Otolith Research Articles

Efficacy of Altered Frequency Dynamics of Ocular-Vestibular Evoked Myogenic Potentials in Type 2 Diabetes Mellitus

Purpose: The study aims to address the gap in understanding the relationship between type 2 diabetes mellitus (T2DM) and vestibular dysfunction, particularly focusing on how T2DM may affect the tuning of the vestibular system. Specifically, the investigation aims to explore the impact of stimulus parameters, particularly stimulus frequency, on ocular vestibular evoked myogenic potentials (oVEMP) in individuals with T2DM.Methods: A case-control study design was used, utilizing non-probability sampling. All participants underwent routine audiological and vestibular evaluations before inclusion in the study. oVEMP’s were compared across 40 healthy individuals (group A) and 40 individuals with T2DM (group B) at 500 Hz, 1 KHz, and 2 KHz.Results: In group A, all 80 participants exhibited oVEMP responses across all frequencies in both ears, while in group B, consisting of individuals with T2DM, response rates were slightly lower, ranging from 70% to 77.5% across frequencies. Statistical analysis revealed significant amplitude differences at all frequencies tested in type 2 diabetic ears compared to healthy ears, although amplitude remained consistent within type 2 diabetic ears. Latencies (first negative [N1] and first positive [P1]) were consistent across groups, with delays observed in P1 latency, particularly noticeable at higher frequencies, both in healthy and type 2 diabetic ears. Gender didn't affect oVEMP frequency dynamics in any of the groups.Conclusion: Diabetes may create an impact in the functioning of otolith organs, the vestibular branch of eighth cranial nerve, and their innervations. VEMP evaluates both the sacculo-collic and utriculo-ocular pathways to detect changes in the functions of vestibular organs. Therefore, it's crucial to consider diabetes when conducting vestibular diagnosis or treatment.

Evaluation of Masseteric Vestibular Evoked Myogenic Potentials in Patients With Migraine.

Masseter vestibular evoked myogenic potentials (mVEMP) involve the connection between the vestibular complex and trigeminal nerve nuclei. Given the theory that migraine is caused by increased activation of the trigeminal nerve, it is believed that mVEMP responses may have influenced in migraine patients. The study included 20 individuals with migraine and 20 healthy controls. Latency, amplitude, and interaural amplitude asymmetry ratio of mVEMP responses recorded in migraine patients were compared with control group. Considering the mVEMP normalization study conducted by Başöz et al. (2021) in a similar age group and in the same clinic, latency prolongation and amplitude decrease were observed in subjects with migraines. Migraine is considered a central pathology, as shown in the cervical and ocular VEMP (cVEMP/oVEMP) literature. No difference was observed in the interaural amplitude asymmetry ratio, which is important in peripheral pathologies. Additionally, when the number of pathological ears was examined in order to understand the total exposure, it was observed that the number of pathological ears was significantly higher in the migraine group. In future studies, using mVEMP together with cVEMP and oVEMP tests, which allow evaluation of otolith organs and vestibular nuclei, will be valuable in determining the lesion location. https://doi.org/10.23641/asha.25607901.

Effect of drilling on otolithic organ functions in mastoidectomy.

This study aimed to assess the effect of drilling during mastoidectomy on otolithic organ functions and development of benign paroxysmal positional vertigo using objective vestibular tests. The study included 45 adult patients diagnosed with chronic otitis media who underwent mastoidectomy with drilling. Pre-operative and post-operative assessments included tests for subjective visual vertical deviation and videonystagmography. Subjective visual vertical deviation was significantly higher in post-operative periods. On the third day, the subjective visual vertical deviation was at its maximum (1.4 degrees). Post-operatively, benign paroxysmal positional vertigo was detected in 14 patients (31.1 per cent). The most common type was ipsilateral lateral canal benign paroxysmal positional vertigo (57.1 per cent). The effect of drilling on otolithic organ functions in mastoidectomy seems to be temporary and subclinical; however, it potentially could be a risk factor for the development of benign paroxysmal positional vertigo.

