Visually Induced Adaptation in Three-Dimensional Organization of Primate Vestibuloocular Reflex

1998 ◽  
Vol 79 (2) ◽  
pp. 791-807 ◽  
Author(s):  
Dora E. Angelaki ◽  
Bernhard J. M. Hess
Keyword(s):  
Oscillation Frequency ◽  
Spatial Organization ◽  
Three Dimensional ◽  
Low Frequency ◽  
Vertical Axis ◽  
Head Movements ◽  
Horizontal Axis ◽  
Vestibuloocular Reflex ◽  
Head Velocity ◽  
Ocular System

Angelaki, Dora E. and Bernhard J. M. Hess. Visually induced adaptation in three-dimensional organization of primate vestibulo-ocular reflex. J. Neurophysiol. 79: 791–807, 1998. The adaptive plasticity of the spatial organization of the vestibuloocular reflex (VOR) has been investigated in intact and canal-plugged primates using 2-h exposure to conflicting visual (optokinetic, OKN) and vestibular rotational stimuli about mutually orthogonal axes (generating torsional VOR + vertical OKN, torsional VOR + horizontal OKN, vertical VOR + horizontal OKN, and horizontal VOR + vertical OKN). Adaptation protocols with 0.5-Hz (±18°) head movements about either an earth-vertical or an earth-horizontal axis induced orthogonal response components as high as 40–70% of those required for ideal adaptation. Orthogonal response gains were highest at the adapting frequency with phase leads present at lower and phase lags present at higher frequencies. Furthermore, the time course of adaptation, as well as orthogonal response dynamics were similar and relatively independent of the particular visual/vestibular stimulus combination. Low-frequency (0.05 Hz, vestibular stimulus: ±60°; optokinetic stimulus: ±180°) adaptation protocols with head movements about an earth-vertical axis induced smaller orthogonal response components that did not exceed 20–40% of the head velocity stimulus (i.e., ∼10% of that required for ideal adaptation). At the same frequency, adaptation with head movements about an earth-horizontal axis generated large orthogonal responses that reached values as high as 100–120% of head velocity after 2 h of adaptation (i.e., ∼40% of ideal adaptation gains). The particular spatial and temporal response characteristics after low-frequency, earth-horizontal axis adaptation in both intact and canal-plugged animals strongly suggests that the orienting (and perhaps translational) but not inertial (velocity storage) components of the primate otolith-ocular system exhibit spatial adaptability. Due to the particular nested arrangement of the visual and vestibular stimuli, the optic flow pattern exhibited a significant component about the third spatial axis (i.e., orthogonal to the axes of rotation of the head and visual surround) at twice the oscillation frequency. Accordingly, the adapted VOR was characterized consistently by a third response component (orthogonal to both the axes of head and optokinetic drum rotation) at twice the oscillation frequency after earth-horizontal but not after earth-vertical axis 0.05-Hz adaptation. This suggests that the otolith-ocular (but not the semicircular canal-ocular) system can adaptively change its spatial organization at frequencies different from those of the head movement.

Inertial representation of angular motion in the vestibular system of rhesus monkeys. II. Otolith-controlled transformation that depends on an intact cerebellar nodulus

1995 ◽  
Vol 73 (5) ◽  
pp. 1729-1751 ◽  
Author(s):  
D. E. Angelaki ◽  
B. J. Hess
Keyword(s):  
Semicircular Canal ◽  
Rhesus Monkeys ◽  
Spatial Organization ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Low Frequency ◽  
Vertical Axis ◽  
Angular Motion ◽  
Response Component ◽  
Temporal Properties

