Vocal Fold Structure Research Articles

Synthetic, self-oscillating vocal fold models for voice production researcha).

Sound for the human voice is produced by vocal fold flow-induced vibration and involves a complex coupling between flow dynamics, tissue motion, and acoustics. Over the past three decades, synthetic, self-oscillating vocal fold models have played an increasingly important role in the study of these complex physical interactions. In particular, two types of models have been established: "membranous" vocal fold models, such as a water-filled latex tube, and "elastic solid" models, such as ultrasoft silicone formed into a vocal fold-like shape and in some cases with multiple layers of differing stiffness to mimic the human vocal fold tissue structure. In this review, the designs, capabilities, and limitations of these two types of models are presented. Considerations unique to the implementation of elastic solid models, including fabrication processes and materials, are discussed. Applications in which these models have been used to study the underlying mechanical principles that govern phonation are surveyed, and experimental techniques and configurations are reviewed. Finally, recommendations for continued development of these models for even more lifelike response and clinical relevance are summarized.

Clinical applications for automatic detection of creaky voice

Creaky voice is a voice quality in which a low amount of subglottal air pressure, a condensed vocal fold structure, and a high closed quotient of vibration combine to create the auditory percept of a series of pulses at a low pitch. While this voice quality is often nonpathological, it can also co-occur with vocal pathologies. Identification of creak in the speech signal is most often done manually. Automatic creak detection algorithms have been created to streamline and produce replicable workflows. These algorithms have steadily increased in reliability, with COVAREP (Degottex et al., 2014) as the newest state-of-the-art. While preliminary studies have demonstrated promising findings using artificial neural networks with clinical data, artificial neural networks typically improve with diverse data testing. The current study implements COVAREP on a novel dataset, both in terms of speakers and speech types. Deidentified patient diagnoses were matched to audio recordings collected from January 2021 through September 2023. Relevant portions of audio recordings were extracted using a Praat script, and COVAREP was implemented on the extracted audio files in MATLAB. Ongoing analyses correlating percentage of creak detected and vocal pathology diagnoses will be discussed. Finally, the results will be compared to those of previous work.

Vocal Fold Submucosal Mesna Injection and Microflap Elevation in a Rabbit Model.

Mesna triggers chemical dissection in tissues by breaking down disulfide bonds and is used during surgical dissections in several areas. In this study, we aimed to investigate the effect of submucosal mesna infiltration on microflap elevation and the histopathological findings of its effects on the vocal fold lamina propria in a rabbit model. Eight adult male New Zealand white rabbits were used in the study. Each vocal fold was randomized, and 0.1 mL of mesna was injected into one-fold and 0.1 mL of saline to the contralateral fold. An incision was made on the epithelium and elevation was performed. The animals were sacrificed after two weeks, and the vocal folds were excised. Inflammatory response, fibrosis, and epithelial thickness were evaluated with hematoxylin eosin and Masson's Trichrome staining. Elevation time and histopathological features were compared between the two groups. The elevation time (20.9 ± 1.6 second) in the saline group was significantly higher (P < 0.05) than in the mesna group (15.0 ± 3.4 second). The inflammation (1.3 ± 0.5 vs. 1.1 ± 1.0, respectively) and fibrosis scores (1.0 ± 0.8 vs. 0.8 ± 0.7, respectively) did not differ significantly (P > 0.05 in both). Epithelial thickness (12.5 ± 4.7 vs. 10.3 ± 5.3, respectively) did not differ significantly (P ˃ 0.05) in the mesna and saline groups either. We determined that mesna facilitates the microflap elevation of the vocal folds in rabbits and does not damage the histological structure of vocal folds. This study encourages future studies to evaluate the use of mesna, now actively used across disciplines, in phonosurgery as well.