Practical instructions for recording vestibular evoked myogenic potentials

Recording of vestibular evoked myogenic potentials (VEMPs) is awell-established method for functional diagnostics of the otolith organs. VEMPs are vestibular reflexes of the sacculus und utriculus to acoustic stimulation by air-conducted sound or bone-conducted vibration and are recorded by surface electrodes from the cervical (cVEMP) and ocular (oVEMP) muscles. The results of VEMP recordings are part of the neuro-otologic test battery and enable diagnosis of various vestibular disorders or differentiation between non-vestibular and peripheral vestibular vertigo. However, the methods for recording VEMPs vary substantially, although recording and stimulation parameters as well as methods of data analysis have asignificant influence on the results. This article provides an overview of recommended parameters as well as practical instructions for the recording, analysis, and interpretation of VEMPs.

Assessment of Otolith Function with Subjective Visual Vertical Test in Sensorineural Hearing Loss: An Analytical Cross - Sectional Study.

The inner ear is responsible for balance and auditory function. Sensorineural hearing loss (SNHL) affects auditory function across various age groups. Vestibular apparatus, particularly the otolith organ can also be affected in cases of SNHL because of the close proximity of the otolith organs with the cochlea inside the bony labyrinth. The otolith organs can be assessed with Subjective Visual vertical test (SVV), which is a simple, rapid, non-invasive test with high sensitivity and specificity. Present study was conducted with the objective to compare the SVV parameters between normal and SNHL patients and to correlate between the degree of tilt in SVV with severity of SNHL. A convenient sample size of 60 was taken of which 30 were control and 30 were SNHL patients. PTA and SVV were performed on both groups and results were analysed in IBM SPSS version 26. Age stratified analysis between the control group and SNHL group for the age group 20-40 years and for > 40 years revealed a significant statistical difference in the average static SVV (P = 0.019 and P = 0.009 for age group 20-40 years and > 40 years respectively) and dynamic anti clockwise SVV (P = 0.024 and P = 0.031 for age group 20-40 years, and > 40 years respectively) between the control group and the SNHL group. Correlational analysis also shows a moderate correlation between the bone conduction threshold and the various SVV parameters. Statistical difference of SVV parameters between the two groups suggests a possible early involvement of the otolith organ in SNHL. As such the utility of SVV as an early marker for otolith dysfunction needs to be further explored. It may be worthwhile to follow up the patients of SNHL longitudinally and assess the otolith function with SVV at periodic intervals to identify any progression.

Acute histological reactions in the otolith organs to inner ear drug delivery through a cochlear implant.

Cochlear implantation is currently regarded as a safe and minimally invasive procedure. However, cochlear implantation can have an impact on vestibular function, despite the lack of correlation between patient symptomatology and damage in vestibular tests. Thus, the present study aims to analyze the presence of hydrops and histological reactions at the level of the vestibule after cochlear implantation with dexamethasone pump delivery in Macaca fascicularis (Mf). A detailed histological study was conducted on a total of 11 Mf. All 11 Mf were divided into three groups: 5 Mf were implanted with an electrode array HL-14 connected to a pump delivering FITC-dextran for 24 h (Group A); 4 Mf were implanted with a CI electrode array attached to a pump for FITC-dextran delivery for 7 days (Group B); and 2 Mf were considered the control group, without any kind of cochlear device implantation (Group C). After drug deliver, the selected macaques were euthanized to collect tissue samples for histological analysis. An experienced observer, focusing on the utricle and saccule areas, conducted a blinded inner ear histology analysis. Surgical procedures were successfully performed in all cases. No signs of cochlear reaction to the device were observed, including neither collapse nor fibrosis. Endolymphatic sinus dilatation was observed in Mf4A and Mf3B, while cochlear hydrops was observed in Mf3A. The mean areas of the utricle and saccule exhibited some statistically significant differences, specifically, in the saccule between groups C and both groups A (p = 0.028) and B (p = 0.029); however, no significant differences were observed between groups A and B or among comparisons of the utricle. A significant concern relates to the safety of cochlear implantation with regard to vestibular preservation and hearing. New advancements in electrode arrays, such as CI devices coupled with delivery pumps, pose a challenge in maintaining minimally traumatic surgical concept-based procedures without affecting the inner ear homeostasis. The implantation of this device may cause vestibular hydrops in the saccule, indicating that the longer the time of substance release, the greater the grade of hydrops evidenced at the saccular level. Apart from this finding, the risk of histological damage to the vestibule is low.

