Abstract
It has been observed that the tonic discharge disappears to some extent immediately preceding the rapid voluntary movements.This phenomenon, premotion silent period, has been considered the learned, rather than automatic, motor response.The present study was designed to reveal the premotion silent period at ballistic voluntary jaw movements. While 7 healthy male subjects (25-27 yr) made slight voluntary clenching and maintained it steadily, they were asked to respond with the maximum voluntary clenching as rapid as possible to acoustic stimulus. The myoelectric signals from masseter muscles, temporal muscles, and anterior bellies of digastric muscles were simultaneously recorded.
The results obtained were as follows:
1.In five out of the seven subjects, the premotion silent period was observed in the masseter muscle.The frequency of the premotion silent period for the seven subjects was 30%.
2.The premotion silent period was also recorded for temporal muscles.
3.When the silence occurred prior to the distinct bursts of the masseter muscle, no bursts was found of the antagonist, i.e.anterior belly of digastric muscle.This finding suggested premotion silent period was not a reciprocal a inhibition.
