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Studies of saccular and utricular function in patients with obstructive sleep apnea (OSA) are rare. We noticed that some OSA patients also had positive results in vestibular function tests, and this inspired our interest in exploring the vestibular function patterns of OSA patients.To investigate otolithic organ function in severe OSA patients who lack vestibular symptoms and systemic disease.32 patients (64 ears) with severe OSA and 22 healthy controls (44 ears) were enrolled. The ocular and cervical vestibular-evoked myogenic potentials (oVEMP and cVEMP) and the caloric test were recorded and analyzed.The response rates of oVEMP (73.4%) and cVEMP (82.8%) in patients with severe OSA were significantly lower than those in controls. In oVEMP, elevated thresholds (Disappearance or impairment of VEMPs could be observed in patients with severe OSA, and reflects different degrees of impairment in the utricle and saccule.

Introduction: Patients with chronic vestibular multi-canalicular canalithiasis (CVMCC) can have serious morbidities, for example, musculoskeletal pain, dizziness, fatigue, and cognitive difficulties. Involvement of the anterior semi-circular canal (SCC) is common in CVMCC. A mono-canalicular diseased anterior SCC is rare.Aim: To examine if the Bending forward test can be used to detect a diseased anterior semi-circular canal in patients with CVMCC.Material and Methods: Prospective consecutive observational cohort study in patients with relapse of an earlier successfully treated chronic CVMCC, where 16 patients have a diseased anterior SCC, 11 without any involvement of the anterior SCC, and 15 healthy controls. Patients are tested in sitting and in bending forward position. The difference in downwards directed nystagmus count and slow phase velocity in the two test positions AND reported movement illusion are the main outcome.Results: The sensitivity of the Bending forward-test is 81%; the specificity 91%. Five of the healthy controls have positional nystagmus without movement illusion. This is interpreted as cupulolithiasis. Positional nystagmus with movement illusion is interpreted as canalithiasis.Conclusions: Bending forward-test is a valuable test. Only positional nystagmus accompanied by a movement illusion, that is canalithiasis, is of clinical relevance.Significance: These findings may assist in diagnosing compound musculoskeletal disorders.

In this paper, we first briefly describe the mechanical model of cupula deformation with the appropriate analytical solution. Then, we present the numerical solution of the same problem and compare it with the analytical one. Besides, we provide another numerical solution based on the Finite Element Method procedure, in an effort to encompass a more realistic approach to the problem such as considering the real geometry of the SCCs and the obstruction of the fluid flow during head movement due to the presence of otoconia. As a result, we obtain fifty solutions for a head rotation angle in a range from 0° to 120°, taking into account that such a manoeuvre lasts exactly 3 seconds. In the end, we present a mobile client-server application for visualising the finite element solutions in a way that is convenient for the clinical practice.

This study revisited seven patients with Lermoyez syndrome over the past 25 years using an inner ear test battery to elucidate its mechanism.From 1992 to 2017, we have experienced 4096 patients with Meniere's disease (MD) and seven patients (5 males and 2 females, 8 ears) with Lermoyez syndrome. Two of the Lermoyez patients were elderly, aged 71 and 85 years. An inner ear test battery comprising audiometry, ocular and cervical vestibular-evoked myogenic potential (oVEMP and cVEMP) tests, and caloric test were performed.Significant improvement of mean hearing levels (MHLs) was identified at low and middle frequencies after vertiginous attack, but not at high frequencies. Inner ear deficits in Lermoyez patients ran from abnormal hearing (100%) to abnormal cVEMP (43%), caloric (38%) and oVEMP (0) tests, exhibiting a significantly declining sequence. This declining sequence differed from that in MD.Lermoyez syndrome is extremely rare, with prevalence relative to MD of 0.2%. The mechanism is considered as blockage in the ductus reuniens caused by dislodged saccular otoconia. Aging and trauma are two precipitating factors for the dislodged saccular otoconia, which may explain why Lermoyez syndrome occurs most frequently in males and some elderly.

To investigate morphology changes of artificial otoconia (CGC) in the presence of magnesium during growth under in vitro conditions.Investigating human otoconia by environmental scanning electron microscope and determining their magnesium content by energy-dispersive X-ray microanalysis (EDX). Comparing structural and morphological data of human and artificial otoconia (CGC, CaEDX- and X-ray data reveals that the inorganic component in human otoconia consists of calcite containing a minor amount of magnesium substitution (CaMagnesium is an intrinsic component of human otoconia by partial substitution of calcium in the calcite crystal structure (Ca

The results showed a gradual detachment of otoconia in the utricle after a single event of head vibration, possibly explaining the frequent recurrence of BPPV attacks and persistent dizziness after trauma.This study developed a murine model of traumatic BPPV and observed the changes in otoconia detachment over time.Six-week-old CBA mice were used in this study. Otoconia detachment was induced by vibrating the head for 2 min. Utricles of mice were harvested from different groups: before the head vibration and 1 day, 1 week, 1 month, and 3 months after vibration application. Using scanning electron microscopy and ImageJ software, the percentage of the intact area of otoconia in the utricle was calculated. Hearing thresholds were compared among the groups.The mean (± SD) percentages of the intact area of otoconia in the utricle were 98.1% ± 1.7% before the vibration and 93.6% ± 1.7%, 88.9% ± 5.3%, 78.2% ± 20.9%, and 38.9% ± 24.1% at 1 day, 1 week, 1 month, and 3 months after the vibration, respectively. The percentage decreased significantly over time after the vibration (p .001). The hearing thresholds were not different among the groups.

The vertebrate inner ear comprises mineralized elements, namely the otoliths (fishes) or the otoconia (mammals). These elements serve vestibular and auditory functions. The formation of otoconia and otoliths is described as a stepwise process, and in fish, it is generally divided into an aggregation of the otolith primordia from precursor particles and then a growth process that continues throughout life.This study was undertaken to investigate the complex transition between these two steps. Therefore, we investigated the developmental profiles of several inner ear structural and calcium-binding proteins during the complete embryonic and larval development of the cichlid fish Oreochromis mossambicus in parallel with the morphology of inner ear and especially otoliths. We show that the formation of otoliths is a highly regulated temporal and spatial process which takes place throughout embryonic and larval development.Based on our data we defined eight phases of otolith differentiation from the primordia to the mature otolith.

