1998 年 65 巻 1 号 p. 64-73
Modulation of the tibialis anterior (T.A.) H reflex and the reciprocal Ia inhibition from the ankle flexor to the extensor were studied during voluntary teeth-clenching in 7 healthy adult volunteers to investigate the correlation between the oral motor activity and the somatic motor function.
The TA. H reflex was significantly facilitated during voluntary teeth-clenching, and the amount of this facilitation increased with the level of masseter EMG activity. Furthermore, the reciprocal Ia inhibition of the soleus H reflex, induced by stimulation of the common peroneal nerve at a subthreshold intensity for evoking the T.A.M wave, was significantly depressed during voluntary teeth-clenching.
It was concluded that 1) the TA. H reflex is facilitated during voluntary teeth-clenching, 2) there is a positive correlation between the amount of facilitation of the TA. H reflex and the level of teeth-clenching force, and 3) the reciprocal Ia inhibition of the crural muscle is reduced during voluntary teeth- clenching. It was suggested that teethclenching contributes to stability of body stance by increasing the stiffness of the ankle joint.