Vocal Fold Physiology Research Articles

Mechanotransduction in the Vocal Fold Microenvironment: A Narrative Review.

The vocal fold tissues undergo nearly continuous and repeated cycles of injury and repair throughout the course of an individual's lifetime. It is well established that certain individuals are at greater risk of lesion development based on personality and behavioral classification. However, these characteristics alone do not wholly predict or explain lesion development or severity. In this review, we discuss current knowledge of mechanotransduction proteins and their potential relevance to tissue homeostasis in the vocal folds. A review of literature surrounding mechanotransduction and tissue homeostasis as it relates to the vocal folds was conducted. Review of the literature included searches of PubMed, Google Scholar, and other various online peer-reviewed sources. Search terms pertained to mechanosensation, mechanotransduction, mechanically activated channels, mechanical cellular regulation, and other associated concepts and terms. Additional literature was identified through the reference lists of identified papers. Findings of this literature review were then applied to known physiology and pathophysiology of the vocal folds in order to speculate on the contribution of mechanically mediated mechanisms within the vocal fold. Because the vocal folds are such mechanically active structures, withstanding nearly constant external forces, there is strong support for the idea that mechanically sensitive molecular pathways within the vocal fold tissue play a major role in tissue homeostasis in the presence of these considerable forces. As such, mechanotransduction within the vocal fold should be considered and targeted in future biological studies of vocal fold physiology.

Describing the Cellular Impact of IQOS™ Smoke Extract and Vibration on Human Vocal Fold Fibroblasts

ObjectivesThe isolated or combined effects of vibration and smoke extract (SE) from the IQOS™ “heat-not-burn” technology on human vocal fold fibroblasts (hVFF) were evaluated in an in vitro setting in order to elucidate their influence on vocal fold (patho-) physiology. Study DesignExperimental pilot study using intervention with IQOS™-SE in vitro. MethodsImmortalized hVFF were exposed to IQOS™-SE or control medium under static or vibrational conditions. A phonomimetic bioreactor was used to deliver vibrational patterns to hVFF over a period of 5 days. Cytotoxicity was quantified by lactate dehydrogenase assay. Effects on extracellular matrix production, inflammation, fibrogenesis, and angiogenesis were assessed by reverse transcription-quantitative polymerase chain reaction, Western Blot, enzyme-linked immunosorbent assay, and Magnetic Luminex assays. ResultsWe observed significant changes induced either by IQOS™-SE exposure alone (matrix metalloproteinase 1, fibronectin, cyclooxygenase (COX)1, interleukin-8 gene expression), or by the combination of IQOS™-SE and vibration (hyaluronidase 2, COX2, interleukin-8 protein levels, vascular endothelial growth factor D). ConclusionShort-term in vitro exposure of hVFF to IQOS™-SE did not result in cytotoxicity and reduced the gene expression of measured inflammation mediators, but had no effect on their protein expression. However, the clinical effects of long-term IQOS™ use are still not known and further research is needed in order to asses, if IQOS™ is in fact less harmful than conventional cigarettes.

Wound Healing and Special Considerations for the Professional and Performing Voice

Purpose: The purpose of this article is to review the wound healing process of the vocal fold following phonomicrosurgery to remove benign vocal fold lesions in professional voice users. Understanding this process and the risk of developing scar tissue at the injury site is important for treatment of these individuals. This review also highlights special considerations during the postinjury rehabilitation period and the unique vocal loading tasks and needs of performing voice users. The goal of this article is to provide clinical tools for wound healing education to nonvoice-specialized speech-language pathologists to inform their rehabilitation of the professional and performing voice user. Conclusions: Implications intrinsic to vocal fold physiology and the stages of wound healing necessitate the avoidance of scar tissue with a rehabilitation plan tailored to the unique vocal loading demands of professional and performing voice users. There is a need to develop specific rehabilitation protocols that are genre-specific to aid in the individual treatment of the elite vocal athlete.

Contribution of laryngeal size to differences between male and female voice production.