Investigation of Pathogenesis and Otolithic Organ Responses in Sailors with Seasickness Using cVEMP.

There are different theories cited as the cause of Motion Sickness. Asymmetrical otolithic organ function is one of the etiology theories of motion sickness. In our study, the aim was to reveal whether there is a cause originating from the sacculocolic reflex pathway in the physiopathology of seasickness. The patient group included 15 man sailors with diagnosis of seasickness and the control group included 15 man sailors without seasickness in our study. Cervical evoked myogenic vestibular potential (cVEMP) findings were compared between the groups. In the right and left ears of sailors with seasickness, the mean latencies of the p13 and n23 waves at 100, 95, and 90dB normal hearing level (nHL) levels were found significantly shorter than in the control group (p < 0.05, for all). In the seasickness group, cVEMP interaural wave amplitude asymmetry ratio at 100 nHL level were found significantly higher than the control group (p = 0.001). The findings of our study indicated that there may be reasons arising rom the sacculocolic reflex pathway in the pathophysiology of seasickness.

Frailty of the.

Vestibular frailty and presbyvestibulopathy, including benign paroxysmal positional vertigo (BPPV), can cause dizziness among elderly patients. Vestibular frailty and presbyvestibulopathy may contribute to the onset of the vicious circle of falling-bone fracture-prolonged bedridden status-senile dementia. Treatment interventions for vestibular frailty and presbyvestibulopathy should be based on vestibular rehabilitation rather than vestibular implantation or regeneration. In acute BPPV, the otolith repositioning maneuver can be used to return otolithic debris to the utricle. At the chronic remission stage, there are nutritional guidelines for improving bone density in otolith organs and rehabilitation guidelines for activating otolith organs to prevent exfoliation. Moreover, sleeping in the head-up position can prevent free-floating debris from entering the semicircular canal. Throughout their old age, the psychiatric care/support is also indispensable to keep their initiative against vestibular frailty.

Head and vestibular kinematics during vertical semicircular canal impulses.

The video head impulse test (vHIT) is a common assessment of semicircular canal function during high-speed impulses. Reliability of the vHIT for assessing vertical semicircular canals is uncertain. Vertical head impulses require a complex head movement, making it difficult to isolate a single semicircular canal and interpret resulting eye rotations. The purpose of this study was to provide descriptive head kinematics and vestibular stimuli during vertical plane impulses to ultimately improve impulse delivery and interpretation of vHIT results for vertical semicircular canals. Six participants received right anterior (RA) and left posterior (LP) semicircular canal impulses. Linear displacements, rotational displacements, and rotational velocities of the head were measured. Peak velocities in semicircular canal planes and peak-to-peak gravitoinertial accelerations at the otolith organs were derived from head kinematics. The largest rotational velocities occurred in the target semicircular canal plane, with non-negligible velocities occurring in non-target planes. Larger vertical displacements and accelerations occurred on the right side of the head compared to the left for RA and LP impulses. These results provide a foundation for designing protocols to optimize stimulation applied to a singular vertical semicircular canal and for interpreting results from the vHIT for vertical semicircular canals.

Diagnostic value of vestibular evoked myogenic potentials in benign paroxysmal positional vertigo

ObjectivesVestibular evoked myogenic potentials (VEMPs) are useful for studying the disturbances along nerve pathways implicated in the transmission of neurological information from otolithic organs related to vestibular function. This study aims to determine the differences in VEMPs in patients affected with benign paroxysmal positional vertigo (BPPV). MethodsWe recruited 36 patients, 9 diagnosed with recurrent BPPV (rBPPV), 9 with only one episode of vertigo (iBPPV), and 18 as a control group. We performed cervical and ocular VEMPs (cVEMPs and oVEMPs). ResultsWe observed differences in asymmetry ratio, which was 41.82% in cVEMPs in iBPPV and 68.27% in oVEMPs in rBPPV, while no asymmetry was found in control cases. Also, there was a lack of both VEMP responses in 22.2% of cases and an absence of cVEMP in 11.1% in iBPPV; in rBPPV, 11.1 % presented no responses in cVEMPs or oVEMPs, 22.2% showed no oVEMP, and 11.1% showed no cVEMP. These values were normal in the control group. ConclusionThe value of VEMPs in BPPV demonstrates the implication of vestibular damage, mainly utricle damage. For better sensitivity in detecting otolith abnormalities, we should perform oVEMPs and cVEMPs in recurrent BPPV and early stages of BPPV.

