Optimal Human Passive Vestibulo-Ocular Reflex Adaptation Does Not Rely on Passive Training

The vestibulo-ocular reflex (VOR) is the main vision-stabilising system during rapid head movements in humans. A visual-vestibular mismatch stimulus can be used to train or adapt the VOR response because it induces a retinal image slip error signal that drives VOR motor learning. The training context has been shown to affect VOR adaptation. We sought to determine whether active (self-generated) versus passive (externally imposed) head rotation vestibular training would differentially affect adaptation and short-term retention of the active and passive VOR responses. Ten subjects were tested, each over six separate 1.5-h sessions. We compared active versus passive head impulse (transient, rapid head rotations with peak velocity ~?150 °/s) VOR adaptation training lasting 15 min with the VOR gain challenged to increment, starting at unity, by 0.1 every 90 s towards one side only (this adapting side was randomised to be either left or right). The VOR response was tested/measured in darkness at 10-min intervals, 20-min intervals, and two single 60-min interval sessions for 1 h post-training. The training was active or passive for the 10- and 20-min interval sessions, but only active for the two single 60-min interval sessions. The mean VOR response increase due to training was ~?10 % towards the adapting side versus ~2 % towards the non-adapting side. There was no difference in VOR adaptation and retention between active and passive VOR training. The only factor to affect retention was exposure to a de-adaptation stimulus. These data suggest that active VOR adaptation training can be used to optimally adapt the passive VOR and that adaptation is completely retained over 1 h as long as there is no visual feedback signal driving de-adaptation.     

Human Vestibulo-Ocular Reflex Adaptation Training: Time Beats Quantity

The vestibulo-ocular reflex (VOR) is the main gaze stabilising system during rapid head movements. The VOR is highly plastic and its gain (eye/head velocity) can be increased via training that induces an incrementally increasing retinal image slip error signal to drive VOR adaptation. Using the unilateral incremental VOR adaptation technique and horizontal active head impulses as the vestibular stimulus, we sought to determine the factors important for VOR adaptation including: the total training time, ratio and number of head impulses to each side (adapting and non-adapting sides; the adapting side was pseudo-randomised left or right) and exposure time to the visual target during each head impulse. We tested 11 normal subjects, each over 5 separate sessions and training protocols. The basic training protocol (protocol one) consisted of unilateral incremental VOR adaptation training lasting 15 min with the ratio of head impulses to each side 1:1. Each protocol varied from the basic. For protocol two, the ratio of impulses were in favour of the adapting side by 2:1. For protocol three, all head impulses were towards the adapting side and the training only lasted 7.5 min. For protocol four, all impulses were towards the adapting side and lasted 15 min. For protocol five, all head impulses were to the adapting side and the exposure time to the visual target during each impulse was doubled. We measured the active and passive VOR gains before and after the training. Albeit with small sample size, our data suggest that the total training time and the visual target exposure time for each head impulse affected adaptation, whereas the total number and repetition rate of head impulses did not. These data have implications for vestibular rehabilitation, suggesting that quality and duration of VOR adaptation exercises are more important than rapid repetition of exercises.     

Unilateral Adaptation of the Human Angular Vestibulo-Ocular Reflex

A recent study showed that the angular vestibulo-ocular reflex (VOR) can be better adaptively increased using an incremental retinal image velocity error signal compared with a conventional constant large velocity-gain demand (×2). This finding has important implications for vestibular rehabilitation that seeks to improve the VOR response after injury. However, a large portion of vestibular patients have unilateral vestibular hypofunction, and training that raises their VOR response during rotations to both the ipsilesional and contralesional side is not usually ideal. We sought to determine if the vestibular response to one side could selectively be increased without affecting the contralateral response. We tested nine subjects with normal vestibular function. Using the scleral search coil and head impulse techniques, we measured the active and passive VOR gain (eye velocity / head velocity) before and after unilateral incremental VOR adaptation training, consisting of self-generated (active) head impulses, which lasted ∼15 min. The head impulses consisted of rapid, horizontal head rotations with peak-amplitude 15 ^o, peak-velocity 150 ^o/s and peak-acceleration 3,000 ^o/s². The VOR gain towards the adapting side increased after training from 0.92 ± 0.18 to 1.11 ± 0.22 (+22.7 ± 20.2 %) during active head impulses and from 0.91 ± 0.15 to 1.01 ± 0.17 (+11.3 ± 7.5 %) during passive head impulses. During active impulses, the VOR gain towards the non-adapting side also increased by ∼8 %, though this increase was ∼70 % less than to the adapting side. A similar increase did not occur during passive impulses. This study shows that unilateral vestibular adaptation is possible in humans with a normal VOR; unilateral incremental VOR adaptation may have a role in vestibular rehabilitation. The increase in passive VOR gain after active head impulse adaptation suggests that the training effect is robust.     