1. We recently studied the spatial representation of angular motion signals in rhesus monkeys by examining the orientation of postrotatory vestibuloocular responses during tilt of the head and body relative to gravity after constant-velocity rotation about an earth-vertical axis. We have reported that low-frequency angular motion signals in the vestibuloocular reflex (VOR) of rhesus monkeys are spatially transformed such that they remain invariant relative to gravity. In the present study we examine the properties of these inertial vestibular signals by employing similar stimulation conditions in animals with either selective semicircular canal plugging or selective lesions of cerebellar lobule X (nodulus) and ventral lobule IX (uvula). 2. We studied the spatial organization of postrotatory VOR in two rhesus monkeys that had either the lateral or one of the vertical canal pairs inactivated by plugging. In both monkeys, the spatiotemporal characteristics of postrotatory velocity after rotation in the plane of an intact canal pair and tilting in the plane of the plugged canal pair were indistinguishable from those of intact animals: postrotatory responses after tilts in the plane of the plugged canal pair were strongly damped, whereas an orthogonal response component was generated that rotated the eye velocity vector toward alignment with gravity. Thus otolith information rather than transient semicircular canal inputs that normally coexist during tilts seem to provide the necessary cues for the central transformation of semicircular canal signals. 3. We studied the three-dimensional VOR properties in two animals in which the cerebellar nodulus and ventral uvula were surgically ablated. After these lesions the temporal properties of the horizontal, vertical, and torsional VOR during earth-vertical-axis rotations were differentially affected. For horizontal VOR, the duration of postrotatory nystagmus was prolonged and the responses acquired strongly underdamped (i.e., oscillatory) properties. Similarly, sinusoidal responses were characterized by smaller phase leads after the lesion. For torsional VOR, the duration of postrotatory nystagmus was significantly shorter after the lesions, reaching postlesion values of 3.6 +/- 1.7 (SD) s and 6.4 +/- 1.1 s compared with prelesion values of 22.4 +/- 4.5 and 33.6 +/- 5.3 s for each animal. In addition, large phase leads characterized the torsional VOR during low-frequency sinusoidal stimulation. The dynamic properties of the vertical VOR in the lesioned animals, on the other hand, were indistinguishable from those in controls. 4. The cerebellar lesions affected the spatial organization of the horizontal and vertical/torsional systems in a differential way. Inertial transformation of lateral canal activity was only partially affected.(ABSTRACT TRUNCATED AT 400 WORDS)

Measurement of the Shortening Effect on the Perceived Path of Stroboscopic Movement

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 288-288
Author(s):  
S Nozawa
Keyword(s):  
Three Dimensional ◽  
Vertical Axis ◽  
Horizontal Axis ◽  
The Other ◽  
Horizontal Line ◽  
Optimal Frequency ◽  
Stimulus Line ◽  
Factors Influencing ◽  
Parallel Motion ◽  
Axis I

When two vertical short lines are alternately flashed at certain SOAs, a shortening of the apparent path of the stroboscopic movement is perceived. In the experiments reported here, factors influencing the shortening effect were studied with lines created on a CRT display. Experiment 1 was designed to study the effect of SOA. Each stimulus line was always presented for 100 ms, but intervals were varied in the range from 25 to 800 ms. With short and long SOAs almost no shortening illusion was observed, whereas the SOA for optimal stroboscopic motion (200 ms) also produced the largest illusion (ca 16%). This agrees with the classic study by Scholz (1924 Psychologische Forschung5 219 – 272) who found the largest illusion (25%) at the optimal frequency for stroboscopic motion. Experiment 2 dealt with the effect of inversions (I), mirror reflections (M), and rotations (R) of the line during the stroboscopic movement (see Kolars and Pomerantz, 1971 Journal of Experimental Psychology87 99 – 108). The particular movements were signalled by means of a short horizontal line added to one end of each of the two vertical lines of experiment 1. The configurations were (1), signifying parallel motion in one plane; (2), locomotion with rotation around the vertical axis (M); (3), locomotion with rotation around the horizontal axis (I); and (4), locomotion with rotation in the plane of the display (R). In all these conditions, the shortening illusion was significantly larger than in experiment 1. The differences between the four conditions were not statistically significant, but the illusion under condition (1) seemed smaller than in the other three conditions. With SOAs for optimal stroboscopic motion, ‘rotation’ paths tended to appear three-dimensional.

