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The remarkable signal-detection capabilities of the auditory and vestibular systems have been studied for decades. Much of the conceptual framework that arose from this research has suggested that these sensory systems rest on the verge of instability, near a Hopf bifurcation, in order to explain the detection specifications. However, this paradigm contains several unresolved issues. Critical systems are not robust to stochastic fluctuations or imprecise tuning of the system parameters. Further, a system poised at criticality exhibits a phenomenon known in dynamical systems theory as critical slowing down, where the response time diverges as the system approaches the critical point. An alternative description of these sensory systems is based on the notion of chaotic dynamics, where the instabilities inherent to the dynamics produce high temporal acuity and sensitivity to weak signals, even in the presence of noise. This alternative description resolves the issues that arise in the criticality picture. We review the conceptual framework and experimental evidence that supports the use of chaos for signal detection by these systems, and propose future validation experiments.

Introduction: The Video Head Impulse Test (vHIT) is a safe and reliable assessment of peripheral vestibular function. Many studies tested its accuracy in clinical settings for differential diagnosis and quantification of the vestibulo-oculomotor reflex (VOR) in various disorders. However, the results of its application after lesions of the CNS are discordant and have never been studied in rehabilitation. This study aims to assess the VOR performance in a sample of stroke survivors. Methods: This is a cross-sectional study on 36 subacute and chronic stroke survivors; only persons with first-ever stroke and able to walk independently, even with supervision, were included. We performed VOR assessments for each semicircular canal by vHIT and balance assessments by the Berg Balance Scale and the MiniBESTest scale. Results: Two hundred and sixteen semicircular canals were assessed using the Head Impulse paradigm (in both the vertical and horizontal planes), while 72 semicircular canals were assessed using the Suppressed Head Impulse paradigm (horizontal plane). There was a high prevalence of participants with dysfunctional canals, particularly for the left anterior and right posterior canals, which were each prevalent in more than one-third of our sample. Furthermore, 16 persons showed an isolated canal dysfunction. The mean VOR gain for the vertical canals had confidence intervals out of the normal values (0.74–0.91 right anterior; 0.74–0.82 right posterior; 0.73–0.87 left anterior). Conclusion: Our findings suggest that peripheral vestibular function may be impaired in people with stroke; a systematic assessment in a rehabilitation setting could allow a more personalized and patient-centred approach. [ABSTRACT FROM AUTHOR]

The Spanish neurohistologist Santiago Ramón y Cajal (1852-1934) is widely regarded as the father of modern Neuroscience. In addition to identifying the individuality of cells in the nervous system (the neuron theory) or the direction followed by nerve impulses (the principle of dynamic polarization), he described numerous details regarding the organization of the different structures of the nervous system. This task was compiled in his magnum opus, "Textura del Sistema Nervioso del Hombre y los Vertebrados," first published in Spanish between 1899 and 1904, and later revised and updated in French as "Histologie du système nerveux de l'homme et des vertébrés" between 1909 and 1911 for wider distribution among the international scientific community. Some of Cajal's findings are fundamental to our understanding of the anatomy and histology of the vestibular system. He depicted the nerve endings in the sensory epithelia, the structure of the vestibular nerve and Scarpa ganglion, afferent vestibular fibers, vestibular nuclei, lateral vestibulospinal tract, vestibulocerebellar connections, and the fine structure of the cerebellum. However, most of these pioneering descriptions were published years earlier in Spanish journals with limited circulation. Our study aimed to gather Cajal's findings on the vestibular system and identify his original publications. After this endeavor, we claim a place for Cajal among the founders of anatomy and histology of the vestibular system. [ABSTRACT FROM AUTHOR]

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Gravity has profoundly influenced life on Earth, yet how organisms adapt to changes in gravity remains largely unknown. This study examines vestibular plasticity, specifically how the vestibular system responds to altered gravity. We subjected male C57BL/6J mice to hypergravity (2 G) followed by normal gravity (1 G) to analyze changes in vestibular function and gene expression. Mice showed significant vestibular dysfunction, assessed by righting reflex tests, which persisted for days but reversed at 1 G after exposure to 2 G. Gene expression analysis in the vestibular ganglion identified significant changes in 212 genes out of 49,585 due to gravitational changes. Specifically, 25 genes were upregulated under 2 G and recovered at 1 G after 2 G exposure, while one gene showed the opposite trend. Key neural function genes like Shisa3, Slc25a37, Ntn4, and Snca were involved. Our results reveal that hypergravity-induced vestibular dysfunction is reversible and highlight genes critical for adaptation. [ABSTRACT FROM AUTHOR]

The vestibular hair cell receptors of anamniotes, designated Type II, are presynaptic to bouton endings of vestibular nerve distal neurites. An additional flask-shaped hair cell receptor, Type I, is present in amniotes, and communicates with a chalice-shaped afferent neuritic ending that surrounds the entire hair cell except its apical neck. Since the full repertoire of afferent fiber dynamics and sensitivities observed throughout the vertebrate phyla can be accomplished through Type II hair cell-bouton synapses, the functional contribution(s) of Type I hair cells and their calyces to vestibular performance remains a topic of great interest. The goal of the present study was to investigate electrical coupling between the Type I hair cell and its enveloping calyx in the mouse semicircular canal crista ampullaris. Since there are no gap junctions between these two cells, evidence for electrical communication would necessarily involve other mechanisms. Simultaneous recordings from the two cells of the synaptic pair were used initially to verify the presence of orthodromic quantal synaptic transmission from the hair cell to the calyx, and then to demonstrate bi-directional communication due to the slow accumulation of potassium ions in the synaptic cleft. As a result of this potassium ion accretion, the equilibrium potentials of hair cell conductances facing the synaptic cleft become depolarized to an extent that is adequate for calcium influx into the hair cell, and the calyx inner face becomes depolarized to a level that is near the threshold for spike initiation. Following this, paired recordings were again employed to characterize fast bi-directional electrical coupling between the two cells. In this form of signaling, cleft-facing conductances in both the hair cell and calyx increase, which strengthens their coupling. Because this mechanism relies on the cleft resistance, we refer to it as resistive coupling. We conclude that the same three forms of hair cell-calyceal transmission previously demonstrated in the turtle are present in the mammalian periphery, providing a biophysical basis for the exceptional temporal fidelity of the vestibular system. [ABSTRACT FROM AUTHOR]

Background: Uni‐ or bilateral peripheral vestibular impairment causes objective spatial orientation deficits, which can be measured using pen‐and‐paper‐tests or sensorimotor tasks (navigation or pointing). For patients' subjective orientation abilities, questionnaires are commonly used (e.g., Santa Barbara sense of direction scale [SBSODS]). However, the relationship between subjective assessment of spatial skills and objective vestibular function has only been scarcely investigated. Methods: A total of 177 patients (mean age 57.86 ± 17.53 years, 90 females) who presented in our tertiary Center for Vertigo and Balance Disorders underwent neuro‐otological examinations, including bithermal water calorics, video head impulse test (vHIT), and testing of the subjective visual vertical (SVV), and filled out the SBSODS (German version). Correlation analyses and linear multiple regression model analyses were performed between vestibular test results and self‐assessment scores. Additionally, groupwise vestibular function for patients with low, average, and high self‐report scores was analyzed. Results: Forty‐two patients fulfilled the diagnostic criteria for bilateral vestibulopathy, 93 for chronic unilateral vestibulopathy (68 unilateral caloric hypofunction and 25 isolated horizontal vestibulo‐ocular reflex deficits), and 42 patients had normal vestibular test results. SBSODS scores showed clear sex differences with higher subjective skill levels in males (mean score males: 4.94 ± 0.99, females 4.40 ± 0.94; Student's t‐test: t‐3.78, p <.001***). No stable correlation between objective vestibular function and subjective sense of spatial orientation was found. A multiple linear regression model could not reliably explain the self‐reported variance. The three patient groups with low, average, and high self‐assessment‐scores showed no significant differences of vestibular function. Conclusion: Self‐reported assessment of spatial orientation does not robustly correlate with objective peripheral vestibular function. Therefore, other methods of measuring spatial skills in real‐world and virtual environments are required to disclose orientation deficits due to vestibular hypofunction. [ABSTRACT FROM AUTHOR]