Human Vestibulo-Ocular Reflex Adaptation: Consolidation Time Between Repeated Training Blocks Improves Retention

We sought to determine if separating vestibulo-ocular reflex (VOR) adaptation training into training blocks with a consolidation (rest) period in between repetitions would result in improved VOR adaptation and retention. Consolidation of motor learning refers to the brain benefitting from a rest period after prior exposure to motor training. The role of consolidation on VOR adaptation is unknown, though clinicians often recommend rest periods as a part of vestibular rehabilitation. The VOR is the main gaze stabilising system during rapid head movements. The VOR is highly plastic and its gain (eye/head velocity) can be increased via training that induces an incrementally increasing retinal image slip error signal to drive VOR adaptation. The unilateral incremental adaptation technique typically consists of one 15-min training block leading to an increase in VOR gain of ~?10 % towards the training side. We tested nine normal subjects, each over six separate sessions/days. Three training protocols/sessions were 5 min each (1?×?5-min training) and three training protocols/sessions were 55 min each. Each 55-min protocol comprised 5-min training, 20-min rest, 5-min training, 20-min rest, 5-min training (3?×?5-min training). Active and passive VOR gains were measured before and after training. For training with consolidation breaks, VOR gain retention was measured over 1 h. The VOR gain increase after 1?×?5-min training was 3.1?±?2.1 % (P?<?0.01). One might expect that repeating this training three times would result in ×?3 total increase of 9.3 %; however, the gain increase after 3?×?5-min training was only 7.1?±?2.8 % (P?<?0.001), suggesting that consolidation did not improve VOR adaptation for our protocols. However, retention was improved by the addition of consolidation breaks, i.e. gains did not decrease over 1 h (P?=?0.43). These data suggest that for optimal retention VOR adaptation exercises should be performed over shorter repeated blocks.     

Headshake versus whole-body rotation testing of the vestibulo-ocular reflex

The vestibulo-ocular reflex (VOR) is usually evaluated by whole-body rotary chair oscillation in darkness, but is limited to ambulatory patients. In order to develop a portable method of VOR assessment, eye movements from 10 normal subjects were studied under three conditions: 1. whole-body rotary chair oscillation in the dark and in the light with a head mounted blank field, 2. passive head-on-body rotation in the light with a blank field, and 3. active head-on-body rotation in the light with a blank field. The influence of visual fixation, neck rotation, and volition on VOR gain was to be assessed. Head oscillations were maintained at 0.5 and 1.0 Hz, 50°/s peak velocity. Mean VOR gains with blank field testing were indistinguishable from those obtained in darkness during whole-body rotation. In addition, there were no significant differences in the mean gain between whole-body, passive head rotation or active head rotation. Two vestibulopathic patients (absent calorics bilaterally and oscillopsia) were also studied to illustrate potential clinical utility of the methods. Rotations under all conditions revealed low but variable gains. The evaluation of the VOR in the light with a blank visual surround and passive or active head rotation is a potentially useful clinical method of bedside assessment of the VOR.     

Eye movements during active head turning with different vestibular and cervical input

Eye movements were measured in 15 volunteers during vestibulo-ocular reflex (VOR), cervico-ocular reflex with the head fixed from the ceiling (passive COR), during voluntary stabilization of the head in space while the trunk was moved sinusoidally (active COR) and active head movements with and without additional vestibular or cervical stimuli. The subjects were sitting with eyes covered on a rotating chair swinging sinusoidally at 40 degrees peak to peak amplitude at 0.05, 0.1 and 0.2 Hz. The saccadic activity during passive COR is below the VOR and increases slightly during active COR. During voluntary head movements it shows a marked increase and is further activated if cervical or vestibular stimuli are added. The amplitudes of eye shifts of passive and active COR are not different. During active head movements and more with additional cervical or vestibular input, they increase significantly. The phase of the maximum eye shifts to head position is anticompensatory during passive COR and compensatory during VOR. The phase lead of about 45 degrees during active head movements is less during active COR but is larger with additional cervical and vestibular stimuli reaching 90 degrees.     

