NeuRRo Lab, Department of Physical Medicine and Rehabilitation, Michigan Medicine, Ann Arbor, MI, USA.
Michigan Robotics Institute, University of Michigan, Ann Arbor, MI, USA.
Restor Neurol Neurosci. 2019;37(4):363-374. doi: 10.3233/RNN-180894.
Short interval intracortical inhibition (SICI) is commonly used to assess inhibition in the motor cortex and is known to be affected by the paired-pulse stimulus parameters (i.e., interstimulus interval [ISI], conditioning stimulus intensity [CSI] and test stimulus intensity [TSI]) used during testing. While the effects of stimulus parameters are well-studied in the upper-extremity, evidence in the lower-extremity is lacking.
To comprehensively examine the effects of alterations in paired-pulse stimulus parameters on the two phases of SICI in the quadriceps muscle group.
Seventeen adults (8 males, 9 females) volunteered to participate in this study. SICI was examined over a range of CSIs (70-90% active motor threshold [AMT]), TSIs (100-140% AMT), and ISIs (1.0-3.0 ms) using both EMG and torque responses elicited by transcranial magnetic stimulation (TMS).
The results indicated that SICI at 1.0 ms ISI was best revealed with a CSI of 70% and TSI ≥110% AMT, whereas SICI at 2.5 ms ISI was best revealed with a CSI of 80-90% and a TSI of ≥130% AMT. Unlike upper-extremity muscles, evaluating SICI with a CSI of 70% AMT and an ISI of 1.0 ms produced the greatest inhibition for all TSIs. In general, inhibitory effects were contaminated by facilitatory effects when using a TSI of 100% AMT.
The amount of inhibition was dependent on the stimulation parameters used during testing. A CSI of 70% AMT, ISI of 1.0 ms, and TSI of ≥110% AMT appear to be optimal for measuring SICI in the quadriceps muscle; however, other parameters can be used if careful consideration is given to the described interaction between the parameters.
短间隔皮质内抑制（SICI）常用于评估运动皮质的抑制情况，其受到测试时使用的成对刺激参数（即刺激间隔[ISI]、刺激强度[CSI]和测试刺激强度[TSI]）的影响。虽然在上肢中已经对刺激参数的影响进行了广泛研究，但下肢的证据却很少。
全面研究改变成对脉冲刺激参数对股四头肌组 SICI 两个阶段的影响。
17 名成年人（8 名男性，9 名女性）自愿参加了这项研究。使用经颅磁刺激（TMS）诱发的肌电图和扭矩反应，在 CSIs（70-90%主动运动阈值[AMT]）、TSIs（100-140% AMT）和 ISIs（1.0-3.0 ms）范围内检查 SICI。
结果表明，CSI 为 70%且 TSI ≥110% AMT 时，1.0 ms ISI 的 SICI 效果最佳，而 CSI 为 80-90%且 TSI ≥130% AMT 时，2.5 ms ISI 的 SICI 效果最佳。与上肢肌肉不同，使用 CSI 为 70% AMT 和 ISI 为 1.0 ms 时，对于所有 TSI，都能产生最大的抑制作用。一般来说，使用 100% AMT 的 TSI 时，抑制效果会受到易化效果的干扰。
抑制量取决于测试期间使用的刺激参数。CSI 为 70% AMT、ISI 为 1.0 ms 和 TSI ≥110% AMT 似乎是测量股四头肌 SICI 的最佳参数；但是，如果仔细考虑到参数之间的相互作用，可以使用其他参数。