Dopaminergic replacement therapy remains the mainstay of symptomatic treatment for Parkinson's disease (PD), but many unmet needs and gaps remain. Device-based treatments or device-aided non-oral therapies are typically used in the advanced stages of PD, ranging from stereotactic deep brain stimulation to levodopa or apomorphine infusion therapies. But there are concerns associated with these late-stage therapies due to a number of procedural, hardware, or long-term treatment-related side effects of these treatments, and their limited nonmotor benefit in PD. Therefore, there is an urgent unmet need for low-risk adjuvants or standalone therapies which can address the range of burdensome motor and nonmotor symptoms that occur in PD. Recent studies suggest that non-invasive neurostimulation of the vestibular system may be able to address these gaps through the stimulation of the vestibular brainstem sensory network which extensively innervates brain regions, regulating both motor and a range of nonmotor functions. Therapeutic non-invasive vestibular stimulation is a relatively modern concept that may potentially improve a broad range of motor and nonmotor symptoms of PD, even at early stages of the disease. Here, we review previous studies supporting the therapeutic potential of vestibular stimulation for the treatment of PD and discuss ongoing clinical trials and potential areas for future investigations. [ABSTRACT FROM AUTHOR]

Background: Otitis media with effusion (OME) frequently leads to vestibular symptoms in children. However, young children face difficulty expressing their symptoms due to their limited language abilities. Methods: The balance of study and patient group evaluated with computer dynamic posturography, single‐leg stance test with eyes closed and regular Head Impulse Test. The study group was assessed once again after the insertion of a ventilation tube two months later. Results: In the Sensory Organization Test, the scores for conditions 5, 6, and composite equilibrium of the preoperative patient group were notably lower compared with both the control and postoperative patient groups (p < 0.05). Additionally, a significant correlation was found between single‐leg stance test with eyes closed results and conditions 5, 6, and composite equilibrium scores. Conclusion: The impact of OME on the vestibular system is negative. This effect can be objectively assessed using Computer Dynamic Posturography and following tube insertion, there is a notable improvement in vestibular function. Furthermore, the single‐leg stance (SLS) test with eyes closed has shown its reliability in assessing balance disorders, notably in children with OME. Level of Evidence: 2 Laryngoscope, 134:4126–4133, 2024 [ABSTRACT FROM AUTHOR]

Several neurodevelopmental disorders are associated with a higher prevalence of atypical laterality (e.g., left‐handedness). Both genetic and non‐genetic factors play a role in this association, yet the underlying neurobiological mechanisms are largely unclear. Recent studies have found that stress, mediated by the hypothalamic–pituitary–adrenal (HPA) axis, could be linked to laterality development. These findings provide an opportunity to explore new theoretical perspectives on the association between atypical laterality and neurodevelopmental disorders. This article aims to provide a theoretical framework demonstrating how perinatal adversities could disrupt the typical developmental trajectories of both laterality and neurodevelopment, potentially impacting both the HPA axis and the vestibular system. Additionally, we argue that the relationship between atypical laterality and neurodevelopmental disorders cannot be understood by simply linking genetic and non‐genetic factors to a diagnosis, but the developmental trajectories must be considered. Based on these ideas, several perspectives for future research are proposed. [ABSTRACT FROM AUTHOR]

Persistent Postural-Perceptual Dizziness (PPPD) is a functional vestibular condition. Despite being the most common chronic neuro-otologic disorder, it remains undertreated. The Niigata PPPD Questionnaire (NPQ), developed by Yagi et al. in 2019 to assess the severity of PPPD, could be a useful tool to help in the screening and diagnosis of this condition. This study aimed to validate a French version of the NPQ and make it an available assessment tool. Moreover, we aimed to understand the characteristics of PPPD patients better. The NPQ was translated and adapted into French. 50 PPPD patients, 50 patients with vestibular disorders without PPPD, and 50 healthy controls were included. They answered the adapted NPQ and additional questionnaires assessing trait (STAI) and state anxiety (HADS-A), depression (HADS-D) and handicap related to dizziness (DHI). The NPQ's reliability was assessed by Cronbach's alpha. Intergroup comparisons and multiple linear regressions were conducted to examine the characteristics of PPPD patients compared to vestibular patients and healthy controls, to validate NPQ's reliability, and to explore the effect of clinical parameters and treatment with selective serotonin reuptake inhibitors. Receiver operating characteristic (ROC) curves were carried out to determine the diagnostic values of the NPQ total score and sub-scores. Relations between NPQ and reported handicap, depression and anxiety were evaluated by correlations between questionnaire scores. The internal consistency was high (>0.8) for all NPQ subscales and the total score. Intergroup comparisons showed a significantly higher NPQ total score and sub-scores in the PPPD group compared to the two others. The ROC curve analysis showed a significant, but poor, discrimination of NPQ (AUC = 0.664) and its subscales. DHI scores, depressive symptoms and trait anxiety were significantly higher in PPPD patients than in vestibular patients and healthy controls. State anxiety did not differ between patients with PPPD and vestibular patients without PPPD. Finally, there was a significant correlation between the NPQ and the DHI. Our study provides a better understanding of PPPD symptomatology and its assessment. It showed that the NPQ is a reliable tool that can assist in symptom assessment for a French-speaking population. [ABSTRACT FROM AUTHOR]

Misperceptions of subjective visual vertical are associated with poor balance, increasing the risk of falls and accidents. The aim of the present study was to evaluate the effect of nomophobia on verticality perception using subjective visual vertical (S.V.V.) test and cervical neuromotor control of the deep neck flexors (DNF) in adults aged 18–29 years old. This cross-sectional study employed convenience sampling and was conducted at a tertiary health institute over an eight-month period.After obtaining the written informed consent, 102 participants were asked to fill the Nomophobia Questionnaire (NMP-Q) and based on the responses participants were stratified into mild (n1 = 34), moderate(n2 = 34), and severe(n3 = 34) nomophobian group. Each nomophobian group underwent testing for verticality perception by using the SVV test and cervical neuromotor control. 102 healthy age and gender matched controls were recruited and underwent testing for verticality perception by using the SVV test and cervical neuromotor control. The mean age of the study participants was 22 ± 3.15 years with 35(33.98%) males and 67(65.04%) females. There was a statistically significant difference between the median scores across the three nomophobian groups with S.V.V. (p = 0.005), activation score (p = 0.012), and endurance score (p = 0.000) of the deep neck flexors in the severe nomophobia group. This study demonstrated that SVV and cervical neuromotor control was predominantly affected in the severe nomophobian group. [ABSTRACT FROM AUTHOR]

Vertiginous epilepsy (VE) is a rare and underrecognized epilepsy subtype in the pediatric population. Vertiginous symptoms are the sole or predominant feature, arise from the vestibular cortex, and seizures are usually brief. The incidence is estimated to be between six and 15 percent of pediatric patients presenting with dizziness. Diagnosis is often delayed for many years following the onset of symptoms, as there are no widely accepted diagnostic criteria. Diagnostic workup should include a detailed history, physical exam, EEG, and brain imaging with MRI. Vestibular testing is helpful if peripheral vestibulopathy is suspected. Vertiginous epilepsy can have many possible causes, but a large majority are idiopathic or suspected to be genetic. Most patients with vertiginous epilepsy achieve seizure freedom with anti-seizure medications. [ABSTRACT FROM AUTHOR]

