Laryngeal Muscles Research Articles

Comparative anatomy of the vocal apparatus in bats and implications for the diversity of laryngeal echolocation

Abstract Most of over 1400 extant bat species produce high-frequency pulses with their larynx for echolocation. However, the debate about the evolutionary origin of laryngeal echolocation in bats remains unresolved. The morphology of the larynx is known to reflect vocal adaptation and thus can potentially help in resolving this controversy. However, the morphological variations of the larynx are poorly known in bats, and a complete anatomical study remains to be conducted. Here, we compare the 3D laryngeal morphology of 23 extant bat species of 11 different families reconstructed by using iodine contrast-enhanced X-ray microtomography techniques. We find that, contrary to previously thought, laryngeal muscle hypertrophy is not a characteristic of all bats and presents differential development. The larynges of Pteropodidae are morphologically similar to those of non-bat mammals. Two morphotypes are described among laryngeal echolocating bats, illustrating morphological differences between Rhinolophoidea and Yangochiroptera, with the main variations being the cricothyroid muscle volume and the shape of the cricoid and thyroid cartilages. For the first time we detail functional specialization for constant frequency echolocation among Rhinolophoidea. Lastly, the nasal-emitting taxa representing a polyphyletic group do not share the same laryngeal form, which raises questions about the potential modular nature of the bat larynx.

Deep Learning for Neuromuscular Control of Vocal Source for Voice Production.

A computational neuromuscular control system that generates lung pressure and three intrinsic laryngeal muscle activations (cricothyroid, thyroarytenoid, and lateral cricoarytenoid) to control the vocal source was developed. In the current study, LeTalker, a biophysical computational model of the vocal system was used as the physical plant. In the LeTalker, a three-mass vocal fold model was used to simulate self-sustained vocal fold oscillation. A constant/ǝ/vowel was used for the vocal tract shape. The trachea was modeled after MRI measurements. The neuromuscular control system generates control parameters to achieve four acoustic targets (fundamental frequency, sound pressure level, normalized spectral centroid, and signal-to-noise ratio) and four somatosensory targets (vocal fold length, and longitudinal fiber stress in the three vocal fold layers). The deep-learning-based control system comprises one acoustic feedforward controller and two feedback (acoustic and somatosensory) controllers. Fifty thousand steady speech signals were generated using the LeTalker for training the control system. The results demonstrated that the control system was able to generate the lung pressure and the three muscle activations such that the four acoustic and four somatosensory targets were reached with high accuracy. After training, the motor command corrections from the feedback controllers were minimal compared to the feedforward controller except for thyroarytenoid muscle activation.

Neurectomy and Myomectomy for Treatment of Spasmodic Dysphonia.

Spasmodic dysphonia (SD) is a debilitating neurological disorder affecting the muscles of voice production. Sudden involuntary movements of the vocal folds lead to phonatory breaks and to forced, strained, and strangled voice quality in adductor SD, or breathy breaks in abductor SD. There is currently no cure for spasmodic dysphonia, and the gold standard for treatment is the injection of botulinum toxin in small amounts to the intrinsic laryngeal musculature.1 However, botulinum treatment requires periodic reinjection, produces vocal instability immediately after injection, lacks uniform results among patients, and patients can develop antibodies to botulinum toxin. Long-term or permanent symptom relief would be ideal. We present four patients with adductor and one patient with abductor spasmodic dysphonia who underwent neurectomy and myomectomy for treatment. The mean age was 64 years (age range 45-83). The mean duration of adductor spasmodic dysphonia was 11.8 years. The duration of abductor spasmodic was 4 years. All patients had previously been treated with voice therapy and botulinum toxin A. The mean duration of follow up was 1.7 years. Four patients had subjective and objective improvement after surgery. One patient had subjective improvement.

Manual Therapy with Neural Mobilization: Immediate Effect on the Vocal Quality of Women with Dysphonia.