Objective tools in pediatric voice therapy: A path to improved outcomes

This is an invited presentation in the Special Session titled, “Voice therapy: objective measurement science and clinical efficacy.” Pediatric dysphonia (hoarseness) is a common condition with prevalence estimates ranging from 1.4% to 23.9%. Dysphonia can be detrimental to children both psychologically and academically; hence, early identification and restoration of optimal vocal health is critical. Direct visualization of vocal fold vibratory patterns is fundamental for appropriate diagnosis and treatment of vocal fold pathology. Thus, evaluation of vocal fold structure and cycle-to-cycle vibratory motion through techniques of direct visualization of the vocal fold is essential for clinical assessment and measurement of treatment outcomes. This session will discuss the most recent advances in objective voice assessment and measurement of voice therapy outcomes in children. The focus will be on discussing an innovative approach that leverages high-speed videoendoscopy and a cutting-edge custom developed laser projection system for quantitative evaluation of lesion size and comprehensive evaluation of opening and closing phase dynamics of the glottal cycle before and after voice therapy in children with vocal fold nodules.

Impact of Rehydration Following Systemic Dehydration on Vocal Fold Gene Expression.

Biological data on the beneficial effects of vocal fold rehydration are lacking. This study aimed to examine the effects of acute systemic dehydration on vocal fold gene expression and determine whether rehydration would reverse these changes. Male New Zealand White rabbits (N = 24, n = 8/group) provided the animal model. Systemic dehydration was induced by 5 days of water volume restriction. Rehydration was provided by ad-lib water for 3 days following dehydration. Euhydrated rabbits were used as the control group. Vocal fold tissue was dissected. Seventeen genes were selected based on physiological function and role in supporting vocal fold structure, oxidative stress, hemodynamics, and extracellular matrix turnover. Relative gene expression was assessed by RT-qPCR. Rehydration following systemic dehydration can modulate gene expression, with expression patterns suggesting that rehydration reverses dehydration-induced changes in over half of the tested genes. CLIC5 (chloride intracellular channel 5) and EFEMP1 (EGF containing fibulin extracellular matrix protein 1) genes were significantly upregulated in the dehydration group compared with the euhydrated control. A1BG (alpha-1B-glycoprotein) and IL1RAP (interleukin 1 receptor accessory protein) were downregulated by rehydration compared with the dehydration group. This study provides molecular evidence for a transcriptional response to rehydration following acute systemic dehydration in the vocal folds. These data are the first to study gene expression following realistic dehydration and rehydration paradigms and provide biological data to support clinical recommendations to increase water intake after acute dehydration. NA Laryngoscope, 133:3499-3505, 2023.

High-Speed Videoendoscopic and Acoustic Characteristics of Inspiratory Phonation.

Given the importance of inspiratory phonation for assessment of vocal fold structure, the aim of this investigation was to evaluate and describe the vocal fold vibratory characteristics of inspiratory phonation using high-speed videoendoscopy in healthy volunteers. The study also examined the empirical relationship between cepstral peak prominence (CPP) and glottal area waveform measurements derived from simultaneous high-speed videoendoscopy and audio recordings. Vocally healthy adults (33 women, 28 men) volunteered for this investigation and completed high-speed videoendoscopic assessment of vocal fold function for two trials of an expiratory/inspiratory phonation task at normal pitch and normal loudness. Twelve glottal area waveform measures and acoustic CPP values were extracted for analyses. Inspiratory phonation resulted in shorter closing time, longer duration of the opening phase, and faster closing phase velocity compared to expiratory phonation. Sex differences were elucidated. CPP changes for inspiratory phonation were predicted by changes in the glottal area index and waveform symmetry index, whereas changes in CPP during expiratory phonation were predicted by changes in asymmetry quotient, glottal area index, and amplitude periodicity. Vocal fold vibratory differences were identified for inspiratory phonation when compared to expiratory phonation, the latter of which has been studied more extensively. This investigation provides important basic inspiratory phonation data to better understand laryngeal physiology in vivo and provides a basic model from which to further study inspiratory phonation in a larger population representing a broader age range. https://doi.org/10.23641/asha.22223812.