This historical review on the semantic evolution of human senses and sensors revealed that Aristotle’s list of the five senses sight, hearing, touch, taste, and smell is still in use among non-scientific lay persons. It is no surprise that his classification in the work “De Anima” (On the Soul) from 350  BC confuses the sensor “touch” with the now more comprehensively defined somatosensory system and that senses are missing such as the later discovered vestibular system and the musculotendinous proprioception of the position of parts of the body in space. However, it is surprising that in the three most influential ancient cultures, Egypt, Greece, and China—which shaped the history of civilization—the concept prevailed that the heart rather than the brain processes perception, cognition, and emotions. This “cardiocentric view” can be traced back to the “Doctrine of Aristotle,” the “Book of the Dead” in ancient Egypt, and the traditional Chinese medicine of correspondence documented in the book “Huang di Neijing.” In Greek antiquity the philosophers Empedocles, Democritus and Aristotle were proponents of the allocation of the spirit and the soul to the heart connected to the body via the blood vessels. Opponents were the pre-Socratic mathematician Pythagoras, the philosopher Plato, and especially the Greek physician Hippocrates who regarded the brain as the most powerful organ in humans in his work “De Morbo Sacro.” The Greek physician Galen of Pergamon further elaborated on the concept of the brain (“cephalocentric hypothesis”) connected to the body by a network of nerves. The fundamental concepts for understanding functions and disorders of the vestibular system, the perception of self-motion, verticality and balance control were laid by a remarkable group of 19th century scientists including Purkynӗ, Mach, Breuer, Helmholtz, and Crum-Brown. It was also in the 19th century that Bell described a new sense of a reciprocal sensorimotor loop between the brain and the muscles which he called “muscular sense,” later termed “kinaesthesia” by Bastian and defined in 1906 as “proprioception” by Sherrington as “the perception of joint and body movements as well as position of the body or body segments, in space.” Both, the vestibular system and proprioception could be acknowledged as senses six or seven. However, we hesitate to recommend “pain”—which is variously assigned to the somatosensory system or extero-, intero-, visceroception—as a separate sensory system. Pain sensors are often not specific but have multisensory functions. Because of this inconsistent, partly contradictory classification even by experts in the current literature on senses and sensors we consider it justified to recommend a comprehensive reorganization of classification features according to the present state of knowledge with an expansion of the number of senses. Such a project has also to include the frequent task-dependent multisensory interactions for perceptual and sensorimotor achievements, and higher functions or disorders of the visual and vestibular systems as soon as cognition or emotions come into play. This requires a cooperation of sensory physiologists, neuroscientists and experienced physicians involved in the management of patients with sensory and multisensory disorders. [ABSTRACT FROM AUTHOR]

Background: Idiopathic intracranial hypertension (IIH) can affect both hearing and balance due to increased inner ear pressure. Aims/Objectives: This study aimed to evaluate the impact of increased inner ear pressure on hearing and balance in patients with IIH using auditory and vestibular tests. Material and Methods: Twenty-four IIH patients and 28 healthy controls underwent oVEMP, pure tone audiometry, tympanometry, and acoustic reflex tests pre-lumbar punctures. IIH patients received acetazolamide. Pre- and post-treatment results, tinnitus, and vertigo scores were compared. Post-treatment oVEMP and audiometry results were compared between groups. Results: Pre-treatment oVEMP showed a significant left N1 latency difference (p = 0.049). Post-treatment, left ear amplitude (p = 0.035) and both ear amplitude ratios (p = 0.044 and p = 0.047) increased significantly. Audiometry had no significant changes (p < 0.05). Tinnitus and vertigo scores decreased significantly (p ≤ 0.001). Conclusion: Prolonged oVEMP latency suggests IIH may impact the brain stem and vestibular nerve, while increased amplitude values indicate peripheral vestibular involvement. IIH affects hearing across all frequencies, especially at 4000 Hz, impacting both hearing and balance. Significance: Understanding the effects of IIH on auditory and vestibular functions can guide effective treatments, improving quality of life for patients by addressing both hearing and balance issues. [ABSTRACT FROM AUTHOR]

Introduction: Aging and sedentary lifestyle are associated with a decrease in physical and mental abilities. The purpose of this study is to investigate the effect of eight weeks of selected vestibular exercises on functional balance, walking speed, and quality of life of sedentary elderly men. Methods: This semi -experimental research was conducted from the winter of 1402 to the summer of 1403 with the participation of 30 sedentary elderly men from Tawheed Golmkan Elderly Care Center in Mashhad. The samples were selected purposefully and based on previous studies (25) and were divided into two experimental and control groups of 15 people. The experimental group performed selected vestibular exercises three sessions a week for eight weeks, while the control group did not perform any exercises. Dynamic comparison test, 10 -meter walking speed and short -term life questionnaire were used to evaluate the quality of life. Data analysis was performed using Shapiro -Wilk test, analysis of covariance, and t -test at a significance level of P<0/05. Results: The results of paired t test showed that dynamic balance (P=0/001), walking speed (P=0/001), and quality of life (P=0/001) of the experimental group improved significantly after the exercise program. This was while there was no improvement in the control group. The covariance results did not show a significant difference between the groups in the pre -test phase, but there was a significant increase in the scores of the experimental group in the post -test phase. Conclusion: It is recommended to use exercises to prevent the disabilities of the elderly and improve their quality of independent life [ABSTRACT FROM AUTHOR]

Sinusoidal galvanic vestibular stimulation (sGVS) induces robust modulation of muscle sympathetic nerve activity (MSNA) alongside perceptions of side-to-side movement, sometimes with an accompanying feeling of nausea. We recently showed that transcranial alternating current stimulation (tACS) of the dorsolateral prefrontal cortex (dlPFC) also modulates MSNA, but does not generate any perceptions. Here, we tested the hypothesis that when the two stimuli are given concurrently, the modulation of MSNA would be additive. MSNA was recorded from 11 awake participants via a tungsten microelectrode inserted percutaneously into the right common peroneal nerve at the fibular head. Sinusoidal stimuli (± 2 mA, 0.08 Hz, 100 cycles) were applied in randomised order as follows: (i) tACS of the dlPFC at electroencephalogram (EEG) site F4 and referenced to the nasion; (ii) bilateral sGVS applied to the vestibular apparatuses via the mastoid processes; and (iii) tACS and sGVS together. Previously obtained data from 12 participants supplemented the data for stimulation protocols (i) and (ii). Cross-correlation analysis revealed that each stimulation protocol caused significant modulation of MSNA (modulation index (paired data): 35.2 ± 19.4% for sGVS; 27.8 ± 15.2% for tACS), but there were no additive effects when tACS and sGVS were delivered concurrently (32.1 ± 18.5%). This implies that the vestibulosympathetic reflexes are attenuated with concurrent dlPFC stimulation. These results suggest that the dlPFC is capable of blocking the processing of vestibular inputs through the brainstem and, hence, the generation of vestibulosympathetic reflexes. [ABSTRACT FROM AUTHOR]

Introduction: The aims of the present study were to evaluate postural balance performance of the subjects on the time-restricted feeding (TRF) and reveal the effect of TRF on the vestibular system by comparing the results to those of traditional daily dietary (DD) condition. Methods: Sixteen adults (3 males, 13 females; mean age: 25.4 ± 4 years) who had experienced at least 1 month of TRF were included in the study. The Sensory Organization Test (SOT) and Head-Shake SOT (HS-SOT) – which evaluate proprioceptive, visual, and vestibular systems – were performed on TRF and DD conditions via the Computerized Dynamic Posturography system. Results: Significant differences were obtained between TRF and DD situations in SOT-5 (p = 0.008), SOT-6 (p = 0.01), and HS-SOT5 (p = 0.007) conditions in which the vestibular system dominated. Conclusion: We revealed that TRF has an effect on postural balance in the absence of proprioceptive and visual systems. This feeding model is a negative stressor that has a substantial effect on the vestibular system, but this impact is minimal once the proprioceptive and visual systems are intact. To the best of our knowledge, it is the first study to evaluate postural balance utilizing vestibular parameters in TRF. [ABSTRACT FROM AUTHOR]

