Abstract
Tongue movements participate in oro-facial motor functions including chewing, sucking, swallowing, speech, respiration and so on. Although previous studies reported the coordination of jaw and tongue movements to clarify the patterns of tongue muscle activity, our knowledge as to the functional role of tongue muscles during chewing and swallowing in humans is still limited due to the technical difficulty to record the dynamic activity of tongue muscles. In this study, we recorded the EMG activity of left tongue protruder (genioglossus, GG), jaw-closer and supra- and infra-hyoid muscles during command swallow and natural mastication of test foods as well as rhythmic experimental open-close jaw movements in healthy subjects. For GG recording, the electrode assembly was fabricated on a dental acrylic resin. During command swallow, the subject was required to swallow test foods in different postures which were upright and head inclined w/ and w/o body reclinced to test the effects of head and body postures on the tongue activity. The activity pattern of GG muscle was different among the postures. During experimental rhythmic open-close jaw movements, all the muscles recorded were well-coordinated while the coordination was not observed in the case of natural mastication. Particularly, the GG activity did not always show the rhythmicity. The results suggest the variability of human tongue activity during mastication and swallowing. [Jpn J Physiol 54 Suppl:S179 (2004)]
