Lang Nicolas, Harms Jochen, Weyh Thomas, Lemon Roger N, Paulus Walter, Rothwell John C, Siebner Hartwig R
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, United Kingdom.
Clin Neurophysiol. 2006 Oct;117(10):2292-301. doi: 10.1016/j.clinph.2006.05.030. Epub 2006 Aug 21.
Low-frequency repetitive transcranial magnetic stimulation (rTMS) can reduce cortical excitability. Here we examined whether inhibitory after effects of low-frequency rTMS are influenced by stimulus intensity, the type of TMS coil and re-afferent sensory stimulation.
In fifteen healthy volunteers, we applied 900 biphasic pulses of 1Hz rTMS to the left primary motor cortex (M1) at an intensity that was 10% below or 15% above resting motor threshold. For rTMS, we used two different figure-of-eight shaped coils (Magstim or Medtronic coil) attached to the same stimulator. We recorded motor evoked potentials (MEPs) evoked with the same set-up used for rTMS (MEP-rTMS) before and twice after rTMS. Using a different TMS setup, we also applied monophasic pulses to the M1 in order to assess the effects of rTMS on corticospinal excitability, intracortical paired-pulse excitability and the duration of the cortical silent period (CSP). In a control experiment, the same measurements were performed after 15min of 1Hz repetitive electrical nerve stimulation (rENS) of the right ulnar nerve.
Analysis of variance revealed an interaction between intensity, coil and time of measurement (p<0.035), indicating that the effect of 1Hz rTMS on MEP-rTMS amplitude depended on the intensity and the type of coil used for rTMS. Suppression of corticospinal excitability was strongest after suprathreshold 1Hz rTMS with the Medtronic coil (p<0.01 for both post-rTMS measurements relative to pre-intervention baseline). Regardless of the type of coil, suprathreshold but not subthreshold rTMS transiently prolonged the CSP and attenuated paired-pulse facilitation. Suprathreshold 1Hz rENS also induced a short-lasting inhibition of MEP-rTMS.
Both the stimulation intensity and the type of TMS coil have an impact on the after effects of 1Hz rTMS. Re-afferent feedback activation may at least in part account for the stronger suppression of corticospinal excitability by suprathreshold 1Hz rTMS.
These data should be considered when rTMS is used as a therapeutic means.
低频重复经颅磁刺激（rTMS）可降低皮质兴奋性。在此，我们研究了低频rTMS的抑制后效应是否受刺激强度、TMS线圈类型和再传入感觉刺激的影响。
在15名健康志愿者中，我们以低于静息运动阈值10%或高于静息运动阈值15%的强度，对左侧初级运动皮层（M1）施加900个1Hz的双相rTMS脉冲。对于rTMS，我们使用连接到同一刺激器的两种不同的8字形线圈（Magstim或美敦力线圈）。我们在rTMS之前以及rTMS之后两次，使用与rTMS相同的设置记录运动诱发电位（MEP）（MEP-rTMS）。使用不同的TMS设置，我们还向M1施加单相脉冲，以评估rTMS对皮质脊髓兴奋性、皮质内配对脉冲兴奋性和皮质静息期（CSP）持续时间的影响。在对照实验中，在右侧尺神经进行15分钟的1Hz重复电神经刺激（rENS）后进行相同的测量。
方差分析显示强度、线圈和测量时间之间存在交互作用（p<0.035），表明1Hz rTMS对MEP-rTMS振幅的影响取决于用于rTMS的强度和线圈类型。使用美敦力线圈进行阈上1Hz rTMS后，皮质脊髓兴奋性的抑制最强（相对于干预前基线，两次rTMS后测量的p均<0.01）。无论线圈类型如何，阈上但非阈下rTMS会短暂延长CSP并减弱配对脉冲易化。阈上1Hz rENS也会诱导MEP-rTMS的短暂抑制。
刺激强度和TMS线圈类型均对1Hz rTMS的后效应有影响。再传入反馈激活可能至少部分解释了阈上1Hz rTMS对皮质脊髓兴奋性的更强抑制。
在将rTMS用作治疗手段时应考虑这些数据。