Objective: Translabyrinthine excision of a vestibular schwannoma is associated with acute vestibular failure. Preoperative intratympanic gentamicin (ITG) injections can improve objective balance function after surgery but its clinical benefits remain to be established. Methods: Adult patients undergoing translabyrinthine removal of a vestibular schwannoma between January 2014 and February 2018 underwent preoperative vestibular function testing. Patients were divided in to 3 groups, those with vestibular function (VF) who received ITG injections, those with VF but did not receive ITG and those with no VF. Groups were compared according to degree of vertigo, length of stay, time to unassisted mobilization, and postoperative anti‐emetic consumption. Results: Forty six patients had ITG injections (Group 1), 7 had residual VF but refused treatment (Group 2), 21 had no VF (Group 3). Group 1 had a significant improvement in vertigo over time whereas groups 2 and 3 did not. There was a statistically significant 70% decrease in time to independent mobilization between Group 1 and other groups and a 19% decrease in length of stay in Group 1 compared to other groups although this did not reach statistical significance. Two patients had injection‐related complications. Group 1 used less anti‐emetics than other groups but this was not statistically significant. Conclusion: Preoperative intratympanic gentamicin injection with vestibular rehabilitation exercises is associated with less postoperative vertigo and earlier postoperative mobilization. There was reduced duration of hospitalization and decreased consumption of anti‐emetic but not significantly so possibly because of low numbers of patients in the no treatment group. Level of Evidence: 2 Laryngoscope, 134:3316–3322, 2024 [ABSTRACT FROM AUTHOR]

Head movements that are synchronized with musical rhythms often emerge during musical activities, such as hip hop dance. Although such movements are known to affect the meter and pulse perception of complex auditory rhythms, no studies have investigated their contribution to the performance of sensorimotor synchronization (SMS). In the present study, participants listened to syncopated auditory rhythms and flexed their dominant hand index finger in time with the perceived pulses (4/4 meters). In the first experiment (Exp. 1), the participants moved their heads via voluntary neck flexion to the pulses in parallel with finger SMS (Nodding condition, ND). This performance was compared with finger SMS without nodding (Without Nodding condition, WN). In the second experiment (Exp. 2), we investigated the specificity of the effect of head SMS on finger SMS confirmed in Exp. 1 by asking participants to flex their bilateral index fingers to the pulses (Bimanual condition, BM). We compared the performance of dominant hand finger SMS between the BM and ND conditions. In Exp. 1, we found that dominant hand finger SMS was significantly more stable (smaller standard deviation of asynchrony) in the ND versus WN condition (p < 0.001). In Exp. 2, dominant hand finger SMS was significantly more accurate (smaller absolute value of asynchrony) in the ND versus BM condition (p = 0.037). In addition, the stability of dominant hand finger SMS was significantly correlated with the index of phase locking between the pulses and head SMS across participants in the ND condition (r = -0.85, p < 0.001). In contrast, the stability of dominant hand finger SMS was not significantly correlated with the index of phase locking between pulses and non-dominant hand finger SMS in the BM condition (r = -0.25, p = 0.86 after multiple comparison correction). These findings suggest that SMS modulation depends on the motor effectors simultaneously involved in synchronization: simultaneous head SMS stabilizes the timing of dominant hand finger SMS, while simultaneous non-dominant hand finger SMS deteriorates the timing accuracy of dominant hand finger SMS. The present study emphasizes the unique and crucial role of head movements in rhythmic behavior. [ABSTRACT FROM AUTHOR]

Dizziness and postural instability are frequently observed symptoms in patient with Parkinson's disease (PD), potentially linked to vestibular dysfunction. Despite their significant impact on quality of life, these symptoms are often overlooked and undertreated in clinical practice. This review aims to summarize symptoms associated with vestibular dysfunction in patients with PD and discusses vestibular-targeted therapies for managing non-specific dizziness and related symptoms. We conducted searches in PubMed and Web of Science using keywords related to vestibular dysfunction, Parkinson's disease, dizziness, and postural instability, alongside the reference lists of relevant articles. The available evidence suggests the prevalence of vestibular dysfunction-related symptoms in patients with PD and supports the idea that vestibular-targeted therapies may be effective in improving PD symptoms. [ABSTRACT FROM AUTHOR]

IntroductionKnowledge of the natural and temporal course of a disease is important when deciding if an intervention is appropriate. In the case of Ménière’s disease (MD), there is some evidence that attacks diminish over time, but the topic remains controversial. A conservative approach to surgery is usually followed in northern Europe, and leads to strict patient selection before considering surgery. Here, we describe the evolution of vertigo attacks among a group of intractable MD patients in whom surgery was considered.MethodsRetrospective cohort study in a Ménière’s disease expert center. Patients with definite unilateral Ménière’s disease and persisting vertigo attacks despite treatment with intratympanic steroid injections were included. All patients had been waitlisted for participation in a planned trial assessing non-ablative surgery. They were waitlisted between June 2016 and June 2021 without undergoing the surgical intervention. In September 2022, data were collected from patient’s files and follow-up telephone interviews were conducted to assess the evolution of their vertigo attacks.ResultsThirty-five patients (54% male, mean age of onset 52 years, 51% right sided) were included in the analysis. Twenty-five patients (71%) eventually declined surgery. Of the 33 patients with complete information on vertigo attacks, 21 (64%) were free of vertigo attacks upon data collection, after a median disease duration of 5.3 years. Patients who did undergo surgery, had longer duration of disease than patients who did not.DiscussionEven in a population with intractable MD, most patients will experience relief of symptoms over time. On one hand, active treatment may accelerate relief of symptoms, but on the other hand, non-ablative therapies are of debatable effect and ablative intervention carries a risk of life long side effects. Therefore, any active intervention should be carefully considered.

Abstract Background Uni‐ or bilateral peripheral vestibular impairment causes objective spatial orientation deficits, which can be measured using pen‐and‐paper‐tests or sensorimotor tasks (navigation or pointing). For patients’ subjective orientation abilities, questionnaires are commonly used (e.g., Santa Barbara sense of direction scale [SBSODS]). However, the relationship between subjective assessment of spatial skills and objective vestibular function has only been scarcely investigated. Methods A total of 177 patients (mean age 57.86 ± 17.53 years, 90 females) who presented in our tertiary Center for Vertigo and Balance Disorders underwent neuro‐otological examinations, including bithermal water calorics, video head impulse test (vHIT), and testing of the subjective visual vertical (SVV), and filled out the SBSODS (German version). Correlation analyses and linear multiple regression model analyses were performed between vestibular test results and self‐assessment scores. Additionally, groupwise vestibular function for patients with low, average, and high self‐report scores was analyzed. Results Forty‐two patients fulfilled the diagnostic criteria for bilateral vestibulopathy, 93 for chronic unilateral vestibulopathy (68 unilateral caloric hypofunction and 25 isolated horizontal vestibulo‐ocular reflex deficits), and 42 patients had normal vestibular test results. SBSODS scores showed clear sex differences with higher subjective skill levels in males (mean score males: 4.94 ± 0.99, females 4.40 ± 0.94; Student's t‐test: t‐3.78, p

Background: Action recognition is a fundamental aspect of human interaction. This process is mediated by the activation of shared sensorimotor representations during action execution and observation. Although complex movements involving balance or head and trunk rotations require vestibular signals for effective execution, their role in the recognition of others' actions is still unknown. Objective: To investigate the causal involvement of the vestibular system in the discrimination of actions performed by others and whether this is influenced by motor familiarity. Methods: In a single-blind design involving 25 healthy participants, Galvanic Vestibular Stimulation (GVS) was administered during an Action Discrimination Task (ADT), in which videos of actions categorized as vestibular/non-vestibular and familiar/unfamiliar were presented. Following each video, participants were required to identify the climax of the previously viewed action between two image options, using a two-alternative forced choice paradigm. The ADT was performed in active and sham GVS conditions, with left or right anodal montages. Response Times (RTs), Accuracy, and subjective motor familiarity were recorded for each action category. Results: In sham GVS condition, an overall familiarity effect was observed, where RTs for familiar actions were faster than RTs for unfamiliar ones, regardless of vestibular engagement (p

The Spanish neurohistologist Santiago Ramón y Cajal (1852–1934) is widely regarded as the father of modern Neuroscience. In addition to identifying the individuality of cells in the nervous system (the neuron theory) or the direction followed by nerve impulses (the principle of dynamic polarization), he described numerous details regarding the organization of the different structures of the nervous system. This task was compiled in his magnum opus, “Textura del Sistema Nervioso del Hombre y los Vertebrados,” first published in Spanish between 1899 and 1904, and later revised and updated in French as “Histologie du système nerveux de l’homme et des vertébrés” between 1909 and 1911 for wider distribution among the international scientific community. Some of Cajal’s findings are fundamental to our understanding of the anatomy and histology of the vestibular system. He depicted the nerve endings in the sensory epithelia, the structure of the vestibular nerve and Scarpa ganglion, afferent vestibular fibers, vestibular nuclei, lateral vestibulospinal tract, vestibulocerebellar connections, and the fine structure of the cerebellum. However, most of these pioneering descriptions were published years earlier in Spanish journals with limited circulation. Our study aimed to gather Cajal’s findings on the vestibular system and identify his original publications. After this endeavor, we claim a place for Cajal among the founders of anatomy and histology of the vestibular system.

