Early components of the human vestibulo-ocular response to head rotation: latency and gain (original) (raw)
Related papers
Dynamic properties of the human vestibulo-ocular reflex during head rotations in roll
Vision Research, 1995
We investigated the dynamic properties of the human vestibulo-ocular reflex (VOR) during roll head rotations in three human subjects using the magnetic search coil technique. In the first of two experiments, we quantify the behavior of the ocular motor plant in the torsional plane. The subject's eye was mechanically displaced into intorsion, extorsion or abduction, and the dynamic course of return of the eye to its resting position was measured. The mean predominant time constants of return were 210 msec from intorsion, 83 msec from extorsion, and 217 msec from abduction, although there was considerable variability of results from different trials and subjects. In the second experiment, we quantify the efficacy of velocity-to-position integration of the vestibular signal. Position-step stimuli were used to test the torsional or horizontal VOR, being applied with subjects heads erect or supine. After a torsional position-step, the eye drifted back to its resting position, but after a horizontal position-step the eye held its new horizontal position. To interpret these responses we used a simple model of the VOR with parameters of the ocular motor plant set to values determined during Expt 1. The time constant of the velocity-to-position neural integrator was smaller (typically 2 sec) in the torsional plane than in the horizontal plane (> 20 sec). No disconjugacy of torsional eye movements was observed. Thus, the dynamic properties of the VOR in roll differ significantly from those of the VOR in yaw, reflecting different visual demands placed on this reflex in these two planes.
Vision Research, 2006
We examined how the gain of the torsional vestibulo-ocular reflex (VOR) (defined as the instantaneous eye velocity divided by inverted head velocity) in normal humans is affected by eye position, target distance, and the plane of head rotation. In six normal subjects we measured three-dimensional (3D) eye and head rotation axes using scleral search coils, and 6D head position using a magnetic angular and linear position measurement device, during low-amplitude ($20°), high-velocity ($200°/s), high-acceleration ($4000°/s 2 ) rapid head rotations or 'impulses.' Head impulses were imposed manually and delivered in five planes: yaw (horizontal canal plane), pitch, roll, left anterior-right posterior canal plane (LARP), and right anterior-left posterior canal plane (RALP). Subjects were instructed to fix on one of six targets at eye level. Targets were either straight-ahead, 20°left or 20°right from midline, at distance 15 or 124 cm from the subject. Two subjects also looked at more eccentric targets, 30°left or 30°right from midline. We found that the vertical and horizontal VOR gains increased with the proximity of the target to the subject. Previous studies suggest that the torsional VOR gain should decrease with target proximity. We found, however, that the torsional VOR gain did not change for all planes of head rotation and for both target distances. We also found a dynamic misalignment of the vertical positions of the eyes during the torsional VOR, which was greatest during near viewing with symmetric convergence. This dynamic vertical skew during the torsional VOR arises, in part, because when the eyes are converged, the optical axes are not parallel to the naso-occipital axes around which the eyes are rotating. In five of six subjects, the average skew ranged 0.9°-2.9°and was reduced to <0.4°by a 'torsional' quick-phase (around the naso-occipital axis) occurring <110 ms after the onset of the impulse. We propose that the torsional quick-phase mechanism during the torsional VOR could serve at least three functions: (1) resetting the retinal meridians closer to their usual orientation in the head, (2) correcting for the 'skew' deviation created by misalignment between the axes around which the eyes are rotating and the line of sight, and (3) taking the eyes back toward Listing's plane.
Context compensation in the vestibuloocular reflex during active head rotations
Journal of neurophysiology, 2000
The vestibuloocular reflex (VOR) needs to modulate its gain depending on target distance to prevent retinal slip during head movements. We investigated gain modulation (context compensation) for binocular gaze stabilization in human subjects during voluntary yaw and pitch head rotations. Movements of each eye were recorded, both when attempting to maintain gaze on a small visual target at straight-ahead in a darkened room and after its disappearance (remembered target). In the analysis, we relied on a binocular coordinate system yielding a version and a vergence component. We examined how frequency and target distance, approached here by using vergence angle, affected the gain and phase of the version component of the VOR and compared the results to the requirements for ideal performance. Linear regression analysis on the version gain-vergence relationship yielded a slope representing the influence of target proximity and an intercept corresponding to the response at zero vergence (...
Experimental Brain Research, 2005
Geometry dictates that when subjects view a near target during head rotation the eyes must rotate more than the head. The relative contribution to this compensatory response by adjustment of the vestibuloocular reflex gain (Gvor), visual tracking mechanisms including prediction, and convergence is debated. We studied horizontal eye movements induced by sinusoidal 0.2-2.8 Hz, en-bloc yaw rotation as ten normal humans viewed a near target that was either earth-fixed (EFT) or head-fixed (HFT). For EFT, group median gain was 1.49 at 0.2 Hz declining to 1.08 at 2.8 Hz. For HFT, group median gain was 0.03 at 0.2 Hz increasing to 0.71 at 2.8 Hz. By applying transient head perturbations (peak acceleration >1,000°s À2 ) during sinusoidal rotation, we determined that Gvor was similar during either EFT or HFT conditions, and contributed only $75% to the compensatory response. We confirmed that retinal image slip contributed to the compensatory response by demonstrating reduced gain during EFT viewing under strobe illumination. Gain also declined during sum-of-sines head rotations, confirming the contribution of predictive mechanisms. The gain of compensatory eye movements was similar during monocular or binocular viewing, although vergence angle was greater during binocular viewing. Comparison with previous studies indicates that mechanisms for generation of eye rotations during near viewing depend on head stimulus type (rotation or translation), waveform (transient or sinusoidal), and the species being tested.
