Effects of thyroarytenoid muscle activation on phonation in an in vivo canine larynx model

Abstract

Previous studies have shown that the thyroarytenoid (TA) muscle plays an important role in the control of vocal fold adduction and stiffness. The effects of TA stimulation on vocal fold vibration, however, are still unclear. In this study, the effects of TA muscle activation on phonation were investigated in an in vivo canine larynx model. Laryngeal muscle activation was achieved through parametric stimulation of the thyroarytenoid, the lateral cricoarytenoid (LCA), and the cricothyroid (CT) muscles. For each stimulation level, the subglottal pressure was gradually increased to produce phonation. The subglottal pressure, the volume flow, and the outside acoustic pressure were measured together with high-speed recording of vocal fold vibration from a superior view. The results show that, without TA activation, phonation was limited to conditions of medium to high levels of LCA and CT activations. TA activation allowed phonation to occur at a much lower activation level of the LCA and CT muscles. Compared to conditions of no TA activation, TA activation led to decreased open quotient. Increasing TA activation also allow phonation to occur at a much larger range of the subglottal pressure while still maintaining certain degree of glottal closure during vibration. [Work supported by NIH.]