Exteroceptive suppression of the trapezius muscle produced by mental nerve stimulation in normal subjects

The purpose of the present study was to evaluate the similarities and differences in exteroceptive suppression produced by mental nerve stimulation between the masseter and trapezius muscles. Six normal subjects were studied using various intensities of stimulation. Although the duration and degree of exteroceptive suppression were increased with stimulus intensity in the masseter muscle, they did not correlate with stimulus intensity in the trapezius muscle. The latency and duration in the trapezius muscle were almost the same as those in the masseter muscle. The degrees in the masseter muscle were significantly larger than those in the trapezius muscle. Exteroceptive suppression of the trapezius muscle might have a similar mechanism as that of the masseter muscle, but it may be mediated by the separate interneurons. The projection from the trigeminal afferent to the trapezius motoneuron might be smaller than that to the masseter motoneuron.