To evaluate the immediate effect of neural mobilization on the voice quality, self-perceived phonatory effort, and laryngeal muscles of women with behavioral dysphonia. This is an intrasubject comparative study. The research included 21 women aged 18 to 59 years with vocal complaints. Therefore, the selection of this sample excluded the lower limit of the voice change period and the upper limit of presbyphonia. The participants were assessed by voice acoustic and auditory-perceptual analysis, self-reported vocal effort, and laryngeal palpation performed at three moments: at baseline, after 10 minutes of vocal resting, and after manual therapy. The participants were divided into two groups: the group with 10 minutes of vocal resting (G1) and the group with intervention (G2). The patients in the intervention group underwent manual therapy using neural mobilization in the laryngeal region. For the statistical analysis, a descriptive analysis of the data was performed first with measures of central tendency and dispersion. Subsequently, the Anderson-Darling test was used to verify sample normality. To analyze the difference between three groups were used the parametric One-Way ANOVA or the non-parametric Friedman's test. The McNemar's or chi-squared tests were used to compare categorical variables and to compare an ordinal variable a non-parametric Wilcoxon test was used. The Gwet's AC1 test was used to assess intra-rater agreement in the auditory-perceptual analysis response. Neural mobilization in the laryngeal region showed no positive effects on the acoustic voice parameters and voice quality of women with dysphonia. Phonatory effort improved after neural mobilization in the laryngeal region (p=0.004). There was no significant change in supralaryngeal resistance, lateral laryngeal resistance, and laryngeal position after neural mobilization in the laryngeal region. Neural mobilization improved phonatory comfort but did have any effect on the voice quality and laryngeal musculature of women with dysphonia.

Next-Generation Sequencing Application: A Systematic Approach for High-Quality RNA Isolation from Skeletal Muscles.

RNA extraction and analyses from tissues using bulk RNA-Sequencing (RNA-Seq) provide a more accurate picture of the gene expression compared to other molecular biology techniques for RNA quantification. Challenges associated with high-quality RNA extraction from skeletal muscles require a modification of standard protocols. Here, we describe a procedure for high-quality RNA isolation from intrinsic laryngeal muscles transferable to skeletal muscles with comparable technical and biological difficulties. Standard protocols for RNA isolation were optimized by maximizing the pooling strategy, determining the sample weight, applying cryogenic muscle disruption, and incorporating RNase-inhibiting reagents during the tissue preparation steps.

Effects of an 11-week vibro-tactile stimulation treatment on voice symptoms in laryngeal dystonia.

Laryngeal dystonia is a task-specific focal dystonia of laryngeal muscles that impairs speech and voice production. At present, there is no cure for LD. The most common therapeutic option for patients with LD involves Botulinum neurotoxin injections. Provide empirical evidence that non-invasive vibro-tactile stimulation (VTS) of the skin over the voice box can provide symptom relief to those affected by LD. Single-group 11-week randomized controlled trial with a crossover between two dosages (20 min of VTS once or 3 times per week) self-administered in-home in two 4-week blocks. Acute effects of VTS on voice and speech were assessed in-lab at weeks 1, 6 and 11. Participants were randomized to receive either 40 Hz or 100 Hz VTS. Primary: smoothed cepstral peak prominence (CPPS) of the voice signal to quantify voice and speech abnormalities, and perceived speech effort (PSE) ranked by participants as a measure of voice effort (scale 1-10). Secondary: number of voice breaks during continuous speech, the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) inventory as a measure of overall disease severity and the Voice Handicap Index 30-item self report. Thirty-nine people with a confirmed diagnosis of adductor-type LD (mean [SD] age, 60.3 [11.3] years; 18 women and 21 men) completed the study. A single application of VTS improved voice quality (median CPPS increase: 0.41 dB, 95% CI [0.20, 0.61]) and/or reduced voice effort (PSE) by at least 30% in up to 57% of participants across the three study visits. Effects lasted from less than 30 min to several days. There was no effect of dosage and no evidence that the acute therapeutic effects of VTS increased or decreased longitudinally over the 11-week study period. Both 100 and 40 Hz VTS induced measurable improvements in voice quality and speech effort. VTS induced an additional benefit to those receiving Botulinum toxin. Participants, not receiving Botulinum treatment also responded to VTS. This study provides the first systematic empirical evidence that the prolonged use of laryngeal VTS can induce repeatable acute improvements in voice quality and reductions of voice effort in LD. ClinicalTrials.gov ID: NCT03746509.

MYH13, a superfast myosin expressed in extraocular, laryngeal and syringeal muscles.

