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)

Spatial organization of visual messages of the rabbit's cerebellar flocculus. II. Complex and simple spike responses of Purkinje cells

1988 ◽  
Vol 60 (6) ◽  
pp. 2091-2121 ◽  
Author(s):  
W. Graf ◽  
J. I. Simpson ◽  
C. S. Leonard
Keyword(s):  
Purkinje Cells ◽  
Horizontal Plane ◽  
Rotation Axis ◽  
Modulation Depth ◽  
Vertical Axis ◽  
Axis Orientation ◽  
Complex Spike ◽  
Full Field ◽  
Simple Spike ◽  
Dominant Eye

1. Complex and simple spike responses of Purkinje cells were recorded in the flocculus of anesthetized, paralyzed rabbits during rotating full-field visual stimuli produced by a three-axis planetarium projector. 2. On the basis of the spatial properties of their complex spike responses, floccular Purkinje cells could be placed into three distinct classes called Vertical Axis, Anterior (45 degrees) Axis and Posterior (135 degrees) Axis. The first two classes occurred in both monocular and binocular forms; the third class was encountered only in binocular form. For the binocular response forms, stimulation through one eye, called the dominant eye, elicited a stronger modulation of the complex spike firing rate than did stimulation of the other eye. The approximate orientation of that axis about which full-field rotation elicited the deepest modulation (the preferred axis) when presented to the dominant eye served as the class label. These classes are the same as those determined qualitatively for inferior olive neurons in the previous paper (47). The present study provides a quantitative description of their spatial tuning. 3. For Vertical Axis cells, the dominant eye was ipsilateral with respect to the flocculus recording site. The preferred axis was vertical and null (no-response) axes were in the horizontal plane. For the binocular response form of Vertical Axis cells (less than 10% of this class), the direction preferences for the two eyes were synergistic with respect to rotation about the vertical axis. 4. The dominant eye for the Anterior (45 degrees) Axis cells was contralateral, with the preferred axis oriented in the horizontal plane at approximately 45 degrees contralateral azimuth. The modulation depth showed a close to cosine relation with the angle between the preferred axis and the stimulus rotation axis. The average orientation (n = 10) for the dominant eye preferred axis, determined by the best-fit sinusoid, was 47 degrees contralateral azimuth. The preferred axis orientation for the ipsilateral (nondominant) eye in the binocular response forms was between 45 and 90 degrees azimuth in the horizontal plane. A null axis for each eye was at approximately 90 degrees to the preferred axis. 5. The Posterior (135 degrees) Axis cells were encountered only in binocular response forms. The dominant eye was ipsilateral, with the preferred axis oriented at approximately 135 degrees ipsilateral azimuth close to the horizontal plane. The modulation depth showed a close to cosine relation with the angle between the preferred axis and the stimulus rotation axis.(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.

scholarly journals Three-dimensional tuning of head direction cells in rats

2019 ◽  
Vol 121 (1) ◽  
pp. 4-37 ◽  
Author(s):  
Michael E. Shinder ◽  
Jeffrey S. Taube
Keyword(s):  
Horizontal Plane ◽  
Reference Frames ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Ventral Surface ◽  
Three Dimensions ◽  
Head Direction ◽  
Horizontal Canal ◽  
Cell Responses ◽  
The Earth

Head direction (HD) cells fire when the animal faces that cell’s preferred firing direction (PFD) in the horizontal plane. The PFD response when the animal is oriented outside the earth-horizontal plane could result from cells representing direction in the plane of locomotion or as a three-dimensional (3D), global-referenced direction anchored to gravity. To investigate these possibilities, anterodorsal thalamic HD cells were recorded from restrained rats while they were passively positioned in various 3D orientations. Cell responses were unaffected by pitch or roll up to ~90° from the horizontal plane. Firing was disrupted once the animal was oriented >90° away from the horizontal plane and during inversion. When rolling the animal around the earth-vertical axis, cells were active when the animal’s ventral surface faced the cell’s PFD. However, with the rat rolled 90° in an ear-down orientation, pitching the rat and rotating it around the vertical axis did not produce directionally tuned responses. Complex movements involving combinations of yaw-roll, but usually not yaw-pitch, resulted in reduced directional tuning even at the final upright orientation when the rat had full visual view of its environment and was pointing in the cell’s PFD. Directional firing was restored when the rat’s head was moved back-and-forth. There was limited evidence indicating that cells contained conjunctive firing with pitch or roll positions. These findings suggest that the brain’s representation of directional heading is derived primarily from horizontal canal information and that the HD signal is a 3D gravity-referenced signal anchored to a direction in the horizontal plane. NEW & NOTEWORTHY This study monitored head direction cell responses from rats in three dimensions using a series of manipulations that involved yaw, pitch, roll, or a combination of these rotations. Results showed that head direction responses are consistent with the use of two reference frames simultaneously: one defined by the surrounding environment using primarily visual landmarks and a second defined by the earth’s gravity vector.

