Analysis of Vestibulo-Ocular Reflex Using Sweep Frequency Active Head Movements

2015 ◽  
pp. 179-183 ◽  
Author(s):  
Dennis P. O�Leary ◽  
Linda L. Davis ◽  
Geli-Ann Kitsigianis
Keyword(s):  
Head Movements ◽  
Sweep Frequency ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex

Viewing Target Distance Influences the Vestibulo-Ocular Reflex Gain when Assessed Using the Video Head Impulse Test

2018 ◽  
Vol 23 (5) ◽  
pp. 285-289 ◽  
Author(s):  
Patricia Castro ◽  
Sara Sena Esteves ◽  
Florencia Lerchundi ◽  
David Buckwell ◽  
Michael A. Gresty ◽  
...  
Keyword(s):  
Head Movements ◽  
Target Distance ◽  
Head Impulse Test ◽  
Video Head Impulse Test ◽  
Gaze Stabilization ◽  
Head Impulse ◽  
Ocular Reflex ◽  
Significant Difference ◽  
Vestibulo Ocular Reflex ◽  
Reflex Gain

Gaze stabilization during head movements is provided by the vestibulo-ocular reflex (VOR). Clinical assessment of this reflex is performed using the video Head Impulse Test (vHIT). To date, the influence of different fixation distances on VOR gain using the vHIT has not been explored. We assessed the effect of target proximity on the horizontal VOR using the vHIT. Firstly, we assessed the VOR gain in 18 healthy subjects with 5 viewing target distances (150, 40, 30, 20, and 10 cm). The gain increased significantly as the viewing target distance decreased. A second experiment on 10 subjects was performed in darkness whilst the subjects were imagining targets at different distances. There were significant inverse relationships between gain and distance for both the real and the imaginary targets. There was a statistically significant difference between light and dark gains for the 20- and 40-cm distances, but not for the 150-cm distance. Theoretical VOR gains for different target distances were calculated and compared with those found in light and darkness. The increase in gain observed for near targets was lower than predicted by geometrical calculations, implying a physiological ceiling effect on the VOR. The VOR gain in the dark, as assessed with the vHIT, demonstrates an enhancement associated with a reduced target distance.

Eye-Head Movement Coordination: Vestibulo-Ocular Reflex Suppression with Head-Fixed Target Fixation1

1991 ◽  
Vol 1 (2) ◽  
pp. 161-170
Author(s):  
Jean-Louis Vercher ◽  
Gabriel M. Gauthier
Keyword(s):  
Eye Movements ◽  
Time Course ◽  
Mental Arithmetic ◽  
Visual Space ◽  
Head Movements ◽  
Total Darkness ◽  
Fixed Target ◽  
Ocular Reflex ◽  
Optokinetic Reflex ◽  
Vestibulo Ocular Reflex

To maintain clear vision, the images on the retina must remain reasonably stable. Head movements are generally dealt with successfully by counter-rotation of the eyes induced by the combined actions of the vestibulo-ocular reflex (VOR) and the optokinetic reflex. A problem of importance relates to the value of the so-called intrinsic gain of the VOR (VORG) in man, and how this gain is modulated to provide appropriate eye movements. We have studied these problems in two situations: 1. fixation of a stationary object of the visual space while the head moves; 2. fixation of an object moving with the head. These two situations were compared to a basic condition in which no visual target was allowed in order to induce “pure” VOR. Eye movements were recorded in seated subjects during stationary sinusoidal and transient rotations around the vertical axis. Subjects were in total darkness (DARK condition) and involved in mental arithmetic. Alternatively, they were provided with a small foveal target, either fixed with respect to earth (earth-fixed target: EFT condition), or moving with them (chair-fixed-target: CFT condition). The stationary rotation experiment was used as baseline for the ensuing experiment and yielded control data in agreement with the literature. In all 3 visual conditions, typical responses to transient rotations were rigorously identical during the first 200 ms. They showed, sequentially, a 16-ms delay of the eye behind the head and a rapid increase in eye velocity during 75 to 80 ms, after which the average VORG was 0.9 ± 0.15. During the following 50 to 100 ms, the gain remained around 0.9 in all three conditions. Beyond 200 ms, the VORG remained around 0.9 in DARK and increased slowly towards 1 or decreased towards zero in the EFT and CFT conditions, respectively. The time-course of the later events suggests that visual tracking mechanisms came into play to reduce retinal slip through smooth pursuit, and position error through saccades. Our data also show that in total darkness VORG is set to 0.9 in man. Lower values reported in the literature essentially reflect predictive properties of the vestibulo-ocular mechanism, particularly evident when the input signal is a sinewave.

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.