MYH13 is a unique type of sarcomeric myosin heavy chain (MYH) first detected in mammalian extraocular (EO) muscles and later also in vocal muscles, including laryngeal muscles of some mammals and syringeal muscles of songbirds. All these muscles are specialized in generating very fast contractions while producing relatively low force, a design appropriate for muscles acting against a much lower load than most skeletal muscles inserting into the skeleton. The definition of the physiological properties of muscle fibres containing MYH13 has been complicated by the mixed fibre type composition of EO muscles and the coexistence of different MYH types within the same fibre. A major advance in this area came from studies on isolated recombinant myosin motors and the demonstration that the affinity of actin-bound human MYH13 for ADP is much weaker than those of fast-type MYH1 (type 2X) and MYH2 (type 2A). This property is consistent with a very fast detachment of myosin from actin, a major determinant of shortening velocity. The MYH13 gene arose early during vertebrate evolution but was characterized only in mammals and birds and appears to have been lost in some teleost fish. The MYH13 gene is located at the 3' end of the mammalian fast/developmental gene cluster and in a similar position to the orthologous cluster in syntenic regions of the songbird genome. MYH13 gene regulation is controlled by a super-enhancer in the mammalian locus and deletion of the neighbouring fast MYH1 and MYH4 genes leads to abnormal MYH13 expression in mouse leg muscles.

Flow-induced oscillations of vocal-fold replicas with tuned extensibility and material properties

Human vocal folds are highly deformable non-linear oscillators. During phonation, they stretch up to 50% under the complex action of laryngeal muscles. Exploring the fluid/structure/acoustic interactions on a human-scale replica to study the role of the laryngeal muscles remains a challenge. For that purpose, we designed a novel in vitro testbed to control vocal-folds pre-phonatory deformation. The testbed was used to study the vibration and the sound production of vocal-fold replicas made of (i) silicone elastomers commonly used in voice research and (ii) a gelatin-based hydrogel we recently optimized to approximate the mechanics of vocal folds during finite strains under tension, compression and shear loadings. The geometrical and mechanical parameters measured during the experiments emphasized the effect of the vocal-fold material and pre-stretch on the vibration patterns and sounds. In particular, increasing the material stiffness increases glottal flow resistance, subglottal pressure required to sustain oscillations and vibratory fundamental frequency. In addition, although the hydrogel vocal folds only oscillate at low frequencies (close to 60 Hz), the subglottal pressure they require for that purpose is realistic (within the range 0.5–2 kPa), as well as their glottal opening and contact during a vibration cycle. The results also evidence the effect of adhesion forces on vibration and sound production.

Comprehensive review of laryngeal nerve

The laryngeal nerve plays a crucial role in vital functions of the larynx, such as breathing, phonation, and airway protection. This review explores its intricate origination, extracranial pathways, anatomical variations, and functions. Emerging from the vagus nerve, it descends through the jugular foramen, exhibiting distinct pathways on each side of the body. Understanding these pathways is vital in surgery to prevent complications. Anatomical variations, including the non-recurrent laryngeal nerve and extralaryngeal branching, pose challenges during thyroid surgery. Surgeons must be vigilant, as failure to recognize these variations can lead to nerve injuries. Meticulous preoperative evaluation and surgical expertise are essential. The superior laryngeal nerve triggers protective reflexes like the cough reflex, safeguarding the respiratory tract. The recurrent laryngeal nerve controls crucial laryngeal muscles for phonation and respiration. Understanding these functions is paramount, especially for surgeons, ensuring optimal patient outcomes. In conclusion, this review underscores the laryngeal nerve's complexity and the need for in-depth knowledge, particularly in surgery. Ongoing research and medical advancements are crucial for refining techniques and enhancing patient care. Acknowledging these complexities empowers medical surgeons contributing to safer and more effective surgeries.

A brainstem circuit for phonation and volume control in mice

Mammalian vocalizations are critical for communication and are produced through the process of phonation, in which expiratory muscles force air through the tensed vocal folds of the larynx, which vibrate to produce sound. Despite the importance of phonation, the motor circuits in the brain that control it remain poorly understood. In this study, we identified a subpopulation of ~160 neuropeptide precursor Nts (neurotensin)-expressing neurons in the mouse brainstem nucleus retroambiguus (RAm) that are robustly activated during both neonatal isolation cries and adult social vocalizations. The activity of these neurons is necessary and sufficient for vocalization and bidirectionally controls sound volume. RAm Nts neurons project to all brainstem and spinal cord motor centers involved in phonation and activate laryngeal and expiratory muscles essential for phonation and volume control. Thus, RAm Nts neurons form the core of a brain circuit for making sound and controlling its volume, which are two foundations of vocal communication.

