Anatomical and electromyographic studies of the digastric muscle

Abstract

The techniques and sites for EMG recordings from the digastric muscles are controversial. To re-evaluate old techniques for recording from the digastric muscles, especially the posterior bellies, the morphology of the muscles was studied by conventional dissections and by examination of specimens sectioned in the frontal and the horizontal planes. Based on these anatomical findings, recording sites and approaches to them were developed for the anterior and posterior bellies of the digastric muscles. EMG recordings from the two bellies of the muscle were obtained from five healthy subjects. The EMG recordings were ranked according to muscle activity level and the activity within single muscles and between muscles compared using the Wilcoxon signed rank test. The anterior and posterior bellies had synchronized activity in all mandibular movements but were silent or had negligible activity with the mandible in the rest position, when the head was rotated, and while clenching. Both bellies had marked to very marked activity during jaw opening, and moderate to marked activity during protrusion, retrusion and lateral movements. During swallowing the anterior and posterior bellies had patterns characterized by bursts of activity of high amplitude and short duration. The two bellies were not, however, always synchronously active.

Asymmetric Activation of Motor Cortex Controlling Human Anterior Digastric Muscles During Speech and Target-Directed Jaw Movements

“…It is generally regarded that the two hemispheres act in concert to control the trigeminal muscles, although there is evidence for a functional differentiation in the dual-hemisphere control of masseter from M1 during unilateral biting (Butler et al 2001). In contrast, the digastric muscles on each side are usually activated in unison (Widmalm et al 1988) and no functional distinctions in the dual-hemisphere control of digastrics from M1 have been identified previously. Until now, however, the cortical control of the trigeminal muscles has been considered virtually exclusively in the context of mastication and the application of force to objects between the teeth.…”

Dynamics of the Human Masticatory System

“…For a complete overview of the applied muscle tensions to be acquired, their physiological crosssections, architecture, and degree of activation must be estimated. Physiological cross-sections have been estimated from anatomic cross-sections (Weijs and Hillen, 1984;Koolstra and van Eijden, 1992) and muscle activation from EMG recordings (Carlsöö, 1952(Carlsöö, , 1956aMøller, 1966;Lehr et al, 1971;Widmalm et al, 1988;Murray et al, 1999a,b), but it is questionable whether such methods can be applied routinely to all muscles involved. Masticatory muscle architecture has been studied in vitro (van Eijden et al, 1997), but the influence of individual variations on model predictions and the possibility of applying relevant corrections have not been established.…”

Ação De Músculos Hióideos Durante Movimentos Da Cabeça Avaliados Pela Eletromiografia

“…Nos trabalhos de [4] com eletrodos de agulha não foram consideradas ativações dos respectivos músculos nas mesmas atividades, assim como nos de [5] que indicam silêncio elétrico ou atividade elétrica mínima em rotação, flexão e extensão da cabeça, isto ocorre devido a diferença das técnicas utilizadas.…”