scholarly journals Normal Performance and Expression of Learning in the Vestibulo-Ocular Reflex (VOR) at High Frequencies

2005 ◽  
Vol 93 (4) ◽  
pp. 2028-2038 ◽  
Author(s):  
Ramnarayan Ramachandran ◽  
Stephen G. Lisberger
Keyword(s):  
Phase Shift ◽  
Harmonic Distortion ◽  
Head Movements ◽  
High Frequencies ◽  
Head Velocity ◽  
Ocular Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Eye Velocity ◽  
Normal Performance

The rotatory vestibulo-ocular reflex (VOR) keeps the visual world stable during head movements by causing eye velocity that is equal in amplitude and opposite in direction to angular head velocity. We have studied the performance of the VOR in darkness for sinusoidal angular head oscillation at frequencies ranging from 0.5 to 50 Hz. At frequencies of ≥25 Hz, the harmonic distortion of the stimulus and response were estimated to be <14 and 22%, respectively. We measured the gain of the VOR (eye velocity divided by head velocity) and the phase shift between eye and head velocity before and after adaptation with altered vision. Before adaptation, VOR gains were close to unity for frequencies ≤20 Hz and increased as a function of frequency reaching values of 3 or 4 at 50 Hz. Eye velocity was almost perfectly out of phase with head velocity for frequencies ≤12.5 Hz, and lagged perfect compensation increasingly as a function of frequency. After adaptive modification of the VOR with magnifying or miniaturizing optics, gain showed maximal changes at frequencies <12.5 Hz, smaller changes at higher frequencies, and no change at frequencies larger than 25 Hz. Between 15 and 25 Hz, the phase of eye velocity led the unmodified VOR by as much as 50° when the gain of the VOR had been decreased, and lagged when the gain of the VOR had been increased. We were able to reproduce the main features of our data with a two-pathway model of the VOR, where the two pathways had different relationships between phase shift and frequency.

Occupation and Visual/Vestibular Interaction in Vestibular Rehabilitation

1995 ◽  
Vol 112 (4) ◽  
pp. 526-532 ◽  
Author(s):  
Helen Cohen ◽  
Maureen Kane-Wineland ◽  
Laura V. Miller ◽  
Catherine L. Hatfield
Keyword(s):  
Motor Skills ◽  
Therapy Group ◽  
Exercise Program ◽  
Head Movements ◽  
Vestibular Disorders ◽  
Essential Factor ◽  
Gross Motor Skills ◽  
Ocular Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex

Otolaryngologists often prescribe head movement exercise programs for patients with vestibular disorders, although the effectiveness of these programs and the critical features of the exercises are poorly understood. Because many patients who dislike exercising do not follow through with their exercises, alternatives to the traditional repetitive exercises would be useful. Subjects diagnosed with vestibular disorders were treated for 6 weeks with either an outpatient exercise program that incorporated interesting, purposeful activities or a simple home program of head movements, comparable with the exercises otolaryngologists often give their patients when they do not refer to rehabilitation. Both treatments incorporated repetitive head movements in all planes in space, graduated in size and speed. Subjects were all tested before and after treatment with standard measures of vestibulo-ocular reflex and balance, level of vertigo, gross motor skills, and self-care independence. Subjects in both groups improved significantly on the functional measures, with slightly greater improvements in the occupational therapy group. The results were maintained 3 months after the cessation of intervention. These data suggest that graded purposeful activities are a useful alternative for treating this patient population and that the essential factor in any exercise program is the use of repetitive head movements.

Predictive Mechanisms of Head-Eye Coordination and Vestibulo-Ocular Reflex Suppression in Humans

1992 ◽  
Vol 2 (3) ◽  
pp. 193-212 ◽  
Author(s):  
G.R. Barnes ◽  
M.A. Grealy
Keyword(s):  
Peak Velocity ◽  
Human Subjects ◽  
Head Movements ◽  
Whole Body ◽  
Head Velocity ◽  
The Gaze ◽  
Ocular Reflex ◽  
Sinusoidal Motion ◽  
Smooth Component ◽  
Vestibulo Ocular Reflex