Mutational screening of GDAP1 in dysphonia associated with Charcot-Marie-Tooth disease: clinical insights and phenotypic effects

IntroductionMutations in GDAP1 (Ganglioside-induced differentiation-associated protein 1) gene are linked to Charcot-Marie-Tooth disease (CMT), a Heterogenous group of disorders with multiple phenotypes, characterized by peripheral nerve dysfunction that can lead to vocal cord paralysis and diaphragmatic dysfunction. Main bodyAll three affected children of this chosen family have manifested the same clinical symptoms with progressive weakness, mild sensory impairment, and absent tendon reflexes in their early years. Electrodiagnostic analysis displayed an axonal type of neuropathy in affected patients. Sequencing of the GDAP1 gene was requested for all members of the family. Diagnostic assessments included pulmonary and vocal cord function tests, as well as phrenic and peripheral nerve conduction studies. Pathogenicity of GDAP1 variant p.Pro419Leu with axonal CMT2 and autosomal recessive inheritance was confirmed via in silico analysis. Patients with GDAP1 mutations showed dysphonia, speech difficulties, and the characteristic symptoms of CMT. The severity of symptoms correlated with the presence of a type of GDAP1 mutation. Patients with normal vocal cords and pulmonary function exhibited milder symptoms compared to those with GDAP1 mutations. Our study provides clinical insights into the phenotypic effects of GDAP1 mutations in CMT patients. The findings highlight the adverse clinical course and severe disability associated with GDAP1 mutations, including weak limb and laryngeal muscles. ConclusionPatients with GDAP1 mutations and autosomal recessive neuropathy present with dysphonia and require interventions such as surgery, braces, physical therapy, and exercise. Early diagnosis and comprehensive clinical evaluations are crucial for managing CMT patients with GDAP1 mutations.

Reliability of Phonemically Loaded Sentences in Spanish for Identifying Laryngeal Dystonia by Non-Spanish Speaking Speech-Language Pathologists

Laryngeal dystonia (LD) is a focal dystonia affecting the intrinsic laryngeal muscles. Clinical diagnosis requires subjective evaluation by experienced clinicians and is primarily based on auditory-perceptual assessment. Several speech tasks are widely accepted to elicit diagnosis specific auditory-perceptual symptoms of glottal stops in adductor LD or breathy breaks in abductor LD in spoken English. With the growing Spanish speaking population in the US and lack of Spanish speech tasks to assist in identifying LD in Spanish speaking subjects, assessing the reliability of phonemically loaded sentences in Spanish for use by non-Spanish speaking providers is critical. The first aim of this study was to develop and assess the reliability of a set of Spanish language phonemically loaded sentences designed to elicit signs and symptoms of LD. The second aim was to determine the effectiveness of non-Spanish speaking speech-language pathologists (SLPs) in identifying LD in Spanish speaking subjects using these stimuli. Phonemically loaded sentences were developed for this study following current guidelines for assessment of LD. Voice samples were obtained from native Spanish speaking individuals. Participant-speakers included 20 people with LD and 20 people without LD who served as controls. All participant-speakers were assessed by a Spanish-speaking laryngologist. Audio samples were presented to non-Spanish speaking SLPs with expertise in working with people with LD who served as raters and classified the samples as either presence or absence of LD. Kappa and the intra-class correlation coefficient were calculated and mixed effects logistic regression was used for prediction. The inter and intra-rater reliability indicated statistically significant agreement. Sensitivity, specificity, and predictive values for the diagnosis of LD by the raters were overall strong. Findings demonstrate that non-Spanish speaking SLPs with expertise in the assessment and treatment of LD can reliably identify the presence of LD using Spanish language stimuli in Spanish-speaking individuals. This study supports the use of newly developed Spanish language phonemically loaded voiced and voiceless sentences by English speaking clinicians as an effective tool for identifying LD in Spanish speakers, perhaps mitigating diagnostic delays experienced by patients with LD.