РОЛЬ ВЕСТИБУЛЯРНОГО СЛУХА В ВОСПРИЯТИИ РЕЧИ (ОБЗОР ЗАРУБЕЖНЫХ ИССЛЕДОВАНИЙ)

The article presents a review of foreign studies on the participation of the vestibular system in speech perception. Although for a long time it was believed that the vestibular system is involved only in the management of balance and motor skills, there is increasing evidence that it is involved in cognitive processes such as memory, attention, and speech. There is no doubt that auditory perception is necessary for speech perception. The peripheral parts of the vestibular and auditory analyzers are anatomically closely related. But there is not enough research on how vestibular organs affect auditory perception. Evolutionarily, the vestibular apparatus appeared in animals much earlier than the peripheral hearing organs. The human vestibular apparatus consists of five paired sections: three semicircular canals and two otolith organs – the utriculus and sacculus. In the process of evolution, the semicircular canals of humans and other mammals underwent maximum changes. The ability to register auditory information was preserved only in one of the parts of the vestibular apparatus – sacculus. Vestibular (saccular) hearing allows us to register low-frequency sounds in the range from 100 to 1000 Hz. This helps speech perception, as this frequency range is associated with the perception of intonation and other prosodic components of the utterance. Saccular hearing also helps speech perception in noise. Data on the role of the vestibular apparatus in speech perception are useful for all speech and language specialists. The ability of the sacculus to respond to sound is used for instrumental diagnostics of the vestibular system – cervical vestibular myogenic evoked potentials (cVEMP).

Blast Overpressures as a Military and Occupational Health Concern.

This tutorial reviews effects of environmental stressors like blast overpressures and other well-known acoustic contaminants (continuous, intermittent, and impulsive noise) on hearing, tinnitus, vestibular, and balance-related functions. Based on the overall outcome of these effects, detailed consideration is given to the health and well-being of individuals. Because hearing loss and tinnitus are consequential in affecting quality of life, novel neuromodulation paradigms are reviewed for their positive abatement and treatment-related effects. Examples of clinical data, research strategies, and methodological approaches focus on repetitive transcranial magnetic stimulation (rTMS) and electrical stimulation of the vagus nerve paired with tones (VNSt) for their unique contributions to this area. Acoustic toxicants transmitted through the atmosphere are noteworthy for their propensity to induce hearing loss and tinnitus. Mounting evidence also indicates that high-level rapid onset changes in atmospheric sound pressure can significantly impact vestibular and balance function. Indeed, the risk of falling secondary to loss of, or damage to, sensory receptor cells in otolith organs (utricle and saccule) is a primary reason for this concern. As part of the complexities involved in VNSt treatment strategies, vocal dysfunction may also manifest. In addition, evaluation of temporospatial gait parameters is worthy of consideration based on their ability to detect and monitor incipient neurological disease, cognitive decline, and mortality. Highlighting these respective areas underscores the need to enhance information exchange among scientists, clinicians, and caregivers on the benefits and complications of these outcomes.

Stimulation Crosstalk Between Cochlear And Vestibular Spaces During Cochlear Electrical Stimulation.

Possible beneficial "crosstalk" during cochlear implant stimulation on otolith end organs has been hypothesized. The aim of this case-control study is to analyze the effect of electrical cochlear stimulation on the vestibule (otolith end-organ), when using a cochleo-vestibular implant, comparing vestibular stimulation (VI) and cochlear stimulation (CI). Four patients with bilateral vestibulopathy were included. A double electrode array research implant was implanted in all cases. Dynamic Gait Index (DGI), VOR gain measured by using vestibular head impulse test (vHIT), acoustic cervical myogenic responses (cVEMP) recordings, and electrical cVEMP were used in all cases. Trans-impedance Matrix (TIM) analysis was used to evaluate the current flow from the cochlea to the vestibule. While patients did not have any clinical vestibular improvement with the CI stimulation alone, gait metrics of the patients revealed improvement when the vestibular electrode was stimulated. The average improvement in the DGI was 38% when the vestibular implant was activated, returning to the normal range in all cases. Our findings suggest that any current flow from the cochlear space to the otolith organs was insufficient for effective cross-stimulation. The functional results correlated with the data obtained in TIM analysis, confirming that there is no current flow from the cochlea to the vestibule. The only way to produce effective electrical otolith end-organ stimulation, demonstrated with this research implant, is by direct electrical stimulation of the otolith end organs. No effective cross-stimulation was found from cochlear electrode stimulation. 4 Laryngoscope, 134:2349-2355, 2024.