Responses of Neurons in the Nucleus of the Basal Optic Root to Translational and Rotational Flowfields

1999 ◽  
Vol 81 (1) ◽  
pp. 267-276 ◽  
Author(s):  
Douglas R. W. Wylie ◽  
Barrie J. Frost
Keyword(s):  
Optic Flow ◽  
Horizontal Plane ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Mesencephalic Reticular Formation ◽  
Companion Paper ◽  
Direction Selectivity ◽  
Large Field ◽  
Adjacent Area

Wylie, Douglas R. W. and Barrie J. Frost. Responses of Neurons in the nucleus of the basal optic root to translational and rotational flowfields. J. Neurophysiol. 81: 267–276, 1999. The nucleus of the basal optic root (nBOR) receives direct input from the contralateral retina and is the first step in a pathway dedicated to the analysis of optic flowfields resulting from self-motion. Previous studies have shown that most nBOR neurons exhibit direction selectivity in response to large-field stimuli moving in the contralateral hemifield, but a subpopulation of nBOR neurons has binocular receptive fields. In this study, the activity of binocular nBOR neurons was recorded in anesthetized pigeons in response to panoramic translational and rotational optic flow. Translational optic flow was produced by the “translator” projector described in the companion paper, and rotational optic flow was produced by a “planetarium projector” described by Wylie and Frost. The axis of rotation or translation could be positioned to any orientation in three-dimensional space. We recorded from 37 cells, most of which exhibited a strong contralateral dominance. Most of these cells were located in the caudal and dorsal aspects of the nBOR complex and many were localized to the subnucleus nBOR dorsalis. Other units were located outside the boundaries of the nBOR complex in the adjacent area ventralis of Tsai or mesencephalic reticular formation. Six cells responded best to rotational flowfields, whereas 31 responded best to translational flowfields. Of the rotation cells, three preferred rotation about the vertical axis and three preferred horizontal axes. Of the translation cells, 3 responded best to a flowfield simulating downward translation of the bird along a vertical axis, whereas the remaining 28 responded best to flowfields resulting from translation along axes in the horizontal plane. Seventeen of these cells preferred a flowfield resulting from the animal translating backward along an axis oriented ∼45° to the midline, but the best axes of the remaining eleven cells were distributed throughout the horizontal plane with no definitive clustering. These data are compared with the responses of vestibulocerebellar Purkinje cells.

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.

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)

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.

scholarly journals Electromechanical Catastrophe

2016 ◽  
Vol 08 (07) ◽  
pp. 1640005 ◽  
Author(s):  
Tongqing Lu ◽  
Sibo Cheng ◽  
Tiefeng Li ◽  
Tiejun Wang ◽  
Zhigang Suo
Keyword(s):  
Nonlinear System ◽  
Horizontal Plane ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Mechanical Force ◽  
The State ◽  
Constant Force ◽  
Constant Voltage ◽  
Three Dimensional Space

A transducer is a system that couples two loads. For example, an electromechanical transducer couples a mechanical force and an electrical voltage. A two-load, nonlinear system can exhibit rich behavior of bifurcation, which can be displayed in a three-dimensional space, with the horizontal plane representing the two loads, and the vertical axis representing the state of the system. In this three-dimensional space, a state of equilibrium at fixed loads corresponds to a point on a surface. The surface is smooth, but its projection to the load plane results in singularities of two types: fold and cusp. Here we identify the fold and cusp for a dielectric elastomer transducer by a combination of experiment and calculation. We conduct two kinds of experiment: electrical actuation under a constant force and mechanical pulling under a constant voltage. The theory and the experiment agree well. The fold and cusp are essential in the design of loading paths to avoid or harness the bifurcation.

