An electromyographic study of mastication in the rhesus monkey ( Macaca mulatta)

Abstract

Twenty-eight monkeys ( Macaca mulatta) were monitored during 84 electromyographic recording sessions to study the function of certain masticatory and facial muscles during mastication. During the period of closing muscle function, strong activity was noted in the temporal and masseter musculature and in the superior head of the lateral pterygoid muscle. The relative participation of the elevator muscles differed among the four age groups. During the period of opening muscle activity, the suprahyoids and the inferior head of the lateral pterygoid muscle functioned during the depression of the lower jaw. A comparison of the results of this study with the numerous human EMG studies of mastication indicate a basic similarity in muscle function during chewing in the two species, although age-related differences in specific muscle group activities do exist.