Human Vestibulo-Ocular Reflex Adaptation Reduces when Training Demand Variability Increases

One component of vestibular rehabilitation in patients with vestibulo-ocular reflex (VOR) hypofunction is gaze-stabilizing exercises that seek to increase (adapt) the VOR response. These prescribed home-based exercises are performed by the patient and thus their use/training is inherently variable. We sought to determine whether this variability affected VOR adaptation in ten healthy controls (× 2 training only) and ten patients with unilateral vestibular hypofunction (× 1 and × 2 training). During × 1 training, patients actively (self-generated, predictable) move their head sinusoidally while viewing a stationary fixation target; for × 2 training, they moved their outstretched hand anti-phase with their head rotation while attempting to view a handheld target. We defined the latter as manual × 2 training because the subject manually controls the target. In this study, head rotation frequency during training incrementally increased 0.5–2 Hz over 20 min. Active and passive (imposed, unpredictable) sinusoidal (1.3-Hz rotations) and head impulse VOR gains were measured before and after training. We show that for controls, manual × 2 training resulted in significant sinusoidal and impulse VOR adaptation of ~ 6 % and ~ 3 %, respectively, though this was ~two-thirds lower than increases after computer-controlled × 2 training (non-variable) reported in a prior study. In contrast, for patients, there was an increase in impulse but not sinusoidal VOR response after a single session of manual × 2 training. Patients had more than double the variability in VOR demand during manual × 2 training compared to controls, which could explain why adaptation was not significant in patients. Our data suggest that the clinical × 1 gaze-stabilizing exercise is a weak stimulus for VOR adaptation.     

VOR adaptation training and retention in a patient with profound bilateral vestibular hypofunction

A novel training method known as incremental VOR adaptation (IVA) can improve the vestibulo‐ocular reflex (VOR) gain for both active and passive head rotation by coupling active head rotations with a laser‐projected target that moves in the opposite direction of the head at a fraction of the head velocity. A 51‐year‐old male with bilateral vestibular hypofunction participated in a research protocol using a portable IVA device for 645 days. Passive VOR gains improved 179% to 600%; standing posture and gait also improved. Motor learning within the vestibular system using the IVA method is possible after severe vestibular pathology. Laryngoscope, 129:2568–2573, 2019     

A rodent model for artificial gravity: VOR adaptation and Fos expression

Vestibulo-ocular reflex (VOR) adaptation and brainstem Fos expression as a result of short radius cross-coupling stimuli were investigated to find neural correlates of the inherent Coriolis force asymmetry from an artificial gravity (AG) environment. Head-fixed gerbils (Meriones unguiculatus, N=79) were exposed, in the dark, to 60--90 minutes of cross-coupled rotations, combinations of pitch (or roll) and yaw rotation, while binocular horizontal, vertical, and torsional eye position were determined using infrared video-oculography. Centripetal acceleration in combination with angular cross-coupling was also studied. Simultaneous sinusoidal rotations in two planes (yaw with roll or pitch) provided a net symmetrical stimulus for the right and left labyrinths. In contrast, a constant velocity yaw rotation during sinusoidal roll or pitch provided the asymmetric stimulus model for AG. We found orthogonally oriented half-cycle VOR gain changes. The results depended on the direction of horizontal rotation during asymmetrical cross-coupling, and other aspects of the stimulus, including the phase relationship between the two rotational inputs, the symmetry of the stimulus, and training. Fos expression also revealed laterality differences in the prepositus and inferior olivary C subnucleus. In contrast the inferior olivary beta and ventrolateral outgrowth were labeled bilaterally. Additional cross-coupling dependent labeling was found in the flocculus, hippocampus, and several cortical regions, including the perirhinal and temporal association cortices. Analyses showed significant differences across the brain regions for several factors (symmetry, rotation velocity and direction, the presence of centripetal acceleration or a visual surround, and training). Finally, animals compensating from a unilateral surgical labyrinthectomy who received multiple cross-coupling training sessions had improved half-cycle VOR gain in the ipsilateral eye with head rotation toward the intact side. We hypothesize that cross-coupling vestibular training can benefit aspects of motor recovery or performance.     

Utility of headshake versus whole-body VOR evaluation during routine electronystagmography.

