Eye movements induced by off-vertical axis rotation (OVAR) at small angles of tilt

1988 ◽  
Vol 73 (1) ◽  
pp. 91-105 ◽  
Author(s):  
C. Darlot ◽  
P. Denise ◽  
J. Droulez ◽  
B. Cohen ◽  
A. Berthoz
Keyword(s):  
Eye Movements ◽  
Vertical Axis ◽  
Axis Rotation

Eye Movements and Motion Perception Induced by Off-vertical Axis Rotation (OVAR) at Small Angles of Tilt after Spaceflight

1995 ◽  
Vol 115 (5) ◽  
pp. 603-609 ◽  
Author(s):  
Gilles Clement ◽  
Christian Darlot ◽  
Anna Petropoulos ◽  
Alain Berthoz
Keyword(s):  
Eye Movements ◽  
Motion Perception ◽  
Vertical Axis ◽  
Axis Rotation

Compensatory and Orienting Eye Movements Induced By Off-Vertical Axis Rotation (OVAR) in Monkeys

2002 ◽  
Vol 88 (5) ◽  
pp. 2445-2462 ◽  
Author(s):  
Keisuke Kushiro ◽  
Mingjia Dai ◽  
Mikhail Kunin ◽  
Sergei B. Yakushin ◽  
Bernard Cohen ◽  
...  
Keyword(s):  
Eye Movements ◽  
Vertical Axis ◽  
Velocity Storage ◽  
Eye Position ◽  
Rotational Axis ◽  
Vestibuloocular Reflex ◽  
Time Constants ◽  
Head Velocity ◽  
Axis Rotation ◽  
Eye Velocity

Nystagmus induced by off-vertical axis rotation (OVAR) about a head yaw axis is composed of a yaw bias velocity and modulations in eye position and velocity as the head changes orientation relative to gravity. The bias velocity is dependent on the tilt of the rotational axis relative to gravity and angular head velocity. For axis tilts <15°, bias velocities increased monotonically with increases in the magnitude of the projected gravity vector onto the horizontal plane of the head. For tilts of 15–90°, bias velocity was independent of tilt angle, increasing linearly as a function of head velocity with gains of 0.7–0.8, up to the saturation level of velocity storage. Asymmetries in OVAR bias velocity and asymmetries in the dominant time constant of the angular vestibuloocular reflex (aVOR) covaried and both were reduced by administration of baclofen, a GABAB agonist. Modulations in pitch and roll eye positions were in phase with nose-down and side-down head positions, respectively. Changes in roll eye position were produced mainly by slow movements, whereas vertical eye position changes were characterized by slow eye movements and saccades. Oscillations in vertical and roll eye velocities led their respective position changes by ≈90°, close to an ideal differentiation, suggesting that these modulations were due to activation of the orienting component of the linear vestibuloocular reflex (lVOR). The beating field of the horizontal nystagmus shifted the eyes 6.3°/ g toward gravity in side down position, similar to the deviations observed during static roll tilt (7.0°/ g). This demonstrates that the eyes also orient to gravity in yaw. Phases of horizontal eye velocity clustered ∼180° relative to the modulation in beating field and were not simply differentiations of changes in eye position. Contributions of orientating and compensatory components of the lVOR to the modulation of eye position and velocity were modeled using three components: a novel direct otolith-oculomotor orientation, orientation-based velocity modulation, and changes in velocity storage time constants with head position re gravity. Time constants were obtained from optokinetic after-nystagmus, a direct representation of velocity storage. When the orienting lVOR was combined with models of the compensatory lVOR and velocity estimator from sequential otolith activation to generate the bias component, the model accurately predicted eye position and velocity in three dimensions. These data support the postulates that OVAR generates compensatory eye velocity through activation of velocity storage and that oscillatory components arise predominantly through lVOR orientation mechanisms.

Off-Vertical Axis Rotation: A Test of the Otolith-Ocular Reflex

1992 ◽  
Vol 101 (8) ◽  
pp. 643-650 ◽  
Author(s):  
Joseph M. R. Furman ◽  
Robert H. Schor ◽  
Timothy L. Schumann
Keyword(s):  
Eye Movements ◽  
Semicircular Canal ◽  
Constant Velocity ◽  
Vertical Axis ◽  
Induced Response ◽  
Movement Response ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Axis Rotation ◽  
Asymptomatic Subjects

The vestibulo-ocular reflex was studied via off-vertical axis rotation (OVAR) in the dark. The axis of the turntable could be tilted from vertical by up to 30°. Eye movements were measured with electro-oculography. Results from healthy asymptomatic subjects indicated that 1) a reliable otolith-induced response could be obtained during constant velocity OVAR using a velocity of 60°/s with a tilt of 30°; 2) constant velocity OVAR rotation was nausea-producing and, especially if subjects were rotated in the dark about an earth-vertical axis prior to being tilted, disorienting; and 3) sinusoidal OVAR produced minimal nausea; the eye movement response appeared to be the result of a combination of semicircular canal and otolith components. We conclude that OVAR has the potential of becoming a useful method for clinically assessing both the otolith-ocular reflex and semicircular canal—otolith interaction.

