scholarly journals Tuning of gravity-dependent and gravity-independent vertical angular VOR gain changes by frequency of adaptation

2012 ◽  
Vol 107 (12) ◽  
pp. 3349-3356 ◽  
Author(s):  
Sergei B. Yakushin
Keyword(s):  
Tuning Curve ◽  
Phase Relationship ◽  
Independent Component ◽  
Head Orientation ◽  
Ocular Reflex ◽  
Tuning Width ◽  
Dependent Component ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Gain Change

The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1–4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz.

Adaptation of the Vestibulo-Ocular Reflex with the Head in Different Orientations and Positions Relative to the Axis of Body Rotation

1993 ◽  
Vol 3 (2) ◽  
pp. 181-195
Author(s):  
Caroline Tiliket ◽  
Mark Shelhamer ◽  
H. Stevie Tan ◽  
David S. Zee
Keyword(s):  
Training Session ◽  
Head Orientation ◽  
Neural Integrator ◽  
Body Rotation ◽  
Ocular Reflex ◽  
Vestibular Adaptation ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation ◽  
Static Head

We investigated the influence of static head orientation and position, relative to the axis of body rotation, upon vestibular adaptation. With the head centered, displaced anterior to the axis of body rotation, or tilted 40∘ to 45∘ in roll or pitch, the gain of the vestibulo-ocular reflex (VOR) was trained (to go either up or down) for one hour using artificial manipulation of the visual surround to produce a visual-vestibular mismatch. Before and after each training session, the VOR was measured in darkness with the head in the training as well as in several non-training positions. We found that transfer of VOR adaptation to non-training positions was almost complete when comparing head eccentric versus head-centered rotations. For tilts, however, transfer of VOR learning was far less complete suggesting that static otolith signals provide a strong contextual cue that gates the expression of an adaptive VOR response. Finally, following training to increase than VOR, gain was greater for centripetally than centrifugally directed slow phases. Centripetally directed postsaccadic drift also developed. These fundings imply that the gain increase paradigm also leads to abnormal function of the velocity-to-position neural integrator, which holds eccentric positions of gaze.

Effect of Incisions in the Brainstem Commissural Network on the Short-Term Vestibulo-Ocular Adaptation of the CAT

1991 ◽  
Vol 1 (3) ◽  
pp. 223-239
Author(s):  
G. Cheron
Keyword(s):  
Low Frequency ◽  
Adaptive Plasticity ◽  
Training Procedure ◽  
Optokinetic Response ◽  
Mean Values ◽  
Ocular Reflex ◽  
Optokinetic Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation

This study was intended to test the adaptive plasticity of the vestibulo-ocular reflex before and after either a midsagittal or parasagittal incision in the brainstem. Eye movements were measured with the electromagnetic search coil technique during the vestibulo-ocular reflex (VORD) in the dark, the optokinetic reflex (OKN), and the visuo-vestibular adaptive training procedure. Two types of visual-vestibular combined stimulation were applied by means of low frequency stimuli (0.05 to 0.10 Hz). In order to increase or decrease the VORD gain, the optokinetic drum was oscillated either 180∘ out-of-phase or in-phase with the vestibular stimulus turntable. This “training” procedure was applied for 4 hours. Initial measurements of the VORD were normal with a mean gain value of 0.92 ± 0.08. After 4 hours of “training” with the out-of-phase condition (180∘), VORD gain reached mean values of 1.33 ± 0.11 (n = 6 cats). In the in-phase combination, the mean VORD gain decreased from 1.0 to 0.63 ± 0.02 (n = 2 cats). No significant change of VORD phase was found in any of the cats. Midsagittal or parasagittal pontomedullary brainstem incisions were performed in 4 cats. Recovery of the VOR was tested on the 2nd, 7th, and 30th day after operation. After the 30th day, recovery of the VORD gain stabilized at about 66% of the initial preoperative value. At this stage of the recovery, the optokinetic response (OKN) of the midsagittal-Iesioned cats was practically normal: in the parasagittal-Jesioned cats, the postoperative OKN responses were asymmetric. After stabilization of recovery, lesioned cats were trained with the same adaptation procedure. Although the direct effect of the visuo-vestibular combined stimulation during the training was still operative in all lesioned cats, the adaptive plasticity was completely abolished by the lesions. These results suggest that the commissural brainstem network may play a crucial role in the acquisition of the forced VOR adaptation.