Evaluation of the vestibulo-ocular reflex (VOR) by caloric testing yields important localizing information, but does not examine the entire frequency spectrum of vestibular function. With the addition of head rotation at 0.5 Hz (50 deg/s) and a velocity sensor to measure head movement, additional unique information regarding higher frequency VOR function can be readily obtained using standard electro-oculography (EOG). Over the past 4 years, active head-on-body and passive whole-body rotation testing with four-channel strip-chart recording and hand analysis have been routinely performed on every patient referred for caloric testing. In 95 percent of cases with normal symmetric caloric responses, headshake VOR gain with either stimulus was normal (greater than 0.51). Similarly, more than 95 percent of patients with unilateral deficits on caloric testing yielded normal rotational VOR gains. In contrast, roughly one third of patients with bilaterally reduced caloric responses demonstrated both abnormally low active headshake and passive whole-body rotational gain (less than 0.5). It appears, therefore, that both active head-on-body and passive whole-body rotation VOR testing at 0.5 Hz are possible using standard recording techniques, and yield valuable added information in cases with reduced bilateral caloric responses.     

Changes in VOR adaptation after local injection of beta-noradrenergic agents in the flocculus of rabbits.

Noradrenaline (NA) has been implicated as a neuromodulator in plasticity, presumably facilitating adaptive processes. Since the flocculus receives noradrenergic afferents, and ablation of the flocculus interferes with the normal adaptive changes in the VOR gain, experiments were performed to find out whether bilateral injection of monoaminergic substances into the flocculus of rabbits could modify the adaptive changes of the VOR. The visual world surrounding the rabbit was oscillated in opposite direction to the platform on which the rabbit was mounted, which resulted in an adaptive increase in the VOR gain; this adaptation was measured either in light or in darkness. Floccular injection of the beta-agonist isoproterenol did not greatly affect the adaptation of the VOR measured in light. In darkness, however, the increase in gain after injection of isoproterenol was larger than during normal adaptation. The beta-antagonist sotalol reduced the adaptation of the VOR gain significantly in light as well as in darkness. In a control condition without pressure for adaptation (only intermittent testing of the VOR gain over a period of 2.5 h), the gain of the VOR was not significantly affected by similar injections of beta-adrenergic agents. We conclude that the noradrenergic system facilitates the adaptation of the VOR gain to retinal slip in rabbits without affecting the VOR gain directly. At least part of this influence is exerted through beta-receptors located in the cerebellar flocculus.     

Comparison of head thrust test with head autorotation test reveals that the vestibulo-ocular reflex is enhanced during voluntary head movements

OBJECTIVES: To compare 2 clinical tests of vestibular function, the head autorotation test (HART) and the head thrust test (HTT), and to determine why they give disparate results in patients with known unilateral vestibular deficiency (UVD) due to labyrinthectomy. METHODS: We used scleral coils to measure the horizontal (yaw) vestibulo-ocular reflex (VOR) in 5 healthy human subjects and in 11 patients who underwent labyrinthectomy. We used 2 paradigms. Using HART, subjects visually fixated a target during self-generated, swept-frequency, sinusoidal, horizontal head rotations. Using HTT, patients fixated the target during horizontal head thrusts delivered randomly in direction and time. RESULTS: In subjects without UVD, eye movements were almost perfectly compensatory for both paradigms. In subjects with UVD, VOR gain for ipsilesional head thrusts was low for both paradigms, but significantly (P<.001) higher (less abnormal) for HART (0.60 +/- 0.13) than for HTT (0.14 +/- 0.13). Contralesional gain was reduced for both, to 0.64 +/- 0.20 for HART and to 0.57 +/- 0.17 for HTT. Because ipsilesional and contralesional gains were not statistically different for HART (P =.69), comparison of VOR gains for half-cycle responses to the HART stimulus could not reliably identify the side of the known lesion. In contrast, HTT consistently identified the side of the lesion for all subjects with UVD. To investigate whether preprogramming contributes to the boost in VOR as measured by HART, we compared the gain and response delay of eye movements during actively self-generated and passively received head thrusts. For subjects without UVD, response delays were shorter for active (6 +/- 1 milliseconds) than for passive (12 +/- 1 milliseconds) HTT. For ipsilesional rotations of subjects with UVD, active HTT yielded a significantly higher gain (0.44 +/- 0.20) (P<.001) and a shorter delay (15 +/- 6 milliseconds) (P<.001) than did passive HTT (0.14 +/- 0.13 and 37 +/- 15 milliseconds, respectively). Contralesional test results revealed a similar performance boost for active head movements. Data are given as mean +/- SD. CONCLUSION: When comparison of half-cycle gains is used to identify the lesion side, self-generated predictable head movement paradigms, such as HART and active HTT, are less accurate than passive HTT in the characterization of UVD, in part because preprogramming can augment the VOR during voluntary head movements.     