The human vestibular system is adversely affected by the aging process. Recent evidence indicates that vestibular information and cognitive functions are related, suggesting that age-related vestibular loss may contribute to cognitive impairment. In this study, we aimed to investigate the effects of repetitive, home-based galvanic vestibular stimulation (GVS) on cognitive functions in healthy older adults. Twenty-one participants (age = 64.66 ± 2.97 years, 12 females) were randomly allocated to either a home-based GVS or an active control group. The GVS intervention lasted 20 min per session, five times a week, for two weeks (10 sessions). Cognitive functions were assessed before and after the intervention using the Stroop Test, Trail Making Test A&B, and Dual-Task (digit recall and paper-pencil tracking test). Our findings revealed a significant group-by-time interaction effect for the tracking accuracy (F(1,18) = 7.713, p = 0.012, η p2 = 0.30), with only the home-based GVS group showing significant improvement (t = −2.544, p = 0.029). The proposed home-based GVS protocol offers a promising non-pharmacological avenue for enhancing visuospatial ability in healthy older adults. Further research is needed to investigate the effects of different GVS protocols on various cognitive functions, particularly in older individuals with different health conditions.

We report an experiment that tested the vestibular syncopation rhythm hypothesis, which holds that the rhythmic effect of syncopation is a form of vestibular reflexive/automated response to a postural perturbation, for example during locomotion. Electrophysiological signals were recorded from the cerebral cortex and cerebellum during processing of rhythmic sequences in a sample of experienced participants. Recordings were made using four different stimulus modalities, auditory, axial, vestibular and visual, under different rhythmic timing conditions, irregular, regular and syncopated/uncertain. Brain current activity was measured using a model with10-dipole source regions of interest in each of the participants, each modality, each timing condition, and for each beat within the bar of the rhythm. The cross-modal spectral power in the frontal electroencephalogram (EEG) and the cerebellar electrocerebellogram (ECeG) was also analysed. The results show that the brain activity increases from the irregular to the regular and then from the regular to the uncertain timing conditions. However, the vestibular modality induces the greatest total brain activity across the regions of interest and exhibits the highest sensitivity to the interaction of beat structure with the timing conditions in both source currents and spectral power. These data provide further evidence to support the primal role of the vestibular system in human processing of rhythm. [ABSTRACT FROM AUTHOR]

Background: Disconjugate eye movements are essential for depth perception in frontal-eyed species, but their underlying neural substrates are largely unknown. Lesions in the midbrain can cause disconjugate eye movements. While vertically disconjugate eye movements have been linked to defective visuo-vestibular integration, the pathophysiology and neuroanatomy of horizontally disconjugate eye movements remains elusive. Methods: A patient with a solitary focal midbrain lesion was examined using detailed clinical ocular motor assessments, binocular videooculography and diffusion-weighted MRI, which was co-registered to a high-resolution cytoarchitectonic MR-atlas. Results: The patient exhibited both vertically and horizontally disconjugate eye alignment and nystagmus. Binocular videooculography showed a strong correlation of vertical and horizontal oscillations during fixation but not in darkness. Oscillation intensities and waveforms were modulated by fixation, illumination, and gaze position, suggesting shared visual- and vestibular-related mechanisms. The lesion was mapped to a functionally ill-defined area of the dorsal midbrain, adjacent to the posterior commissure and sparing nuclei with known roles in vertical gaze control. Conclusion: A circumscribed region in the dorsal midbrain appears to be a key node for disconjugate eye movements in both vertical and horizontal planes. Lesioning this area produces a unique ocular motor syndrome mirroring hallmarks of developmental strabismus and nystagmus. Further circuit-level studies could offer pivotal insights into shared pathomechanisms of acquired and developmental disorders affecting eye alignment. [ABSTRACT FROM AUTHOR]

The semicircular canals of the inner ear are involved in balance and velocity control. Being crucial to ensure efficient mobility, their morphology exhibits an evolutionary conservatism attributed to stabilizing selection. Release of selection in slow‐moving animals has been argued to lead to morphological divergence and increased inter‐individual variation. In its natural habitat, the house mouse Mus musculus moves in a tridimensional space where efficient balance is required. In contrast, laboratory mice in standard cages are severely restricted in their ability to move, which possibly reduces selection on the inner ear morphology. This effect was tested by comparing four groups of mice: several populations of wild mice trapped in commensal habitats in France; their second‐generation laboratory offspring, to assess plastic effects related to breeding conditions; a standard laboratory strain (Swiss) that evolved for many generations in a regime of mobility reduction; and hybrids between wild offspring and Swiss mice. The morphology of the semicircular canals was quantified using a set of 3D landmarks and semi‐landmarks analyzed using geometric morphometric protocols. Levels of inter‐population, inter‐individual (disparity) and intra‐individual (asymmetry) variation were compared. All wild mice shared a similar inner ear morphology, in contrast to the important divergence of the Swiss strain. The release of selection in the laboratory strain obviously allowed for an important and rapid drift in the otherwise conserved structure. Shared traits between the inner ear of the lab strain and domestic pigs suggested a common response to mobility reduction in captivity. The lab‐bred offspring of wild mice also differed from their wild relatives, suggesting plastic response related to maternal locomotory behavior, since inner ear morphology matures before birth in mammals. The signature observed in lab‐bred wild mice and the lab strain was however not congruent, suggesting that plasticity did not participate to the divergence of the laboratory strain. However, contrary to the expectation, wild mice displayed slightly higher levels of inter‐individual variation than laboratory mice, possibly due to the higher levels of genetic variance within and among wild populations compared to the lab strain. Differences in fluctuating asymmetry levels were detected, with the laboratory strain occasionally displaying higher asymmetry scores than its wild relatives. This suggests that there may indeed be a release of selection and/or a decrease in developmental stability in the laboratory strain. [ABSTRACT FROM AUTHOR]

The perceptual and motor coordination problems experienced following return from spaceflight reflect the sensory adaptation to altered gravity. The purpose of this study was to develop a ground-based analog that replicates similar sensorimotor impairment using a standard measures test battery and subjective feedback from experienced crewmembers. This Sensorimotor Disorientation Analog (SDA) included varying levels of sensorimotor disorientation through combined vestibular, visual, and proprioceptive disruptions. The SDA was evaluated on five previously flown astronauts to compare with their postflight experience and functional motor performance immediately (Return (R)+0 days) and +24 h (R+1) after landing. The SDA consisted of galvanic vestibular stimulation (GVS), visual disruption goggles, and a weighted suit to alter proprioceptive feedback and replicate perceived heaviness postflight. Astronauts reported that GVS alone replicated ~50-90% of their postflight performance with the weighted suit fine-tuning the experience to replicate an additional 10%-40% of their experience. Astronauts did not report feeling that the disruption goggles represented either the visual disruptions or illusory sensations that they experienced, nor did they impact motor performance in postflight tasks similarly. Based on these results, we recommend an SDA including the GVS and the weighted suit. These results provide a more realistic and portable SDA framework to provide transient spaceflight-relevant sensorimotor disruptions for use in countermeasure testing and as a pre-flight training tool. [ABSTRACT FROM AUTHOR]