Subtle alterations of vestibulomotor functioning in conductive hearing loss.

Conductive hearing loss (CHL) attenuates the ability to transmit air conducted sounds to the ear. In humans, severe hearing loss is often accompanied by alterations to other neural systems, such as the vestibular system; however, the inter-relations are not well understood. The overall goal of this study was to assess vestibular-related functioning proxies in a rat CHL model. Male Sprague-Dawley rats (N=134, 250g, 2months old) were used in a CHL model which produced a >20dB threshold shift induced by tympanic membrane puncture. Auditory brainstem response (ABRs) recordings were used to determine threshold depth at different times before and after CHL. ABR threshold depths were assessed both manually and by an automated ABR machine learning algorithm. Vestibular-related functioning proxy assessment was performed using the rotarod, balance beam, elevator vertical motion (EVM) and Ferris-wheel rotation (FWR) assays. The Pre-CHL (control) threshold depth was 27.92dB±11.58dB compared to the Post-CHL threshold depth of 50.69dB±13.98dB (mean±SD) across the frequencies tested. The automated ABR machine learning algorithm determined the following threshold depths: Pre-CHL=24.3dB, Post-CHL same day=56dB, Post-CHL 7 days=41.16dB, and Post-CHL 1 month=32.5dB across the frequencies assessed (1, 2, 4, 8, 16, and 32kHz). Rotarod assessment of motor function was not significantly different between pre and post-CHL (~1week) rats for time duration (sec) or speed (RPM), albeit the former had a small effect size difference. Balance beam time to transverse was significantly longer for post-CHL rats, likely indicating a change in motor coordination. Further, failure to cross was only noted for CHL rats. The defection count was significantly reduced for CHL rats compared to control rats following FWR, but not EVM. The total distance traveled during open-field examination after EVM was significantly different between control and CHL rats, but not for FWR. The EVM is associated with linear acceleration (acting in the vertical plane: up-down) stimulating the saccule, while the FWR is associated with angular acceleration (centrifugal rotation about a circular axis) stimulating both otolith organs and semicircular canals; therefore, the difference in results could reflect the specific vestibular-organ functional role. Less movement (EVM) and increase time to transverse (balance beam) may be associated with anxiety and alterations to defecation patterns (FWR) may result from autonomic disturbances due to the impact of hearing loss. In this regard, vestibulomotor deficits resulting in changes in balance and motion could be attributed to comodulation of auditory and vestibular functioning. Future studies should manipulate vestibular functioning directly in rats with CHL.

Prognosis of vestibular dysfunction in idiopathic sudden sensorineural hearing loss with vertigo: a prospective cohort study.