Benign paroxysmal positional vertigo (BPPV) could be treated with specific maneuvers for the involved canals. Management on a daily basis gave earlier relief than weekly treatment, especially in apogeotropic BPPV. Apogeotropic and multi-canal BPPVs were related to the increased numbers of follow-ups and trauma was related to the increased recurrence.We aimed to report the short-term outcomes of our protocol for BPPV and evaluate the factors influencing the results and recurrence.In 210 BPPV patients, posterior semicircular canal (PSCC), geotropic and apogeotropic lateral canal BPPVs were treated with the Epley maneuver, barbecue maneuver, and barbecue maneuver after head-shaking. The total number of follow-ups needed to have no provoked nystagmus, success rates at 1 week and 1 month, and factors for repeated maneuvers or recurrence were identified.Apogeotropic and multi-canal BPPV needed more follow-ups than PSCC BPPV. Multi-canal BPPV showed a significantly lower 1-week success rate than other types. Anterior and multi-canal BPPV showed significantly lower 1-month success rates than other types. The 1-week success rates for PSCC and geotropic and apogeotropic BPPV in patients followed up on a daily basis were higher than those in patients with weekly follow-up and the difference was significant only in apogeotropic BPPV. The overall 1-year recurrence rate was 16% and higher recurrence rate was related to trauma.

This study showed a transient increase of ocular vestibular evoked myogenic potential (oVEMP) amplitudes in the affected ear after successful liberatory maneuvers and no changes in cervical VEMP (cVEMP) amplitudes. These findings support the hypothesis that successful liberatory maneuvers can lead to a repositioning of otoconia to the utricle.To evaluate whether oVEMP amplitudes increase after successful liberatory maneuvers in patients with posterior semicircular canal benign paroxysmal positioning vertigo (pc-BPPV), while cVEMP amplitudes do not change. These findings may indicate a successful repositioning of dislodged otoconia to the utricular macula, but not to the saccular macula.Thirty patients with unilateral pc-BPPV were prospectively examined with bone-conducted oVEMP and air-conducted cVEMP at four time points: before, after, 1 week after, and 1 month after the liberatory maneuvers (Sémont maneuvers).At the 1-week follow-up, 20 of 30 patients were asymptomatic (responders); BPPV could still be induced in the other 10 (non-responders). In responders the mean n10 amplitude on the affected side increased from 12 ± 6.5 µV at baseline (before the treatment) to 15.9 ± 7.1 µV at 1 week after treatment; this increase was significantly (p = 0.001) higher in responders than in non-responders. cVEMP did not differ significantly.

Conclusion: In the present study, classification of the patterns of 3D CT images of the ductus reuniens (reuniting duct) (RD), saccular duct (SD), and endolymphatic sinus (ES) gave more precise information for assessing the pathological condition of Meniere's disease (MD) than our previous study. Objective: This study attempted to provide more detailed information on MD by classifying the patterns of 3D CT images of the RD, SD, and ES in patients with MD. Methods: We examined the ears of 62 patients with definitely diagnosed unilateral MD based on the criteria of the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) using 3D CT. The 3D CT images of bony grooves of RD, SD, and ES (BRD, BSD, and BES) were classified into patterns according to aspects of their patency. Results: BRD could be classified into six types by assessing their patency defined using the criteria in this study. In the ears on the affected side of patients with MD, the BRD, BSD, and BES lost continuity in 3D CT images along their bony routes and were significantly different from normal healthy ears (p < 0.01). There were no significant differences among each stage of MD in the distributions of BRD and BES except for BSD.

Inferior vestibular neuritis (IVN) is a relatively minor subtype of vestibular neuritis (VN) and its clinical characteristics are unique.To clarify clinical characteristics of IVN in comparison with conventional VN.This was a retrospective case series review. Caloric responses and cervical vestibular evoked myogenic potential (cVEMP) responses were measured in 71 patients with VN. The patients were classified into three groups: (1) IVN group, who showed only asymmetrical cVEMP responses; (2) superior VN (SVN) group, who showed only asymmetrical caloric responses; (3) total VN (TVN) group, who showed asymmetrical responses in both tests. The clinical records of time course of subjective symptoms (duration of attack, duration of hospitalization, and time to remission) were reviewed and other profiles (age, sex, affected side, acute symptoms, and sequelae) were evaluated.Of the 71 patients with VN, 13 (18%) were classified as having IVN. The mean age and time to remission of patients with IVN (44.2 ± 4.8 years, 0.9 ± 0.5 months) were significantly lower and shorter, respectively, than those of patients with TVN (57.3 ± 2.5 years, 4.9 ± 4.7 months). There were no significant differences in other symptoms and profiles among the three groups. No patients with IVN showed benign paroxysmal positional vertigo as a sequela.

The clinical presentation and outcome of post-traumatic benign paroxysmal positional vertigo (t-BPPV) are different from those idiopathic BPPV (i-BPPV). It appears that t-BPPV is more difficult to treat than i-BPPV.To identify the clinical presentation and outcome of t-BPPV.We reviewed the medical records of 40 patients with BPPV after head injury during the period 2004-2011. The outcome was compared with the outcome of 46 patients with i-BPPV who were treated over the same period.In all, 55% of patients with t-BPPV had involvement of two or more semicircular canals (SCCs) in comparison with 6.5% of patients with i-BPPV (p0.01). Also, 25% of patients with t-BPPV had involvement of bilateral SCCs in comparison with 2% of patients with i-BPPV (p0.01). We found that 35% of patients with t-BPPV were free of the symptoms and signs after a single physical repositioning maneuver, in comparison with 84% of patients with i-BPPV (p0.001). During a 1-year follow-up, 67% of patients with t-BPPV and 12% of patients with i-BPPV had a recurrent attack (p0.001).

This study suggests that adjuvant anti-anxiety medication may be helpful for patients with benign paroxysmal positional vertigo (BPPV) even after a successful canalith repositioning procedure (CRP).Although the CRP is an effective treatment for BPPV, many patients suffer from persistent dizziness despite successful CRPs. The aim of this study was to evaluate the effect of adjuvant anxiolytic medication on residual dizziness after successful CRP.Between January 2011 and March 2011, 73 patients were diagnosed with BPPV and they underwent successful treatment with CRPs. The patients were randomly assigned to either the medication group or the control group. The patients in the medication group were prescribed low dose etizolam for 2 weeks whereas the patients in the control group were not prescribed any medication. All patients were scheduled to return 2 weeks after evaluation of subjective visual vertical. Subjective symptoms before and after CRP were measured using the Dizziness Handicap Inventory (DHI) and the Activities-specific Balance Confidence (ABC) scale.Both groups demonstrated a significant improvement in DHI scores. However, the medication group showed significantly greater decrease in the functional (p = 0.018) and emotional (p = 0.030) subscale scores, as well as in the total DHI (p = 0.038) score.

