ipsilateral motor resonance responses, indexed by atypical facilitation of corticospinal excitability by the view of ipsilateral hand movements. This effect occurred only if the associative stimulation followed the chronometry of motor control (ISI of 25 ms) and if the visual stimulus of the m-PAS depicts a biological movement (human hand action).
The present findings provide the first empirical evidence that Hebbian learning induced by a PAS protocol shapes the visual-motor matching properties of the human Mirror Neuron System.
联想可塑性是赫伯学习的神经生理学基础，它被暗示存在于镜像神经元系统中感觉和运动动作表示之间的关联形成中；然而，这种诱导作用仍需要实证支持。
目的/假设：我们评估了配对关联刺激（PAS）是否可以诱导形成异常（在正常情况下不存在）的视动关联，从而重塑运动共振。这种 PAS 已知可以激活赫伯联想可塑性。
健康参与者接受了一种新的 PAS 方案（镜像-PAS，m-PAS），在此期间，他们接受了经颅磁刺激（TMS）重复对右初级运动皮层（M1）的刺激，与右手（同侧）食指运动的视觉刺激同步。在第一个实验中，视觉-动作刺激与 TMS 脉冲之间的刺激间间隔（ISI）是可变的。在每个 m-PAS 疗程前后，通过记录单脉冲 TMS 施加于右 M1 时引起的运动诱发电位，评估运动共振，同时观察对侧（左）和同侧（右）食指运动。在第二个实验中，通过呈现描绘非生物运动的视觉刺激来评估 m-PAS 的特异性。
在 m-PAS 之前，皮质脊髓兴奋性的易化仅发生在观察对侧（相对于 TMS 侧）食指运动时。m-PAS 诱导了新的同侧运动共振反应，通过对同侧手运动的视觉观察来标记皮质脊髓兴奋性的异常易化。这种效应仅在关联刺激遵循运动控制的时间关系（ISI 为 25 毫秒）并且 m-PAS 的视觉刺激描绘生物运动（人手动作）时发生。
本研究结果首次提供了实证证据，表明 PAS 方案诱导的赫伯学习塑造了人类镜像神经元系统的视觉-运动匹配特性。
