Staines W R, Brooke J D, Misiaszek J E, McIlroy W E
Department of Human Biology and Nutritional Sciences, and Biophysics Interdepartmental Group, University of Guelph, Ontario, Canada.
Exp Brain Res. 1997 Jun;115(1):156-64. doi: 10.1007/pl00005676.
Attenuation of initial somatosensory evoked potential (SEP) gain becomes more pronounced with increased rates of movement. Manipulation of the range of movement also might alter the SEP gain. It could alter joint receptor discharge; it should alter the discharge of muscle stretch receptors. We hypothesized that: (1) SEP gain reduction correlates with both the range and the rate of movement, and (2) manipulation of range and rate of movement to achieve similar estimated rates of stretch of a leg extensor muscle group (the vasti) results in similar decreases in SEP gain. SEPs from Cz', referenced to Fpz' (2 cm caudal to Cz and Fpz, respectively, according to the International 10-20 System), along with soleus H-reflexes were elicited by electrical stimulation of the tibial nerve at the popliteal fossa. Stable magnitudes of small M-waves indicated stability of stimulation. A modified cycle ergometer with an adjustable pedal crank and electric motor was used to passively rotate the right leg over three ranges (producing estimated vasti stretch of 12, 24 and 48 mm) and four rates (0, 20, 40 and 80 rpm) of movement. Two experiments were conducted. Ranges and rates of pedalling movement were combined to produce two or three equivalent estimated rates of tissue stretch of the vasti muscles at each of 4, 16, 32 and 64 mm/s. Tibial nerve stimuli were delivered when the knee was moved through its most flexed position and the hip was nearing its most flexed position. Means of SEP, H-reflex and M-wave magnitudes were tested for rate and range effects (ANOVA). A priori contrasts compared means produced by equivalent estimated rates of vasti stretch. Increasing the rate of movement significantly increased the attenuation of SEP and H-reflex gain (P<0.05). Increasing the range of movement also significantly increased these gain attenuations (P<0.05). Combining these to achieve equivalent rates of stretch, through different combinations of rate and range, resulted in equivalent depressions of SEP gain. H-reflex gains were similarly conditioned. These results suggest that muscle stretch receptors play a more important role than joint or cutaneous receptors in regulating SEP gain consequent to movement. We note that the present calculation only considers the knee extensors; however, the biomechanical model of stretch applies also to receptors in the hip extensors. This paper and the companion one show that primary factors in the kinaesthetic components of the movement regulate activity-induced gain attenuation of SEPs.
随着运动速度的增加，初始体感诱发电位（SEP）增益的衰减变得更加明显。运动范围的改变也可能会改变SEP增益。它可能会改变关节感受器的放电；也应该会改变肌肉牵张感受器的放电。我们假设：（1）SEP增益的降低与运动范围和速度都相关，并且（2）通过改变运动范围和速度来实现腿部伸肌肌群（股四头肌）相似的估计拉伸速率，会导致SEP增益出现相似的降低。根据国际10 - 20系统，在腘窝处电刺激胫神经，引出参考Fpz'（分别位于Cz和Fpz尾侧2 cm处）的Cz'处的SEP，同时引出比目鱼肌H反射。小M波的稳定幅度表明刺激的稳定性。使用带有可调节踏板曲柄和电动机的改良型自行车测力计，使右腿在三个运动范围（产生股四头肌估计拉伸量为12、24和48 mm）和四个运动速度（0、20、40和80 rpm）下被动旋转。进行了两个实验。将蹬踏运动的范围和速度组合起来，在4、16、32和64 mm/s的速度下，使股四头肌产生两到三种等效的估计组织拉伸速率。当膝盖处于最屈曲位置且髋关节接近最屈曲位置时，施加胫神经刺激。对SEP、H反射和M波幅度的平均值进行速度和范围效应测试（方差分析）。先验对比比较了由股四头肌等效估计拉伸速率产生的平均值。增加运动速度显著增加了SEP和H反射增益的衰减（P<0.05）。增加运动范围也显著增加了这些增益衰减（P<0.05）。通过速度和范围的不同组合将两者结合以实现等效的拉伸速率，会导致SEP增益出现等效的降低。H反射增益也受到类似的影响。这些结果表明，在运动导致的SEP增益调节中，肌肉牵张感受器比关节或皮肤感受器发挥着更重要的作用。我们注意到，目前的计算仅考虑了膝关节伸肌；然而，拉伸的生物力学模型也适用于髋关节伸肌中的感受器。本文及其配套论文表明，运动的动觉成分中的主要因素调节了活动诱导的SEP增益衰减。