Vertical and torsional components occur from the horizontal semicircular canal, and the response to ampullopetal flow is greater than that to ampullofugal flow in every component.To clarify whether positional nystagmus of horizontal canalolithiasis contains vertical and torsional components, and to quantify the asymmetry of nystagmus.Twenty patients with transient direction-changing geotropic positional nystagmus were examined, and we performed three-dimensional video-oculography and measured the maximum slow-phase velocity (MSV) of three components.Positional nystagmus was not purely horizontal. Fifteen (75%) patients revealed a vertical component and 19 (95%) patients had a torsional component. The mean value of MSV of the horizontal component in the affected-ear-down position was 51.5°/s and that in the healthy-ear-down position was 19.1°/s. The mean value of MSV of the vertical component in the affected-ear-down position was 8.7°/s and that in the healthy-ear-down position was 3.0°/s. The mean value of MSV of the torsional component in the affected-ear-down position was 12.8°/s and that in the healthy-ear-down position was 6.5°/s. For every component, MSV in the affected-ear-down position was significantly greater than that in the healthy-ear-down position (p0.01).

Substantial numbers of patients with posterior canal benign paroxysmal positional vertigo (p-BPPV) have signs of utricular dysfunction at baseline. This improves after performing the canalith repositioning procedure.To evaluate the changes of subjective visual horizontal (SVH) in patients with p-BPPV before and after treatment with the canalith repositioning procedure.Twenty-six patients with p-BPPV were treated with the canalith repositioning procedure, Epley's maneuver, according to the affected side. Baseline SVH measurements were taken before performing the Dix-Hallpike maneuver and Epley's maneuver, for comparison with measurements taken just after Epley's maneuver, and 2 weeks after Epley's maneuver.Among 26 patients with p-BPPV, 11 (42%) showed abnormal deviation of SVH at baseline. Just after performing Epley's maneuver, the number of patients who showed an abnormal deviation of SVH decreased significantly to 15% (4 of 26 patients; p0.05). Two weeks after performing Epley's maneuver, only two patients (8%) showed an abnormal deviation of SVH (p0.001).

The enhanced sound- and vibration-induced vestibular evoked myogenic potentials (VEMPs) and their lower threshold in patients with a thinning of the bony wall of the superior semicircular canal (superior canal dehiscence, SCD) have been interpreted as being due to the dehiscence allowing sound and vibration to activate, unusually, the receptors of the dehiscent semicircular canal. We report a patient with bilateral SCD, as verified by high resolution CT scans, who had bilaterally decreased superior semicircular canal function, as shown by rotational tests of canal function. This patient also showed enhanced VEMPs and reduced thresholds. We conclude that in this patient the enhanced VEMP responses are thus probably due to enhanced otolithic stimulation by sound and vibration after dehiscence.

Postural restrictions are probably not necessary after the canalith repositioning procedure (CRP).Epley reported the effect of CRP for benign paroxysmal positional vertigo (BPPV). After CRP, patients are often requested to restrict postural change. However, some studies suggested that CRP may work without postural restrictions. The present study aimed to determine the necessity of post-maneuver postural restriction using the frog labyrinth model.The otoconial mass from the sacculus was placed on the utricular macular otoconia, mimicking a condition after CRP. The stability of the otoconial mass was observed by tilting the preparation, immediately, 3 min, and 5 min after it was placed on the macular otoconia. The utricular macula was maintained in the vertical plane for 10 s, during which period the behavior of the otoconial mass was observed. In experiment 1 the utricular macula was intact, in experiment 2 otoconia were partially removed, and in experiment 3 they were totally removed from the macula.In experiments 1 and 2, in all preparations the otoconial mass became stabilized after 3 min. Even in experiment 3, in most preparations the otoconial mass became stabilized after 5 min.

The findings demonstrate that an enduring unilateral utricular dysfunction, possibly together with canal hypofunction, can occur after labyrinthine disease or injury. They also suggest that unilateral, isolated utricular dysfunction - or utricle paresis - can occur, representing a novel entity in the differential diagnosis of peripheral vestibular function. The occurrence of subjective visual vertical (SVV) asymmetry in the presence of symmetric vestibular evoked myogenic potentials (VEMPs) also confirms that the information from the utricles, rather than the saccules, dominates SVV estimation.To determine the incidence of unilateral utricular hypofunction.The retrospective clinical study deals with a selection of those vestibular patients who showed pathological responses to utricle testing. Peripheral vestibular function was examined in a group of 110 patients. Utricular function was evaluated by estimation of SVV during unilateral centrifugation. Bithermal caloric testing was performed to assess unilateral semicircular canal function. Saccular function was tested by measurement of VEMPs.A total of 46 patients were found with asymmetric SVV findings (p0.001 for healthy versus lesioned ear), but symmetric caloric responses and VEMPs. Statistical testing also verified that their SVV asymmetry factors were significantly higher than those calculated for caloric responses and VEMPs (p0.001).

After forced prolonged position type one (FPP-one) and the appropriate repositioning maneuvers, or FPP-two, 95.45% of patients with cupulolithiasis of the horizontal semicircular canal benign paroxysmal positional vertigo (HSC-BPPV).were symptom-free.To treat patients with cupulolithiasis of the HSC-BPPV.This was a prospective study including 22 subjects with HSC-BPPV (cupulolithiasis) based on apogeotropic direction-changing positional nystagmus (apo-DCPN). Patients adopted FPP-one, which means lying down on the side of the weaker nystagmus during nightly rest for 2 weeks. If apo-DCPN persisted, subjects adopted type two FPP (FPP-two), which means lying on the strongest nystagmus side during nightly rest for 2 weeks.No vertigo or nystagmus was observed in 15 subjects after FPP-one. One subject experienced geotropic DCPN (geo-DCPN), two subjects had posterior BPPV, and another had superior BPPV. Three subjects had persistent apo-DCPN and they were subjected to FPP-two. After that, no vertigo or nystagmus was detected in two subjects. Apo-DCPN persisted in the other remaining subject after FPP-two.