Experimental Brain Research, 1996
We recorded three-dimensional eye movements during angular acceleration steps from 0 to 250~ at 20~ 2 about an earth-vertical axis. Experiments were performed on 27 normal subjects and on 19 patients who had recovered well from unilateral vestibular deafferentation on the right or left side. In addition to compensatory horizontal eye movements, significant vertical and torsional eye movement components were elicited. These vertical and torsional eye velocity traces led to a shift of the axis of eye velocity away from the axis of head velocity. Horizontal, vertical, and torsional velocity components showed clear differences between normals and patients with unilateral vestibular deafferentation. In normals, the axis of eye velocity tilted backward and slightly away from the axis of head velocity. Patients showed similar, but more pronounced, shifts during rotations toward the intact ear and shifts in the opposite direction for rotations toward the operated ear. Eye velocity traces were analyzed with special consideration given to the orientation of the axis of eye velocity. We speculate that the vertical and torsional velocity components may be due to the effects of Listing's plane, as well as the contributions of the otolith signals.
Peaks and Troughs of Three-Dimensional Vestibulo-ocular Reflex in Humans
Journal of the Association for Research in Otolaryngology, 2010
The three-dimensional vestibulo-ocular reflex (3D VOR) ideally generates compensatory ocular rotations not only with a magnitude equal and opposite to the head rotation but also about an axis that is collinear with the head rotation axis. Vestibulo-ocular responses only partially fulfill this ideal behavior. Because animal studies have shown that vestibular stimulation about particular axes may lead to suboptimal compensatory responses, we investigated in healthy subjects the peaks and troughs in 3D VOR stabilization in terms of gain and alignment of the 3D vestibuloocular response. Six healthy upright sitting subjects underwent whole body small amplitude sinusoidal and constant acceleration transients delivered by a sixdegree-of-freedom motion platform. Subjects were oscillated about the vertical axis and about axes in the horizontal plane varying between roll and pitch at increments of 22.5°in azimuth. Transients were delivered in yaw, roll, and pitch and in the vertical canal planes. Eye movements were recorded in with 3D search coils. Eye coil signals were converted to rotation vectors, from which we calculated gain and misalignment. During horizontal axis stimulation, systematic deviations were found. In the light, mis-alignment of the 3D VOR had a maximum misalignment at about 45°. These deviations in misalignment can be explained by vector summation of the eye rotation components with a low gain for torsion and high gain for vertical. In the dark and in response to transients, gain of all components had lower values. Misalignment in darkness and for transients had different peaks and troughs than in the light: its minimum was during pitch axis stimulation and its maximum during roll axis stimulation. We show that the relatively large misalignment for roll in darkness is due to a horizontal eye movement component that is only present in darkness. In combination with the relatively low torsion gain, this horizontal component has a relative large effect on the alignment of the eye rotation axis with respect to the head rotation axis.
The influence of visual input on the vestibulo-ocular reflex
Documenta ophthalmologica. Advances in ophthalmology, 1999
In order to stabilise a fixation target on the retina, eye movements have to compensate for head movements. During slow head movements visual feedback can control these eye movements. During fast movements of the head, mainly the vestibulo-ocular reflex (VOR) controls eye movements, as visual feedback is too slow. However, visual feedback is an important factor in controlling the VOR; e.g. the gain of the VOR depends on the distance of the target. This study investigates the influence of retinal image position during fast head movements. The experiments were carried out in five human subjects using scleral search coils. The adaptation of each eye individually to a change of retinal position of a target was examined during head shaking. The change in visual input was carried out by placing Fresnel prisms of different strengths in front of both eyes, thus inducing a change in retinal image position without changing the retinal slip. The results show, that both eyes make the appropriat...
Journal of neurophysiology, 1996
1. The kinematics of the human angular vestibuloocular reflex (VOR) in three dimensions was investigated in 12 normal subjects during high-acceleration head rotations (head "impulses"). A head impulse is a passive, unpredictable, high-acceleration (3,000-4,000 degrees/s2) head rotation of approximately 10-20 degrees in roll, pitch, or yaw, delivered with the subject in the upright position and focusing on a fixation target. Head and eye rotations were measured with dual search coils and expressed as rotation vectors. The first of these two papers describes a vector analysis of the three-dimensional input-output kinematics of the VOR as two indexes in the time domain: magnitude and direction. 2. Magnitude is expressed as speed gain (G) and direction as misalignment angle (delta). G is defined as the ratio of eye velocity magnitude (eye speed) to head velocity magnitude (head speed). delta is defined as the instantaneous angle by which the eye rotation axis deviates from per...