A STUDY OF CONVENTIONAL METHOD AND MICROFLAP BASED TECHNIQUE FOR EXCISION OF NON MALIGNANT VOCAL FOLD NODULAR LESIONS

Introduction: Management of benign vocal fold nodular lesion provides a particularly good window into the revolution of voice surgery. The changes in approach to surgical management have resulted largely because of advancement in knowledge of anatomy and physiology of the vocal fold layered structures &amp; technological developments that have improved our ability to examine and quantify voice function and the availability of better surgical instruments. Aims: Comparison of Microap technique with conventional method for benign vocal fold nodular lesion and Comparison of Intropertive and post-operative parameters like operative time, primary bleeding, operative procedures, residual tissue, collateral damage, postoperative complication, recovery time and so on between two methods. Materials and Methods: This study was Prospective Randomised single blind trial study. This study was conducted at Patna Medical College &amp; Hospital, Department of ENT from Feb 2020-August 2022. Result: We found in Conventional Group, the mean Total Score of Pre-op Video Stroboscopy (Individual) (mean± s.d.) of patients was 9.2632± 1.9268. In Micro Flap Group, the mean Total Score of Pre-op Video Stroboscopy (Individual) (mean± s.d.) of patients was 8.7857± 1.6898. Difference of mean Total Score of Pre-op Video Stroboscopy (Individual) with both Group was not statistically signicant (p=0.2413). In Conventional Group, the mean Total Score of Post-op Video Stroboscopy (mean± s.d.) of patients was 2.2895 ± 3.3684. Conclusion:We found that Mean Total Score of Post-op Video Stroboscopy was higher in Conventional compared to Micro Flap group which was statistically signicant. It was showed that Mean Video Stroboscopy Outcome Difference (Pre-Post) was less in Conventional compared to Micro Flap group which was statistically signicant

Proteomic analysis reveals that aging rabbit vocal folds are more vulnerable to changes caused by systemic dehydration

BackgroundOlder adults are more prone to develop systemic dehydration. Systemic dehydration has implications for vocal fold biology by affecting gene and protein expression. The objective of this study was to quantify vocal fold protein changes between two age groups and hydration status, and to investigate the interaction of age and hydration status on protein expression, which has not been investigated in the context of vocal folds before. Comparative proteomics was used to analyze the vocal fold proteome of 6.5-month-old and > 3-year-old rabbits subjected to water ad libitum or water volume restriction protocol.ResultsYoung and older adult rabbits (n = 22) were either euhydrated (water ad libitum) or dehydrated by water volume restriction. Dehydration was confirmed by body weight loss of − 5.4% and − 4.6% in young and older groups, respectively, and a 1.7-fold increase of kidney renin gene expression in the young rabbits. LC-MS/MS identified 2286 proteins in the rabbit vocal folds of young and older adult rabbits combined. Of these, 177, 169, and 81 proteins were significantly (p ≤ 0.05) affected by age, hydration status, or the interaction of both factors, respectively. Analysis of the interaction effect revealed 32 proteins with opposite change patterns after dehydration between older and young rabbit vocal folds, while 31 proteins were differentially regulated only in the older adult rabbits and ten only in the young rabbits in response to systemic dehydration. The magnitude of changes for either up or downregulated proteins was higher in the older rabbits. These proteins are predominantly related to structural components of the extracellular matrix and muscle layer, suggesting a disturbance in the viscoelastic properties of aging vocal fold tissue, especially when subjected to systemic dehydration.ConclusionsWater restriction is a laboratory protocol to assess systemic dehydration-related changes in the vocal fold tissue that is translatable to human subjects. Our findings showed a higher number of proteins differentially regulated with a greater magnitude of change in the vocal folds of older adult rabbits in the presence of systemic dehydration compared to younger rabbits. The association of these proteins with vocal fold structure and biomechanical properties suggests that older human subjects may be more vulnerable to the effects of systemic dehydration on vocal function. The clinical implications of these protein changes warrant more investigation, but age should be taken into consideration when evaluating vocal treatment recommendations that interfere with body fluid balance.