Conclusion: The bony saccular orifice to the bony groove of the ductus reuniens (reuniting duct) could not be visualized in the Meniere's ear with significantly greater frequency compared with normal subjects, which suggests that the reuniting duct is affected by radio-opaque substances in CT findings. Objective: This study investigated a more specific, objective, and simpler strategy to diagnose Meniere's disease by assessing the reuniting duct. Subjects and methods: We examined the cars of 12 patients with definitely diagnosed unilateral Meniere's disease in stage 3 based on Meniere's disease criteria proposed by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), and the ears of 12 normal control subjects using three-dimensional (3D) cone beam CT. Results: The bony groove of the reuniting duct between the saccule and cochlea was visualized in all control subjects. However, the bony saccular orifice to the bony groove could not be visualized in the lesional ear of Meniere's patients with significantly greater frequency compared with those of the contralateral non-lesional ears and control ears (p < 0.01). This orifice was not patent in 66.7% (8 of 12 cars) on the lesional side but all contralateral non-lesional cars of the patients and normal control cars were patent.

The otolithic organs of patients with vestibular drop attack (VDA) secondary to Meniere's disease were damaged but the damage was not complete. In other words, the otolithic functions of patients with VDA were unstable.To evaluate otolithic function using vestibular evoked myogenic potential (VEMP) in patients with VDA secondary to Meniere's disease.Clinical records of three patients with VDA secondary to Meniere's disease were reviewed with special reference to VEMP testing.The three patients were classified as stage II or III Meniere's disease. A long-term follow-up of VEMP in two patients showed reversible changes of VEMP reflexes, and VEMP testing with glycerol administration in two patients revealed the recovery of VEMP responses after taking glycerol, and the existence of saccular endolymphatic hydrops.

Our results show that among the patients with inner ear malformations, there were two patients with sensory cells of sacculus and inferior vestibular neurons and at least five patients with inferior vestibular neurons only, but no patients without sensory cells and vestibular neurons, as determined on the basis of vestibular evoked myogenic potentials (VEMPs).The aim of this study was to investigate whether sensory cells of sacculus or inferior vestibular neurons or both are present in cochlear implant patients with inner ear malformations, particularly common cavity (CC) deformity, using VEMPs.Seven children with inner ear malformation who underwent cochlear implantation (CI) participated in this study. The patients had CC deformity (n=2), incomplete partition type I (n=2), incomplete partition type II (n=1), or a narrow internal auditory canal (IAC) (n=2). It was possible to record VEMPs before and after CI in three patients and not before but after CI in four patients. After surgery, VEMPs were recorded with the cochlear implant device switched both off and on.Before the CI, two patients showed VEMPs and one patient showed no VEMPs, whereas in four patients no VEMPs could be recorded. All the patients showed VEMPs with the cochlear implant on.

Two patients showing two rotational axes of their positional nystagmus had canalolithiasis in bilateral posterior semicircular canals (PSCCs), leading to the diagnosis of true bilateral benign paroxysmal positional nystagmus (P-BPPN). Another 18 patients had a single rotation axis of their positional nystagmus with short time constant (TC) on one side and long TC on the other. Since canalolithiasis in the uppermost PSCC may be transient cupulolithiasis, evoking positional nystagmus with long TC, the diagnosis of the latter patients should be pseudo-bilateral P-BPPN.To differentiate the true bilateral posterior canal type of P-BPPN from pseudo-bilateral P-BPPN.The rotational axis and TC of positional nystagmus were three-dimensionally analyzed in 20 patients showing geotropic torsional nystagmus on the left and right Dix-Hallpike (D-H) maneuvers.Two patients showed two rotational axes of their positional nystagmus, which were perpendicular to the plane of the PSCCs. There were no differences in TCs of their positional nystagmus between bilateral D-Hs. Another 18 patients showed a single rotational axis of their positional nystagmus, which was perpendicular to the plane of either the left or right PSCC. TCs of their positional nystagmus were short on one side and long on the other.

The lagena of pigeons is a unique organ and it is concluded that it is a key element in the magnetic sensor system of pigeons and migrating birds. The lagenal otolith in pigeons contains more iron than saccular and utricular otoliths. The function of the lagena of pigeons was clarified because the homing ability of pigeons was largely disrupted after unilateral lagenal nerve section and attachment of magnetic balls with a magnetic field strength under 5 Gauss. The lagena of pigeons may have a navigational function as a geomagnetic sensor.Otoliths of many kinds of fishes and birds were analyzed.The otoliths of fish and birds were analyzed using synchrotron X-ray fluorescence analysis. Behavioral experiments concerning homing ability of pigeons were done by sectioning their lagenal nerves or interfering with the function of the lagena using a magnet. Twenty-one birds were treated in this way and 30 birds from the same loft of racing pigeons were used as controls.By comparing the compositions of the three different kinds of otoliths among several species of sea fish and birds, it was found that the saccular and utricular otoliths contain scarcely detectable levels of iron but that iron is present in significant quantities in the lagenal otoliths of the birds and sea fish. The results of homing tests clearly revealed a magnetic influence on the function of the lagena in terms of navigation ability of pigeons. The treated pigeons were either lost or significantly delayed while the controls returned within 30 min of release.

We observed 4 cases of paroxysmal positional vertigo (PPV) among 62 cochlear implant (CI) recipients. They occurred in the implanted ear without chronological relation with the surgical procedure or the implant's activation. All of them relapsed within 3 months after an initially successful repositioning maneuver, and finally recovered after the second one. None of the patients showed labyrinthine weakness in the implanted ear. The outbreak of PPV did not affect the patients' speech perception performances.To report and discuss the occurrence of PPV after cochlear implantation.Among 32 adult patients who received a Nucleus CI, 4 suffered from PPV on the basis of Dix-Hallpike's maneuvers. After a Semont's repositioning maneuver, recurrences were similarly addressed. An electro-nystagmography (ENG) recording of caloric irrigation tests was obtained once the symptoms subsided.The observed incidence of 12.5% exceeds the figures reported in the literature. No anatomic abnormalities were identified in these patients, nor were any intraoperative or postoperative complications reported. PPV developed 1-12 months after CI surgery in the posterior canal and relapsed within 3 months. ENG showed a normal reflectivity in two patients, while the other two had a significant prevalence of the implanted side. The outcomes of the speech perception tests after CI in all the four patients matched those of their corresponding categories.

