Ragert Patrick, Camus Mickael, Vandermeeren Yves, Dimyan Michael A, Cohen Leonardo G
Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20817, USA.
J Neurophysiol. 2009 Aug;102(2):766-73. doi: 10.1152/jn.00274.2009. Epub 2009 May 27.
The excitability of the human primary motor cortex (M1) as tested with transcranial magnetic stimulation (TMS) depends on its previous history of neural activity. Homeostatic plasticity might be one important physiological mechanism for the regulation of corticospinal excitability and synaptic plasticity. Although homeostatic plasticity has been demonstrated locally within M1, it is not known whether priming M1 could result in similar homeostatic effects in the homologous M1 of the opposite hemisphere. Here, we sought to determine whether down-regulating excitability (priming) in the right (R) M1 with 1-Hz repetitive transcranial magnetic stimulation (rTMS) changes the excitability-enhancing effect of intermittent theta burst stimulation (iTBS) applied over the homologous left (L) M1. Subjects were randomly allocated to one of four experimental groups in a sham-controlled parallel design with real or sham R M1 1-Hz TMS stimulation always preceding L M1 iTBS or sham by about 10 min. The primary outcome measure was corticospinal excitability in the L M1, as measured by recruitment curves (RCs). Secondary outcome measures included pinch force, simple reaction time, and tapping speed assessed in the right hand. The main finding of this study was that preconditioning R M1 with 1-Hz rTMS significantly decreased the excitability-enhancing effects of subsequent L M1 iTBS on RCs. Application of 1-Hz rTMS over R M1 alone and iTBS over L M1 alone resulted in increased RC in L M1 relative to sham interventions. The present findings are consistent with the hypothesis that homeostatic mechanisms operating across hemispheric boundaries contribute to regulate motor cortical function in the primary motor cortex.
经颅磁刺激（TMS）测试显示，人类初级运动皮层（M1）的兴奋性取决于其先前的神经活动历史。稳态可塑性可能是调节皮质脊髓兴奋性和突触可塑性的一种重要生理机制。尽管已在M1局部证明了稳态可塑性，但尚不清楚对M1进行预刺激是否会在对侧半球的同源M1中产生类似的稳态效应。在此，我们试图确定用1赫兹重复经颅磁刺激（rTMS）下调右侧（R）M1的兴奋性（预刺激）是否会改变施加在同源左侧（L）M1上的间歇性theta爆发刺激（iTBS）的兴奋性增强效果。在一项假对照平行设计中，受试者被随机分配到四个实验组之一，真实或假的R M1 1赫兹TMS刺激总是在L M1 iTBS或假刺激之前约10分钟进行。主要结局指标是通过募集曲线（RCs）测量的L M1中的皮质脊髓兴奋性。次要结局指标包括右手的捏力、简单反应时间和敲击速度。本研究的主要发现是，用1赫兹rTMS对R M1进行预处理可显著降低随后L M1 iTBS对RCs的兴奋性增强作用。单独对R M1施加1赫兹rTMS和单独对L M1施加iTBS相对于假干预导致L M1中的RC增加。目前的研究结果与以下假设一致，即跨半球边界运行的稳态机制有助于调节初级运动皮层中的运动皮质功能。