Approximately 28%-57% of patients with idiopathic sudden sensorineural hearing loss (ISSNHL) have an acute vertigo attack and probable vestibular dysfunction; however, the prognosis of vestibular function in these patients remains unclear. A prospective cohort study of patients with ISSNHL and vertigo was conducted to evaluate the prognosis of vestibular function, especially the roles of peripheral vestibular restoration and central compensation, in patients with ISSNHL and vertigo. Clinical data were recorded at baseline and at 60days from onset in participants with unilateral ISSNHL with vertigo. Enrolment occurred from May 1, 2019 to May 1, 2022 in the outpatient clinics and inpatient departments of the Eye and ENT Hospital of Fudan University in Shanghai. The primary outcome measure was the recovery rate of vestibular function 60days after onset as assessed by vestibular function tests, including caloric tests, cervical and ocular vestibular-evoked myogenic potential tests (cVEMP, oVEMP), video head impulse tests (vHIT), and sensory organization tests (SOT). The secondary outcome measure was the recovery of subjective evaluations in vestibular dysfunction (the dizziness handicap inventory [DHI], and the visual analogue scale for vertigo [VAS-V]) and hearing assessments (pure-tone audiometry [PTA]). Overall, 86 patients were recruited, with an average duration of disease of 11.7days and follow-up time of 60.7days. Vestibular function was significantly improved (p < 0.05) after 60days. The recovery rates were 100% for anterior semicircular canal (ASC), 56% for posterior semicircular canal (PSC), 41% for horizontal semicircular canal (HSC), 28% for saccule, and 23% for utricle. The recovery of vestibular function was not significantly related to changes in DHI (p = 0.245), VAS-V score (p = 0.509), or hearing outcome (p = 0.390). Restoration of peripheral vestibular sensory input and central vestibular compensation can occur during the course of ISSNHL with vertigo. The otolith organs are at a higher risk of being affected and have worse recovery than the semicircular canals. Incomplete and in-process restoration of vestibular dysfunction may perturb and delay the establishment of central compensation for balance. Neither hearing outcomes nor subjective vestibular symptoms are related to recovery from vestibular dysfunction. ClinicalTrials.gov (identifier NCT03951584).

Balance beam crossing times are slower after noise exposure in rats.

The vestibular system integrates signals related to vision, head position, gravity, motion, and body position to provide stability during motion through the environment. Disruption in any of these systems can reduce agility and lead to changes in ability to safely navigate one's environment. Causes of vestibular decline are diverse; however, excessive noise exposure can lead to otolith organ dysfunction. Specifically, 120 decibel (dB) sound pressure level (SPL) 1.5 kHz-centered 3-octave band noise (1.5 kHz 3OBN) causes peripheral vestibular dysfunction in rats, measured by vestibular short-latency evoked potential (VsEP) and reduced calretinin-immunolabeling of calyx-only afferent terminals in the striolar region of the saccule. The present study examined the functional impact of this noise exposure condition, examining changes in motor performance after noise exposure with a balance beam crossing task. Balance beam crossing time in rats was assessed for 19 weeks before and 5 weeks after noise exposure. Balance beam crossings were scored to assess proficiency in the task. When animals were proficient, they received a single exposure to 120 dB SPL 3-octave band noise. During the initial training phase slower crossing times and higher scores, including multiple failures were observed. This was followed by a period of significant improvement leading to proficiency, characterized by fast and stable crossing times and consistently low scores. After noise exposure, crossing times were significantly elevated from baseline for 4-weeks. A total of 5 weeks after noise exposure, crossing times improved, and though still trending higher than baseline, they were no longer significantly different from baseline. These findings show that the noise-induced peripheral vestibular changes we previously observed at cellular and electro-physiological levels also have an impact at a functional level. It has been previously shown that imbalance is associated with slower walking speed in older adults and aged rats. These findings in noise-exposed rats may have implications for people who experience noisy environments and for seniors with a history of noise exposure who also experience balance disorders and may be at increased fall risk.

Normal Serum Levels of Otolin-1 in Patients with Meniere Disease in Remission.

Introduction Degenerative changes in the otolithic organs have been theorized to be caused by the mechanical obstruction to endolymphatic flow, possibly resulting in endolymphatic hydrops (ELH). Otolin-1 is an otoconial matrix protein that crosses the blood labyrinth barrier and has been found in the serum of healthy and diseased patients. Objective To measure the serum levels of Otolin-1 in Meniere disease (MD) patients and compared them with the healthy individuals. Methods This pilot, cross-sectional study was performed at our tertiary care referral center to compare the serum Otolin-1 levels of healthy individuals with those of MD patients. The blood samples were obtained during patients' visit to the vertigo clinic following remission of an acute episode. The data was analyzed using the Stata/SE version 12.0 (StataCorp. College Station, TX, USA). Comparison between the serum Otolin-1 levels in the two groups was performed using the unpaired t -test. A p -value of 0.05 was considered to be statistically significant. Results The participants were divided into two groups, with 31 MD patients, and 30 age and gender-matched members of the control group. The serum levels of Otolin-1 in MD patients (247.6, ± 44.2 pg/ml) were not found to be significantly different from those of the control group (236.2, ± 43.5 pg/ml) ( p = 0.31). Conclusion The current study reveals that the serum levels of Otolin-1 are not significantly different between the patients with MD in the interictal phase and the control group's healthy ones.