Background and Aim: Path integration refers to the capability of utilizing self-motion information produced by one's own bodily movements to accurately determine and maintain one's position in space. Typically, path integration mechanisms come into play when visual information is limited or absent. The objective of this study was to develop a path integration test that relies solely on self-motion cues derived from body movements, without the involvement of visual cues. Methods: The study involved 157 volunteers (86 females and 71 males) aged between 18 and 70 years. Participants were asked to walk on a coordinated ground with their closed eyes and follow the six different commands. They were, after that, requested to return their initial position. Movement time was manually measured by the stopwatch. The distance between the original reference point and estimated starting point was recorded. Results: The second command that showed the lowest standard deviation out of the six commands given to the participants was observed as the more reliable test among the other commands (47.51±33.75). In addition, the completion time of the second command increased with increasing age (p<0.001). Conclusion: This study introduces an innovative spatial navigation approach utilizing the second command set. As an alternative, this command can be used to assess the human spatial navigation system. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to determine the precautions that can be taken to increase the reliability of the vestibular evoked myogenic potentials test without being affected by the asymmetry of the sternocleidomastoid muscle and the issues that should be considered in the interpretation of vestibular evoked myogenic potential results if these precautions are not taken. Method: Individuals with sternocleidomastoid muscle activity of less than 30 μV in cervical vestibular evoked myogenic potential testing and an asymmetry ratio of more than 0.35 were excluded. In our study, individuals were divided into different groups according to sternocleidomastoid muscle asymetry. Results: A total of 53 individuals were included in the study. Intergroup comparisons were made to determine the effect of electromyogram scaling and filter use on amplitude asymmetry ratio according to sternocleidomastoid muscle asymmetry. Conclusion: Keeping the sternocleidomastoid muscle asymmetry not exceeding 10 μV maximises the reliability of cervical vestibular evoked myogenic potentials. As a result of our study, it can be concluded that in clinical applications the asymmetry should not exceed 20 μV. [ABSTRACT FROM AUTHOR]

The aim was to evaluate the vestibular system of children who had undergone cochlear implant surgery and to compare them with the healthy population by vestibulo-ocular reflex (VOR) gains in unilateral and bilateral implant users, with the implants both on and off. Patients older than 5 years who had undergone cochlear implant surgery between 2012 and 2020 and who were cochlear implant users for at least one year were included. After consent was obtained, a video head impulse test (VHIT) was performed to evaluate the three semicircular canals, with devices on and off, and VOR gains were evaluated. VHIT was also used to assess VOR gains in the control group. The VOR gains of the study and control groups, VOR gains of unilateral and bilateral implant users, and VOR gains with implants on and off were compared. When the VOR gains of 24 unilateral and 13 bilateral cochlear implant users and the control group (n = 30) were compared, a significant difference was found only in the anterior semicircular canal, although the VOR gains were found to be low in all three semicircular canals in the implant users (p < 0.05). There was no significant difference between the VOR gains of unilateral and bilateral implant users. There was no significant difference between the VOR gains when either on or off. There was no correlation between cochlear implant usage time, implant insertion age, patient age and VOR gain. The effects of cochlear implant surgery on the vestibular system continue in the late period, but no correlation was observed between implant usage time and VOR gain after the first year. It was observed that having the cochlear implant on or off had no effect on VOR gain. Furthermore, bilateral implant surgery did not lead to additional vestibular dysfunction compared to unilateral implant surgery. [ABSTRACT FROM AUTHOR]

* Purpose: Neurocognitive, vestibulo-ocular, and balance assessments can assist in screening and management of potential sports-related concussions. This cross-sectional study aimed to examine the effect of age on neurocognitive performance, vestibulo-ocular function, dynamic visual acuity, and postural control in high-level adolescent ball sport athletes. * Methods: In 139 male adolescent soccer and basketball players (under-11, under-15, under-19) assessments of neurocognitive performance (CNS Vital Signs), vestibulo-ocular reflex (video head impulse test), dynamic visual acuity (dynamic visual acuity test), and postural control (stability evaluation test) were performed. ANOVA and Kruskal-Wallis tests (post-hoc Bonferroni correction) were used for comparisons between age groups. * Results: Neurocognitive functioning (composite memory, psychomotor speed, reaction time, complex attention, cognitive flexibility, processing speed; p<0.008, η²=0.24 to 0.71), vestibulo-ocular reflex gain (p=0.018, η²=0.06), dynamic visual acuity loss (p<0.001, η²=0.11), and sway velocity (p<0.001, η²=0.36) differed significantly between age groups. Medium to large effects, with better performance in older compared to under-11 males, were found. * Conclusion: Under-11 male athletes revealed considerably lower neurocognitive, vestibulo-ocular reflex, dynamic visual acuity, and postural control performance compared to older youth athletes. Hence, this age group should be tested in smaller intervals to assess age-adequate performance and post-injury impairment. Further longitudinal studies may aid in the development of normative vestibulo-ocular reflex gain, dynamic visual acuity, and sway velocity values for ball sports. [ABSTRACT FROM AUTHOR]

Objectives: Vestibular dysfunction occasionally accompanies sensorineural hearing loss (SNHL) due to anatomical proximity of cochlea and vestibule. The aim of the present study was to evaluate the vestibular system objectively and subjectively in 40-to 65-year-old individuals with and without SNHL. Methods: This study included participants of both sexes, between the ages of 40 and 65 years old. There were 31 participants with SNHL and 31 control participants. First of all, participants were grouped in the control and SNHL groups based on the results of their hearing test, which included audiometry and immitance evaluation. Subsequently, for vestibular evaluation, each participant was evaluated subjective with "Dizziness Handicap Inventory" (DHI) as well as with objective tests battery that included positional tests with videonystagmogrophy (VNG) and vestibuloocular reflex (VOR) assessment using the vestibular head impulse test (vHIT). Results: Peripheral nystagmus was found to be significantly higher in patients with SNHL based on the head shake and positional tests (p<0.05). There was a positive correlation between DHI scores and positional test findings of the participants with SNHL (p<0.05). When the VHIT VOR gain values were compared between groups, there was no significant difference (p<0.05). Conclusion: In our study, vestibular involvement was frequently observed in 40- to 65-year-old individuals with SNHL. Therefore, vestibular evaluation should be considered along with the assessment of hearing in individuals with SNHL who are over 40 years old. [ABSTRACT FROM AUTHOR]

Objective: Bilateral superior canal dehiscence (SCD) may warrant surgeries on both sides. With repairs of unilateral SCD as reference, we investigate the comparative effectiveness of first‐side and second‐side repairs, in hopes of establishing knowledge that can guide clinical decision‐making pertaining the appropriateness of second‐side surgeries. Methods: Middle fossa SCD repairs at an institution between 2011 and 2022 were analyzed. Multivariable regression models assessed symptom resolution and audiometric improvement with surgery cohort (unilateral SCD repair vs. first‐side repair vs. second‐side repair) as the primary predictor. All models controlled for patient age, sex, surgery duration, prior ear surgery, and follow‐up. Results: A total of 407 repairs (180 unilateral SCD, 172 first‐side, and 55 second‐side repairs) were analyzed. The rates of overall symptom improvement for auditory and vestibular symptoms were as follows: 81% and 67% for unilateral SCD repairs; 73% and 54% for first‐side repairs; and 43% and 51% for second‐side repairs, respectively. Compared with first‐side repairs, which resolved auditory symptoms at similar rates (aOR 95% C.I. 0.36–1.07) but resolved vestibular symptoms at significantly lower rates (aOR 95% C.I. 0.35–0.93) compared with unilateral SCD repairs, second‐side repairs resolved auditory symptoms at significantly lower rates (aOR 95% C.I. 0.10–0.51) but resolved vestibular symptoms at similar rates (aOR 95% C.I. 0.45–2.01). Conclusions: Careful consideration of perioperative symptomatology may inform the appropriateness of second‐side surgeries. If auditory symptoms persisted following first‐side surgeries, second‐side surgeries are less likely to yield resolution. If vestibular symptoms persisted following first‐side repairs, second‐side repairs may lead to resolution at similar rates as first‐side repairs. Level of Evidence: 3 Laryngoscope, 134:1882–1888, 2024 [ABSTRACT FROM AUTHOR]

