Hashemi Niloufaralsadat, Chau Tom, Beal Deryk S
Bloorview Research Institute, Holland Bloorview Kid's Rehabilitation Hospital, Toronto, Ontario, Canada.
Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
Imaging Neurosci (Camb). 2025 Jan 3;3. doi: 10.1162/imag_a_00419. eCollection 2025.
The response of the motor neuron system to the observation of lateralized movements and expectation mismatches remains elusive. We investigated how observation of hand movement modulates corticospinal excitability as measured by motor evoked potentials to single pulse transcranial magnetic stimulation (TMS). Twenty-seven adults watched a series of egocentric video recordings of hands, with one hand either squeezing a foam ball as expected or both hands remaining stationary. Task conditions comprised observation-only and observation with synchronous imitation of the depicted motor action. Single TMS pulses were delivered to the motor cortex contralateral to the dominant hand at the video frame of maximal hand closure for squeeze videos and randomly for no-squeeze videos (in both observation-only or observation with synchronous imitation). We analyzed MEPs, from the First Dorsal Interosseous (FDI) muscle of the dominant hand. Observation alone (absence of motor intention) did not enhance corticospinal excitability; however, when paired with imitation (presence of motor intention), it tended to increase MEP amplitudes, regardless of the attended side (dominant or non-dominant) or depicted action (squeeze or not). Among conditions in which the dominant hand remained stationary, MEP amplitudes were elevated (p = 0.004) in observation with imitation of non-dominant hand squeezing, suggesting hemispheric dominance in coordinating motor actions. Additionally, MEP latencies tended to decrease during synchronous imitation of squeeze videos. Our findings support the consideration of observation with synchronous imitation as a task for brain state-dependent brain stimulation protocols for optimizing neuromotor recovery.
运动神经元系统对侧化运动观察和预期不匹配的反应仍然难以捉摸。我们研究了手部运动观察如何调节皮质脊髓兴奋性，该兴奋性通过对单脉冲经颅磁刺激（TMS）的运动诱发电位来测量。27名成年人观看了一系列以自我为中心的手部视频记录，其中一只手按预期挤压泡沫球，或者双手保持静止。任务条件包括仅观察和观察并同步模仿所描绘的运动动作。对于挤压视频，在手部最大闭合的视频帧时，将单个TMS脉冲发送到优势手对侧的运动皮层；对于无挤压视频（在仅观察或观察并同步模仿两种情况下），则随机发送。我们分析了优势手第一背侧骨间肌（FDI）的运动诱发电位。仅观察（无运动意图）并不会增强皮质脊髓兴奋性；然而，当与模仿（有运动意图）配对时，无论关注的是哪一侧（优势侧或非优势侧）或所描绘的动作（挤压或不挤压），它都倾向于增加运动诱发电位的幅度。在优势手保持静止的条件下，在观察并模仿非优势手挤压时，运动诱发电位幅度升高（p = 0.004），这表明在协调运动动作方面存在半球优势。此外，在同步模仿挤压视频期间，运动诱发电位潜伏期倾向于缩短。我们的研究结果支持将观察并同步模仿作为一种任务，用于依赖脑状态的脑刺激方案，以优化神经运动恢复。
