Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland.
J Neurosci Methods. 2011 Feb 15;195(2):241-8. doi: 10.1016/j.jneumeth.2010.11.022. Epub 2010 Dec 7.
To characterize the behaviour of primary motor cortex and to determine appropriate measurement parameters for short-interval cortical inhibition (SICI) and intracortical facilitation (ICF) by paired-pulse transcranial magnetic stimulation (TMS) with the aid of MRI-based neuronavigation.
Paired-pulse TMS was targeted to the optimal cortical representation sites of the abductor pollicis brevis (APB) muscle in 48 healthy right-handed volunteers. Motor evoked potentials (MEPs) were recorded from the APB and abductor digiti minimi (ADM) muscles. The conditioning stimulus (CS) intensities were 80% and 90% and the test stimulus was 120% of the resting motor threshold (rMT). The interstimulus intervals (ISIs) were 3, 7, 13, 22 and 28 ms.
Inhibition was observed at 3 ms with a CS of 80%. Facilitation emerged at ISIs of 7 and 13 ms with both CS intensities, more prominently with 90%. At ISI of 22 ms, facilitation was observed in ADM (p<0.01) but not in APB. No uniform amplitude change was observed at ISI of 28 ms. For both muscles, MEP latencies were shortened (p<0.01) at ISIs of 3 and 7 ms and prolonged (p<0.01) at 28 ms.
Inhibition is most prominent at ISI of 3 ms and CS of 80% of rMT, whereas CS of 90% of rMT and ISIs of 7 and 13 ms are preferable for facilitation. Latencies appear to be stable and independent indicators of both phenomena should be taken into account.
Both the latency and amplitude of MEPs are important parameters when paired-pulse paradigms are used in clinical studies.
借助 MRI 引导的神经导航技术，对初级运动皮层的行为进行特征描述，并确定短程皮质抑制（SICI）和皮质内易化（ICF）的合适测量参数。
在 48 名健康的右利手志愿者中，将成对的经颅磁刺激（TMS）靶向到外展拇指短肌（APB）的最佳皮质代表区。从 APB 和小指展肌（ADM）记录运动诱发电位（MEP）。刺激强度为 80%和 90%的条件刺激（CS）和 120%的静息运动阈值（rMT）的测试刺激。刺激间隔（ISIs）为 3、7、13、22 和 28 ms。
在 CS 为 80%时，在 3 ms 时观察到抑制。在两种 CS 强度下，在 ISI 为 7 和 13 ms 时出现易化，以 90%时更为明显。在 ISI 为 22 ms 时，ADM 中观察到易化（p<0.01），而在 APB 中则没有。在 ISI 为 28 ms 时，没有观察到一致的幅度变化。对于两种肌肉，在 ISI 为 3 和 7 ms 时，MEP 潜伏期缩短（p<0.01），而在 ISI 为 28 ms 时延长（p<0.01）。
在 ISI 为 3 ms 和 CS 为 rMT 的 80%时，抑制最为明显，而 CS 为 rMT 的 90%和 ISI 为 7 和 13 ms 时则有利于易化。潜伏期似乎是稳定的，应考虑将其作为两种现象的独立指标。
在临床研究中使用成对脉冲范式时，MEP 的潜伏期和幅度都是重要的参数。