The influence of cognitive tasks on vestibular-induced eye movements in young and older adults

2008 ◽  
Vol 18 (4) ◽  
pp. 187-195
Author(s):  
Bryan K. Ward ◽  
Mark S. Redfern ◽  
J. Richard Jennings ◽  
Joseph M. Furman
Keyword(s):  
Eye Movements ◽  
Cognitive Processing ◽  
Auditory Processing ◽  
Cognitive Task ◽  
Age Groups ◽  
Vertical Axis ◽  
Cognitive Tasks ◽  
Central Auditory Processing ◽  
Before And After ◽  
Axis Rotation

The purpose of this study was to further investigate the mechanism of the influence of concurrent cognitive tasks on eye movements induced by earth-vertical axis rotation (EVAR) in young and older participants. Ten young (ages 21–34), ten young-old (ages 65–74) and nine older participants (ages 75–84) each performed five different cognitive tasks during sinusoidal EVAR in darkness at 0.02 Hz for three cycles, 0.05 Hz for four cycles, and 0.1 Hz for five cycles, all at a peak velocity of 50 degrees per second. The five tasks differed from one another in terms of their inherent sensory and motor components and were designed to provide insight into the effect of cognitive processing on VOR dynamics. Tasks included auditory frequency and lateralization disjunctive reaction time (DRT) tasks, silent and audible backward counting, and a question-response clinical standard task. For the DRT trials, tones were presented to the participant through earphones. Participants were instructed to respond as accurately and as quickly as possible. Eye movements were recorded with electro-oculography and calibrations were performed before and after every five rotations in all subjects. Participants had an increase in VOR phase lead while performing DRT tasks as compared to the clinical standard and counting tasks. The effect was most noticeable at the 0.02 Hz frequency and was present in all age groups. In addition, we observed a decrease in VOR gain while subjects performed auditory DRT tasks during EVAR at 0.02 Hz, 0.05 Hz and 0.1 Hz as compared to the clinical standard and counting tasks. These results suggest cognitive task-dependent interference between central auditory processing and vestibular processing primarily at the sensory rather than at the motor level.

Zircon geochronology and paleomagnetism of an Archean harzburgite intrusion, eastern Bighorn Mountains, Wyoming

2020 ◽  
Vol 57 (1) ◽  
pp. 21-40
Author(s):  
Alexandra Wallenberg ◽  
Michelle Dafov ◽  
David Malone ◽  
John Craddock
Keyword(s):  
Hanging Wall ◽  
Vertical Axis ◽  
Shear Zones ◽  
Strike Slip ◽  
Zircon Geochronology ◽  
Weighted Mean ◽  
Mafic Complex ◽  
Laramide Orogeny ◽  
Axis Rotation ◽  
Bighorn Mountains

A harzburgite intrusion, which is part of the trailside mafic complex) intrudes ~2900-2950 Ma gneisses in the hanging wall of the Laramide Bighorn uplift west of Buffalo, Wyoming. The harzburgite is composed of pristine orthopyroxene (bronzite), clinopyroxene, serpentine after olivine and accessory magnetite-serpentinite seams, and strike-slip striated shear zones. The harzburgite is crosscut by a hydrothermally altered wehrlite dike (N20°E, 90°, 1 meter wide) with no zircons recovered. Zircons from the harzburgite reveal two ages: 1) a younger set that has a concordia upper intercept age of 2908±6 Ma and a weighted mean age of 2909.5±6.1 Ma; and 2) an older set that has a concordia upper intercept age of 2934.1±8.9 Ma and a weighted mean age 2940.5±5.8 Ma. Anisotropy of magnetic susceptibility (AMS) was used as a proxy for magmatic intrusion and the harzburgite preserves a sub-horizontal Kmax fabric (n=18) suggesting lateral intrusion. Alternating Field (AF) demagnetization for the harzburgite yielded a paleopole of 177.7 longitude, -14.4 latitude. The AF paleopole for the wehrlite dike has a vertical (90°) inclination suggesting intrusion at high latitude. The wehrlite dike preserves a Kmax fabric (n=19) that plots along the great circle of the dike and is difficult to interpret. The harzburgite has a two-component magnetization preserved that indicates a younger Cretaceous chemical overprint that may indicate a 90° clockwise vertical axis rotation of the Clear Creek thrust hanging wall, a range-bounding east-directed thrust fault that accommodated uplift of Bighorn Mountains during the Eocene Laramide Orogeny.

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