Physiological Analysis of Correlation Between Rhythmical Jaw Movements and Monosynaptic Spinal Reflex in Humans

我们以前报道过，人类比目鱼肌H反射（S.H-R）在咬牙过程中显著易化，且易化程度随着咬牙力的增加而增加。在这项研究中，我们调查是否有任何调制的S.H-R在有节奏的下颌运动无牙齿接触（RJM）和有节奏的咀嚼口香糖（RGC）。实验在5名无口颌功能障碍的男性志愿者（年龄：22-27岁）中进行。受试者坐在一把扶手躺椅上。将双腿分别固定在约120 mm和100 mm处的膝关节和踝关节上。同时记录右侧比目鱼肌、两侧咬肌和二腹肌前肌的表面肌电图。电刺激腘窝胫神经诱发S.H-R。受试者进行自起搏RJM和RGC，比较下颌运动时和保持下颌静止时S.H-R的峰-峰振幅。结果发现：（1）RJM和RGC时，S.H-R易化（P<0.05，t检验）;（2）咬肌活动时相和二腹肌前肌活动时相的易化程度无显著性差异（P>0.05，ANOVA）。结果表明：（1）人咀嚼运动时比目鱼肌单突触反射具有张力易化作用;（2）口内机械感受器的传入冲动不是咀嚼运动易化的必要条件。一般认为，口腔运动对身体运动功能有很大的影响。

We previously reported that human soleus H-reflex (S.H-R) was remarkably facilitated during teeth clenching, and that the magnitude of the facilitation increased with teeth clenching force. In this study, we investigated whether there was any modulation of S.H-R during rhythmical jaw movements with no teeth contacts (RJMs) and rhythmical gum chewing (RGC) . Experiments were carried out in 5 male volunteers (age : 22-27 years) with no stomatognathic dysfunction. The subjects were seated in a reclining armchair. Both legs were fixed with the knee and ankle joints at approximately 120ﾟ and 100ﾟ, respectively. Surface EMG was simultaneously recorded from the right soleus musle as well as the masseter and the anterior digastric muscles bilaterally. Electrical stimulation was applied to the tibial nerve at the popliteal fossa to elicit S.H-R. The subject performed self-paced RJMs and RGC.The peak-to-peak amplitude of the S.H-R during jaw movements was compared with that during maintaining the jaw at rest position. We found that (1) S.H-R was facilitated during RJMs and RGC (P<0.05, t-test) , and (2) there was no significant difference in the magnitude of the facilitation between the phase when the masseter muscle was active and that when the anterior digastric muscle was active (P>0.05, ANOVA) . It was concluded that (1) human soleus monosynaptic reflex is tonically facilitated during mastication, and (2) afferent impulses from intraoral mechanoreceptors are not indispensable for the facilitation. It is assumed that the oral motor activity exerts a strong influence on the bodily motor function in general.