Head and eye movements of human subjects have been recorded during head-free pursuit in the horizontal plane of a target executing sinusoidal motion at a frequency of 0.26 to 0.78 Hz and a peak velocity of ±96∘/s. The target was not presented continuously but was exposed for brief durations of 120 to 320 ms as it passed through the centre of the visual field at peak velocity. This technique allowed the timing of each response to be assessed in relation to the onset of target appearance. During the first 3 to 4 target presentations, there was a progressive buildup of both head velocity and the smooth component of gaze velocity, while, simultaneously, the responses became more phase-advanced with respect to target onset. In the steady state, similar temporal response trajectories were observed for head and gaze velocity, which were initiated approximately 500 ms prior to target on-set, rose to a peak that increased with the duration of target exposure, and then decayed with a time constant of 0.5 to 1 s. Whenever the target failed to appear as expected, the gaze and head velocity trajectories continued to be made, indicating that predictive suppression of the vestibulo-ocular reflex (VOR) was taking place in darkness. In a further experiment, subjects attempted to suppress the VOR during whole body oscillation at 0.2 or 0.4 Hz on a turntable by fixating, a head-fixed target that appeared for 10 to 160 ms at the time of peak head velocity. Again, VOR suppression was initiated prior to target appearance in the same manner as for natural head movements, and when the target suddenly disappeared but rotation continued, predictive VOR suppression was observed in darkness. The similarity of these predictive effects to those obtained previously for head-fixed pursuit provides further support for the hypothesis that both pursuit and visual suppression of the VOR are controlled primarily by identical visual feedback mechanisms.

Vestibular adaptation to centrifugation does not transfer across planes of head rotation

2008 ◽  
Vol 18 (1) ◽  
pp. 25-37
Author(s):  
Ian Garrick-Bethell ◽  
Thomas Jarchow ◽  
Heiko Hecht ◽  
Laurence R. Young
Keyword(s):  
Sagittal Plane ◽  
Head Rotation ◽  
Head Movements ◽  
Control Group ◽  
Illusory Motion ◽  
Ocular Reflex ◽  
Before And After ◽  
Out Of Plane ◽  
Vestibulo Ocular Reflex ◽  
Axis Rotation

Out-of-plane head movements performed during fast rotation produce non-compensatory nystagmus, sensations of illusory motion, and often motion sickness. Adaptation to this cross-coupled Coriolis stimulus has previously been demonstrated for head turns made in the yaw (transverse) plane of motion, during supine head-on-axis rotation. An open question, however, is if adaptation to head movements in one plane of motion transfers to head movements performed in a new, unpracticed plane of motion. Evidence of transfer would imply the brain builds up a generalized model of the vestibular sensory-motor system, instead of learning a variety of individual input/output relations separately. To investigate, over two days 9 subjects performed pitch head turns (sagittal plane) while rotating, before and after a series of yaw head turns while rotating. A Control Group of 10 subjects performed only the pitch movements. The vestibulo-ocular reflex (VOR) and sensations of illusory motion were recorded in the dark for all movements. Upon comparing the two groups we failed to find any evidence of transfer from the yaw plane to the pitch plane, suggesting that adaptation to cross-coupled stimuli is specific to the particular plane of head movement. The findings have applications for the use of centrifugation as a possible countermeasure for long duration spaceflight. Adapting astronauts to unconstrained head movements while rotating will likely require exposure to head movements in all planes and directions.

Visual-Vestibular Interaction with Telescopic Spectacles

1991 ◽  
Vol 1 (3) ◽  
pp. 263-277 ◽  
Author(s):  
J.L. Demer ◽  
J. Goldberg ◽  
F.I. Porter ◽  
H.A. Jenkins ◽  
K. Schmidt
Keyword(s):  
Eye Movements ◽  
Retinal Image ◽  
Head Rotation ◽  
Normal Subjects ◽  
Head Movements ◽  
Head Velocity ◽  
Ocular Reflex ◽  
Clear Vision ◽  
Visual Vestibular Interaction ◽  
Vestibulo Ocular Reflex

