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

我们以前曾报道，人比目鱼肌H反射(S.H-R)在咬合过程中显著地被促进，并且这种促进的程度随着咬合力的增加而增加。在这项研究中，我们调查了在没有牙齿接触的有节奏的下颌运动(RJM)和有节奏的咀嚼口香糖(RGC)的过程中，S.H-R是否有任何的调制。实验对象为5名男性志愿者，年龄22~27岁，无口腔颌面功能障碍。受试者坐在一张倾斜的扶手椅上。用膝关节和踝关节分别以大约120ﾟ和100ﾟ的速度固定双腿。同时记录双侧比目鱼肌、咬肌和前二腹肌的表面肌电信号。电刺激肘窝的胫神经诱发SH-R。受试者进行自律RJM和RGC，比较颌骨运动和静止状态下SH-R的峰间波幅。我们发现：(1)在RJMS和RGC中，S.H-R被促进(P&lt；0.05，t检验)；(2)咬肌活动时相和前二腹肌活动时相之间的促进程度没有显著差异(P&gt；0.05，ANOVA)。结果表明：(1)人比目鱼肌单突触反射在咀嚼过程中是张力易化的；(2)口内机械感受器的传入冲动并不是易化所必需的。一般认为，口腔运动活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.