Eye-head coordination during large gaze shifts

1995 ◽  
Vol 73 (2) ◽  
pp. 766-779 ◽  
Author(s):  
D. Tweed ◽  
B. Glenn ◽  
T. Vilis
Keyword(s):  
Degrees Of Freedom ◽  
Human Subjects ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Head Movements ◽  
Gaze Shifts ◽  
Healthy Human ◽  
Vertical Movements ◽  
The Gaze ◽  
Acceleration And Deceleration

1. Three-dimensional (3D) eye and head rotations were measured with the use of the magnetic search coil technique in six healthy human subjects as they made large gaze shifts. The aims of this study were 1) to see whether the kinematic rules that constrain eye and head orientations to two degrees of freedom between saccades also hold during movements; 2) to chart the curvature and looping in eye and head trajectories; and 3) to assess whether the timing and paths of eye and head movements are more compatible with a single gaze error command driving both movements, or with two different feedback loops. 2. Static orientations of the eye and head relative to space are known to resemble the distribution that would be generated by a Fick gimbal (a horizontal axis moving on a fixed vertical axis). We show that gaze point trajectories during eye-head gaze shifts fit the Fick gimbal pattern, with horizontal movements following straight "line of latitude" paths and vertical movements curving like lines of longitude. However, horizontal (and to a lesser extent vertical) movements showed direction-dependent looping, with rightward and leftward (and up and down) saccades tracing slightly different paths. Plots of facing direction (the analogue of gaze direction for the head) also showed the latitude/longitude pattern, without looping. In radial saccades, the gaze point initially moved more vertically than the target direction and then curved; head trajectories were straight. 3. The eye and head components of randomly sequenced gaze shifts were not time locked to one another. The head could start moving at any time from slightly before the eye until 200 ms after, and the standard deviation of this interval could be as large as 80 ms. The head continued moving for a long (up to 400 ms) and highly variable time after the gaze error had fallen to zero. For repeated saccades between the same targets, peak eye and head velocities were directly, but very weakly, correlated; fast eye movements could accompany slow head movements and vice versa. Peak head acceleration and deceleration were also very weakly correlated with eye velocity. Further, the head rotated about an essentially fixed axis, with a smooth bell-shaped velocity profile, whereas the axis of eye rotation relative to the head varied throughout the movement and the velocity profiles were more ragged. 4. Plots of 3D eye orientation revealed strong and consistent looping in eye trajectories relative to space.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of the Effect of a Slotted Flap Mechanism on the Performance of an H-Darrieus Turbine Using CFD

2014 ◽  
Author(s):  
László Daróczy ◽  
Mohamed H. Mohamed ◽  
Gábor Janiga ◽  
Dominique Thévenin
Keyword(s):  
Three Dimensional ◽  
Vertical Axis ◽  
Operating Conditions ◽  
Horizontal Axis ◽  
Pollutant Emissions ◽  
Power Coefficient ◽  
Major Drawback ◽  
Systematic Analysis ◽  
Low Wind Speed ◽  
Low Efficiency

Wind energy represents nowadays a very important source of energy for many countries. It provides an efficient and effective solution to reduce fuel consumption as well as pollutant emissions. VAWTs (vertical axis wind turbines) were originally considered as very promising, before being superseded by the present, horizontal axis turbines. There is now a resurgence of interests for VAWTs, in particular Darrieus turbines. VAWTs like the H-rotor Darrieus turbine appear to be particularly promising for low wind speed conditions, but suffer from a low efficiency compared to horizontal axis turbines. Additionally, Darrieus turbines are not self-starting, which is a major drawback. The present paper introduces a new idea to improve the global performance of Darrieus rotors, relying on a slotted flap. Due to its low manufacturing costs and size, a two-bladed H-rotor with a radius of 2 meters was retained as a first application example. The blade airfoil relies on the S1046 profile, which was shown in previous studies to be superior under relevant operating conditions [1]. The solidity (Nc/R) of the rotor is kept at 0.25 for all the computations. In the first step a parametric geometry is created, where the end of the blade is converted into a slotted flap (with appropriate rounding). The main parameters are the distance between the main part of the blade and the flap (width of gap), the angle of the slot and the angle of the flap. In the second step a systematic analysis of the effect of those variables on the force and power coefficient is carried out using three-dimensional full factorial Design-of-Experiment with an in-house parameterization and optimization software. For each configuration, force and power coefficients are calculated for four different tip-speed ratios (including the value, where the S1046 profile without flap shows its maximal power coefficient). The evaluation of each configuration is performed using a commercial CFD software. The flow is assumed in this first study to be two-dimensional and unsteady. Turbulence intensities follow the relevant norms (DIN EN 61400). Finally the results are compared to each other and to the reference design (S1046 without flap) and conclusions are given regarding power coefficient and flap load.