In this study we investigated the effect of sex- and age-related differences in vocal fold length, thickness, and depth on voice production in a three-dimensional vocal fold model. The results showed that the cause-effect relationships between vocal fold physiology and voice production previously identified in an adult male-like vocal fold geometry remained qualitatively the same in vocal folds with geometry representative of adult females and children. We further showed that the often-observed differences in voice production between adult males, adult females, and children can be explained by differences in length and thickness. The lower F0, higher flow rate, larger vocal fold vibration amplitude, and higher sound pressure level (SPL) in adult males as compared to adult females and children can be explained by differences in vocal fold length. In contrast, the thickness effect dominated and contributed to the larger closed quotient of vocal fold vibration, larger normalized maximum flow declination rate, and lower H1-H2 in adult males as compared to adult females and children. The effect of differences in vocal fold depth was generally small. When targeting a specific SPL, adult males experienced a lower peak vocal fold contact pressure during phonation than adult females and children.

Self-Organization in Vocal Mechanics and Physiology

Self-Organization in Vocal Mechanics and Physiology Ingo R. Titze (bio) VOICE RESEARCH AND TECHNOLOGY Self-organization is now an accepted concept in biological systems. Complex systems with many interactive components do not need microcontrol of each component to produce a well coordinated output of the system. If given enough individual freedom, the components will interact in such a way as to produce an organization for optimum efficiency. Contrary to classical thinking, regularity can be produced with much variability in the system, or even irregularity in the input. Heartbeat is a good example. The neural inputs to the heart muscles are not as regular as the heartbeat itself. The muscles self-organize for their collective output. In the old way of thinking, noise-in always meant noise-out. In the new way of thinking, some added noise can actually help in self-organization. It gives the system more choices for possible coordinated activity. Feedback and ample exchange of energy between components is a requirement. Feedback can be positive or negative. Positive feedback reinforces the output of a component by taking a portion of the output and adding it to the input in phase. Negative feedback subtracts some of the output from the input. With the two forms of feedback, many forms of interaction are possible between subsystems. Consider some examples in vocalization. The subsystems can be the left vocal fold, the right vocal fold, the subglottal resonator, and the supraglottal resonator. Each has its own natural resonance properties. They all can be thought of as oscillators. Energy transfer is facilitated by glottal aerodynamics and acoustic wave propagation in the airways. Without energy transfer and feedback between the subsystems, the components all would likely have their own frequency, amplitude, and phase in their oscillatory patterns. The output would not be periodic (harmonic) unless each is controlled with precision. With interaction, however, they can synchronize their motions and the forces that keep them in motion. No separate control is needed. However, synchronization is more likely if the subsystems have great flexibility, a wide range of operation. So, what is the take-home message for singers? To obtain regularity and predictability in our vocal output, we need to resist the tendency to restrict the range of operation of some of the components. The theory suggests that we not limit the range of tongue or lip movements, or the range of lung pressure, or the choice of vowels, or the choice of larynx position. Allowing for maximal self-organization would speak against such restrictions. Focusing on the desired output and its repeatability pays the higher dividends. If the system [End Page 233] knows what to produce, it will use its internal variability to produce it. We should not constrain the interaction between the system components. This is especially the case if there is a deficiency or abnormality in one or more of the components. The rest of the system has to compensate, which means that the range of operation and mobility of some components has to increase. In summary, the message is: Let the vocal system organize itself. Give it the right output targets and it will find a way to get there with lots of alternative solutions. [Dr. Titze's bio is republished here because his updated version regrettably was omitted in the last issue.] [End Page 234] Ingo R. Titze Ingo R. Titze, PhD, is Emeritus Distinguished Professor of Speech Science and Voice at the University of Iowa and Executive Director of the National Center for Voice and Speech at the University of Utah. His formal education is in physics and electrical engineering, but he has devoted much of his studies to vocal music and speech. Dr. Titze has published more than 500 articles in scientific and educational journals, coedited two books titled Vocal Fold Physiology, and now has four books in print: Principles of Voice Production, The Myoelastic Aerodynamic Theory of Phonotion, Vocology: The Science and Practice of Voice Habilitation, and Fascinations with the Human Voice. He has lectured throughout the world and has appeared on such educational television series as Innovation, Quantum, and Beyond 2000. He is a recipient of the William and Harriott Gould Award for laryngeal physiology...