The velocity storage integrator does not play a dominant role in the postural response to vertical visual cues; more likely, retinal slip provides the main driving force. By contrast, sideways eye movement can drive the velocity storage integrator and preserve a gravitational cue, which would be observed as a cross-coupling effect on the postural response.To investigate the mechanism by which optokinetic stimulation causes the body to translate and to determine whether the optokinetic information is accompanied by a gravitational cue, which would appear as a cross-coupling effect.Directionally diverse optokinetic stimuli were presented to seven healthy subjects, with and without a fixation target, and the body-translation of the subjects was recorded.Horizontal optokinetic stimulation with a fixation target caused the body to translate in the same direction as the optic flow. Upward or downward vertical optokinetic stimulation caused the body to translate backward or forward, respectively, only when a fixation target was present. When the subject's interaural axis was parallel to the optokinetic flow, diagonal optokinetic stimulation in the absence of a fixation target elicited responses in the pitch plane similar to those elicited by vertical stimulation in the presence of a fixation target.

Benign paroxysmal positional vertigo (BPPV) is a high-prevalence vestibular end-organ disorder caused by the detachment of utricular otoconia which float in the posterior or lateral semicircular canal. In the majority of cases the etiology of BPPV is unknown and it may follow viral infection, vascular disorders or head trauma. BPPV may be recurrent, with some authors demonstrating a correlation between recurrence and female gender. We report herein on ten cases (out of 289 diagnoses of BPPV) of recurrent idiopathic BPPV, occurring in healthy women receiving oral contraceptive treatment, which ceased after treatment suspension. It has been hypothesized that the impaired water and electrolyte balance, the variations of endolymphatic pH and the impairment of glucose or lipid metabolism induced by oral contraceptive treatment may cause otoconial degeneration and subsequent otoconia detachment and BPPV. The rarity of the finding (10/289) could account for the poor attention paid to the hormonal pathogenesis of BPPV.

CONCLUSIONS: DVA may be useful for assessing the functional consequences of an impaired gaze stabilization mechanism or for testing the effectiveness of a rehabilitation paradigm. Because target distance influences the relative contributions of canal and otolith inputs, the ability to measure DVA at near and far viewing distances may also lead to tests that will independently assess canal and otolith function. OBJECTIVE: To present and test a methodology that uses dynamic visual acuity (DVA) to assess the efficacy of compensatory gaze mechanisms during a functionally relevant activity that differentially measures canal and otolith function. MATERIAL AND METHODS: The effect of treadmill walking at a velocity of 1.79 m/s on subjects' visual acuity was assessed at each of two viewing distances. A custom-written threshold determination program was used to display Landolt C optotypes on a laptop computer screen during a "far" (4 m) target condition and on a micro-display for a "near" (50 cm) target condition. The walking acuity scores for each target distance were normalized by subtracting a corresponding acuity measure obtained while standing still on the treadmill belt. RESULTS: As predicted by subjective reports of relative target motion, the decrease in visual acuity was significantly greater (p < 0.00001) for the near compared to the far condition.

Reduction in bone formation may have been the main reason for the lower calcium content of the otoconia after simulated weightlessness in rats. The head-ward distribution of blood volume may explain the morphological changes observed in the middle and inner ears. To observe morphological changes in the vestibular organs and measure the calcium content of otoconia in rats after simulated weightlessness. We used a tail suspension model of simulated weightlessness and then investigated changes in the vestibular organs using scanning electron microscopy and X-ray microanalysis. In comparison to untreated rats, the vestibular otoconia of the rats subjected to simulated weightlessness were small, irregularly shaped or fissured, and were arranged loosely and out of order. In addition, the calcium content of the otoconia was markedly decreased.

Benign positional vertigo (BPV) is caused by detached otolith debris that enters the semicircular canal and moves with changes in head position. Movement in the plane of the affected canal triggers brief but violent episodes of vertigo. The posterior semicircular canal variant (PC-BPV) is by far the most common because once the debris enters the canal it becomes trapped and can remain there for months and even years. We are just beginning to understand how the otolithic membrane is formed, how it is maintained and what happens to otolithic debris floating in the endolymphatic space.

Humans taking part in parabolic aircraft flights (PAFs) may suffer from space motion sickness, which is a form of kinetosis. As it has been repeatedly shown that some fish in a given batch also reveal kinetotic behaviour (especially so-called spinning movements and looping responses) during PAFs, and as a result of the homology of the vestibular apparatus of all vertebrates, fish can be used as model systems to investigate the origin of susceptibility to motion sickness. Therefore. we were prompted to examine the utricular maculae, which are responsible for the internalization of gravity in teleosteans of fish swimming kinetotically in microgravity (microg) in comparison with those of animals from the same batch who swam normally.Larval cichlid fish (Oreochromis mossambicus) were subjected to PAFs. Post-flight, animals which had behaved normally or kinetotically during the microg phases were examined histologically The sizes of the inner ear utricular maculae as well as the numbers of sensory and supporting cells were determined.The total numbers of both sensory and supporting cells of the utricular maculae did not differ between kinetotic and normally swimming fish. Cell density (number of sensory and supporting cells/100 microm2) was, however, reduced in kinetotic animals (p0.0001), which seemed to be due to the presence of malformed epithelial cells of increased size in the kinetotic specimens.These results indicate that susceptibility to kinetosis may originate from genetically predisposed malformed sensory epithelia.

Whole membranous labyrinths of bullfrogs were used in order to replicate the human vestibule. The posterior semicircular canals (PSCs) were exposed, leaving the remaining membranous labyrinth encapsulated in the otic capsule. Vibration was applied to the surface of the bony capsule using a conventional surgical drill in order to dislodge the otoconia from the utricle. The position of the preparation was controlled so that the dislodged otoconia were attached to the cupular surface. This was regarded as a cupulolithiasis model. The action potentials changed instantaneously according to the gravitational force on the cupula. When the otoconia were dislodged and held within the PSC lumen, the position of the whole preparation was changed so that the otoconia moved back and forth within the canal lumen. This is a model of canalolithiasis. The action potentials changed in combination with the otoconial movement after a latent period. Both cupulolithiasis and canalolithasis are potentially valid mechanisms of benign paroxysmal positional vertigo (BPPV). However, canalolithiasis is the most likely mechanism of BPPV, which is usually characterized by nystagmus of short duration and long latency. A vibratory stimulus was able to detach the otoconia from the utricle, suggesting that mechanical insult could be a possible etiology of BPPV.