Vestibularly and visually driven eye movements interact to compensate for head movements to maintain the necessary retinal image stability for clear vision. The wearing of highly magnifying telescopic spectacles requires that such compensatory visual-vestibular interaction operate in a quantitative regime much more demanding than that normally encountered. We employed electro-oculography to investigate the effect of wearing of 2×, 4×, and 6× binocular telescopic spectacles on visual-vestibular interactions during sinusoidal head rotation in 43 normal subjects. All telescopic spectacle powers produced a large, immediate increase in the gain (eye velocity/head velocity) of compensatory eye movements, called the visual-vestibulo-ocular reflex (VVOR). However, the amount of VVOR gain augmentation became limited as spectacle magnification and the amplitude of head velocity increased. Optokinetic responses during wearing of telescopic spectacles exhibited a similar nonlinearity with respect to stimulus amplitude and spectacle magnification. Computer simulation was used to demonstrate that the nonlinear response of the VVOR with telescopic spectacles is a result of nonlinearities in visually guided tracking movements. Immediate augmentation of VVOR gain by telescopic spectacles declined significantly with increasing age in the subject pool studied. Presentation of unmagnified visual field peripheral to the telescopic spectacles reduced the immediate VVOR gain-enhancing effect of central magnified vision. These results imply that the VVOR may not be adequate to maintain retinal image stability during head movements when strongly magnifying telescopic spectacles are worn.

A review of the effects of space flight on the asymmetry of vertical optokinetic and vestibulo-ocular reflexes

2003 ◽  
Vol 13 (4-6) ◽  
pp. 255-263
Author(s):  
Gilles Clément
Keyword(s):  
Phase Velocity ◽  
Optokinetic Nystagmus ◽  
Visual Stimulation ◽  
Head Movements ◽  
Slow Phase ◽  
Eye Position ◽  
Slow Phase Velocity ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Eye Velocity

Prolonged microgravity during orbital flight is a unique way to modify the otolith inputs and to determine the extent of their contribution to the vertical vestibulo-ocular reflex (VOR) and optokinetic nystagmus (OKN). This paper reviews the data collected on 10 astronauts during several space missions and focuses on the changes in the up-down asymmetry. Both the OKN elicited by vertical visual stimulation and the active VOR elicited by voluntary pitch head movements showed an asymmetry before flight, with upward slow phase velocity higher than downward slow phase velocity. Early in-flight, this asymmetry was inverted, and a symmetry of both responses was later observed. An upward shift in the vertical mean eye position in both OKN and VOR suggests that these effects may be related to otolith-dependent changes in eye position which, in themselves, affect slow phase eye velocity.

scholarly journals Human vestibulo-ocular reflex adaptation is frequency selective

2019 ◽  
Vol 122 (3) ◽  
pp. 984-993 ◽  
Author(s):  
Carlo N. Rinaudo ◽  
Michael C. Schubert ◽  
William V. C. Figtree ◽  
Christopher J. Todd ◽  
Americo A. Migliaccio
Keyword(s):  
High Frequency ◽  
Head Rotation ◽  
Head Movements ◽  
Head Impulse ◽  
Ocular Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation ◽  
Frequency Selective ◽  
Head Rotations

The vestibulo-ocular reflex (VOR) is the only system that maintains stable vision during rapid head rotations. The VOR gain (eye/head velocity) can be trained to increase using a vestibular-visual mismatch stimulus. We sought to determine whether low-frequency (sinusoidal) head rotation during training leads to changes in the VOR during high-frequency head rotation testing, where the VOR is more physiologically relevant. We tested eight normal subjects over three sessions. For training protocol 1, subjects performed active sinusoidal head rotations at 1.3 Hz while tracking a laser target, whose velocity incrementally increased relative to head velocity so that the VOR gain required to stabilize the target went from 1.1 to 2 over 15 min. Protocol 2 was the same as protocol 1, except that head rotations were at 0.5 Hz. For protocol 3, head rotation frequency incrementally increased from 0.5 to 2 Hz over 15 min, while the VOR gain required to stabilize the target was kept at 2. We measured the active and passive, sinusoidal (1.3Hz) and head impulse VOR gains before and after each protocol. Sinusoidal and head impulse VOR gains increased in protocols 1 and 3; however, although the sinusoidal VOR gain increase was ~20%, the related head impulse gain increase was only ~10%. Protocol 2 resulted in no-gain adaptation. These data show human VOR adaptation is frequency selective, suggesting that if one seeks to increase the higher-frequency VOR response, i.e., where it is physiologically most relevant, then higher-frequency head movements are required during training, e.g., head impulses. NEW & NOTEWORTHY This study shows that human vestibulo-ocular reflex adaptation is frequency selective at frequencies >0.3 Hz. The VOR in response to mid- (1.3 Hz) and high-frequency (impulse) head rotations were measured before and after mid-frequency sinusoidal VOR adaptation training, revealing that the mid-frequency gain change was higher than high-frequency gain change. Thus, if one seeks to increase the higher-frequency VOR response, where it is physiologically most relevant, then higher-frequency head movements are required during training.