Quantitative evaluation of the human vocal fold extracellular matrix using multiphoton microscopy and optical coherence tomography

Identifying distinct normal extracellular matrix (ECM) features from pathology is of the upmost clinical importance for laryngeal diagnostics and therapy. Despite remarkable histological contributions, our understanding of the vocal fold (VF) physiology remains murky. The emerging field of non-invasive 3D optical imaging may be well-suited to unravel the complexity of the VF microanatomy. This study focused on characterizing the entire VF ECM in length and depth with optical imaging. A quantitative morphometric evaluation of the human vocal fold lamina propria using two-photon excitation fluorescence (TPEF), second harmonic generation (SHG), and optical coherence tomography (OCT) was investigated. Fibrillar morphological features, such as fiber diameter, orientation, anisotropy, waviness and second-order statistics features were evaluated and compared according to their spatial distribution. The evidence acquired in this study suggests that the VF ECM is not a strict discrete three-layer structure as traditionally described but instead a continuous assembly of different fibrillar arrangement anchored by predominant collagen transitions zones. We demonstrated that the ECM composition is distinct and markedly thinned in the anterior one-third of itself, which may play a role in the development of some laryngeal diseases. We further examined and extracted the relationship between OCT and multiphoton imaging, promoting correspondences that could lead to accurate 3D mapping of the VF architecture in real-time during phonosurgeries. As miniaturization of optical probes is consistently improving, a clinical translation of OCT imaging and multiphoton imaging, with valuable qualitative and quantitative features, may have significant implications for treating voice disorders.

Estimation of vocal fold physiology from voice acoustics using machine learning.

The goal of this study is to estimate vocal fold geometry, stiffness, position, and subglottal pressure from voice acoustics, toward clinical and other voice technology applications. Unlike previous voice inversion research that often uses lumped-element models of phonation, this study explores the feasibility of voice inversion using data generated from a three-dimensional voice production model. Neural networks are trained to estimate vocal fold properties and subglottal pressure from voice features extracted from the simulation data. Results show reasonably good estimation accuracy, particularly for vocal fold properties with a consistent global effect on voice production, and reasonable agreement with excised human larynx experiment.

An in vitro scaffold-free epithelial-fibroblast coculture model for the larynx.

Physiologically relevant, well-characterized in vitro vocal fold coculture models are needed to test the effects of various challenges and therapeutics on vocal fold physiology. We characterize a healthy state coculture model, created by using bronchial/tracheal epithelial cells and immortalized vocal fold fibroblasts. We also demonstrate that this model can be induced into a fibroplastic state to overexpress stress fibers using TGFβ1. In vitro. Cell metabolic activity of immortalized human vocal fold fibroblasts incubated in different medium combinations was confirmed with an MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide) assay. Fibroblasts were grown to confluence, and primary bronchial/tracheal epithelial cells suspended in coculture medium were seeded directly over the base layer of the fibroblasts. Cells were treated with transforming growth factor β1 (TGFβ1) to induce myofibroblast formation. Cell shape and position were confirmed by live cell tracking, fibrosis was confirmed by probing for α smooth muscle actin (αSMA), and phenotype was confirmed by immunostaining for vimentin and E-cadherin. Fibroblasts retain metabolic activity in coculture epithelial medium. Live cell imaging revealed a layer of epithelial cells atop fibroblasts. αSMA expression was enhanced in TGFβ1-treated cells, confirming that both cell types maintained a healthy phenotype in coculture, and can be induced into overexpressing stress fibers. Vimentin and E-cadherin immunostaining show that cells retain phenotype in coculture. These data lay effective groundwork for a functional coculture model that retains the reproducibility necessary to serve as a viable diagnostic and therapeutic screening platform. NA Laryngoscope, 127:E185-E192, 2017.