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.

Vestibuloocular Reflex Signal Modulation During Voluntary and Passive Head Movements

2002 ◽  
Vol 87 (5) ◽  
pp. 2337-2357 ◽  
Author(s):  
Jefferson E. Roy ◽  
Kathleen E. Cullen
Keyword(s):  
Eye Movement ◽  
Head Movements ◽  
Body Motion ◽  
Whole Body ◽  
Type I ◽  
Vestibuloocular Reflex ◽  
Body Rotation ◽  
Gaze Shifts ◽  
Head Velocity ◽  
Wide Range

The vestibuloocular reflex (VOR) effectively stabilizes the visual world on the retina over the wide range of head movements generated during daily activities by producing an eye movement of equal and opposite amplitude to the motion of the head. Although an intact VOR is essential for stabilizing gaze during walking and running, it can be counterproductive during certain voluntary behaviors. For example, primates use rapid coordinated movements of the eyes and head (gaze shifts) to redirect the visual axis from one target of interest to another. During these self-generated head movements, a fully functional VOR would generate an eye-movement command in the direction opposite to that of the intended shift in gaze. Here, we have investigated how the VOR pathways process vestibular information across a wide range of behaviors in which head movements were either externally applied and/or self-generated and in which the gaze goal was systematically varied (i.e., stabilize vs. redirect). VOR interneurons [i.e., type I position-vestibular-pause (PVP) neurons] were characterized during head-restrained passive whole-body rotation, passive head-on-body rotation, active eye-head gaze shifts, active eye-head gaze pursuit, self-generated whole-body motion, and active head-on-body motion made while the monkey was passively rotated. We found that regardless of the stimulation condition, type I PVP neuron responses to head motion were comparable whenever the monkey stabilized its gaze. In contrast, whenever the monkey redirected its gaze, type I PVP neurons were significantly less responsive to head velocity. We also performed a comparable analysis of type II PVP neurons, which are likely to contribute indirectly to the VOR, and found that they generally behaved in a quantitatively similar manner. Thus our findings support the hypothesis that the activity of the VOR pathways is reduced “on-line” whenever the current behavioral goal is to redirect gaze. By characterizing neuronal responses during a variety of experimental conditions, we were also able to determine which inputs contribute to the differential processing of head-velocity information by PVP neurons. We show that neither neck proprioceptive inputs, an efference copy of neck motor commands nor the monkey's knowledge of its self-motion influence the activity of PVP neurons per se. Rather we propose that efference copies of oculomotor/gaze commands are responsible for the behaviorally dependent modulation of PVP neurons (and by extension for modulation of the status of the VOR) during gaze redirection.

Lesion of the nodulus and ventral uvula abolish steady-state off-vertical axis otolith response

1995 ◽  
Vol 73 (4) ◽  
pp. 1716-1720 ◽  
Author(s):  
D. E. Angelaki ◽  
B. J. Hess
Keyword(s):  
Steady State ◽  
Constant Velocity ◽  
Rhesus Monkeys ◽  
Low Frequency ◽  
Vertical Axis ◽  
Primary Afferents ◽  
Vestibuloocular Reflex ◽  
Neural Substrate ◽  
Sinusoidal Oscillations ◽  
Otolith System

1. During rotations that dynamically activate utricular and saccular primary afferents, the otolith system centrally detects the velocity and direction of rotation of the head in space. This property is experimentally manifested as a steady-state compensatory nystagmus during constant velocity off-vertical axis rotations. The computational, physiological, and anatomic details of this response remain presently unknown. Here we report that surgical inactivation of the cerebellar nodulus and ventral uvula abolished the ability of the otolith system to generate steady-state nystagmus during constant velocity rotation and to improve the dynamics of the vestibuloocular reflex (VOR) during low-frequency sinusoidal oscillations about off-vertical axes in rhesus monkeys. These results suggest that the cerebellar nodulus and/or ventral uvula comprise part of the neural substrate that is involved in these computations.

