Talis Vera L, Kazennikov Oleg V, Solopova Irina A, Ioffe Marat E
Laboratory of Neurobiology of Motor Control, Institute for Information Transmission Problems, Russian Academy of Science, Moscow, Russian Federation.
J Integr Neurosci. 2009 Dec;8(4):409-16. doi: 10.1142/s0219635209002289.
Using the transcranial magnetic stimulation (TMS) of motor cortex we examined changes in the motor evoked potential (MEP) during natural bimanual unloading, during lifting of an equivalent weight by the contralateral arm while the ipsilateral forearm was held stationary (CONTRA) and during practice of unnatural unloading. During natural unloading, MEP amplitude decreased proportionally to the muscle activity. In CONTRA task MEP amplitude decreased, but the muscle activity was not changed. It suggests that the motor cortex activity related to the "postural" arm was inhibited by the contralateral motor cortex related to the "lifting" arm. This inhibition was diminished during the unloading task. When learning the unnatural unloading, the muscle activity decreased significantly with insignificant changes of MEP amplitude. Active role of the motor cortex during learning of the new task might be related to the reduction of the contralateral inhibition. This suggestion is supported by the observation that MEP amplitude decreased stronger than muscle activity in the first learning session similar to that in CONTRA task. MEP amplitude and background activity of the muscle proportionally decreased in the last learning trial. The results show that motor cortex activity in natural and unnatural unloading task might be related to the reduction of the interhemispheric inhibition.
我们使用运动皮层的经颅磁刺激（TMS），研究了自然双手卸载、在同侧前臂保持静止时对侧手臂提起同等重量物体（对侧任务）以及非自然卸载练习过程中运动诱发电位（MEP）的变化。在自然卸载过程中，MEP波幅与肌肉活动成比例下降。在对侧任务中，MEP波幅下降，但肌肉活动未改变。这表明与“姿势”手臂相关的运动皮层活动受到了与“提起”手臂相关的对侧运动皮层的抑制。在卸载任务期间，这种抑制作用减弱。在学习非自然卸载时，肌肉活动显著下降，而MEP波幅变化不明显。在新任务学习过程中运动皮层的积极作用可能与对侧抑制的降低有关。这一观点得到了如下观察结果的支持：在第一次学习过程中，MEP波幅的下降比肌肉活动更明显，类似于对侧任务中的情况。在最后一次学习试验中，MEP波幅和肌肉的背景活动成比例下降。结果表明，自然和非自然卸载任务中的运动皮层活动可能与半球间抑制的降低有关。