Japanese “street seller’s voice”

The term “Street Seller’s Voice” (henceforth SSV) refers to a category of voice quality which can be uttered only by, but not all, Japanese young girls, especially selling something cute and fashionable. We can hear this voice at cake shops, but never at “wagashi” (i.e., Japanese cake) shops, since “wagashi” is not cute and fashionable, unlike western cake which for Japanese people is cute. In order to catch the nature of SSV we recorded voices of several street sellers, and also conducted MRI experiments with 3 subjects. The results suggest that SSV has a twang quality [e.g., Estill et al. 1983, Proc. Stockholm Music Acoustics Conference, 157-174; Honda et al. 1995, Vocal Fold Physiology; Voice Quality Control, 23-38], which is manifested in the acoustic signal by, among other things, sustained high energy in the upper frequency regions, and may possibly be produced with high larynx and change in pharyngeal cavity size. One advantage to this type of voice production is it is easily heard in a noisy environment and puts minimum strain on the vocal folds [Estill, personal communication]. [This work was supported by the following grants: JSPS Grants A #15H02605 and A #25240026.]

Cause-effect relationship between vocal fold physiology and voice production in a three-dimensional phonation model

The goal of this study is to better understand the cause-effect relation between vocal fold physiology and the resulting vibration pattern and voice acoustics. Using a three-dimensional continuum model of phonation, the effects of changes in vocal fold stiffness, medial surface thickness in the vertical direction, resting glottal opening, and subglottal pressure on vocal fold vibration and different acoustic measures are investigated. The results show that the medial surface thickness has dominant effects on the vertical phase difference between the upper and lower margins of the medial surface, closed quotient, H1-H2, and higher-order harmonics excitation. The main effects of vocal fold approximation or decreasing resting glottal opening are to lower the phonation threshold pressure, reduce noise production, and increase the fundamental frequency. Increasing subglottal pressure is primarily responsible for vocal intensity increase but also leads to significant increase in noise production and an increased fundamental frequency. Increasing AP stiffness significantly increases the fundamental frequency and slightly reduces noise production. The interaction among vocal fold thickness, stiffness, approximation, and subglottal pressure in the control of F0, vocal intensity, and voice quality is discussed.

Busted, Plausible or Confirmed

Busted, Plausible or Confirmed

Interactive Augmentation of Voice Quality and Reduction of Breath Airflow in the Soprano Voice

In 1985, at a conference sponsored by the National Institutes of Health, Martin Rothenberg first described a form of nonlinear source-tract acoustic interaction mechanism by which some sopranos, singing in their high range, can use to reduce the total airflow, to allow holding the note longer, and simultaneously enrich the quality of the voice, without straining the voice. (M. Rothenberg, "Source-Tract Acoustic Interaction in the Soprano Voice and Implications for Vocal Efficiency," Fourth International Conference on Vocal Fold Physiology, New Haven, Connecticut, June 3-6, 1985.) In this paper, we describe additional evidence for this type of nonlinear source-tract interaction in some soprano singing and describe an analogous interaction phenomenon in communication engineering. We also present some implications for voice research and pedagogy.

Gender differences in the acoustic realization of creaky voice: Evidence from conversational data collected in Northern California

Although several sociophonetic studies report greater breathiness among female speakers, a pattern often attributed to sexual dimorphism in vocal fold physiology (Södersten and Lindestad, 1990), recent studies in North America report that young women use more creaky voice than men (Yuasa, 2011; Podesva, 2013). While these recent studies examine conversational data, they rely on auditory techniques to identify creaky phonation, leaving its acoustic realization in conversational speech largely unexplored. The present study investigates the acoustic properties of creaky voice in hour-long sociolinguistic interviews with 30 speakers (15 females, 15 males; age 18–86) from Northern California. Measures of spectral tilt were taken at the midpoint of all vowels in the corpus (N = 362,429), and data were fitted to a mixed effects linear regression model. As expected, several linguistic factors influence H1-H2 values (previous and following segment, intensity, F0, F1, vowel duration, stress, phrase position, phrase duration), alone and in interaction. With regard to social factors, H1-H2 is significantly lower for female speakers, indicating greater creak, even though the H1-H2 measure under-captures creakiness for female speakers (Simpson, 2012), and no age effect was observed. In sum, while females are generally creakier, apparent time data do not indicate that this is a recent trend.