Effects of adaptation of vestibulo-ocular reflex function on manual target localization

2000 ◽  
Vol 10 (2) ◽  
pp. 75-86 ◽  
Author(s):  
Jacob J. Bloomberg ◽  
Lauren A. Merkle ◽  
Susan R. Barry ◽  
William P. Huebner ◽  
Helen S. Cohen ◽  
...  
Keyword(s):  
Adaptive Modulation ◽  
Normal Subjects ◽  
Target Localization ◽  
Whole Body ◽  
Spatial Coding ◽  
Ocular Reflex ◽  
Manual Responses ◽  
Vestibular Cues ◽  
Before And After ◽  
Vestibulo Ocular Reflex

The goal of the present study was to determine if adaptive modulation of vestibulo-ocular reflex (VOR) function is associated with commensurate alterations in manual target localization. To measure the effects of adapted VOR on manual responses we developed the Vestibular-Contingent Pointing Test (VCP). In the VCP test, subjects pointed to a remembered target following passive whole body rotation in the dark. In the first experiment, subjects performed VCP before and after wearing 0.5X minifying lenses that adaptively attenuate horizontal VOR gain. Results showed that adaptive reduction in horizontal VOR gain was accompanied by a commensurate change in VCP performance. In the second experiment, bilaterally labyrinthine deficient (LD) subjects were tested to confirm that vestibular cues were central to the spatial coding of both eye and hand movements during VCP. LD subjects performed significantly worse than normal subjects. These results demonstrate that adaptive change in VOR can lead to alterations in manual target localization.

scholarly journals Kinematic Principles of Primate Rotational Vestibulo-Ocular Reflex II. Gravity-Dependent Modulation of Primary Eye Position

1997 ◽  
Vol 78 (4) ◽  
pp. 2203-2216 ◽  
Author(s):  
Bernhard J. M. Hess ◽  
Dora E. Angelaki
Keyword(s):  
Slow Phase ◽  
Head Orientation ◽  
Eye Position ◽  
Single Plane ◽  
Fast Phase ◽  
Ocular Reflex ◽  
Listing's Plane ◽  
Vestibulo Ocular Reflex ◽  
Torsional Component ◽  
Listing’S Plane

Hess, Bernhard J. M. and Dora E. Angelaki. Kinematic principles of primate rotational vestibulo-ocular reflex. II. Gravity-dependent modulation of primary eye position. J. Neurophysiol. 78: 2203–2216, 1997. The kinematic constraints of three-dimensional eye positions were investigated in rhesus monkeys during passive head and body rotations relative to gravity. We studied fast and slow phase components of the vestibulo-ocular reflex (VOR) elicited by constant-velocity yaw rotations and sinusoidal oscillations about an earth-horizontal axis. We found that the spatial orientation of both fast and slow phase eye positions could be described locally by a planar surface with torsional variation of <2.0 ± 0.4° (displacement planes) that systematically rotated and/or shifted relative to Listing's plane. In supine/prone positions, displacement planes pitched forward/backward; in left/right ear-down positions, displacement planes were parallel shifted along the positive/negative torsional axis. Dynamically changing primary eye positions were computed from displacement planes. Torsional and vertical components of primary eye position modulated as a sinusoidal function of head orientation in space. The torsional component was maximal in ear-down positions and approximately zero in supine/prone orientations. The opposite was observed for the vertical component. Modulation of the horizontal component of primary eye position exhibited a more complex dependence. In contrast to the torsional component, which was relatively independent of rotational speed, modulation of the vertical and horizontal components of primary position depended strongly on the speed of head rotation (i.e., on the frequency of oscillation of the gravity vector component): the faster the head rotated relative to gravity, the larger was the modulation. Corresponding results were obtained when a model based on a sinusoidal dependence of instantaneous displacement planes (and primary eye position) on head orientation relative to gravity was fitted to VOR fast phase positions. When VOR fast phase positions were expressed relative to primary eye position estimated from the model fits, they were confined approximately to a single plane with a small torsional standard deviation (∼1.4–2.6°). This reduced torsional variation was in contrast to the large torsional spread (well >10–15°) of fast phase positions when expressed relative to Listing's plane. We conclude that primary eye position depends dynamically on head orientation relative to space rather than being fixed to the head. It defines a gravity-dependent coordinate system relative to which the torsional variability of eye positions is minimized even when the head is moved passively and vestibulo-ocular reflexes are evoked. In this general sense, Listing's law is preserved with respect to an otolith-controlled reference system that is defined dynamically by gravity.

Click-evoked vestibulo-ocular reflex

Neurology ◽  
2006 ◽  
Vol 66 (7) ◽  
pp. 1079-1087 ◽  
Author(s):  
S. T. Aw ◽  
M. J. Todd ◽  
G. E. Aw ◽  
J. S. Magnussen ◽  
I. S. Curthoys ◽  
...  
Keyword(s):  
Semicircular Canal ◽  
Rotation Axis ◽  
Head Orientation ◽  
Superior Canal Dehiscence ◽  
Ocular Reflex ◽  
Eye Rotation ◽  
Vestibulo Ocular Reflex ◽  
Low Threshold ◽  
Canal Dehiscence ◽  
Click Polarity

