Function of the Thyroarytenoid Muscle in a Canine Laryngeal Model

Abstract

Fundamental frequency is controlled by contraction of the thyroarytenoid (TA) and cricothyroid (CT) muscles. While activity of the CT muscle is known to tense and thin the vocal folds, little is known about the effect of the TA muscle on vocal fold vibration. An in vivo canine laryngeal model was used to examine the role of the TA muscle in controlling phonation. Isolated TA muscle activation was obtained by stimulating sectioned terminal TA branches through small thyroid cartilage windows. Subglottic pressure measures, electroglottographic and photoglottographic signals, and acoustic signals were obtained in 5 mongrel dogs during dynamic and static variations in TA muscle activity. Results indicated that TA muscle activation is a major determinant in sudden shifts from high-frequency to modal phonation. Subglottic pressure increased and open quotient decreased gradually with increasing TA activation.

Neuromuscular control of fundamental frequency and glottal posture at phonation onset

“…One animal was used for each experimental condition (described below). Surgical exposure of the larynx and the laryngeal nerves was as described previously (Chhetri et al, 2010;Choi et al, 1993a). In brief, a low tracheotomy was performed for intraoperative ventilation.…”

“…To activate all the laryngeal adductors (TA/LCA/ IA), the RLN was stimulated by cuff electrodes around the RLN nerve trunk approximately 5 cm from the inferior border of the larynx. For selective activation of the adductors (TA or LCA/IA muscle complex), identification of the laryngeal adductor nerve branches from the RLN were performed (Choi et al, 1993a) by following the RLN distally and dissecting the nerve under magnification until the TA and LCA branches were exposed. The TA branch was tied off with silk sutures, divided to separate from the RLN trunk, and a tripolar cuff electrode was placed around the TA nerve branch to activate the TA muscle.…”

“…However their study is limited by not measuring the concurrent P sub . Choi et al (1993a) studied the role of TA in an in vivo canine model and found that increasing TA activation resulted in an increase in P sub . However, the effect on F 0 varied from decreasing to increasing.…”

Restraining mechanisms in regulating glottal closure during phonation

“…In humans, such "greater force" or restraining function may be provided by the contraction of the thyroarytenoid (TA) muscle, which stiffens the deep body layer of the vocal fold, and the cricothyroid (CT) muscle, which stretches and stiffens the vocal fold tension in the anterior-posterior (AP) direction. Although the importance of TA and CT muscle contraction in regulating phonation has long been recognized and has been the subject of numerous studies (e.g., Isshiki, 1964;Hirano et al, 1969;Gay et al, 1972;Tanabe et al, 1972;Ward et al, 1977;Moore et al, 1987;Choi et al, 1993), most of these studies focused on the roles of TA and CT muscle contraction in pitch and vocal loudness control. There has essentially no systematic investigation regarding the possible restraining effects that contraction of the TA and CT muscles may provide to maintain vocal fold position against the subglottal pressure.…”

Excised larynx experimentation: history, current developments, and prospects for bioacoustic research

“…The contraction of the thyroarytenoid (TA) muscle, however, which is among other things responsible for shortening and thickening the vocal folds, is virtually impossible to simulate (apart from over-adducting the vocal folds at the position of the vocal processes, which might constitute an unphysiological maneuver). This highlights some limit to the use of ELE, because contraction of the TA is assumed to be mainly responsible for modal voice ('chest register') (Choi et al, 1993), i.e. the main glottal configuration for human speech.…”