True Vocal Fold Research Articles

声帯の物性について

Simple and objective methods were developed to evaluate the mechanical properties of the vocal fold in relation to mobility of the vocal fold mucosa and stiffness of the vocal fold. Mobility of the vocal fold mucosa was measured with a fine suction tube, and stiffness of the vocal fold was evaluated by analyzing stress-strain curves in human and canine excised larynges under various conditions.1) Mobility of the vocal fold mucosa was greatest in the middle of the membranous portion and less around the anterior commissure and the vocal process. Stiffness of the membranous portion of the vocal fold was least at the middle and greater around the anterior commissure and the vocal process. Mobility of the false vocal fold mucosa was much greater, and stiffness of the false vocal fold was much less, than those of the true vocal fold.2) As the vocal fold tension increased, mobility of the vocal fold mucosa decreased and stiffness of the vocal fold increased as the vocal pitch rose. Marked differences of the mechanical properties were observed between the “body” and the “cover” of the vocal fold, especially when tension was applied to the vocal fold.3) When the vocalis muscle contracted, the vocal fold tended to be less stiff and more viscous.4) When the vocal fold mucosa became dry, stiffness of the vocal fold became greater.5) Submucosal injection of saline solution reduced mobility of the vocal fold mucosa and increased stiffness and viscosity of the vocal fold.

声帯のｓｔｉｆｆｎｅｓｓに関する実験的研究

A simple and objective method was developed of evaluating the mechanical property of the vocal fold in relating to stiffness by analyzing stress-strain curves. Stiffness of the true and false vocal fold was examined in human and canine excised larynges under various conditions.1) Stiffness of the membranous portion of the vocal fold was least at the middle and greater around the anterior commissure and vocal process. Stiffness of the false vocal fold was much less than that of the true vocal fold.2) As vocal fold tension increased, stiffness of the vocal fold increased.3) Stiffness of the vocal fold was decreased and hysteresis was increased when the thyroarytenoid (vocalis) muscle contracted.

Existence of vocal folds in the larynx of odontoceti (toothed whales).

Odontocetes (toothed whales) vocalize for communication and echolocation. The mechanisms of sound production, however, remain unclear. Their larynx has long been thought to lack vocal folds and, thus, was considered incapable of generating sounds. This study investigates internal anatomy of the odontocete larynx to: 1) describe the morphology of any folds found, 2) determine any structural homologies between these folds and the vocal folds of terrestrial mammals, and 3) assess their possible function in sound production. Larynges of 24 odontocetes representing ten genera (Delphinus, Stenella, Lagenorhynchus, Tursiops, Grampus, Delphinapterus, Globicephala, Kogia, Mesoplodon, and Phocoena) were studied post mortem. Nine specimens were cut midsagittally, and the remainder were dorsally opened to reveal internal anatomy. Results show that, contrary to established belief, vocal folds are consistently present. They are not isolated bands or "cords," but appear continuous with the internal laryngeal membrane. The attachments of these folds are the same as in terrestrial mammals, thus indicating homology with true mammalian vocal folds. These folds extend from the midline of the thyroid cartilage to the base of the arytenoid cartilages, sometimes to a discrete process. The vocal folds are elongated and oriented in a vertical plane, parallel to airflow direction. Vocal fold morphology varies, appearing as true bifurcated structures, a trifurcated fold, or a single midline fold. Laryngeal ventricles and vestibular folds are also consistently found lateral to the vocal folds. The vocal folds may divide the airstream within the larynx into three separate air currents. Fold vibrations may produce initial laryngeal sound used in echolocation or communication.

Variations in normal human laryngeal anatomy and physiology as viewed fiberscopically

<h2>Summary</h2> The purpose of this study was to observe and document variations in configuration and movement of the lower vocal tract and selected laryngeal structures in a sample of normal speakers. Ten men and ten women, ranging in age from 21 to 33 years, judged to have normal voices, were examined fiber-optically. Each subject engaged in a set protocol of phonatory and nonphonatory tasks and all examinations were videotaped. Judges reviewed these recordings with special attention to the following structures: pharyngeal wall, epiglottis, pyriform sinuses, ventricular folds, true vocal folds and the arytenoid complex. Extensive variability among these normals was observed anatomically and physiologically.

Treatment for aspiration related to dysphagia: An overview

Aspiration of food during ingestion is the entry of material into the airway below the true vocal folds. It may occur as the result of a number of anatomical and physiological disturbances in deglutition in the oral, pharyngeal, or esophageal stages. In order for aspiration to be treated effectively and efficiently, it should be defined according to its etiology and timing in relation to the reflexive swallow, i.e., before, during, or after the swallow. Each physiological or anatomical etiology for aspiration requires a different management strategy. Treatment may involve compensatory strategies, such as postural changes or diet restraints, which alter the way food flows through the oral cavity or pharynx and usually have an immediate effect on aspiration. Or treatment may consist of exercise programs designed to have a long-term effect on neuromuscular control during the swallow and that require a longer time to take effect. Both compensatory techniques and exercise programs may be instituted simultaneously in some patients. Treatment procedures for the most frequently occurring physiological disorders of deglutition are described.

