Hess A, Kunesch E, Classen J, Hoeppner J, Stefan K, Benecke R
Department of Neurology, University of Rostock, Germany.
Exp Brain Res. 1999 Feb;124(3):321-30. doi: 10.1007/s002210050629.
In 11 healthy subjects motor-evoked potentials (MEPs) and silent periods (SPs) were measured in the right first dorsal interosseus (FDI) and abductor pollicis brevis muscles (APB): (1) when transcranial magnetic cortex stimulation (TMS) was applied at tonic isometric contraction of 20% of maximum force, (2) when TMS was applied during tactile exploration of a small object in the hand, (3) when TMS was applied during visually guided goal-directed isometric ramp and hold finger flexion movements, and (4) when at tonic isometric contraction peripheral electrical stimulation (PES) of the median nerve was delivered at various intervals between PES and TMS. Of the natural motor tasks, duration of SPs of small hand muscles was longest during tactile exploration (APB 205+/-42 ms; FDI 213+/-47 ms). SP duration at tonic isometric contraction amounted to 172+/-35 ms in APB and 178+/-31 ms in FDI, respectively. SP duration in FDI was shortest when elicited during visually guided isometric finger movements (159+/-15 ms). At tonic isometric contraction, SP was shortened when PES was applied at latencies -30 to +70 ms in conjunction with TMS. The latter effect was most pronounced when PES was applied 20 ms before TMS. PES-induced effects increased with increasing stimulation strength up to a saturation level which appeared at the transition to painful stimulation strengths. Both isolated stimulation of muscle afferents and of low-threshold cutaneous afferents shortened SP duration. However, PES of the contralateral median nerve had no effect on SPs. Amplitudes of MEPs did not change significantly in any condition. Inhibitory control of motor output circuitries seems to be distinctly modulated by peripheral somatosensory and visual afferent information. We conclude that somatosensory information has privileged access to inhibitory interneuronal circuits within the primary motor cortex.
在11名健康受试者中，测量了右侧第一背侧骨间肌（FDI）和拇短展肌（APB）的运动诱发电位（MEP）和静息期（SP）：（1）在最大力量的20%的强直等长收缩时施加经颅磁皮层刺激（TMS）；（2）在手部对小物体进行触觉探索时施加TMS；（3）在视觉引导的目标导向等长斜坡和保持手指屈曲运动时施加TMS；（4）在强直等长收缩时，在正中神经的外周电刺激（PES）与TMS之间的不同间隔施加PES。在自然运动任务中，手部小肌肉的SP持续时间在触觉探索时最长（APB为205±42毫秒；FDI为213±47毫秒）。强直等长收缩时，APB的SP持续时间分别为172±35毫秒，FDI为178±31毫秒。在视觉引导的等长手指运动时诱发的FDI中的SP持续时间最短（159±15毫秒）。在强直等长收缩时，当在潜伏期-30至+70毫秒结合TMS施加PES时，SP缩短。当在TMS前20毫秒施加PES时，后一种效应最为明显。PES诱导的效应随着刺激强度的增加而增加，直至达到饱和水平，该饱和水平出现在向疼痛刺激强度转变时。单独刺激肌肉传入神经和低阈值皮肤传入神经均缩短了SP持续时间。然而，对侧正中神经的PES对SP没有影响。在任何情况下，MEP的幅度均无显著变化。运动输出回路的抑制性控制似乎明显受到外周体感和视觉传入信息的调节。我们得出结论，体感信息可优先进入初级运动皮层内的抑制性中间神经元回路。