Responses of pigeon vestibulocerebellar neurons to optokinetic stimulation. II. The 3-dimensional reference frame of rotation neurons in the flocculus

1993 ◽  
Vol 70 (6) ◽  
pp. 2647-2659 ◽  
Author(s):  
D. R. Wylie ◽  
B. J. Frost
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Receptive Fields ◽  
Semicircular Canals ◽  
Vertical Axis ◽  
Horizontal Axis ◽  
Monocular Stimulation ◽  
Contralateral Eye ◽  
Ipsilateral Stimulation ◽  
Stimulation Of

1. The complex spike activity of Purkinje cells in the flocculus in response to rotational flowfields was recorded extracellularly in anesthetized pigeons. 2. The optokinetic stimulus was produced by a rotating “planetarium projector.” A light source was placed in the center of a tin cylinder, which was pierced with numerous small holes. A pen motor oscillated the cylinder about its long axis. This apparatus was placed above the bird's head and the resultant rotational flow-field was projected onto screens that surrounded the bird on all four sides. The axis of rotation of the planetarium could be oriented to any position in three-dimensional space. 3. Two types of responses were found: vertical axis (VA; n = 43) neurons responded best to visual rotation about the vertical axis, and H-135i neurons (n = 34) responded best to rotation about a horizontal axis. The preferred orientation of the horizontal axis was at approximately 135 degrees ipsilateral azimuth. VA neurons were excited by rotation about the vertical axis producing forward (temporal to nasal) and backward motion in the ipsilateral and contralateral eyes, respectively, and were inhibited by rotation in the opposite direction. H-135i neurons in the left flocculus were excited by counterclockwise rotation about the 135 degrees ipsilateral horizontal axis and were inhibited by clockwise motion. Thus, the VA and H-135i neurons, respectively, encode visual flowfields resulting from head rotations stimulating the ipsilateral horizontal and ipsilateral anterior semicircular canals. 4. Sixty-seven percent of VA and 80% of H-135i neurons had binocular receptive fields, although for most binocular cells the ipsilateral eye was dominant. Binocular stimulation resulted in a greater depth of modulation than did monocular stimulation of the dominant eye for 69% of the cells. 5. Monocular stimulation of the VA neurons revealed that the best axis for the contralateral eye was tilted back 11 degrees, on average, to the best axis for ipsilateral stimulation. For the H-135i neurons, the best axes for monocular stimulation of the two eyes were approximately the same. 6. By stimulating circumscribed portions of the monocular receptive fields of the H-135i neurons with alternating upward and downward largefield motion, it was revealed that the contralateral receptive fields were bipartite. Upward motion was preferred in the anterior 45 degrees of the contralateral field, and downward motion, was preferred in the central 90 degrees of the contralateral visual field.(ABSTRACT TRUNCATED AT 400 WORDS)

Vestibular Convergence Patterns in Vestibular Nuclei Neurons of Alert Primates

2002 ◽  
Vol 88 (6) ◽  
pp. 3518-3533 ◽  
Author(s):  
J. David Dickman ◽  
Dora E. Angelaki
Keyword(s):  
Body Movement ◽  
Three Dimensional ◽  
Head Rotation ◽  
Vertical Axis ◽  
Vestibular Nuclei ◽  
Head Movements ◽  
Maximum Sensitivity ◽  
Otolith Organs ◽  
Response Dynamics ◽  
Central Neurons

