The Brain and Mind Institute, University of Western Ontario, London, Ontario, N6A 3K7, Canada.
Movement Control and Neuroplasticity Research Group, Department of Movement Sciences, Biomedical Sciences Group, KU Leuven, 3001, Leuven, Belgium; KU Leuven, Leuven Brain Institute, 3001, Leuven, Belgium.
Neuropsychologia. 2021 Jun 18;156:107836. doi: 10.1016/j.neuropsychologia.2021.107836. Epub 2021 Mar 26.
Transcranial magnetic stimulation (TMS) studies showed that corticospinal excitability (CSE) is modulated during observation of object lifting, an effect termed 'motor resonance'. Specifically, motor resonance is driven by movement features indicating object weight, such as object size or observed movement kinematics. We investigated in 16 humans (8 females) whether motor resonance is also modulated by an object's weight distribution. Participants were asked to lift an inverted T-shaped manipulandum with interchangeable center of mass after first observing an actor lift the same manipulandum. Participants and actor were instructed to minimize object roll and rely on constrained digit positioning during lifting. Constrained positioning was either collinear (i.e., fingertips on the same height) or noncollinear (i.e., fingertip on the heavy side higher than the one on the light side). The center of mass changed unpredictably before the actor's lifts and participants were explained that their weight distribution always matched the actor's one. Last, TMS was applied during both lift observation and planning of lift actions. Our results showed that CSE was similarly modulated during lift observation and planning: when participants observed or planned lifts in which the weight distribution was asymmetrically right-sided, CSE recorded from the thumb muscles was significantly increased compared to when the weight distribution was left-sided. During both lift observation and planning, this increase seemed to be primarily driven by the weight distribution and not specifically by the (observed) digit positioning or muscle contraction. In conclusion, our results indicate that complex intrinsic object properties such as weight distributions can modulate activation of the motor system during both observation and planning of lifting actions.
经颅磁刺激（TMS）研究表明，在观察物体提起的过程中，皮质脊髓兴奋性（CSE）会发生变化，这种现象被称为“运动共振”。具体来说，运动共振是由指示物体重量的运动特征驱动的，例如物体大小或观察到的运动运动学。我们在 16 名人类参与者（8 名女性）中研究了运动共振是否也会受到物体重量分布的调节。参与者被要求在观察到演员提起相同的操纵器后提起倒置的 T 形操纵器，该操纵器的质心可以互换。参与者和演员被指示尽量减少物体滚动，并在提起过程中依靠约束指尖位置。约束位置可以是共线的（即指尖在同一高度），也可以是非共线的（即重侧指尖高于轻侧指尖）。在演员举起物体之前，质心会不可预测地变化，并且告知参与者他们的重量分布总是与演员的重量分布相匹配。最后，在观察提升和规划提升动作期间应用 TMS。我们的结果表明，在提升观察和规划期间，CSE 受到类似的调节：当参与者观察或规划重量分布不对称右侧的提升时，与重量分布在左侧时相比，从拇指肌肉记录的 CSE 显著增加。在提升观察和规划期间，这种增加似乎主要是由重量分布驱动的，而不是由（观察到的）指尖位置或肌肉收缩驱动的。总之，我们的结果表明，复杂的内在物体属性，如重量分布，可以在提升动作的观察和规划期间调节运动系统的激活。