A100Simulating to manage post thyroidectomy haematoma safely: Improving fidelity whilst reducing cost

Simulation training sessions were designed at the University Hospital of Wales in order to implement the new national guidelines for the management of suspected haematoma following thyroid surgery [1]. Opportunities included on site portable training with a part task trainer and high-fidelity scenarios simulating patient deterioration following thyroid surgery in an immersive environment. Our initial design for the high-fidelity set-up included a simulated neck haematoma achieved by using a second generation supraglottic airway device (SAD) with an inflatable cuff placed in the manikin’s neck with the laryngeal opening outwards and tubing inside the chest. The opening was filled with red jelly, covered by simulated strap muscles (made from simulated small bowel with interrupted sutures) and simulated neck skin (which presented a sutured incision complete with steri-strips). Ongoing bleeding was simulated by injecting liquid jelly through the SAD’s gastric port via a long connecting tube in the manikin’s thorax. This simulation training increased confidence and familiarity with the steps required to manage post thyroid surgery haematomas in 100% (15/15) of candidates, with 73% grading the mannikin ≥4/5 for realism. However, it was costly to provide and time-consuming to set up. It was decided to try to make the set-up cheaper and easier to reproduce without impairing quality. Equipment costs were reviewed and alternative options identified. Expensive components included the SAD and bowel material, which were replaced with a cheaper SAD and a disposable tourniquet fashioned as shown in Making the simulation larynx and strap muscles. A step by step guide The cost of disposable props used in each session was reduced from £133.04 to £8.52 with the new equipment. The designers also felt it was significantly more robust and easier to reproduce. This approach could also be easily adapted for mobile part-task training, improving multi-disciplinary access to training. Feedback showed 47% of candidates felt the new set-up to be better, and 47% reported non-inferiority. Changing to new equipment resulted in a design that was significantly cheaper, easier to source and set-up, while being at least as realistic and offering training opportunities outside the high-fidelity environment. Authors confirm that all relevant ethical standards for research conduct and dissemination have been met. The submitting author confirms that relevant ethical approval was granted, if applicable.

A rare variation of omohyoid and its embryological correlations- A case report

The omohyoid muscle is important in radical neck dissection, as it is a landmark for this operation. Because it divides the anterior and posterior cervical triangles into smaller triangles and its particular relationship to the large cervical vessels, the presence of an anatomical variation of the omohyoid muscle is important. Either belly may be absent or double; and the inferior belly may be attached directly to the clavicle and the superior is sometimes fused with sternohyoid. Variations in the omohyoid muscle might be linked to differences in embryological development, which could influence the muscle’s final form and function. Anderson (Anderson, 1881) theorized that the superior belly of the omohyoid muscle is a true infrahyoid muscle, whereas the inferior belly most likely shares a common embryology with the subclavius muscle. As omohyoid mucle is used to achieve the reconstruction of the laryngeal muscles and bowed vocal folds, the knowledge of the possible anomalies of the omohyoid muscle is important.In the present study, we have found a case with two inferior bellies & aberrant course of superior belly of omohyoid on right side of 40 years female cadaver embalmed with formalin during routine dissection at Department of Anatomy AIIMS Gorakhpur.Omohyoid muscle is closely related to large vessels of neck & brachial plexus, so variations in this muscle are clinically important.

Incidence and risk factors for secondary extralaryngeal dystonia in patients with laryngeal dystonia

Background and objectivesLaryngeal dystonia (LD) is a focal dystonia affecting adductor and/or abductor muscles of the larynx. It can be isolated or may spread to extra laryngeal muscles. The aim of this study was to report the characteristics of LD over time in a large single-center study with a long follow-up. MethodsRetrospective review of patients with LD referred to our institution between 1991 and 2021. Demographic data, time to diagnosis, type of LD, follow-up and spread of dystonia [SD] were recorded. Risk factors for spread of dystonia during follow-up were analyzed. ResultsOver the 30-year period, 516 patients (77.3 % female, median age 50 years, range 5–87 years) were analyzed. Three hundred and fifteen patients (61 %) had adduction laryngeal dystonia, 136 patients (26.4 %) had abduction laryngeal dystonia, 46 patients (8.9 %) had adductor respiratory laryngeal dystonia, 12 patients (2.3 %) had mixed laryngeal dystonia, and seven patients (1.4 %) had singer's laryngeal dystonia. A previous history of dystonia was found in 47 patients (9.1 %). A laryngeal tremor was found in 68 patients (13.2 %). Since the onset of symptoms, LD was diagnosed after a median of 3 years (IQR: 1.0, 7.0). SD occurred in 55 patients (10.7 %) after a median time of 4 year (IQR: 1.5, 13.0). Patients with mixed laryngeal dystonia had higher probability of SD (p = 0.018). DiscussionThis study reports a large European study of LD, with a long follow-up. SD occurred in 10.5 % of patients. Patients with mixed laryngeal dystonia had a higher probability of SD. A close follow-up may be recommended for patients with mixed laryngeal dystonia.