scholarly journals Concept design and numerical analysis of hybrid solar–wind turbine

2021 ◽  
Vol 850 (1) ◽  
pp. 012032
Author(s):  
K S Ackshaya Varshini ◽  
Alenkar K Aswin ◽  
H Rajan ◽  
K S Maanav Charan
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Fluid Dynamic ◽  
Mechanical Energy ◽  
Vertical Axis ◽  
Horizontal Axis ◽  
Maximum Efficiency ◽  
Concept Design ◽  
Lower Efficiency ◽  
Axis Orientation

Abstract A wind turbine is a device that converts wind energy to electrical energy. External factors such as wind speed and direction shift, as well as turbine blade design considerations, cause a significant amount of energy to be wasted throughout the conversion process. Considering all these losses, a turbine’s average efficiency is roughly 45 percent. The blades of a wind turbine are one of the most crucial factors in determining the turbine’s efficiency. The design and geometry of the blades have a direct impact on performance since it determines how much kinetic energy from the wind is converted into mechanical energy. Many concepts and technologies are being used to improve the efficiency of wind turbines while lowering their maintenance costs. Wind turbines based on their axis orientation are classified as vertical axis and horizontal axis. Vertical axis wind turbines are not as widespread as their horizontal-axis counterparts due to their lower efficiency. In this study, we will use a Savonius vertical axis wind turbine to investigate a way of enhancing its efficiency by installing solar panels on its vertical blades and determining the best performance angle at which the turbine should be kept achieving maximum efficiency. Computation fluid dynamic analysis and thermal and structural analysis has been performed to check the efficiency of the designed blade. As a result, an optimized wind turbine design has been developed.

Effect of Semicircular Canal Stimulation on the Perception of the Visual Vertical

2003 ◽  
Vol 90 (2) ◽  
pp. 622-630 ◽  
Author(s):  
Marousa Pavlou ◽  
Nicole Wijnberg ◽  
Mary E. Faldon ◽  
Adolfo M. Bronstein
Keyword(s):  
Semicircular Canal ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Normal Subjects ◽  
Slow Phase ◽  
Visual Vertical ◽  
Axis Rotation ◽  
Highly Correlated ◽  
Head Positions ◽  
Direction Opposite

The subjective visual vertical (SVV) is usually considered a measure of otolith function. Herewith we investigate the influence of semicircular canal (SCC) stimulation on the SVV by rotating normal subjects in yaw about an earth-vertical axis, with velocity steps of ± 90°/s, for 60 s. SVV was assessed by setting an illuminated line to perceived earth vertical in darkness, during a per- and postrotary period. Four head positions were tested: upright, 30° backward (chin up) or forward, and ∼40° forward from upright. During head upright/backward conditions, a significant SVV tilt ( P < 0.01) in the direction opposite to rotation was found that reversed during postrotary responses. The rotationally induced SVV tilt had a time constant of decay of ∼30 s. Rotation with the head 30° forward did not affect SVV, whereas the 40° forward tilt caused a direction reversal of SVV responses compared with head upright/backward. Spearman correlation values (Rho) between individual SCC efficiencies in different head positions and mean SVV tilts were 0.79 for posterior, 0.34 for anterior, and – 0.80 for horizontal SCCs. Three-dimensional video-oculography showed that SVV and torsional eye position measurements were highly correlated (0.83) and in the direction opposite to the slow phase torsional vestibuloocular reflex. In conclusion: 1) during yaw axis rotation without reorientation of the head with respect to gravity, the SVV is influenced by SCC stimulation; 2) this effect is mediated by the vertical SCCs, particularly the posterior SCCs; 3) rotationally induced SVV changes are due to torsional ocular tilt; 4) SVV and ocular tilts occur in the “anticompensatory,” fast phase direction of the torsional nystagmus; and 5) clinically, abnormal SVV tilts cannot be considered a specific indication of otolith system dysfunction.

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