Analysis of human vestibulo-ocular reflex during active head movements

The human vestibulo-ocular reflex (VOR) was investigated during active head movements utilizing spectral analysis techniques in order to extract phase and gain characteristics for the most natural stimulus conditions. Three different experimental conditions were examined: 1) head rotation in darkness to obtain data permitting a comparison with that mode of VOR analysis which has been mose frequently employed in the past; 2) head rotation while fixating a stationary target light in order to quantify natural compensatory eye movements; and 3) head rotation while fixating a target light which moved with the head as a fast method for the quantification of visuo-vestibular interaction. High frequency head rotation in darkness yielded gains not significantly different from unity-unlike previously reported results for passive rotation (Benson, 1970; Keller, 1978). Possible mechanisms which might explain these results are discussed.     

Pursuit opposite to the vestibulo-ocular reflex (VOR) during sinusoidal stimulation in humans

Pursuit opposite to a simultaneously activated vestibulo-ocular reflex (VOR) was tested during passive sinusoidal body oscillations (0.1-1.0 Hz, amplitudes 10-80 degrees) about the vertical axis in 4 healthy humans, while subjects were asked to pursue a small target moving in phase with the rotating chair with about half its amplitude relative to the head and 1.5 times its amplitude with respect to space. The decrease in gain of the pursuit opposite to the VOR occurred at lower stimulus frequency, stimulus velocity and stimulus acceleration than pure visual pursuit when gain was calculated in relation to target motion in head coordinates. It resembles that of pure pursuit when calculated in relation to target motion in space (earth coordinates, sum of the displacements of the mirror image and of the chair) thus taking the oppositely directed VOR into account. The data fit the assumption of a linear interaction of the VOR (in counterphase) and pursuit.     

Vestibular rehabilitation using visual displays: preliminary study

OBJECTIVES/HYPOTHESIS: Interactive computer displays can alter vestibular function. We hypothesized that by placing a vestibulopathic subject with chronic vertigo in a computer scene, slowing the visual scene motion to a rate slightly higher than their vestibuloocular reflex (VOR) gain, and gradually speeding up the scene, we could cause VOR improvement and symptom reduction. STUDY DESIGN: Randomized, nonblinded treatment/control study. METHODS: Subjects were selected for VOR gain less than 0.5 at 0.16, 0.32, or 0.64 Hz. They wore a computer display that interacted with the movement of their head. The scene magnification controlling image motion was initially set approximately 5% higher than the VOR gain. Subjects had interaction tasks for 10 sessions of 30 minutes twice daily for 5 days. The scene magnification was gradually increased over the sessions. Control subjects had a similar procedure but were shown a normal, x 1.0 magnification for each interaction session. RESULTS: Nine subjects and six control subjects were tested. Test subjects showed an average increase in VOR gain of 0.05 at 0.16 Hz, 0.048 at 0.32 Hz, and 0.098 at 0.64 Hz. In contrast, control subjects showed a decrease of 0.008 at 0.16 Hz, an increase of 0.016 at 0.32 Hz, and a decrease of 0.058 at 0.64 Hz. Improvement remained after 1 week but at a lower level than immediately after testing. Subject Dizziness Handicap Inventory scores decreased by 2.8 from 38.5 in the first week. Control subjects reported no symptom improvement. CONCLUSION: Immersive computer environments can improve VOR function and reduce vertigo.     

Adaptation of the vertical vestibulo-ocular reflex in cats during low-frequency vertical rotation

Objective

We examined plastic changes in the vestibulo-ocular reflex (VOR) during low-frequency vertical head rotation, a condition under which otolith inputs from the vestibular system are essential for VOR generation.

Dynamics of the vestibulo-ocular reflex in patients with the horizontal semicircular canal variant of benign paroxysmal positional vertigo

Objective Two types of direction-changing positional nystagmus, the geotropic and apogeotropic variants, are observed in patients with the horizontal semicircular canal (HSCC) type of benign paroxysmal positional vertigo (H-BPPV). In this study, we assessed the dynamics of the vestibulo-ocular reflex (VOR) of the HSCC in patients with H-BPPV.

Material and Methods Patients were rotated about the earth-vertical axis at frequencies of 0.1, 0.3, 0.5, 0.7 and 1.0 Hz with a maximum angular velocity of 50°/s. Eye movements were recorded on a video imaging system using an infrared charge-coupled device (CCD) camera, and our new technique for analyzing the rotation vector of eye movements in three dimensions was used.