The larynx in 3 dimensions: A digital anatomical model derived from radiographic imaging, refined with peer-reviewed literature, and optimized with medical illustration

ObjectivesDevelopment of an anatomically accurate three-dimensional (3D) digital model of the human larynx derived from published literature and radiographic imaging. Materials and MethodsThe laryngeal framework was segmented from a computed tomography (CT) angiogram of a healthy 29-year-old female. Data derived from published anatomical studies were compiled to provide additional anatomical detail to each structure. Anatomical details beyond the resolution of the imaging study or which could not be elucidated from the study were refined according to descriptions in the anatomic literature. The 3D model was refined by the medical illustrator, and its mesh was reformatted to optimize online viewing and manipulation. ResultsDue to the small size of the laryngeal muscles, there was no attempt to segment these muscles using radiographic imaging. All intrinsic laryngeal muscles were generated de novo, as were the superior laryngeal nerve and recurrent laryngeal nerve. CT imaging was utilized to generate meshes of the hyoid bone, epiglottis, thyroid cartilage, cricoid cartilage, and thyrohyoid membrane. Additionally, the airway space was segmented to provide size and spatial location to the vallecula, false vocal folds, true vocal folds, piriform sinus, subglottis, and a scaffold for the mucosa. These meshes were processed to limit radiographic artifact and serve as a foundation for the construction of the remainder of the laryngeal anatomy. The model was uploaded to a 3D repository, which can be accessed here (https://shorturl.at/nJPYZ). ConclusionThe larynx is a highly specialized organ essential for speech, swallowing, and airway protection. This study describes a digital 3D model of the larynx, created by combining radiographic imaging with critical review of anatomic literature. Utilizing the expertise of neuroradiology, laryngeal surgery, and medical illustration, we highlight surgically-relevant anatomic relationships and important aspects to consider during laryngeal surgery.

Domestic cat larynges can produce purring frequencies without neural input

Most mammals produce vocal sounds according to the myoelastic-aerodynamic (MEAD) principle, through self-sustaining oscillation of laryngeal tissues.1,2 In contrast, cats have long been believed to produce their low-frequency purr vocalizations through a radically different mechanism involving active muscle contractions (AMC), where neurally driven electromyographic burst patterns (typically at 20-30Hz) cause the intrinsic laryngeal muscles to actively modulate the respiratory airflow. Direct empirical evidence for this AMC mechanism is sparse.3 Here, the fundamental frequency (fo) ranges of eight domestic cats (Felis silvestris catus) were investigated in an excised larynx setup, to test the prediction of the AMC hypothesis that vibration should be impossible without neuromuscular activity, and thus unattainable in excised larynx setups, which are based on MEAD principles. Surprisingly, all eight excised larynges produced self-sustained oscillations at typical cat purring rates. Histological analysis of cat larynges revealed the presence of connective tissue masses, up to 4mm in diameter, embedded in the vocal fold.4 This vocal fold specialization appears to allow the unusually low fo values observed in purring. While our data do not fully reject the AMC hypothesis for purring, they show that cat larynges can easily produce sounds in the purr regime with fundamental frequencies of 25 to 30Hz without neural input or muscular contraction. This strongly suggests that the physical and physiological basis of cat purring involves the same MEAD-based mechanisms as other cat vocalizations (e.g., meows) and most other vertebrate vocalizations but is potentially augmented by AMC.

