Investigation of excitability and fatigue phenomenon in the corticospinal tract using transcortical magnetic stimulation.

(1)对照实验研究：采用经颅磁刺激，研究了健康志愿者在进行两种不同体力劳动时第一背骨间肌（FDI）的疲劳现象；食指屈外展结合（FXA）和握力（GP）。运动诱发反应（MEPs）在FXA任务中被显著抑制，而在GP任务中被显著抑制。而在磁刺激前进行指神经刺激时，MEP的衰减率较低。此外，刺激周时间直方图（PSTH）显示，MEP大小的抑制和维持是由皮层的运动单位计数（i波）的变化引起的。其他手部远端肌肉也出现了疲劳，而腿部肌肉没有出现疲劳。(2)临床研究为了验证帕金森氏病患者的皮质脊髓兴奋性是否受损，在获得信息后，对10名患者和10名年龄匹配的对照组进行了研究。在病人组，他们在两个不同的日子里接受研究；在接受左旋多巴常规治疗的当天（on -day）和停药至少12小时的当天（OFF-day）。运动诱发反应（MEPs）记录在第一背骨间肌（FDI）。采用双磁刺激技术（调节-试验设计）。10个试验的测试或条件休克，随机对侧靶肌肉。第一次调适性电击强度调整为目标肌肉静止运动阈值的1.5倍。调整试验冲击强度，使静息时MEP峰间幅值在1.0mV左右。调节测试间隔每25毫秒变化一次，最多125毫秒。所有申请人都在两种情况下进行了研究；在休息和活动中。在较大的mep后，调节冲击诱导的沉默期持续约150ms。休息；两组在CTI作用50 ms后，MEPs均被显著抑制。相比之下，对照组受试者在CTIs的25 - 125 ms激活时表现出增强的皮质脊髓兴奋性。平均兴奋性为195%。在患者组中，ON-DAY的发生率为85%。在不考虑左旋多巴治疗的情况下，患者组的兴奋性明显降低，提示帕金森病患者的疲劳可能与皮层有关。少

(1) Experimental study in controlsBy using transcranial magnetic stimulation, fatigue phenomenon in the first dorsal interosseous muscle (FDI) was investigated in healthy volunteers during performance of two different manual tasks ; combination of flexion and abduction of index finger (FXA), and power grip (GP). Motor evoked responses (MEPs) were greatly suppressed in FXA task rather than in GP task. When conditionig digital nerve stimulation preceded the magnetic shocks, however, the decrement of MEP remained poor in ratio. In addition, peristimulus time histogram (PSTH) suggested that the suppression and maintenance of MEP in size were of cortical origin because of change of the number of motor unit counts (I-wave). The fatigue was also shown in other distal hand muscles, not in leg muscles.(2) Clinical studyIn order to verify whether corticospinal excitability was impaired in patients with Pakinson's disease, 10 patients and 10 age-matched controls were studied, after receiving info … More rmed consent. In the patient group, they were studied in two different days ; on the day they had ordinal L-DOPA therapy (ON-day) and on the day they were withdrawn from taking their medicine (OFF-day) at least over 12 hours. Motor evoked responses (MEPs) were recorded in the first dorsal interosseus muscle (FDI). Double magnetic stimulation technique (conditioning-test design) was applied. 10 trials for the test or conditioned shock were delivered, contralaterally to the target muscle at random. The intensity of the first conditionig shock was adjusted as 1.5 times of motor threshold of the target muscle at rest. The intensity of test shock was adjusted so that MEP at rest was around 1.0mV in the peak-to-peak amplitude. Conditioning-test intervals varied each 25 ms up to 125 ms. All applicants were studied in two situations ; at rest and and in activation. The conditioning shock induced silent period lasting up to around 150ms, following larger MEPs. At rest ; MEPs were greatly suppressed after 50 ms of CTI in both groups. In contrast, control subjects showed enhanced corticospinal excitability in activation between 25 and 125 ms of CTIs. Mean average of the excitability was 195%. In the patient group, it was 85% ON-DAY.Irrespective of L-DOPA therapy, the excitability in the patient group was greatly decreased, which suggests that the fatigue in patients with Parkinson's disease is probably in cortical origin. Less