Demjan Michal, Säisänen Laura, Reijonen Jusa, Rissanen Saara, Määttä Sara, Julkunen Petro
Department of Clinical Neurophysiology, Kuopio University Hospital, POB 100, 70200 KYS Kuopio, Finland; Department of Technical Physics, University of Eastern Finland, POB 1627, 70210 Kuopio, Finland; Bittium Biosignals Oy, Pioneerinkatu 6, 70800 Kuopio, Finland.
Department of Technical Physics, University of Eastern Finland, POB 1627, 70210 Kuopio, Finland.
Brain Res. 2023 Apr 15;1805:148284. doi: 10.1016/j.brainres.2023.148284. Epub 2023 Feb 14.
Transcranial magnetic stimulation (TMS) can induce motor evoked potentials (MEPs). In TMS applications, near-threshold stimulation intensities (SIs) are often used for characterizing corticospinal excitability using MEPs. We aimed to characterize the individual near-threshold recruitment of MEPs and to test the assumptions related to selection of the suprathreshold SI. We utilized MEP data from a right-hand muscle induced at variable SIs. The single-pulse TMS (spTMS) data from previous studies (27 healthy volunteers), as well as data from new measurements (10 healthy volunteers) that included also MEPs modulated by paired-pulse TMS (ppTMS), were included. The probability of MEP (p) was represented with individually fitted cumulative distribution function (CDF) with two parameters: resting motor threshold (rMT) and spread relative to rMT. MEPs were recorded with 110% and 120% of rMT as well as with Mills-Nithi upper threshold (UT). The individual near-threshold characteristics varied with CDF parameters: the rMT and the relative spread (median: 0.052). The rMT was lower with ppTMS than with spTMS (p < 0.001), while the relative spread remained similar (p = 0.812). At suprathreshold SIs, the probability of MEP was similar between UT and 110% of rMT (p > 0.88), and higher for 120% of rMT (p > 0.98). The individual near-threshold characteristics determine how probably MEPs are produced at common suprathreshold SIs. At the population level, the used SIs UT and 110% of rMT produced MEPs at similar probability. The individual variability in the relative spread parameter was large; therefore, the method of determining the proper suprathreshold SI for TMS applications is of crucial importance.
经颅磁刺激（TMS）可诱发出运动诱发电位（MEP）。在TMS应用中，常使用接近阈值的刺激强度（SI），通过MEP来表征皮质脊髓兴奋性。我们旨在描述MEP的个体接近阈值募集情况，并检验与选择阈上SI相关的假设。我们利用了在不同SI下诱发的右手肌肉的MEP数据。纳入了先前研究（27名健康志愿者）的单脉冲TMS（spTMS）数据，以及新测量（10名健康志愿者）的数据，新测量数据还包括由双脉冲TMS（ppTMS）调制的MEP。MEP的概率（p）用具有两个参数的个体拟合累积分布函数（CDF）表示：静息运动阈值（rMT）和相对于rMT的离散度。以rMT的110%和120%以及米尔斯 - 尼蒂上阈值（UT）记录MEP。个体接近阈值的特征随CDF参数而变化：rMT和相对离散度（中位数：0.052）。与spTMS相比，ppTMS时的rMT更低（p < 0.001），而相对离散度保持相似（p = 0.812）。在阈上SI时，UT和rMT的110%时MEP的概率相似（p > 0.88），rMT的120%时更高（p > 0.98）。个体接近阈值的特征决定了在常见阈上SI时产生MEP的可能性。在群体水平上，所使用的SI即UT和rMT的110%产生MEP的概率相似。相对离散度参数的个体变异性很大；因此，确定TMS应用中合适阈上SI的方法至关重要。
