The Lower Jaw And Tongue Movement Coordination Of The Neuromuscular Mechanism

To demonstrate the basic mechanism of coordination of jaw, tongue and hyoid movement, cortically induced rhythmic jaw and tongue movements(CRJTMs) were recorded by means of cinefluororadiography, and electromyographs(EMG) of jaw mus-cles(masseter, Ma and digastric, Di.) , tongue muscles(stylo-glossus, Sg and genioglossus, Gg) and hyoid muscles(sterno-hyoideus, Sh and geniohyoideus, Gh) were monitored simulta-neously, in the anesthetized rabbit. The following resultswere obtained: 1) The rhythms of jaw, tongue and hyoidmovements wore identical during CRJTMs; 2) Among CRJTMs, thetongue movements for type B (resemble to transport cycle innatural mastication) were characterized with a largeantero-posterior movements, especially in the tongue tip,while those for type D (resemble to chewing cycle in naturalmastication) were predominant in dorso-ventral movements,rather than antero-posterior one; 3) An orbit of the hyoidmovements showed either an eight-figure shape or an ellipse.Similar to the tongue movements, the orbit of the hyoidmovements was greater antero-posteriorly for type B than fortype D. Its most anterior position was attained in the jaw-...