The mystery of the homing ability of pigeons has been the subject of much interest and it is widely believed that information from the earth's magnetic field may be involved. However, no specific magnetic sensory organ has yet been identified. The recent finding of magnetic materials in the lagenal otolith of fish and birds raises the possibility that these structures may be key elements in the elusive magnetic sensory system. For the elemental analysis of materials X-ray fluorescence using synchrotron radiation is one of the most powerful techniques available and was used in this study for analysis of the otoliths. By comparing the compositions of the three different kinds of otoliths among several species of sea fish and birds, we found that the saccular and utricular otoliths rarely contain detectable levels of iron but that iron is present in significant quantities in the lagenal otoliths of the birds. The lagenal otolith comprises tiny magnetic particles of low inertia that are displaced by imposed magnetic fields, providing the animal with geomagnetic sensory input, from which the brain would infer navigational information.

3D analysis of eye movements during off vertical axis rotation (OVAR) was carried out in seven subjects with unilateral labyrinthine loss (ULL). The modulation component (MOC) of these patients was not different from that of normal subjects. However, the horizontal MOC was significantly smaller when the rotation was directed towards the diseased side as opposed to the healthy side. With rotation to the diseased side, most subjects exhibited a horizontal bias component (BIC) to the opposite side as compared with the diseased side in normal subjects. The vertical and torsional BICs were also influenced to some extent by lack of input from the unilateral labyrinth. These results indicate that a unilateral otolith organ plays a major role in the production of the horizontal BIC contralateral to the direction of rotation, which is strongly related to the velocity storage mechanism in the central nervous system. In addition, the unilateral otolith organ exerts some influence on the generation of the horizontal MOC and also the BIC of vertical and torsional eye movements.

In the present study, attention is directed to the unilateral response of the otolith system to static and dynamic tilt, as reflected by subjective estimation of the visual vertical (oculogravic perception). Measurements were performed with a variable radius rotary chair, which permits controlled modulation of the centripetal, or radial, acceleration. By limiting the radius, i.e. eccentric displacement of the head by 3.5 cm during constant-velocity rotation about the earth-vertical axis, adequate unilateral stimulation of the otolith organ--predominantly the utricle--is generated, without involving the semicircular canals. This paradigm has been employed to measure the unilateral utriculo-ocular response. In contrast to the otolith-ocular response (OOR), the subjective visual vertical (SVV) reflects the processing of otolithic information in the higher brain centres (thalamus, vestibular cortex). Exploitation of these two complementary approaches provides useful information for both experimental and clinical scientists. The findings also reveal that centripetal acceleratory stimulation during constant angular velocity with the subject centred on axis is sufficient to localize peripheral otolith dysfunction by means of SVV estimation. This represents a novel test of otolith function that can be easily integrated into routine clinical testing.

The structure of the vestibular organs of the teleost fish (bluegill), newts (Japanese fire-belly newt), frogs (black-spotted pond frog), snapping turtles and birds (chicks) was morphologically compared, with particular attention to the lagena macula, and the differences between animal species with relation to evolution were considered. Teleost fish had no striola on the lagena macula. The striola of newts were short and restricted to the central area of the macula, but those of frogs, snapping turtles and chicks extended from the anterior to posterior edges of the macula. This indicates that the frog is more highly evolved than the newt. The length of the kinocilium of sensory hairs was equal to that of the longest stereocilium in teleost fish and newts, but the kinocilia of frogs, snapping turtles and chicks were longer than the longest stereocilium. This indicates that the function of the lagena of teleost fish and newts is for hearing whilst in the other animals they are for posture. The diameter of the sensory hair bundles is small in teleost fish and frogs, but large in newts and snapping turtles. This indicates that the sensitivity of the sensory cells of the lagena towards outer force is low in teleost fish and frogs, high in newts and snapping turtles and intermediate in birds. The lagena of snapping turtles protrudes from the basilar papilla into the vestibule but the lagena of chicks lies on the tip of the long projecting basilar papilla. From observation of the locations of lagenae it is natural to speculate that there must have been some species of animal now extinct that had the evolving location of the lagena prior to that of chicks. In future it will be very interesting and useful to identify this extinct animal using DNA techniques.

Short latency vestibular evoked potentials (VsEPs) to linear acceleration impulses (L-VsEPs) are initiated in the otolith organs (saccule and utricle). Some of the saccule afferents have been reported to respond not only to linear acceleration, but also to high intensity acoustic stimuli. If so, the L-VsEP recorded from the saccule (elicited with the stimulus orientated relative to the head so as to optimally activate the saccule, i.e. stimulus in the vertical plane, Z-VsEP) should be reduced during high intensity broad band noise (BBN) "masking". Conversely, the utricular afferents have been reported to be less auditory-sensitive. Therefore, an L-VsEP which is mainly utricular in origin (stimulus in the horizontal plane, X-VsEP) should be less affected by this noise "masking". This was investigated in rats by recording X-VsEPs and Z-VsEPs and angular VsEPs (A-VsEPs), originating in the lateral semi-circular canals, before, during and after exposure to short duration, high intensity (113 dB SPL) BBN. This intensity completely masked auditory nerve evoked responses. The Z-VsEP did appear to be slightly more affected by the noise "masking" than the X-VsEP, implying the presence of more auditory-sensitive elements in the saccule. The A-VsEP was also affected by the BBN. The overall effect was relatively small (on average, 10-25% depression of the first wave of the different VsEPs). The responses showed recovery 5 min later.

Quantitative electron probe microanalysis and electron spectroscopic diffraction analysis was used to determine the gradient of distribution of calcium and its crystalline pattern at different levels (lower gelatinous membrane, upper gelatinous membrane and otoliths) in the otoconial membrane of adult OF1 mice. Our quantitative electron probe microanalytical data, obtained with scanning-transmission electron microscopy, indicated that there was a gradient in calcium concentration which increased from the vestibular surface towards the otoliths. Differences between the three regions of the otoconial membrane were statistically significant in both the utricle and saccule. Our results with electron spectroscopic diffraction revealed an increasing crystalline development from the lower gelatinous membrane towards the otoliths. Our findings with both techniques suggest that the gelatinous membrane is involved in the maturation and crystallization of the otoliths.