Pantothenate Kinase-Associated Neurodegeneration Causing Paradoxical Vocal Fold Motion

We report a patient with paradoxical vocal fold motion (PVFM) due to pantothenate kinase-associated neurodegeneration, a rare neurodegenerative disease and a subclass of neurodegeneration with brain iron accumulation disorders. PVFM is marked by normal vocal fold anatomy and physiology with intermittent adduction during the respiratory cycle. Many etiologies have been reported and include laryngeal hypersensitivity such as asthma and gastroesophageal reflux, functional disorders, and neurologic disorders such as focal respiratory dystonia. This case highlights the occasional association of PVFM with underlying neurologic disorders, especially those that disrupt autonomic functioning.

Observations of phonation threshold pressure and fundamental frequency in the in vivo canine larynx using graded neuromuscular stimulation

Phonation threshold pressure is an objective measure of the relative ease of phonation. Previous studies of the in vivo canine larynx have reported values of phonation threshold pressure in the range of 3.5-5.5 kPa. Such studies are often cited to argue that canine and human vocal fold physiology may differ significantly, since threshold pressures in human phonation are often measured to be as low as 0.2-0.3 kPa. Similarly, the frequency range observed in canine phonation has generally been reported to be more limited than that found in human phonation. In this study, our hypothesis was that through the use of a newly-developed method of graded stimulation to both the superior laryngeal nerve and the individual branches of the recurrent laryngeal nerve, the ranges of phonation threshold pressure and fundamental frequency observed in the in vivo canine model would overlap significantly with that of human phonation. This hypothesis was confirmed. In particular, phonation threshold pressures were observed to be as low as 0.2-0.3 kPa, and the fundamental frequency range was observed to span nearly four octaves. Previous studies of in vivo canine phonation may have been limited by an inadvertent, exclusive focus on hyper-stimulation of the thyroarytenoid muscle.

Demographic and Videostroboscopic Assessment of Vocal Pathologies

Successful treatment of bilateral vocal fold lesions depends on the accuracy of the diagnosis. The application of stroboscopy to the study of vocal fold vibration has led to dramatic advances in the understanding of vocal fold physiology. Laryngeal stroboscopy is the state of the art diagnostic tool and this technique provides valuable information about the nature of the vibration and a visual image that can be used both for immediate analysis and as a permanent record for comparison of repeated examination at a later date. In this study we are presenting demographic analysis and videostroboscopic assessment in 112 cases of different vocal pathologies. Stroboscopic parameters like glottic closure, amplitude, vocal fold edge, symmetry, periodicity and mucosal wave pattern were studied and statistically significant relationship with different vocal pathologies were obtained.

Use of laryngeal high-speed videoendoscopy systems to study voice production mechanisms in human subjects

Advances in laryngeal high-speed videoendoscopy (HSV) are making it possible to investigate critical relationships between vocal fold physiology and acoustic voice production in human subjects. Our group has developed HSV systems for clinical research with synchronous acquisition of acoustics, electroglottography, neck skin acceleration, and, in the most comprehensive setup, airflow and intraoral pressure. Key results will be presented from examinations of source-filter coupling and studies of the acoustic impact of vocal fold vibratory asymmetry in subjects with and without voice disorders. Findings hold potential clinical significance by revealing acoustic-HSV relationships not observable using standard stroboscopic imaging, as well as contributing to the direct evaluation and eventual improvement of voice production models. The work of T. F. Quatieri was supported by the Department of Defense under Air Force contract FA8721-05-C-0002. The work of other authors was supported by grants from the NIH National Institute on Deafness and Other Communication Disorders (T32 DC00038 and R01 DC007640) and by the Institute of Laryngology and Voice Restoration.