Sensory signal convergence is a fundamental and important aspect of brain function. Such convergence may often involve complex multidimensional interactions as those proposed for the processing of otolith and semicircular canal (SCC) information for the detection of translational head movements and the effective discrimination from physically congruent gravity signals. In the present study, we have examined the responses of primate rostral vestibular nuclei (VN) neurons that do not exhibit any eye movement-related activity using 0.5-Hz translational and three-dimensional (3D) rotational motion. Three distinct neural populations were identified. Approximately one-fourth of the cells exclusively encoded rotational movements (canal-only neurons) and were unresponsive to translation. The canal-only central neurons encoded head rotation in SCC coordinates, exhibited little orthogonal canal convergence, and were characterized with significantly higher sensitivities to rotation as compared to primary SCC afferents. Another fourth of the neurons modulated their firing rates during translation (otolith-only cells). During rotations, these neurons only responded when the axis of rotation was earth-horizontal and the head was changing orientation relative to gravity. The remaining one-half of VN neurons were sensitive to both rotations and translations (otolith + canal neurons). Unlike primary otolith afferents, however, central neurons often exhibited significant spatiotemporal (noncosine) tuning properties and a wide variety of response dynamics to translation. To characterize the pattern of SCC inputs to otolith + canal neurons, their rotational maximum sensitivity vectors were computed using exclusively responses during earth-vertical axis rotations (EVA). Maximum sensitivity vectors were distributed throughout the 3D space, suggesting strong convergence from multiple SCCs. These neurons were also tested with earth-horizontal axis rotations (EHA), which would activate both vertical canals and otolith organs. However, the recorded responses could not be predicted from a linear combination of EVA rotational and translational responses. In contrast, one-third of the neurons responded similarly during EVA and EHA rotations, although a significant response modulation was present during translation. Thus this subpopulation of otolith + canal cells, which included neurons with either high- or low-pass dynamics to translation, appear to selectively ignore the component of otolith-selective activation that is due to changes in the orientation of the head relative to gravity. Thus contrary to primary otolith afferents and otolith-only central neurons that respond equivalently to tilts relative to gravity and translational movements, approximately one-third of the otolith + canal cells seem to encode a true estimate of the translational component of the imposed passive head and body movement.

Three-dimensional organization of optokinetic responses in the rabbit

1993 ◽  
Vol 69 (2) ◽  
pp. 303-317 ◽  
Author(s):  
H. S. Tan ◽  
J. van der Steen ◽  
J. I. Simpson ◽  
H. Collewijn
Keyword(s):  
Control System ◽  
Horizontal Plane ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Horizontal Axis ◽  
Constant Speed ◽  
Slow Phase ◽  
Optokinetic Stimulation ◽  
Axis Orientation ◽  
Maximum Gain

1. Three-dimensional rotations of both eyes were measured in alert rabbits during optokinetic stimulation about axes lying in the horizontal plane or about an earth-vertical axis, with either one or both eyes viewing the stimulus. Optokinetic stimulus speed was 2 degrees /s, either continuous or alternating in polarity (triangular stimulus). In addition to the gains of the responses, the orientations of the response axes relative to the stimulus axes were determined. 2. In comparison to the response to constant-speed optokinetic stimulation about the vertical axis, the response to constant-speed optokinetic stimulation about horizontal axes was characterized by the lack of a speed buildup. In many cases, slow phase tracking was good as long as the eye was within the central oculomotor range but deteriorated when eye deviation became more eccentric and fast phases failed to be generated. These features suggest that the optokinetic reflex about horizontal axes functions as a position-control system, rather than as a velocity-control system. 3. Binocular optokinetic stimulation at constant speed (2 degrees/s) about the roll axis (0 degrees azimuth horizontal axis) elicited disconjugate responses. Although the gain of the response was not significantly different in the two eyes (0.38 for downward and 0.44 for upward stimulation), the response axes of the two eyes differed by as much as 51 degrees. 4. Monocular, horizontal axis optokinetic stimulation at constant speed elicited responses that were grossly dissociated between the two eyes. The magnitude of the responses was anisotropic in that it varied with the azimuthal orientation of the stimulus axis; the maximum gain for each eye (0.41 for the seeing and 0.33 for the covered eye) was at 135 degrees azimuth for each eye. The axis orientation and direction (sense of rotation) of the optokinetic stimulus eliciting the maximal response for each eye coincided with the optic flow normally associated with the maximal excitation of the corresponding ipsilateral anterior canal. 5. Binocular, triangular optokinetic stimulation with small excursions (+/- 10 degrees), which avoided the saturation problems of constant-speed stimulation, elicited adequate responses without systematic directional asymmetries. Gain was approximately 0.9 for all stimulus axis orientations in the horizontal plane. 6. During monocular stimulation with triangular stimuli, the response of the seeing eye showed a gain of approximately 0.5 for all orientations of the stimulus axis. In contrast, the covered eye showed anisotropic responses, with a maximum gain of approximately 0.5 during stimulation of the seeing eye about its 45 degree axis.(ABSTRACT TRUNCATED AT 400 WORDS)

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