Evoked EMG of masseter and temporal muscles in man

Following a percutaneous stimulation on the mandibular notch skin, two kinds of responses were recorded in the ipsilateral masseter and temporal muscles in man. The two responses had their proper stimulating points. The early response appeared with about a 2 ms latency and the late one with about a 6 ms latency which was shorter than that of T wave of the same muscle by about 1 ms. No responses were induced in the contralateral masseter and temporal muscles. Regarding the recovery process of the late response following double stimuli, a testing late response was released about 100% from the effect of conditioning shock at a longer interval than 80 approximately 95 ms. It might be safe to consider that the previous assumption, i.e. those two responses seemed to be M and H waves respectively, had been fortified. H response evoked in muscles tested seems to be sensitive enough to show the difference between excitatory states of its reflex arc.