Inner ear morphogenesis requires tightly regulated epigenetic and transcriptional control of gene expression. CHD7, an ATP-dependent chromodomain helicase DNA-binding protein, and SOX2, an SRY-related HMG box pioneer transcription factor, are known to contribute to vestibular and auditory system development, but their genetic interactions in the ear have not been explored. Here, we analyzed inner ear development and the transcriptional regulatory landscapes in mice with variable dosages of Chd7 and/or Sox2. We show that combined haploinsufficiency for Chd7 and Sox2 results in reduced otic cell proliferation, severe malformations of semicircular canals, and shortened cochleae with ectopic hair cells. Examination of mice with conditional, inducible Chd7 loss by Sox2CreER reveals a critical period (~E9.5) of susceptibility in the inner ear to combined Chd7 and Sox2 loss. Data from genome-wide RNA-sequencing and CUT&Tag studies in the otocyst show that CHD7 regulates Sox2 expression and acts early in a gene regulatory network to control expression of key otic patterning genes, including Pax2 and Otx2. CHD7 and SOX2 directly bind independently and cooperatively at transcription start sites and enhancers to regulate otic progenitor cell gene expression. Together, our findings reveal essential roles for Chd7 and Sox2 in early inner ear development and may be applicable for syndromic and other forms of hearing or balance disorders. [ABSTRACT FROM AUTHOR]

The active control of the lumbar musculature provides a stable platform critical for postures and goal-directed movements. Voluntary and perturbation-evoked motor commands can recruit individual lumbar muscles in a task-specific manner according to their presumed biomechanics. Here, we investigated the vestibular control of the deep and superficial lumbar musculature. Ten healthy participants were exposed to noisy electrical vestibular stimulation while balancing upright with their head facing forward, left, or right to characterize the differential modulation in the vestibular-evoked lumbar extensor responses in generating multidirectional whole body motion. We quantified the activation of the lumbar muscles on the right side using indwelling [deep multifidus, superficial multifidus, caudal longissimus (L4), and cranial longissimus (L1)] and high-density surface recordings. We characterized the vestibular-evoked responses using coherence and peak-to-peak cross-covariance amplitude between the vestibular and electromyographic signals. Participants exhibited responses in all lumbar muscles. The vestibular control of the lumbar musculature exhibited muscle-specific modulations: responses were larger in the longissimus (combined cranio-caudal) compared with the multifidus (combined deep-superficial) when participants faced forward (P < 0.001) and right (P = 0.011) but not when they faced left. The high-density surface recordings partly supported this observation: the location of the responses was more lateral when facing right compared with left (P < 0.001). The vestibular control of muscle subregions within the longissimus or the multifidus was similar. Our results demonstrate muscle-specific vestibular control of the lumbar muscles in response to perturbations of vestibular origin. The lack of differential activation of lumbar muscle subregions suggests the vestibular control of these subregions is co-regulated for standing balance. NEW & NOTEWORTHY We investigated the vestibular control of the deep and superficial lumbar extensor muscles using electrical vestibular stimuli. Vestibular stimuli elicited preferential activation of the longissimus muscle over the multifidus muscle. We did not observe clear regional activation of lumbar muscle subregions in response to the vestibular stimuli. Our findings show that the central nervous system can finely tune the vestibular control of individual lumbar muscles and suggest minimal regional variations in the activation of lumbar muscle subregions. [ABSTRACT FROM AUTHOR]

The vestibular hair cell receptors of anamniotes, designated Type II, are presynaptic to bouton endings of vestibular nerve distal neurites. An additional flask-shaped hair cell receptor, Type I, is present in amniotes, and communicates with a chalice-shaped afferent neuritic ending that surrounds the entire hair cell except its apical neck. Since the full repertoire of afferent fiber dynamics and sensitivities observed throughout the vertebrate phyla can be accomplished through Type II hair cell-bouton synapses, the functional contribution(s) of Type I hair cells and their calyces to vestibular performance remains a topic of great interest. The goal of the present study was to investigate electrical coupling between the Type I hair cell and its enveloping calyx in the mouse semicircular canal crista ampullaris. Since there are no gap junctions between these two cells, evidence for electrical communication would necessarily involve other mechanisms. Simultaneous recordings from the two cells of the synaptic pair were used initially to verify the presence of orthodromic quantal synaptic transmission from the hair cell to the calyx, and then to demonstrate bi-directional communication due to the slow accumulation of potassium ions in the synaptic cleft. As a result of this potassium ion accretion, the equilibrium potentials of hair cell conductances facing the synaptic cleft become depolarized to an extent that is adequate for calcium influx into the hair cell, and the calyx inner face becomes depolarized to a level that is near the threshold for spike initiation. Following this, paired recordings were again employed to characterize fast bi-directional electrical coupling between the two cells. In this form of signaling, cleft-facing conductances in both the hair cell and calyx increase, which strengthens their coupling. Because this mechanism relies on the cleft resistance, we refer to it as resistive coupling. We conclude that the same three forms of hair cell-calyceal transmission previously demonstrated in the turtle are present in the mammalian periphery, providing a biophysical basis for the exceptional temporal fidelity of the vestibular system.

Persistent Postural-Perceptual Dizziness (PPPD) is a functional vestibular condition. Despite being the most common chronic neuro-otologic disorder, it remains undertreated. The Niigata PPPD Questionnaire (NPQ), developed by Yagi et al. in 2019 to assess the severity of PPPD, could be a useful tool to help in the screening and diagnosis of this condition. This study aimed to validate a French version of the NPQ and make it an available assessment tool. Moreover, we aimed to understand the characteristics of PPPD patients better. The NPQ was translated and adapted into French. 50 PPPD patients, 50 patients with vestibular disorders without PPPD, and 50 healthy controls were included. They answered the adapted NPQ and additional questionnaires assessing trait (STAI) and state anxiety (HADS-A), depression (HADS-D) and handicap related to dizziness (DHI). The NPQ’s reliability was assessed by Cronbach’s alpha. Intergroup comparisons and multiple linear regressions were conducted to examine the characteristics of PPPD patients compared to vestibular patients and healthy controls, to validate NPQ’s reliability, and to explore the effect of clinical parameters and treatment with selective serotonin reuptake inhibitors. Receiver operating characteristic (ROC) curves were carried out to determine the diagnostic values of the NPQ total score and sub-scores. Relations between NPQ and reported handicap, depression and anxiety were evaluated by correlations between questionnaire scores. The internal consistency was high (>0.8) for all NPQ subscales and the total score. Intergroup comparisons showed a significantly higher NPQ total score and sub-scores in the PPPD group compared to the two others. The ROC curve analysis showed a significant, but poor, discrimination of NPQ (AUC = 0.664) and its subscales. DHI scores, depressive symptoms and trait anxiety were significantly higher in PPPD patients than in vestibular patients and healthy controls. State anxiety did not differ between patients with PPPD and vestibular patients without PPPD. Finally, there was a significant correlation between the NPQ and the DHI. Our study provides a better understanding of PPPD symptomatology and its assessment. It showed that the NPQ is a reliable tool that can assist in symptom assessment for a French-speaking population.