Clinical study of injectable collagen scaffold with autologous fat cells for repair of severe vocal fold injury

Cell retention and survival after transplantation remains a major problem for long-term efficiency in therapy of severe vocal fold injury with autologous cells. In this study, injectable collagen scaffold was used to deliver autologous fat cells (AFCs) for repairing of severe vocal fold injury. We found injectable collagen scaffold could enhance the retention and survival of green fluorescent protein (GFP) labeled fat cells in the transplantation sites in rats. Based on these data, a randomized controlled clinical trial was conducted to evaluate the safety and efficiency of transplantation of collagen scaffold with AFCs for severe vocal fold injury. Ten patients with vocal fold paralysis were randomly assigned to control (AFCs only) and intervention (AFCs + collagen) groups. AFCs with or without collagen scaffold were injected into vocal folds of patients under general anesthesia, respectively. The safety and efficacy were regularly assessed during 24 months post-surgery. No obvious complications occurred in all patients during the follow-up. The collagen scaffold maintained the stability of implants after injection and reconstructed the vocal fold structure. The improvement of voice quality of patients was observed through voice quality evaluation with the voice handicap index (VHI) questionnaire, as well as acoustic analysis of maximum phonation time, jitter, and shimmer. The VHI score of patients in AFCs + collagen group improved significantly than those in AFCs group at 6, 12 and 24 months post-surgery. It demonstrates the injectable collagen scaffold is safe and efficient for delivering AFCs for vocal fold injury.

A Tissue Engineered Construct for Laryngeal Regeneration: A Proof-of-Concept Device Design Study.

Develop a patient-specific tissue engineered construct for laryngeal reconstruction following a partial laryngectomy. Bench and animal research. A construct made from a porous polyethylene scaffold shaped in a canine-specific configuration and seeded with autologous canine adipose-derived stem cells in fibrin glue was implanted in a canine following a partial laryngectomy. After 1 year, the construct was first evaluated in vivo with high-speed imaging and acoustic-aerodynamic measures. It was then explanted and evaluated histologically. The canine study at 1 year revealed the construct provided voicing (barking) with acoustic and aerodynamic measures within normal ranges. The canine was able to eat and breathe normally without long-term support. The construct was integrated with epithelialization of all areas except the medial portion of the vocal fold structure. No anti-infective agents were needed after the standard perioperative medications were completed. This study provided a successful first step toward developing a patient-specific composite construct for patients undergoing partial laryngectomies. NA Laryngoscope, 132:S1-S11, 2022.

Computational Modeling of Voice Production Using Excised Canine Larynx.

A combined experimental-numerical work was conducted to comprehensively validate a subject-specific continuum model of voice production in larynx using excised canine laryngeal experiments. The computational model is a coupling of the Navier-Stokes equations for glottal flow dynamics and a finite element model of vocal fold dynamics. The numerical simulations employed a cover-body vocal fold structure with the geometry reconstructed from magnetic resonance imaging scans and the material properties determined through an optimization-based inverse process of experimental indentation measurement. The results showed that the simulations predicted key features of the dynamics observed in the experiments, including the skewing of the glottal flow waveform, mucosal wave propagation, continuous increase of the divergent angle and intraglottal swirl strength during glottal closing, and flow recirculation between glottal jet and vocal fold. The simulations also predicted the increase of the divergent angle, glottal jet speed, and intraglottal flow swirl strength with the subglottal pressure, same as in the experiments. Quantitatively, the simulations over-predicted the frequency and jet speed and under-predicted the flow rate and divergent angle for the larynx under study. The limitations of the model and their implications were discussed.

