Neuromuscular control of fundamental frequency and glottal posture at phonation onset

Abstract

The laryngeal neuromuscular mechanisms for modulating glottal posture and fundamental frequency are of interest in understanding normal laryngeal physiology and treating vocal pathology. The intrinsic laryngeal muscles in an in vivo canine model were electrically activated in a graded fashion to investigate their effects on onset frequency, phonation onset pressure, vocal fold strain, and glottal distance at the vocal processes. Muscle activation plots for these laryngeal parameters were evaluated for the interaction of following pairs of muscle activation conditions: (1) cricothyroid (CT) versus all laryngeal adductors (TA/LCA/IA), (2) CT versus LCA/IA, (3) CT versus thyroarytenoid (TA) and, (4) TA versus LCA/IA (LCA: lateral cricoarytenoid muscle, IA: interarytenoid). Increases in onset frequency and strain were primarily affected by CT activation. Onset pressure correlated with activation of all adductors in activation condition 1, but primarily with CT activation in conditions 2 and 3. TA and CT were antagonistic for strain. LCA/IA activation primarily closed the cartilaginous glottis while TA activation closed the mid-membranous glottis.

Influence and interactions of laryngeal adductors and cricothyroid muscles on fundamental frequency and glottal posture control

“…The canine larynx is a close match to the human larynx in terms of its gross, microscopic, and histologic anatomy, and the validity of the in vivo canine model in voice research is well established (Berke et al, 1987;Garrett et al, 2000;Chhetri et al, 2010Chhetri et al, , 2012. The study protocol was approved by the Institutional Animal Research Committee (ARC) of the University of California, Los Angeles.…”

“…Surgical exposure of the larynx and graded stimulation of the laryngeal nerves were performed as described previously (Chhetri et al, 2010(Chhetri et al, , 2012. The neck was exposed surgically and the recurrent laryngeal nerves (RLNs) were identified at the tracheo-esophageal grooves bilaterally and followed distally toward the larynx.…”

“…The previous investigation on the role of ILMs in phonatory control was limited by the number of muscles concurrently activated (Chhetri et al, 2012). In that study, left-right paired graded stimulation was applied to two nerves on each side of the larynx.…”

“…We then investigated the interactions of the following pairs of muscle groups on F0 and phonatory posture (Chhetri et al, 2012): CT and all laryngeal adductors (TA/LCA/IA) (IA: interarytenoid muscle); CT and LCA/IA; CT and TA; and TA and LCA/IA. These interactions were reported: CT activation elongated the vocal folds, TA activation shortened and caused medial bulging of the vocal folds thus closing the mid-membranous glottis, and LCA/IA closed the posterior cartilaginous glottis but had negligible effects on vocal fold strain.…”

Complex vibratory patterns in an elephant larynx

“…In particular, in contrast to human or canine phonation (Zemlin, 1988;Hunter et al, 2004;Herbst et al, 2011;Chhetri et al, 2012), the subglottal air pressure ranges and the exact laryngeal configuration for vocal fold adduction in elephants are not known. The position of the arytenoid cartilages in the excised larynx experiment had to be inferred from careful examination of the available CT data and the functional and mechanical possibilities offered by the excised elephant larynx.…”