Results In the patients with geotropic positional nystagmus, there were no differences in VOR gain between rotation to the affected and unaffected sides at frequencies of 0.1–1.0 Hz. Although no differences in VOR gain at frequencies of 0.3–1.0 Hz were noticed in patients with apogeotropic positional nystagmus, the VOR gain at 0.1 Hz was significantly smaller on rotation to the affected compared to the unaffected side.

Conclusion The results indicate that cupulolithiasis in the HSCC affected the dynamics of the HSCC-ocular reflex at 0.1 Hz, but not at higher frequencies, and that canalolithiasis in the HSCC does not change the VOR gain of the HSCC at any frequency. It is suggested that cupulolithiasis causes transient impairment of HSCC function by means of its mechanical restriction of movements of the cupula.     

Fixation suppression of the vestibulo-ocular reflex (VOR) during sinusoidal stimulation in humans as related to the performance of the pursuit system

Fixation suppression (FS) of the vestibulo-ocular reflex (VOR) was tested during passive sinusoidal body rotation with a frequency of 0.1 to 1.0 Hz and stimulus amplitudes ranging from 10 degrees to 240 degrees. To test whether FS can be explained by an internal pursuit signal opposite to the VOR, pursuit and the VOR under different instructional sets were studied. Both pursuit and FS decrease with increasing frequency and stimulus amplitude and seem to be limited by stimulus acceleration. Gains in FS calculated on the basis of the VOR during mental arithmetic correspond closely to the frequency and amplitude dependent pursuit gain, suggesting that an internal pursuit signal plays a major role in VOR suppression.     

Core Body Temperature Effects on the Mouse Vestibulo-ocular Reflex

Core body temperature has been shown to affect vestibular end-organ and nerve afferents so that their resting discharge rate and sensitivity increase with temperature. Our aim was to determine whether these changes observed in extracellular nerve recordings of anaesthetized C57BL/6 mice corresponded to changes in the behavioural vestibulo-ocular reflex (VOR) of alert mice. The VOR drives eye rotations to keep images stable on the retina during head movements. We measured the VOR gain (eye velocity/head velocity) and phase (delay between vestibular stimulus and response) during whole-body sinusoidal rotations ranging 0.5–12 Hz with peak velocity 50 or 100 °/s in nine adult C57BL/6 mice. We also measured the VOR during whole-body transient rotations with acceleration 3000 or 6000 °/s² reaching a plateau of 150 or 300 °/s. These measures were obtained while the mouse’s core body temperature was held at either 32 or 37 °C for at least 35 min before recording. The temperature presentation order and timing were pseudo-randomized. We found that a temperature increase from 32 to 37 °C caused a significant increase in sinusoidal VOR gain of 17 % (P < 0.001). Temperature had no other effects on the behavioural VOR. Our data suggest that temperature effects on regularly firing afferents best correspond to the changes that we observed in the VOR gain.     

Manual rotational testing of the vestibulo-ocular reflex

OBJECTIVES/HYPOTHESIS: Manual whole-body and head-on-body rotational testing of the vestibuloocular reflex (VOR) is comparable to conventional rotary chair methods with and without visual fixation from 0.025 to 1 Hz. STUDY DESIGN: Summary of four previously published trials from our laboratory and a fifth prospective blinded study comparing whole-body and head-on-body rotation with rotational chair results from 0.025 to 1 Hz in 10 patients with bilateral vestibular dysfunction. METHODS: Subjects were fitted with standard electro-oculogram (EOG) electrodes and placed in the rotary chair for testing at 0.025, 0.05, 0.1, 0.25, 0.5, and 1 Hz in the dark (VOR) and in the light with a stationary target (VVOR). They were then placed in an otolaryngology examination, chair where an adjustable headband containing the velocity sensor and an opaque visor were placed on the forehead. Whole-body rotational trials from 0.025 to 1 Hz and both passive and active head-on-body trials from 0.25 to 1 Hz were performed with and without visual fixation. Data from each frequency were analyzed cycle-by-cycle and averaged for gain, phase, and asymmetry. These values were then compared to the results obtained during rotational chair testing. RESULTS: Throughout the five studies, no systematic differences were noted between the manual rotational methods and the rotary chair results. Specifically, no consistent effect of volition or cervico-ocular reflex (COR) enhancement was demonstrated. CONCLUSIONS: Manual rotational testing is a reliable technique for measuring the VOR up to 1 Hz as compared with standard rotary chair methods. Advantages to this technique include portability, lower equipment costs, and potential application up to 6 Hz using head-on-body rotation.