Investigating the cepstral acoustic characteristics of voice in healthy children

ObjectivesThis study aimed to determine the cepstral acoustic parameters that vary depending on age and gender in vocally healthy children, and to establish normative data for cepstral analysis. BackgroundCepstral measurements are among the strongest predictors of auditory-perceptual evaluation of voice and differentiate between healthy and dysphonic voices. More spesificially, ceptral peak prominence is accepted to be as a strong acoustic predictor of breathiness and overall severity of dysphonia. Cepstral measures determine voice quality reliably not only in sustained vowel samples but also in running speech samples. Determining the parameters related to the acoustic profile of children with normal voices can lead us to a better understanding of the effect of changes in the larynx and vocal fold structure during growth and development. There is a limited number of norm studies examining the cepstral acoustic properties of pediatric voice. Determining norm-specific values and clinical guidelines of cepstral acoustics according to the age and gender in vocally healthy children are utmost important. MethodsA total of 160 vocally healthy children were divided into the following four age groups: Group-I included children within the age range of 4–7 years, Group-II included 7–11 years, Group-III 11–14 years, and Group-IV included children within the age range of 14–18 years. An equal number of male and female participants were assigned to each group. PENTAX Medical CSL Model 4500 was used for recording all tasks. For acoustic analysis, Multi-Dimensional Voice Program and Analysis of Dysphonia in Speech and Voice were used. ResultsCepstral Peak Prominence (CPP), Cepstral Peak Prominence Standard Deviation (CPP SD), and Low-To-High Spectral Ratio (L/H Ratio) increased with age. It is found that the CPP parameter of all-voiced sentences and nasal-weighted sentences increased with age in boys, while no significant pattern was observed in any sample for girls. For L/H ratio, it can be said that there is a general increase with age in all speech samples, except for the vowel-weighted and voiceless plosive sentence samples, evident especially in the group above the age of 15 years. This study concluded that the CPP SD parameter in the vowel-weighted sentences increased with age in boys. It was also noticed in this study that CPP F0 standard deviation (SD) intervals were narrower in vowel-weighted, easy onset, and voiceless plosive sentence samples than in all-voiced, hard glottal attack and nasal-weighted sentence samples. ConclusionThis study established cepstral acoustic normative values for a wide age range of the pediatric population. It is thought that age and gender specific cepstral acoustic findings presented in this study contributed to the related literature. In addition, to our knowledge, this is the first study that provides a normative cepstral acoustic database of the CAPE-V/Turkish sentences in the pediatric population.

Behavioral Treatment for Benign Vocal Fold Lesions in Children: A Systematic Review

Purpose This systematic review aims to identify, classify, and evaluate existing information regarding treatment for benign vocal fold lesions in children and to identify gaps and limitations that may limit effective pediatric voice treatment. Method A literature search was performed using electronic databases (PubMed and Google Scholar) as well as reference lists from previous reviews, studies, and books. Included in the present review are studies that described behavioral treatment for children with benign vocal fold lesions presumed to be phonotraumatic (vocal fold nodules and edema). Results Twenty-one studies were eligible for inclusion in the review. Eight different research designs were used, and three intervention types were identified: direct voice intervention (voice training), indirect treatment (vocal hygiene or counseling), and comparative studies that contrasted different treatment methods. The most commonly used treatment method was eclectic direct intervention, which focused on vocal exercises or voicing patterns. Postintervention improvement was reported in all studies. In general, findings suggested an advantage of direct over indirect intervention and of longer treatment duration over short-term approaches. Conclusions The findings suggest that behavioral voice therapy may be generally effective in treating children with vocal fold nodules. Several limitations emerged in the corpus of studies reviewed including heterogeneity of research methods, missing information about outcome measures, and inappropriate statistical analyses. Thus, a need exists for further well-designed controlled studies to enhance the body of knowledge about developmental factors affecting vocal treatment outcomes, in particular, vocal fold structure as well as cognitive and linguistic development.

