[Neurophysiological mechanism of jaw-tongue reflex in man]

The present study was carried out to examine if the jaw-tongue reflex (JTR) could be elicited in man and if afferent fibers from the jaw-closing muscles were involved in this reflex. Electromyographic (EMG) activities were simultaneously recorded from the genioglossus (GG), the tongue retruding (TR) muscles, and the anterior temporal (TA), the posterior temporal (TP), the masseteric (Mass) and the digastric (Dig) muscles under various conditions. The results were as follows: 1. EMG activities of the GG and the TR muscles were increased during clenching, voluntary and passive jaw-opening, and chin-tapping. 2. Electrical stimulation of the deep temporal and masseteric nerves evoked H-reflex in the TA and the Mass muscles. EMG activities in the GG and the TR muscles were detected as the intensity of the electrical stimulation were increased. 3. The tonic vibration reflex (TVR) was induced in the jaw-closing muscles by applying vibratory stimulation to the bellies of the TA and the Mass muscles. EMG activities of the GG and the TR muscles were increased as the TA muscle activity was increased. It is concluded that the JTR is elicited in man and suggested that low threshold afferent fibers from the jaw-closing muscles, mainly the temporal muscle, were involved in eliciting the JTR in man.