Size and asymmetry (size difference between the left and right sides) of inner ear otoliths of larval cichlid fish were determined after a long-term stay in moderate hypergravity conditions (3g; centrifuge), in the course of which the animals completed their ontogenetic development from hatch to freely swimming. Neither the normal morphogenetic development nor the timely onset and gain of performance of swimming behaviour were impaired by the experimental conditions. However, both utricular and saccular otoliths (lapilli and sagittae, respectively) were significantly smaller after hyper-g exposure compared to 1g control specimens raised in parallel. The asymmetry of sagittae was significantly increased in the experimental animals, whereas the respective asymmetry of lapilli was pronouncedly decreased compared with the 1g controls. These findings suggest that growth and development of bilateral asymmetry of otoliths are guided by the environmental gravity vector. Some of the hyper-g animals revealed a kinetotic behaviour on transfer to normal 1g earth conditions, which was similar to the behaviour observed in previous experiments on the transfer from 1g to microgravity (parabolic aircraft flights). The lapillar asymmetry of kinetotic samples was found to be significantly higher than that of normally behaving experimental specimens. No differences in asymmetry of sagittae were obtained between the two groups. This supports an earlier theoretical concept, according to which human static space sickness might be based on asymmetric utricular otoliths.

The goal of this investigation was to determine whether there is a familial tendency in the development of benign paroxysmal positional vertigo (BPPV). We hypothesized an increased frequency of BPPV among relatives of patients with the same diagnosis. BPPV is caused by dislodged otoconia from the utricular macula floating in the semicircular canals. At least half of BPPV cases are idiopathic and most pathological associations provide no clue as to the reason otoconia become dislodged. We have noted a number of BPPV patients with family histories of BPPV, suggesting a genetic predisposition to the condition. We surveyed 120 successive BPPV patients and 120 successive dizzy patients without BPPV regarding the frequency of dizziness and BPPV (diagnosed by a physician) among family members. Patients in our group with BPPV were 5 times as likely to have relatives with BPPV compared to the dizzy control group (chi2=5.95, DF=1, p=0.015). We have demonstrated that there is a familial tendency for the occurrence of BPPV. There is nothing in our data that would distinguish between a hereditary or environmental influence in the development of the disease, however.

Three normal human subjects were oscillated about their naso-occipital axis in a supine position at 0.4 Hz and 0.1 Hz, both in darkness and in the light with a structured fixation target. The same subjects were oscillated in roll about an upright position, at the same frequencies, in darkness; and also about axes directed 20 degrees and 40 degrees to the left and to the right of the midsagittal plane, at 0.4 Hz, in darkness. Three-dimensional binocular eye movements were recorded using video-oculography. All stimuli induced a predominantly torsional nystagmus with small disconjugate head-vertical (skew) and conjugate head-horizontal components. For roll oscillation, the torsional slow phase velocity gain was higher in the light and generally increased with the stimulation frequency. In darkness, only one subject had significantly higher torsional gains in the upright compared to the supine position (12% difference), suggesting that the otolith contribution to the roll response is minimal at the frequencies tested. The slow phase velocity gain of the skew increased with fixation in two subjects. but decreased in the third subject; these changes were related to changes in eye vergence. In the upright position, with oblique axes of rotation, the head-vertical eye movements were asymmetrical, with the outermost eye executing a larger amplitude movement. The disconjugate head-vertical eye movements observed can be explained by the pattern of vertical semicircular canal stimulation and their connections to the extraocular muscles. In humans, skewing of the eyes may compensate for the eccentricity of the foveae which lie in the temporal retina and undergo vertical translations in opposite directions when the eyes tort.

In order to clarify the mechanism of otoconia formation, the pathway of calcium transport in the utricular supporting cells was investigated. Potassium pyroantimonate (PA) precipitation, which indicates the localization of calcium ions, was seen not only in otoconia but also in supporting cell cytoplasm. In the latter, deposits of PA were detected in the secretory granules and endoplasmic reticulum (ER). These deposits were not present in cells pretreated with ethylene glycol-O,O,-bis (2-aminoethyl)-N,N,N',N'-tetra-acetic acid (EGTA). Exposure of the supporting cells to streptomycin sulfate (SM) increased the number of lysosomes. These lysosomes contained many small deposits of PA. The remaining granules and ER in cytoplasm also contained small deposits of PA. The findings suggest that otoconia are formed by the vestibular supporting cells in which calcium ions might be transported via ER-secretory granule-lysosome-cytoplasmic protrusion.

We evaluated changes in the subjectively perceived gravitational vertical as an index of imbalance in the function of the right and left otolith organs. In addition to normal subjects (n = 25), we measured patients with a longstanding (mean 4.5 year +/- 3.2 SD; range 0.5-11.5 years) unilateral vestibular loss after surgery for acoustic neuroma (n = 32), patients with partial unilateral vestibular loss (n = 7) and patients with bilateral vestibular hyporeflexia (n = 8). Normal subjects could accurately align a vertical luminous bar to the gravitational vertical in an otherwise completely dark room (mean setting -0.14 degree +/- 1.11 SD). Patients with left-sided (complete; n = 13) or right-sided (complete; n = 19 and partial; n = 7) unilateral vestibular loss made mean angular settings at 2.55 degrees +/- 1.57 (SD) leftward and 2.22 degrees (+/-1.96 SD) rightward, respectively. These means differed highly significantly from the normal mean (p < 0.00001). In the time interval investigated (0.5-11.5 years) the magnitude of the tilt angle showed no correlation with the time elapsed since the operation. The mean setting by patients with clinically bilateral vestibular loss (-1.17 degrees +/- 1.96 SD; n = 8) did not significantly differ from the control group. The systematic tilts of the subjective vertical in patients with a unilateral vestibular impairment were correlated with their imbalance in canal-ocular reflexes, as reflected by drift during head-oscillation at 2 Hz (r2 = 0.44) and asymmetries in VOR-gain for head-steps (r2 = 0.48-0.67). These correlations were largely determined, by the signs of the asymmetries; correlation between the absolute values of the VOR gain asymmetries and subjective vertical angles proved to be virtually absent. We conclude that the setting of the subjective vertical is a very sensitive tool in detecting a left-right imbalance in otolith function, and that small but significant deviations towards the defective side may persist for many years (probably permanently) after unilateral lesions of the labyrinth or the vestibular nerve.