Finite-element modeling of vocal fold self-oscillations in interaction with vocal tract: Comparison of incompressible and compressible flow model

Finite-element modeling of self-sustained vocal fold oscillations during voice production has mostly considered the air as incompressible, due to numerical complexity. This study overcomes this limitation and studies the influence of air compressibility on phonatory pressures, flow and vocal fold vibratory characteristics. A two-dimensional finite-element model is used, which incorporates layered vocal fold structure, vocal fold collisions, large deformations of the vocal fold tissue, morphing the fluid mesh according to the vocal fold motion by the arbitrary Lagrangian-Eulerian approach and vocal tract model of Czech vowel [i:] based on data from magnetic resonance images. Unsteady viscous compressible or incompressible airflow is described by the Navier-Stokes equations. An explicit coupling scheme with separated solvers for structure and fluid domain was used for modeling the fluid-structure-acoustic interaction. Results of the simulations show clear differences in the glottal flow and vocal fold vibration waveforms between the incompressible and compressible fluid flow. These results provide the evidence on the existence of the coupling between the vocal tract acoustics and the glottal flow (Level 1 interactions), as well as between the vocal tract acoustics and the vocal fold vibrations (Level 2 interactions).

Влияние мезенхимных стромальных клеток на восстановление структуры голосовых складок при рубцовых изменениях. Контролируемое экспериментальное исследование

Влияние мезенхимных стромальных клеток на восстановление структуры голосовых складок при рубцовых изменениях. Контролируемое экспериментальное исследование

Three-dimensional vocal fold structural change due to implant insertion in medialization laryngoplasty.

Glottal insufficiency due to vocal fold paralysis, paresis, or atrophy often leads to degraded voice quality. One of the primary surgical intervention procedures to treat glottal insufficiency is medialization laryngoplasty, in which an implant is inserted through a lateral window on the thyroid cartilage to medialize the vocal folds. While the goal of medialization is to modify the vocal fold structure to restore normal phonation, few studies have attempted to quantify such structural changes of the vocal folds. The goal of this study is to quantify the three-dimensional structural changes of the vocal folds due to implant insertion in medialization laryngoplasty, and evaluate its potential effect on voice production. Medialization laryngoplasty were performed in excised human larynges using implants of different stiffness. Magnetic resonance images of the larynges were obtained with and without implant insertion. The results showed that implant insertion significantly changed the original body-cover structure of the vocal folds, with the implant taking over the large space used to be occupied by the original body layer and the vocal fold being stretched into a thin layer wrapped around the implant. The medial-lateral dimension of the vocal fold was significantly reduced from about 4 mm to 1 mm, and the vocal fold was stretched in the coronal plane by about 70%. It is hypothesized that use of implants with stiffness comparable to that of the vocal folds is beneficial because the degree of medialization can be adjusted without much negative effects on phonation frequency, phonation threshold pressure, or vibration amplitude.

Structure, Function and Insertion of the Human Vocal Folds.

We here summarize the structures of the laryngeal vocal fold as well as its insertion structures at the anterior commissure and at the area of the vocal process and place these findings within the context of biomechanical, functional, and clinical implications.

Using intraoperative optical coherence tomography to image pediatric unilateral vocal fold paralysis

ObjectivesUnilateral vocal fold paralysis (UVFP) impairs communication and reduces academic performance and social interactions in children. Deciding between temporary, permanent, or potentially destructive surgical interventions can be challenging, as there currently exists no reliable means of predicting vocal fold recovery or assessing the presence of vocal fold atrophy. Regarding vocal fold atrophy, optical coherence tomography (OCT) has been shown to be an appealing non-invasive alternative for accessing vocal fold structures. This study describes UVFP microanatomy and identifies possible vocal fold atrophy using OCT. MethodsThree UVFP patients (ages 1, 11, and 17 years) underwent bilateral OCT imaging using a handheld probe while under general anesthesia for direct laryngoscopy, and the laryngoscopic images were compared with images obtained from OCT. Structural morphological features were extracted and compared to a healthy patients' cohort. ResultsWhile endoscopy showed no evidence of vocal fold atrophy in two of three cases, OCT images revealed distinct differences between the lamina propria of the paralyzed and functional vocal folds in all patients. In two cases, the paralyzed vocal fold morphology was similar to a healthy patient at the age of nerve injury. The third case exhibited extensive scarring in the lamina propria of the paralyzed vocal fold. ConclusionThis pilot study characterizes and compares vocal fold microanatomy in three UVFP patients. In most cases, lamina propria development halted at the age of paralysis, suggesting that lamina propria maturation may be dependent on vocal fold functionality. OCT shows potential to aid UVFP assessment and treatment decisions by evaluating the presence of atrophy.

