Neuroscience Research Australia, Sydney, Australia.
University of New South Wales, Sydney, Australia.
J Neurophysiol. 2020 May 1;123(5):1969-1978. doi: 10.1152/jn.00607.2019. Epub 2020 Apr 15.
Paired corticospinal-motoneuronal stimulation (PCMS) is the repeated pairing of transcranial magnetic stimulation (TMS) with peripheral nerve stimulation to modify corticospinal synapses; however, it has yet to be determined whether PCMS modulates cortical excitability in a manner similar to paired-associative stimulation protocols. In this study, we first examined the effects of PCMS on adductor pollicis motor evoked potentials (MEPs). In , on 2 separate days PCMS (repetitive, high-intensity TMS and ulnar nerve stimulation pairs; 1.5-ms interstimulus interval; 0.1 Hz) was compared with control conditioning of repetitive high-intensity TMS-only stimuli (0.1 Hz). Before and after conditioning, adductor pollicis MEPs were elicited using low-intensity TMS in three different coil orientations to preferentially activate corticospinal axons directly (thus bypassing cortical effects) or indirectly (cortical effects present). Unexpectedly, similar MEP increases were seen for all orientations on both PCMS (129 to 136% of baseline) and control days (108 to 129% of baseline). Given the common factor between conditioning protocols was repeated, high-intensity TMS, further experiments were performed to characterize this repetitive TMS (rTMS) protocol. In , an intensity dependence of the rTMS protocol was revealed by a lack of change in MEPs elicited after repetitive low-intensity TMS (0.1 Hz; = 0.37). In , MEP recruitment curve and paired pulse analyses showed that the high-intensity rTMS protocol increased MEPs over a range of stimulus intensities but that effects were not accompanied by changes in intracortical inhibition or facilitation ( > 0.12). These experiments reveal a novel high-intensity, low-frequency rTMS protocol for enhancing corticospinal excitability. In this study, we present a novel, intensity-dependent repetitive transcranial magnetic stimulation (rTMS) protocol that induces lasting, plastic changes within the corticospinal tract. High-intensity rTMS at a frequency of 0.1 Hz induces facilitation of motor evoked potentials (MEPs) lasting at least 35 min. Additionally, these changes are not limited only to small MEPs but occur throughout the recruitment curve. Finally, facilitation of MEPs following high-intensity rTMS does not appear to be due to changes in intracortical inhibition or facilitation.
成对皮质脊髓运动神经元刺激（PCMS）是经颅磁刺激（TMS）与外周神经刺激的重复配对，以改变皮质脊髓突触；然而，尚不清楚 PCMS 是否以类似于成对联想刺激方案的方式调节皮质兴奋性。在这项研究中，我们首先检查了 PCMS 对拇内收肌运动诱发电位（MEPs）的影响。在 中，在 2 个不同的日子里，PCMS（重复、高强度 TMS 和尺神经刺激对；1.5ms 刺激间隔；0.1Hz）与重复高强度 TMS 仅刺激的对照条件（0.1Hz）进行了比较。在条件作用之前和之后，使用低强度 TMS 在三个不同的线圈方向诱发拇内收肌 MEPs，以优先直接（从而绕过皮质效应）或间接（存在皮质效应）激活皮质脊髓轴突。出乎意料的是，在 PCMS（129%至 136%的基线）和对照日（108%至 129%的基线）的所有方向上均观察到类似的 MEP 增加。鉴于条件作用方案之间的共同因素是重复的高强度 TMS，因此进一步进行了实验以表征这种重复 TMS（rTMS）方案。在 中，通过重复低强度 TMS（0.1Hz； = 0.37）后 MEPs 无变化揭示了 rTMS 方案的强度依赖性。在 中，MEP 募集曲线和成对脉冲分析表明，高强度 rTMS 方案在刺激强度范围内增加了 MEPs，但效应不伴有皮质内抑制或易化的变化（ > 0.12）。这些实验揭示了一种新颖的高强度、低频 rTMS 方案，用于增强皮质脊髓兴奋性。在这项研究中，我们提出了一种新颖的、强度依赖性的重复经颅磁刺激（rTMS）方案，该方案可在皮质脊髓束内引起持久的、可塑的变化。频率为 0.1Hz 的高强度 rTMS 可诱导持续至少 35 分钟的运动诱发电位（MEPs）易化。此外，这些变化不仅限于小 MEPs，而是发生在整个募集曲线中。最后，高强度 rTMS 后 MEPs 的易化似乎不是由于皮质内抑制或易化的变化所致。