A Novel Acoustic Evaluation Method for the Diagnosis of Adductor Spasmodic Dysphonia

Introduction: Adductor spasmodic dysphonia (ADSD) is characterized by involuntary laryngeal muscle spasms. Due to the lack of a quantitative evaluation method, most measurements have demonstrated difficulty in validity and reliability for diagnosing ADSD. This study aimed to establish a novel indicator for ADSD and determine its diagnostic effects. Methods: We investigated 98 voice samples from 49 patients with ADSD and 49 healthy participants. A sustained vowel was recorded by a high-definition audio recorder. Voice samples underwent regular acoustic evaluation and a novel global dimension (GD) method. GD, Jitter, Shimmer, HNR, Frequency shift, and CPPS were measured for both groups. Results: Statistical analysis revealed that the GD method effectively differentiated ADSD patients from healthy participants (p < 0.001, D′>0.8). Subsequent multiclass receiver operating characteristic analysis demonstrated that GD possessed the most significant classification accuracy (area under the curve = 0.988) compared with other acoustic parameters. Conclusion: GD was an effective metric for objective differentiation between ADSD patients and healthy participants. This metric could assist clinicians in the diagnosis of ADSD patients.

An Euler–Bernoulli-type beam model of the vocal folds for describing curved and incomplete glottal closure patterns

Incomplete glottal closure is a laryngeal configuration wherein the glottis is not fully obstructed prior to phonation. It has been linked to inefficient voice production and voice disorders. Various incomplete glottal closure patterns can arise and the mechanisms driving them are not well understood. In this work, we introduce an Euler–Bernoulli composite beam vocal fold (VF) model that produces qualitatively similar incomplete glottal closure patterns as those observed in experimental and high-fidelity numerical studies, thus offering insights into the potential underlying physical mechanisms. Refined physiological insights are pursued by incorporating the beam model into a VF posturing model that embeds the five intrinsic laryngeal muscles. Analysis of the combined model shows that co-activating the lateral cricoarytenoid (LCA) and interarytenoid (IA) muscles without activating the thyroarytenoid (TA) muscle results in a bowed (convex) VF geometry with closure at the posterior margin only; this is primarily attributed to the reactive moments at the anterior VF margin. This bowed pattern can also arise during VF compression (due to extrinsic laryngeal muscle activation for example), wherein the internal moment induced passively by the TA muscle tissue is the predominant mechanism. On the other hand, activating the TA muscle without incorporating other adductory muscles results in anterior and mid-membranous glottal closure, a concave VF geometry, and a posterior glottal opening driven by internal moments induced by TA muscle activation. In the case of initial full glottal closure, the posterior cricoarytenoid (PCA) muscle activation cancels the adductory effects of the LCA and IA muscles, resulting in a concave VF geometry and posterior glottal opening. Furthermore, certain maneuvers involving co-activation of all adductory muscles result in an hourglass glottal shape due to a reactive moment at the anterior VF margin and moderate internal moment induced by TA muscle activation. These findings have implications regarding potential laryngeal maneuvers in patients with voice disorders involving imbalances or excessive tension in the laryngeal muscles such as muscle tension dysphonia.

Volitional inspiration is mediated by two independent output channels in the primary motor cortex.

The diaphragm is a multifunctional muscle that mediates both autonomic and volitional inspiration. It is critically involved in vocalization, postural stability, and expulsive core-trunk functions, such as coughing, hiccups, and vomiting. In macaque monkeys, we used retrograde transneuronal transport of rabies virus injected into the left hemidiaphragm to identify cortical neurons that have multisynaptic connections with phrenic motoneurons. Our research demonstrates that representation of the diaphragm in the primary motor cortex (M1) is split into two spatially separate and independent sites. No cortico-cortical connections are known to exist between these two sites. One site is located dorsal to the arm representation within the central sulcus and the second site is lateral to the arm. The dual representation of the diaphragm warrants a revision to the somatotopic map of M1. The dorsal diaphragm representation overlaps with trunk and axial musculature. It is ideally situated to coordinate with these muscles during volitional inspiration and in producing intra-abdominal pressure gradients. The lateral site overlaps the origin of M1 projections to a laryngeal muscle, the cricothyroid. This observation suggests that the coordinated control of laryngeal muscles and the diaphragm during vocalization may be achieved, in part, by co-localization of their representations in M1. The neural organization of the two diaphragm sites underlies a new perspective for interpreting functional imaging studies of respiration and/or vocalization. Furthermore, our results provide novel evidence supporting the concept that overlapping output channels within M1 are a prerequisite for the formation of muscle synergies underlying fine motor control.