Automated Indentation Mapping of Vocal Fold Structure and Cover Properties Across Species.

Various animal models have been employed to investigate vocal fold (VF) and phonatory function. However, biomechanical testing techniques to characterize vocal fold structural properties vary and have not compared critical properties across species. We adapted a nondestructive, automated indentation mapping technique to simultaneously quantify VF structural properties (VF cover layer and intact VF) in commonly used species based on the hypothesis that VF biomechanical properties are largely preserved across species. Ex vivo animal model. Canine, leporine, and swine larynges (n = 4 each) were sagittally bisected, measured, and subjected to normal indentation mapping (indentation at 0.3 mm; 1.2 mm/s) with a 2-mm spherical indenter to quantify normal force along the VF cover layer, structural stiffness, and displacement at 0.8 mN; two-dimensional maps of the free VF edge through the conus elasticus were created for these characterizations. Structural stiffness was 7.79 gf/mm (0.15-74.55) for leporine, 2.48 gf/mm (0.20-41.75) for canine, and 1.45 gf (0.56-4.56) for swine. For each species, the lowest values were along the free VF edge (mean ± standard deviation; leporine: 0.40 ± 0.21 gf/mm, canine: 1.14 ± 0.49 gf/mm, swine: 0.89 ± 0.28 gf/mm). Similar results were obtained for the cover layer normal force at 0.3 mm. On the free VF edge, mean (standard deviation) displacement at 0.08 gf was 0.14 mm (0.05) in leporine, 0.11 mm (0.03) in canine, and 0.10 mm (0.02) in swine. Automated indentation mapping yielded reproducible biomechanical property measurement of the VF cover and intact VF. Divergent VF structural properties across canine, swine, and leporine species were observed. NA Laryngoscope, 129:E26-E31, 2019.

Vocalization as a novel endpoint of atypical attachment behavior in 2,3,7,8-tetrachlorodibenzo-p-dioxin-exposed infant mice.

Mammalian attachment behaviors, such as crying, are essential for infant survival by receiving food, protection, and warmth from caregivers. Ultrasonic vocalization (USV) of infant rodents functions to promote maternal proximity. Impaired USV emission has been reported in mouse models of autism spectrum disorder, suggesting that USV is associated with higher brain function. In utero and lactational dioxin exposure is known to induce higher brain function abnormalities in adulthood; however, whether perinatal dioxin exposure affects behavior during infancy is unclear. Therefore, we studied the impact of dioxin exposure on USV emission in infant mice born to dams treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 0.6 or 3.0µg/kg) on gestational day 12.5. On postnatal days 3-9, USVs of the offspring were recorded for 1min using a microphone in a sound-attenuated chamber. The total USV and mean call durations in infant mice exposed to 3.0µg/kg, but not 0.6µg/kg, were shorter than those in the control mice. In addition, the percentages of complicated call types (i.e., chevron and wave) in mice exposed to 3.0µg/kg were decreased. Dioxin-induced gene expression changes occurred in the brains of mice exposed to 3.0µg/kg; however, body weight, motor activity, and vocal fold structure were not significantly affected. These results suggest that infant USV is a useful behavioral endpoint in developmental neurotoxicity assessment that may be used to evaluate effects of chemical exposure on the infant-caregiver interaction.