Stabilogram diffusion analysis and the vestibular system features

The method of stabilogram diffusion analysis is discussed. It is known that the sta-bilogram diffusion functions for the frontal and sagittal directions are different and their logarithmic plot has a characteristic bend (critical point). It is assumed that this bend is associated with a change in the persistence behavior for different time intervals in the presence of feedback in the postural control system. The article considers possible de-pendence between the features of the stabilogram diffusion function in question and the existence of a dead zone in the signal of the vestibular apparatus. Models of posture sta-bilization for the frontal and sagittal directions are designed. These models use modified motion equations for an inverted pendulum stabilized by a PID controller based on posi-tional measurements. The control is supplemented with feedback from the model of the otolith organ, which has a dead zone. It is assumed that the signal of the vertical canal of the otoliths and semicircular canals are subthreshold and are not used by the motor con-trol system. The results of diffusion analysis for a set of representations of numerical model of a person's postural control are presented. The parameters of the control system are corrected through comparing the simulation results with subjects examination data. Numerical modeling has shown that the effect of the otolith organ when a healthy person is standing in the “feet shoulder width apart” position in the frontal plane is minimal or absent. Though in the sagittal plane there are values of the otolith signal gain at which the influence of these control components becomes noticeable. The presented modeling enables detection of the main directions for analyzing the relationship between the indi-cators of the stabilogram diffusion analysis and the features of the vestibular signals and other sensory modalities.

Behavioral and neural responses to high-strength magnetic fields are reduced in otolith mutant mice.

Static high magnetic fields (MFs) interact with the vestibular system of humans and rodents. In rats and mice, exposure to MFs causes perturbations such as head movements, circular locomotion, suppressed rearing, nystagmus, and conditioned taste aversion acquisition. To test the role of otoconia, two mutant mouse models were examined, head-tilt Nox3het (het) and tilted Otop1 (tlt), with mutations, respectively, in Nox3, encoding the NADPH oxidase 3 enzyme, and Otop1, encoding the otopetrin 1 proton channel, which are normally expressed in the otolith organs, and are critical for otoconia formation. Consequently, both mutants show a near complete loss of otoconia in the utricle and saccule, and are nonresponsive to linear acceleration. Mice were exposed to a 14.1 Tesla MF for 30 min. After exposure, locomotor activity, conditioned taste aversion and c-Fos (in het) were assessed. Wild-type mice exposed to the MF showed suppressed rearing, increased latency to rear, locomotor circling, and c-Fos in brainstem nuclei related to vestibular processing (prepositus, spinal vestibular, and supragenual nuclei). Mutant het mice showed no response to the magnet and were similar to sham animals in all assays. Unlike het, tlt mutants exposed to the MF showed significant locomotor circling and suppressed rearing compared with sham controls, although they failed to acquire a taste aversion. The residual responsiveness of tlt versus het mice might reflect a greater semicircular deficit in het mice. These results demonstrate the necessity of the otoconia for the full effect of exposure to high MFs, but also suggest a semicircular contribution.

CERVICAL VESTIBULAR EVOKED MYOGENIC POTENTIALS IN PATIENTS WITHTYPE IIDIABETES MELLITUS

Introduction:Vestibular impairment has been demonstrated in patients with diabetes mellitus. Vestibular evoked myogenic potential (VEMP) is a short latency electromyographic response to sound or vibration stimuli that may reflect otolith organ or related reflex functions. cVEMPs are summation responses recorded from the contracted sternocleidomastoid inresponse to synchronized acoustic stimulation of the ipsilateral ear/saccule.In diabetic patients. Objective: Here, we asses prevalence of vestibular dysfunction by measuring cVEMP findings in patients with diabetes mellitus typeII. Methods: This study was carried out on two groups of subjects including 20 adult subjects with diabetes mellitustypeIIand 20 adult subjectsnon-diabetics, both group their aged ranged from 20-60 years. Results:showed statistically significant difference in cVEMP between diabetes mellitus type 2 control group with increase in latencies of P1 and N1 and decrease in amplitude. Conclusion: In diabetic individuals who are asymptomatic and never complained of vestibular dysfunction, cVEMPsis able to identify these patients.