Parameters quantifying dehydration in canine vocal fold lamina propria

The goal of this study was to measure the solid and liquid volume and mass of canine vocal fold lamina propria tissue at varying dehydration levels, and to calculate parameters to test the biphasic theory of vocal fold physiology and biomechanics. Open, controlled, experimental trial. The vocal fold lamina propria was dissected from 15 canine larynges, yielding 30 tissue samples. The initial volumes and masses of the tissue samples were measured. The masses of the tissue samples were then measured every 2 minutes during 30%, 50%, and 70% dehydration, with 10 samples subjected to each of the three treatments, followed by complete dehydration to yield the solid component of the tissue. The liquid mass and volume fractions and liquid:solid mass and volume ratios of the vocal fold lamina propria samples were calculated. The liquid mass and volume fractions and liquid:solid mass and volume ratios were significantly different at each dehydration level, except for the liquid:solid volume ratios at 30% versus 50% dehydration. Linear regression analysis suggested that all of the solid and liquid parameters measured could be predicted by dehydration level based on inverse, linear relationships. These results provide further experimental evidence supporting the biphasic theory and suggest that the extent of vocal fold lamina propria tissue dehydration may be quantified based on the biphasic model parameters.

The role of hydration in vocal fold physiology

Increased vocal fold hydration is a popular target in the prevention and management of voice disorders. Current intervention strategies focus on enhancing both systemic (internal) and superficial (surface) hydration. We review relevant bench and human research on the role of hydration in vocal fold physiology. Bench and human studies provide converging evidence that systemic and superficial dehydration are detrimental to vocal fold physiology. Dehydration challenges increase the viscous properties of excised vocal fold tissue. Systemic, superficial, and combined drying challenges increase aerodynamic and acoustic measures of voice production in speakers. Emerging theoretical and clinical data suggest that increasing both systemic and superficial hydration levels may benefit voice production; however, robust evidence for positive outcomes of hydration treatments is lacking. Increased systemic and superficial vocal fold hydration as a component of vocal hygiene may improve overall health and efficiency of the vocal apparatus. However, continued exploration of biological mechanisms regulating vocal fold hydration is needed to optimize clinical hydration interventions. Specifically, the development of hydration treatments that maximize positive phonatory outcomes will necessitate understanding of the signaling pathways linking systemic and superficial hydration.

Soft phonation index - a sensitive parameter?

The diagnosis of voice disorders is based on perceptual and acoustic paradigms. Modern acoustic analysis systems are relatively inexpensive and user friendly. One aspect of laryngeal function that is of great interest is the extent of vocal fold closure. Soft phonation index (SPI) is the parameter in Multi Dimensional Voice Program, which reflects the approximation of vocal folds. High values of SPI are stated to correlate with incomplete vocal fold adduction and are a better indicator of breathiness than EGG. This study aims to determine the sensitivity of this acoustic parameter of SPI, as a reflective indicator of incomplete vocal fold adduction in male patients diagnosed with unilateral vocal nodules. 60 participants were included in the study; 30 with normal vocal fold functioning in the control group and 30 with unilateral vocal nodules in the experimental group. The phonation sample of vowel /a/ was recorded into CSL 4150 of Kay Elemetrics, in a sound treated room. The readings of SPI on the MDVP analysis was extracted and subjected to statistical analysis using independent samples 't-test' using SPSS Version 11. The results of the study reveal that there was a statistically significant difference between the means of the SPI values between the control and the experimental groups. It can be understood that SPI is a sensitive parameter to detect abnormalities in vocal fold approximation in the considered population of individuals with vocal nodules. This is in coherence with a study done on patients with vocal fold palsy and cordectomy, wherein SPI was found to be a good indicator of breathiness. The SPI mean obtained for participants in the control group was higher than the Western normative mean specified in MDVP, which highlights the importance of establishing normative values for Indian population. It can be concluded that SPI was sensitive to detect changes affecting vocal fold closure in unilateral vocal nodules. But this conclusion has to be generalized with caution keeping in mind that only one population with vocal pathology was studied. The factors of vocal fold physiology and mechanical properties of vocal tract, which may contribute to individual variations in SPI values, have to be considered for further research.