Formation and fate of abnormal (giant) otoconia of the guinea pig following streptomycin intoxication were investigated using scanning electron microscopy. The giant otoconia formed as multifaceted morphology in their early developmental period. They grew up the the transitional type and finally to the cylindrical type. It has been suggested that the giant otoconia found following streptomycin intoxication may be formed mainly by dissolution of normal otoconia due to the loss of environmental calcium, followed by recrystallization as giant crystals. These phenomena seemed to be closely related to the otoconial dynamics which may regulate calcium ion homeostasis of the endolymph.

Using the electron probe X-ray microanalysis technique, the elemental composition of otoconia was analysed in both young and old normal pigmented guinea pigs. Calcium concentration in both the utricular and the saccular otoconia was lower in the old animals, which indicates that the loss of calcium from otoconia and/or decrease in calcium ion uptake may occur in the old animals. The present study has established that calcium and other elements (P, S, Cl and K) in the otoconia of the young animals are related via a linear function, indicating that P, S, Cl and K are present in the mineral phase of the otoconia. The associations of Ca-P, Ca-K and Ca-S are not maintained in the old animals. It has been suggested that the aging phenomenon may influence the ionic metabolism in the vestibular end organs resulting in the altered mineral composition of otoconia.

According to the otolith asymmetry hypothesis for susceptibility to motion sickness, the interlabyrinthine asymmetry in the otoconial mass, which is normally compensated in the circuity of the vestibular system by appropriate neuronal weighting, becomes disrupted as a result of unfamiliar movement patterns or force environments. Measurements in various species have demonstrated a large scatter in the otoconial mass. As the utricle and saccule have distinct functions in the vestibular system it seems appropriate to deal with these organs separately. Results are presented on mass distribution and lateral preponderance of the otoconial mass in the utricles and saccules of the salmon (Salmo salar) and trout (Salmo irideus). The measurements revealed considerably larger dimensions of the saccular otoconia in these species, amounting to twenty-fold. This substantial difference indicates that different regulatory principles underlie the otoconial generation of each of the organs and is presumably related to their specific functions. The lateral preponderance was found to be normally distributed for both organs in both species, with standard deviations of approx. 4% except for the utricular otoconia of the salmon (13%). In a second set of experiments, fish were exposed to a Coriolis force environment. Their sealed aquarium was subjected to constant vertical axis rotation combined with pendular oscillation around the horizontal axis. The aquarium was illuminated by a light source fixed to project through the top, and a video camera recorded the movements of the fish. During combined rotation and pendular oscillation, one group of fish maintained an active compensatory swimming behaviour, whereas the movements of a second group became uncoordinated and often led to passive behaviour. Analysis of the otoconia of these two groups of fish promises to yield further evidence relevant to the otolith asymmetry hypothesis.

The effects of streptomycin on the calcium ion turnover into otoconia of adult guinea-pigs investigated by the use of tetracycline. The oral administration of tetracycline induced the deposition of tetracycline (fluorescence) on the outer surface of otoconia indicating the existence of dynamic exchange and/or uptake of calcium ions in the otoconia. The significant finding is that streptomycin specifically interfered with calcium uptake into the otoconia which indicated that the decrease in calcium uptake caused by streptomycin may be closely related to the loss of otoconia as well as to a decrease in the calcium contents of otoconia. The decrease in calcium incorporation into otoconia caused by streptomycin was recovered within 6 weeks after the last injection of streptomycin. The number of otoconia with fluorescence in the central portion as well as their outer surface was increased. It is therefore suggested that the recovery of calcium uptake as well as new otoconial regeneration may play an important role for the recovery from loss of otoconia.

Peripheral vestibular equilibrium disorders may originate in various parts of the labyrinth or the vestibular nerve. Traditionally, the function of the lateral semicircular canals has been assessed with caloric irrigation, and sometimes falsely been interpreted as a vestibular nerve lesion. The vertical semicircular canals are not easily assessed. Caloric testing with the head in different positions is not very helpful, but the canals may pairwise be tested using specific rotational techniques. Often the otolithic organs, capable of detecting linear acceleration forces, are forgotten as a source of vertigo and dizziness. We have implemented horizontal rotatory testing with the subject seated eccentrically facing the direction of rotation as a means of assessing otolithic function. The subject experiences a lateral tilt and is instructed in darkness to put a short light bar in the position he thinks a water surface would have, which is identical to his perceived tilt. In 39 normal subjects, a theoretical tilt of 24 degrees was estimated as approximately 19.5 degrees, and the standard deviation was 6 degrees. A side difference index was proposed to be normal if below 25%. The preliminary findings in a few patients with known labyrinthine lesions are presented. We propose that otolithic as well as lateral semicircular canal functions are useful to monitor in patients with suspected peripheral equilibrium disorders.

The fact that the labyrinths are positioned at approx. 3.5 cm from the head-centric axis leads to the generation of systematic radial acceleratory, or centrifugal, forces during physiological head rotations. Under physiological conditions, the forces exerted on the right and left maculae are generally assumed to be equal and opposite. In the present test, however, the subject was displaced eccentrically during constant angular velocity so that one labyrinth was aligned concentrically with the rotatory axis, whilst the other was exposed to the radial acceleration component generated by the chair rotation. In comparison with previous testing based on subjective setting of the visual vertical, three-dimensional eye movements were recorded in order to obtain an objective measure of the otolith-ocular response mechanisms in the brainstem. The results obtained from normal subjects demonstrate a predominant ocular counterroll (OCR) response to this asymmetric, or unilateral application of linear acceleration. The direction of the OCR response proved to be independent of direction of rotation. The findings demonstrate a symmetrical response magnitude for stimulation of the left and right maculae. In comparison with the OCR response to head-tilt, which can be described as critically damped, the time course of the present response appeared to be underdamped.

The vestibular sensors are the necessary source of information for estimating self-displacement during passive linear transport. Displacement has to be computed from the otolith signal by means of an integration process (path integration), which provides a measure of linear acceleration. However, the onset of self-motion perception is delayed due to perceptual thresholds. We investigated the effect of these thresholds on the estimation of passive displacement. Subjects seated on a linear acceleration device (ESA-SLED) were displaced to their left or right. Two tasks were performed: (1) subjects pressed a button when they perceived self-motion; (2) subjects pressed a button when they thought they had reached a previously seen visual target located above the sled rail. Displacement estimation (task 2) was found to depend upon the acceleration magnitude and on the individual motion perception threshold measured in task 1. The results can be explained by assuming that self-displacement computation starts at the onset of self-motion perception and is initialised by a value that is independent of the amplitude of acceleration, thereby compensating for the displacement information lost due to the thresholds.