Absence of a vergence-mediated vestibulo-ocular reflex gain increase does not preclude adaptation

2021 ◽  
pp. 1-9
Author(s):  
Béla Büki (Family name Büki) ◽  
László T. Tamás (Family name Tamás) ◽  
Christopher J. Todd ◽  
Michael C. Schubert ◽  
Americo A. Migliaccio
Keyword(s):  
Laser Target ◽  
Head Velocity ◽  
Gain Enhancement ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation ◽  
Reflex Gain ◽  
Head Impulses ◽  
Eye Velocity ◽  
Vestibular Pathways

BACKGROUND: The gain (eye-velocity/head-velocity) of the angular vestibuloocular reflex (aVOR) during head impulses can be increased while viewing near-targets and when exposed to unilateral, incremental retinal image velocity error signals. It is not clear however, whether the tonic or phasic vestibular pathways mediate these gain increases. OBJECTIVE: Determine whether a shared pathway is responsible for gain enhancement between vergence and adaptation of aVOR gain in patients with unilateral vestibular hypofunction (UVH). MATERIAL AND METHODS: 20 patients with UVH were examined for change in aVOR gain during a vergence task and after 15-minutes of ipsilesional incremental VOR adaptation (uIVA) using StableEyes (a device that controls a laser target as a function of head velocity) during horizontal passive head impulses.A 5 % aVOR gain increase was defined as the threshold for significant change. RESULTS: 11/20 patients had >5% vergence-mediated gain increase during ipsi-lesional impulses. For uIVA, 10/20 patients had >5% ipsi-lesional gain increase. There was no correlation between the vergence-mediated gain increase and gain increase after uIVA training. CONCLUSION: Vergence-enhanced and uIVA training gain increases are mediated by separate mechanisms and/or vestibular pathways (tonic/phasic).The ability to increase the aVOR gain during vergence is not prognostic for successful adaptation training.

Ocular Motor Responses to Abrupt Interaural Head Translation in Normal Humans

2003 ◽  
Vol 90 (2) ◽  
pp. 887-902 ◽  
Author(s):  
Stefano Ramat ◽  
David S. Zee
Keyword(s):  
Viewing Distance ◽  
Head Acceleration ◽  
Ideal Behavior ◽  
Head Velocity ◽  
Ocular Reflex ◽  
High Acceleration ◽  
Median Position ◽  
Vestibulo Ocular Reflex ◽  
Normal Humans ◽  
Eye Velocity

We characterized the interaural translational vestibulo-ocular reflex (tVOR) in 6 normal humans to brief (∼200 ms), high-acceleration (0.4–1.4 g) stimuli, while they fixed targets at 15 or 30 cm. The latency was 19 ± 5 ms at 15-cm and 20 ± 12 ms at 30-cm viewing. The gain was quantified using the ratio of actual to ideal behavior. The median position gain (at time of peak head velocity) was 0.38 and 0.37, and the median velocity gain, 0.52 and 0.62, at 15- and 30-cm viewing, respectively. These results suggest the tVOR scales proportionally at these viewing distances. Likewise, at both viewing distances, peak eye velocity scaled linearly with peak head velocity and gain was independent of peak head acceleration. A saccade commonly occurred in the compensatory direction, with a greater latency (165 vs. 145 ms) and lesser amplitude (1.8 vs. 3.2 deg) at 30- than 15-cm viewing. Even with saccades, the overall gain at the end of head movement was still considerably undercompensatory (medians 0.68 and 0.77 at 15- and 30-cm viewing). Monocular viewing was also assessed at 15-cm viewing. In 4 of 6 subjects, gains were the same as during binocular viewing and scaled closely with vergence angle. In sum the low tVOR gain and scaling of the response with viewing distance and head velocity extend previous results to higher acceleration stimuli. tVOR latency (∼20 ms) was lower than previously reported. Saccades are an integral part of the tVOR, and also scale with viewing distance.