Analysis of Human Vestibulo-Ocular Reflex During Active Head Movements

1980 ◽  
Vol 90 (1-6) ◽  
pp. 184-190 ◽  
Author(s):  
R. D. Tomlinson ◽  
G. E. Saunders ◽  
D. W. F. Schwarz
Keyword(s):  
Head Movements ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex

The Horizontal Vestibulo-Ocular Reflex Gain During Active and Passive High-Frequency Head Movements

1994 ◽  
Vol 101 (2) ◽  
pp. 140???145 ◽  
Author(s):  
Borys Hoshowsky ◽  
David Tomlinson ◽  
Julian Nedzelski
Keyword(s):  
High Frequency ◽  
Head Movements ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Reflex Gain

scholarly journals The Effect of Different Head Movement Paradigms on Vestibulo-Ocular Reflex Gain and Saccadic Eye Responses in the Suppression Head Impulse Test in Healthy Adult Volunteers

2021 ◽  
Vol 12 ◽  
Author(s):  
Dmitrii Starkov ◽  
Bernd Vermorken ◽  
T. S. Van Dooren ◽  
Lisa Van Stiphout ◽  
Miranda Janssen ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Healthy Adult ◽  
Head Movements ◽  
Head Impulse Test ◽  
Head Impulse ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Reflex Gain ◽  
Head Impulses ◽  
Adult Volunteers

Objective: This study aimed to identify differences in vestibulo-ocular reflex gain (VOR gain) and saccadic response in the suppression head impulse paradigm (SHIMP) between predictable and less predictable head movements, in a group of healthy subjects. It was hypothesized that higher prediction could lead to a lower VOR gain, a shorter saccadic latency, and higher grouping of saccades.Methods: Sixty-two healthy subjects were tested using the video head impulse test and SHIMPs in four conditions: active and passive head movements for both inward and outward directions. VOR gain, latency of the first saccade, and the level of saccade grouping (PR-score) were compared among conditions. Inward and active head movements were considered to be more predictable than outward and passive head movements.Results: After validation, results of 57 tested subjects were analyzed. Mean VOR gain was significantly lower for inward passive compared with outward passive head impulses (p < 0.001), and it was higher for active compared with passive head impulses (both inward and outward) (p ≤ 0.024). Mean latency of the first saccade was significantly shorter for inward active compared with inward passive (p ≤ 0.001) and for inward passive compared with outward passive head impulses (p = 0.012). Mean PR-score was only significantly higher in active outward than in active inward head impulses (p = 0.004).Conclusion: For SHIMP, a higher predictability in head movements lowered gain only in passive impulses and shortened latencies of compensatory saccades overall. For active impulses, gain calculation was affected by short-latency compensatory saccades, hindering reliable comparison with gains of passive impulses. Predictability did not substantially influence grouping of compensatory saccades.

scholarly journals The Vestibulo-Auricular Reflex

2009 ◽  
Vol 101 (3) ◽  
pp. 1258-1266 ◽  
Author(s):  
Daniel J. Tollin ◽  
Janet L. Ruhland ◽  
Tom C. T. Yin
Keyword(s):  
Eye Movements ◽  
Orienting Response ◽  
Head Position ◽  
Efference Copy ◽  
Head Movements ◽  
Fixed Position ◽  
Gaze Shift ◽  
The Gaze ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex

The mammalian orienting response to sounds consists of a gaze shift that can be a combination of head and eye movements. In animals with mobile pinnae, the ears also move. During head movements, vision is stabilized by compensatory rotations of the eyeball within the head because of the vestibulo-ocular reflex (VOR). While studying the gaze shifts made by cats to sounds, a previously uncharacterized compensatory movement was discovered. The pinnae exhibited short-latency, goal-directed movements that reached their target while the head was still moving. The pinnae maintained a fixed position in space by counter-rotating on the head with an equal but opposite velocity to the head movement. We call these compensatory ear movements the vestibulo-auricular reflex (VAR) because they shared many kinematic characteristics with the VOR. Control experiments ruled out efference copy of head position signals and acoustic tracking (audiokinetic) of the source as the cause of the response. The VAR may serve to stabilize the auditory world during head movements.

scholarly journals Eye and head movements and vestibulo-ocular reflex in the context of indirect, referent control of motor actions

2020 ◽  
Vol 124 (1) ◽  
pp. 115-133 ◽  
Author(s):  
Anatol G. Feldman ◽  
Lei Zhang
Keyword(s):  
Empirical Studies ◽  
Head Rotation ◽  
Physical Principle ◽  
Task Demands ◽  
Head Movements ◽  
Ocular Reflex ◽  
Motor Outcome ◽  
Vestibulo Ocular Reflex ◽  
Motor Actions ◽  
The Brain

Conventional explanations of the vestibulo-ocular reflex (VOR) and eye and head movements are revisited by considering two alternative frameworks addressing the question of how the brain controls motor actions. Traditionally, biomechanical and/or computational frameworks reflect the views of several prominent scholars of the past, including Helmholtz and von Holst, who assumed that the brain directly specifies the desired motor outcome and uses efference copy to influence perception. However, empirical studies resulting in the theory of referent control of action and perception (an extension of the equilibrium-point hypothesis) revealed that direct specification of motor outcome is inconsistent with nonlinear properties of motoneurons and with the physical principle that the brain can control motor actions only indirectly, by changing or maintaining the values of neurophysiological parameters that influence, but can remain independent of, biomechanical variables. Some parameters are used to shift the origin (referent) points of spatial frames of reference (FRs) or system of coordinates in which motor actions emerge without being predetermined. Parameters are adjusted until the emergent motor actions meet the task demands. Several physiological parameters and spatial FRs have been identified, supporting the notion of indirect, referent control of movements. Instead of integration of velocity-dependent signals, position-dimensional referent signals underlying head motion can likely be transmitted to motoneurons of extraocular muscles. This would produce compensatory eye movement preventing shifts in gaze during head rotation, even after bilateral destruction of the labyrinths. The referent control framework symbolizes a shift in the paradigm for the understanding of VOR and eye and head movement production.

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