Background: An enlarged, low-threshold click-evoked vestibulo-ocular reflex (VOR) can be averaged from the vertical electro-oculogram in a superior canal dehiscence (SCD), a temporal bone defect between the superior semicircular canal and middle cranial fossa.Objective: To determine the origin and quantitative stimulus–response properties of the click-evoked VOR.Methods: Three-dimensional, binocular eye movements evoked by air-conducted 100-microsecond clicks (110 dB normal hearing level, 145 dB sound pressure level, 2 Hz) were measured with dual-search coils in 11 healthy subjects and 19 patients with SCD confirmed by CT imaging. Thresholds were established by decrementing loudness from 110 dB to 70 dB in 10-dB steps. Eye rotation axis of click-evoked VOR computed by vector analysis was referenced to known semicircular canal planes. Response characteristics were investigated with regard to enhancement using trains of three to seven clicks with 1-millisecond interclick intervals, visual fixation, head orientation, click polarity, and stimulation frequency (2 to 15 Hz).Results: In subjects and SCD patients, click-evoked VOR comprised upward, contraversive-torsional eye rotations with onset latency of approximately 9 milliseconds. Its eye rotation axis aligned with the superior canal axis, suggesting activation of superior canal receptors. In subjects, the amplitude was less than 0.01°, and the magnitude was less than 3°/second; in SCD, the amplitude was up to 60 times larger at 0.66°, and its magnitude was between 5 and 92°/second, with a threshold 10 to 40 dB below normal (110 dB). The click-evoked VOR magnitude was enhanced approximately 2.5 times with trains of five clicks but was unaffected by head orientation, visual fixation, click polarity, and stimulation frequency up to 10 Hz; it was also present on the surface electro-oculogram.Conclusion: In superior canal dehiscence, clicks evoked a high-magnitude, low-threshold, 9-millisecond-latency vestibulo-ocular reflex that aligns with the superior canal, suggesting superior canal receptor hypersensitivity to sound.

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.

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.

Dynamics of Adaptive Change in Human Vestibulo-Ocular Reflex Direction

1990 ◽  
Vol 1 (1) ◽  
pp. 23-29
Author(s):  
T.T. Khater ◽  
J.F. Baker ◽  
B.W. Peterson
Keyword(s):  
Eye Movements ◽  
Vertical Component ◽  
Onset Time ◽  
Eye Position ◽  
Complete Darkness ◽  
Ocular Reflex ◽  
Before And After ◽  
Adaptation Procedure ◽  
Vestibulo Ocular Reflex ◽  
Horizontal Rotations

Adaptive modification of vestibulo-ocular reflex (VOR) direction was characterized in humans by recording vertical and horizontal VOR eye movements during horizontal rotations in darkness at frequencies of 0.05 to 1 Hz before and after exposure to a VOR direction adaptation procedure. This procedure paired yaw horizontal vestibular rotation at 0.25 Hz with synchronous pitch vertical optokinetic motion. Saccades were removed from eye position records and VOR gain and phase were recorded. With an onset time constant of 36 min, the VOR measured during horizontal rotation in complete darkness acquired a vertical component in phase with the optokinetic stimulus presented during adaptation. The amplitude of this newly acquired vertical VOR component was maximal during rotation at the frequency of adaptation; at other frequencies, the amplitude was lower, but still significant. Unlike VOR direction adaptation in cats, the phase of the adaptive VOR component in humans did not show significant leads or lags at test frequencies below or above the adaptation frequency. These data suggest that, like the cat, the human VOR can be directionally adapted, and the pathways involving the adaptive component of the VOR are frequency specific.

Context-Specific Adaptation of the Gain of the Vestibulo-Ocular Reflex in Humans

1992 ◽  
Vol 2 (1) ◽  
pp. 89-96
Author(s):  
M. Shelhamer ◽  
D.A. Robinson ◽  
H.S. Tan
Keyword(s):  
Visual Feedback ◽  
Fixation Target ◽  
Situational Context ◽  
Specific Adaptation ◽  
Ocular Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Context Specific ◽  
S Peak ◽  
Gain Adjustment

Previous experiments show that altered visual feedback can change VOR gain. Such changes also presumably occur when eyeglasses are donned and doffed, or when bifocals are worn. In these cases, a nonvisual cue accompanies the required gain adjustment (frames on/off for eyeglasses, looking up/down for bifocals). We set out to show that a subject can establish two VOR gains, and to determine if one of the associated nonvisual cues alone is sufficient to subsequently determine which gain to employ. Each of three subjects sat in a rotating chair inside an OKN drum during 2 hours of sinusoidal rotation at 0.2 Hz, 30∘/s peak. For 10 minutes the chair and drum counterrotated, driving VOR gain toward 1.7, while subjects looked up 20∘. Chair and drum were then coupled for 10 minutes, driving gain toward zero, during which subjects looked down 20∘. This sequence was repeated for 2 hours. Immediately thereafter, VOR gains were measured while subjects looked alternately up and down, using 20∘ to 40∘ step rotations. A fixation target, presented before and after each step, provided accurate gain determination by measuring the size of the re-fixation saccade. Results show a consistent reduced VOR gain looking downward (average 6%) and increased gain looking upward (average 8%). We conclude that humans carn adjust their VOR gain dependent on a situational context; we speculate that this context can take many forms.

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