The Vestibular and Optokinetic Systems

2008 ◽  
Author(s):  
Agnes Wong
Keyword(s):  
Visual Information ◽  
Brain Structures ◽  
Head Movements ◽  
Head Motion ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Position And Orientation ◽  
Change Position ◽  
Direction Information ◽  
Eye Velocity

The vestibulo-ocular and optokinetic reflexes are the earliest eye movements to appear phylogenetically. The vestibulo-ocular reflex (VOR) stabilizes retinal images during head motion by counter-rotating the eyes at the same speed as the head but in the opposite direction. Information about head motion passes from the vestibular sensors in the inner ear to the VOR circuitry within the brainstem, which computes an appropriate eye velocity command. The eyes, confined in their bony orbits, normally do not change position, and their motion relative to the head is restricted to a change in orientation. However, the head can both change position and orientation relative to space. Thus, the function of the VOR is to generate eye orientation that best compensates for changes in position and orientation of the head. Because the drive for this reflex is vestibular rather than visual, it operates even in darkness. To appreciate the benefits of having our eyes under vestibular and not just visual control, hold a page of text in front of you, and oscillate it back and forth horizontally at a rate of about two cycles per second. You will find that the text is blurred. However, if you hold the page still and instead oscillate your head at the same rate, you will be able to read the text clearly. This is because when the page moves, only visual information is available. Visual information normally takes about 100 msec to travel from the visual cortices, through a series of brain structures, to the ocular motoneurons that move the eyes. This delay is simply too long for the eyes to keep up with the oscillating page. However, when the head moves, both vestibular and visual information are available. Vestibular information takes only about 7–15 msec to travel from the vestibular sensors, through the brainstem, to the ocular motoneurons. With this short latency, the eyes can easily compensate for the rapid oscillation of the head. Thus, damages to the vestibular system often cause oscillopsia, an illusion of motion in the stationary environment, especially during head movements.

DYNAMICS OF COMPENSATORY EYE MOVEMENT CONTROL: AN OPTIMAL ESTIMATION ANALYSIS OF THE VESTIBULO-OCULAR REFLEX

1989 ◽  
Vol 01 (01) ◽  
pp. 23-29 ◽  
Author(s):  
Michael G. Paulin ◽  
Mark E. Nelson ◽  
James M. Bower
Keyword(s):  
Eye Movements ◽  
Phase Shift ◽  
Transfer Function ◽  
Movement Control ◽  
Optimal Estimation ◽  
Head Movements ◽  
Visual Images ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Unity Gain

Head movements in vertebrates give rise to involuntary eye movements that stabilize visual images on the retina. Previous models of the vestibulo-ocular reflex (VOR), one of the neural mechanisms responsible for stabilizing the eyes during head movements, have assumed that the VOR transfer function should have unity gain and 180° phase shift. Experimental measurements of VOR gain and phase, however, exhibit frequency dependencies that are not easily interpreted within the framework of existing models. We reanalyze the problem of VOR control using stochastic optimal estimation theory and show that VOR dynamics, in general, should differ from the "ideal" unity-gain, 180° phase shift transfer function. We illustrate this approach by computing the optimal VOR transfer function for a simple, second-order dynamical model of a head–neck system. Despite its simplicity, this model is able to give some insight into the dynamical properties of the VOR. In particular, it qualitatively reproduces an experimentally observed gain peak in monkey VOR at high frequencies. The model also predicts that the gain and phase characteristics of the optimal VOR transfer function should depend on the spectrum of natural head movements, possibly giving rise to species-dependent and gait-dependent differences in the VOR transfer function. We suggest that the applicability of optimal estimation extends beyond the control of compensatory eye movements and that it is probably a universal component of movement control in the nervous system.

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