Brain macropotentials related to self-paced skilled performance in Parkinson's disease

The Bereitschaftspotential (BP) is a slow negative-going cortical potential associated with preparation for volitional movement. Studies since the 1960s have provided evidence for a BP preceding speech-related volitional motor acts. However, the BP associated specifically with voice initiation (i.e. a volitional motor act involving bilateral true vocal fold adduction) has not to date been systematically investigated. The current investigation utilizes a novel experimental design to address methodological confounds typically found in studies of movement-related cortical potentials, to demonstrate the existence and localization of generators for the voice-related cortical potential (VRCP). Using high-density EEG, we recorded scalp potentials in preparation for voice onset and for exhalation in a stimulus-induced voluntary movement task. Results showed a slow, increasingly negative cortical potential in the time window of up to 2500 ms prior to the mean onset of phonation. This VRCP peaked at a greater amplitude and shorter latency than the BP associated with exhalation alone. VRCP sources were localized to the anterior rostral regions of the medial frontal gyrus (Supplementary Motor Area (SMA)) and in bilateral laryngeal motor areas before and immediately following the mean initiation of phonation. Additional sources were localized to the bilateral cerebellum and occipital lobe in the time window following the mean onset of phonation. We speculate that these results provide additional support for fine somatotopic organization of the SMA. Further examination of the spatiotemporal change of the VRCP yielded source models which indicated involvement of the laryngeal motor cortices and cerebellum, likely responsible for the initiation and continuation of phonation.

Aspiration in Head and Neck Surgical Patients

Aspiration, the entry of material into the airway below the true vocal folds, has been reported in various types of postsurgical head and neck patients. This study was designed to examine radiographically a group of 30 head and neck surgical patients with postoperative swallowing difficulties and to identify the relationship between the physiologic causes of aspiration in each patient and the surgical procedure. The modified barium swallow technique is needed to identify the nature of aspiration in these patients. Aspiration before, during, and after the swallow was caused by a variety of problems including reduced tongue control, delayed triggering of the swallowing reflex, reduced glottic closure, reduced laryngeal elevation, and reduced pharyngeal peristalsis. Eight patients exhibited two causes of aspiration. No one food consistency caused greater aspiration in all patients. The best and worst food consistencies varied with the cause of aspiration.

Aberrant laryngeal devoicing gestures produced by deaf speakers: Evidence from high speed laryngeal films

Recent acoustic, aerodynamic, and glottographic data (R. Whitehead and D. Metz, following abstract, this meeting) suggest that deaf speakers may produce aberrant abductory and adductory devoicing gestures associated with the /h/ segment in /ihi/ syllables. These aberrant devoicing gestures apparently interact with respiratory and upper airway dynamics to such a degree that the normal temporal contiguity of the syllable is disturbed. To gain a more precise understanding of the physiological nature of these gestures, high speed laryngeal films were obtained from four deaf speakers. The films illustrate that aberrant abductory devoicing is characterized by an excessively wide separation of the vocal folds during the production of /h/, while aberrant adductory devoicing is characterized by glottal constriction during /h/ production. In some instances, the glottis is constricted by both the true vocal folds and the ventricular folds which prohibits normal reinitiation of vocal fold vibration for the adjacent /i/ segment. Photographic sequences of individual frames excised at 50-ms intervals from films exposed at 4000 frames/s will be shown to illustrate these aberrant laryngeal gestures. [Work supported by U.S. Department of Education.]

Immunopathological Study of the Larynx

Using immunofluorescent and histopathological techniques, we studied the distribution and secretory activity of the glands of the larynx from 55 humans. The cavity of the larynx was covered with secretory glandular cells with the exception of the true vocal cords, aryepiglottic folds and upper part of the laryngeal surface of the epiglottis. Immunofluorescent study revealed the presence of IgG and other immunoglobulins throughout the connective tissue ground in each laryngeal mucosa. The most striking was seen in the staining pattern of IgA. Diffuse fluorescence for IgA was observed not only in the submucosal or periglandular connective tissue area but also in the intraeptithelial or submucosa glands. Secretory component synthesis was found mainly in each serous-type glandular epithelium or acinus. In the submucosa or periglandular area, IgA producing plasma cells were numerous. Our observations suggest that IgA, produced locally, is secreted via the glandular cells as secretory component--SIgA. Secretory activity of SIgA in these glandular tissues indicates that the larynx is possibly an immunologically active organ in the upper respiratory tract.

Laminagraphic Investigation of Pulse Register (Vocal Fry) Phonation

The physiologic and aerodynamic parameters of modal register phonation have been extensively investigated; not so well researched are these same parameters for the loft (falsetto) and, especially, the pulse (vocal fry) registers. The present study was designed to add to the knowledge being accumulated for the pulse register—in this case, with regard to the relationships of both vocal fold and ventricular fold area and thickness correlates of variation in f0. Subjects were seven males and six females, with normal healthy larynges, who could sustain pulse at high and low repetition rates. Coronal cross-sectional laminagrams were obtained by means of the stroboscopic laminagraphic (STROL) technique. It was found that there were no trends of any type for area or thickness change as a function of frequency variation. However, it was found also that the ventricular folds impinge upon, or load, the true vocal folds for this type of phonation. Hence, it is suggested that the ventricular folds may act to damp vocal fold vibration by coupling their passive mass with that of the true folds. Implications relative to theories of phonation will be discussed.

The Laryngeal Ventricle Considered as an Acoustical Filter

The ventriculus laryngis is a pocket-shaped slit which extends laterally between the false and true vocal folds. It is deepest in the middle, and from its anterior half there projects vertically upward a blind sack called the appendix. Its physiological function is supposedly that of a lubricant for the vocal cords. The presence of fibrous tissue in the ventricular fold would seem to indicate the possibility of muscular control of the volume of the ventricle and the area of the orifice into the larynx, thus suggesting the possible action of the laryngeal ventricle as an acoustical filter. The necessary conditions are thus established for the consideration of a resonator of variable volume, neck, and orifice. Unique frequency resonance is obviously not to be expected from such a resonator with its highly damping walls. The theory of Stewart's Acoustic Filters is applied in consideration of the effect on tone quality of the human voice. Some of the practices in vocal training are discussed, bearing such possible effects in mind.