The remarkable signal-detection capabilities of the auditory and vestibular systems have been studied for decades. Much of the conceptual framework that arose from this research has suggested that these sensory systems rest on the verge of instability, near a Hopf bifurcation, in order to explain the detection specifications. However, this paradigm contains several unresolved issues. Critical systems are not robust to stochastic fluctuations or imprecise tuning of the system parameters. Further, a system poised at criticality exhibits a phenomenon known in dynamical systems theory as critical slowing down, where the response time diverges as the system approaches the critical point. An alternative description of these sensory systems is based on the notion of chaotic dynamics, where the instabilities inherent to the dynamics produce high temporal acuity and sensitivity to weak signals, even in the presence of noise. This alternative description resolves the issues that arise in the criticality picture. We review the conceptual framework and experimental evidence that supports the use of chaos for signal detection by these systems, and propose future validation experiments.

Vertiginous epilepsy (VE) is a rare and underrecognized epilepsy subtype in the pediatric population. Vertiginous symptoms are the sole or predominant feature, arise from the vestibular cortex, and seizures are usually brief. The incidence is estimated to be between six and 15 percent of pediatric patients presenting with dizziness. Diagnosis is often delayed for many years following the onset of symptoms, as there are no widely accepted diagnostic criteria. Diagnostic work-up should include a detailed history, physical exam, EEG, and brain imaging with MRI. Vestibular testing is helpful if peripheral vestibulopathy is suspected. Vertiginous epilepsy can have many possible causes, but a large majority are idiopathic or suspected to be genetic. Most patients with vertiginous epilepsy achieve seizure freedom with anti-seizure medications.

This historical review on the semantic evolution of human senses and sensors revealed that Aristotle’s list of the five senses sight, hearing, touch, taste, and smell is still in use among non-scientific lay persons. It is no surprise that his classification in the work “De Anima” (On the Soul) from 350 BC confuses the sensor “touch” with the now more comprehensively defined somatosensory system and that senses are missing such as the later discovered vestibular system and the musculotendinous proprioception of the position of parts of the body in space. However, it is surprising that in the three most influential ancient cultures, Egypt, Greece, and China—which shaped the history of civilization—the concept prevailed that the heart rather than the brain processes perception, cognition, and emotions. This “cardiocentric view” can be traced back to the “Doctrine of Aristotle,” the “Book of the Dead” in ancient Egypt, and the traditional Chinese medicine of correspondence documented in the book “Huang di Neijing.” In Greek antiquity the philosophers Empedocles, Democritus and Aristotle were proponents of the allocation of the spirit and the soul to the heart connected to the body via the blood vessels. Opponents were the pre-Socratic mathematician Pythagoras, the philosopher Plato, and especially the Greek physician Hippocrates who regarded the brain as the most powerful organ in humans in his work “De Morbo Sacro.” The Greek physician Galen of Pergamon further elaborated on the concept of the brain (“cephalocentric hypothesis”) connected to the body by a network of nerves. The fundamental concepts for understanding functions and disorders of the vestibular system, the perception of self-motion, verticality and balance control were laid by a remarkable group of 19th century scientists including Purkynӗ, Mach, Breuer, Helmholtz, and Crum-Brown. It was also in the 19th century that Bell described a new sense of a reciprocal sensorimotor loop between the brain and the muscles which he called “muscular sense,” later termed “kinaesthesia” by Bastian and defined in 1906 as “proprioception” by Sherrington as “the perception of joint and body movements as well as position of the body or body segments, in space.” Both, the vestibular system and proprioception could be acknowledged as senses six or seven. However, we hesitate to recommend “pain”—which is variously assigned to the somatosensory system or extero-, intero-, visceroception—as a separate sensory system. Pain sensors are often not specific but have multisensory functions. Because of this inconsistent, partly contradictory classification even by experts in the current literature on senses and sensors we consider it justified to recommend a comprehensive reorganization of classification features according to the present state of knowledge with an expansion of the number of senses. Such a project has also to include the frequent task-dependent multisensory interactions for perceptual and sensorimotor achievements, and higher functions or disorders of the visual and vestibular systems as soon as cognition or emotions come into play. This requires a cooperation of sensory physiologists, neuroscientists and experienced physicians involved in the management of patients with sensory and multisensory disorders.

Reactive oxygen species (ROS) were formerly known as mere byproducts of metabolism with damaging effects on cellular structures. The discovery and description of NADPH oxidases (Nox) as a whole enzyme family that only produce this harmful group of molecules was surprising. After intensive research, seven Nox isoforms were discovered, described and extensively studied. Among them, the NADPH oxidase 3 is the perhaps most underrated Nox isoform, since it was firstly discovered in the inner ear. This stigma of Nox3 as "being only expressed in the inner ear" was also used by me several times. Therefore, the question arose whether this sentence is still valid or even usable. To this end, this review solely focuses on Nox3 and summarizes its discovery, the structural components, the activating and regulating factors, the expression in cells, tissues and organs, as well as the beneficial and detrimental effects of Nox3-mediated ROS production on body functions. Furthermore, the involvement of Nox3-derived ROS in diseases progression and, accordingly, as a potential target for disease treatment, will be discussed. [ABSTRACT FROM AUTHOR]

Engineering artificial mechanosensory hair cells offers a promising avenue for developing diverse biosensors spanning applications from biomedicine to underwater sensing. Unfortunately, current artificial sensory hair cells do not have the ability to simultaneously achieve ultrahigh sensitivity with low-frequency threshold detection (e.g., 0.1 Hz). This work aimed to solve this gap by developing an artificial sensory hair cell inspired by the vestibular sensory apparatus, which has such functional capabilities. For device characterization and response testing, the sensory unit was inserted in a 3D printed lateral semicircular canal (LSCC) mimicking the environment of the labyrinth. The sensor was fabricated based on platinum (Pt) thin film which was reinforced by carbon nanofibers (CNFs). A Pi-shaped hair cell sensor was created as the sensing element which was tested under various conditions of simulated head motion. Results reveal the hair cell sensor displayed markedly higher sensitivity compared to other reported artificial hair cell sensors (e.g., 21.47 mV Hz−1 at 60°) and low frequency detection capability, 0.1 Hz < f < 1.5 Hz. Moreover, like the LSCC hair cells in biology, the fabricated sensor was most sensitive in a given plane of rotational motion, demonstrating features of directional sensitivity. [ABSTRACT FROM AUTHOR]

The ability to stand with eyes closed on a sinusoidal translational moving platform may be affected by spatial orientation owing to vestibular input information. Moreover, changes in the frequency of the moving platform may affect the sensory reweighting through somatosensory and vestibular sensations. However, it is unclear whether noisy galvanic vestibular stimulation (nGVS), which activates vestibular-related brain regions, affects the stability of individuals standing on a platform moving at different frequencies. Do vestibular stimulation by nGVS and changes in the frequency of translationally moving platforms affect the standing stability of individuals? Thirty-one healthy young adult participants were provided both sham and nGVS interventions while they maintained a static standing position, with their eyes closed, on an anterior-posterior sinusoidal translation platform. The nGVS was adapted to an optimal intensity below the perceptual threshold (frequency band: 100–640 Hz), and the sham stimulus was adapted to 0 µA. The participants were randomly assessed for postural stability at 0.2, 0.6, and 1.2 Hz moving platform frequencies for 80 s each under both stimulus conditions. Postural stability was calculated as the root mean square (RMS) sway from head accelerations in the anteroposterior (AP) and mediolateral (ML) directions for 50 s between 20 and 70 s during the 80 s period, measured using an inertial sensor placed on the external occipital ridge. nGVS significantly reduced the RMS sway of head acceleration in the AP direction compared with sham stimulation. Furthermore, nGVS significantly reduced RMS sway in the ML direction compared with sham stimulation at a 1.2 Hz moving platform oscillation. These findings suggest that postural adjustment by the vestibular system influences head stability on a moving platform at specific sinusoidal translation frequencies, suggesting that nGVS may reduce head sway. • Standing stability on a moving platform may be affected by the vestibular system. • Applied nGVS was tested for changes in head stability on a moving platform. • Head RMS sway decreased at specific moving platform velocities. • Postural stability on the moving platform can directly assess vestibular function. [ABSTRACT FROM AUTHOR]