Dissociated Hysteresis of Static Ocular Counterroll in Humans

2006 ◽  
Vol 95 (4) ◽  
pp. 2222-2232 ◽  
Author(s):  
A. Palla ◽  
C. J. Bockisch ◽  
O. Bergamin ◽  
D. Straumann
Keyword(s):  
Second Harmonic ◽  
Human Subjects ◽  
Body Position ◽  
Three Dimensional ◽  
Upright Position ◽  
Whole Body ◽  
Eye Position ◽  
Healthy Human ◽  
Ocular Counterroll ◽  
Head Roll

In stationary head roll positions, the eyes are cyclodivergent. We asked whether this phenomenon can be explained by a static hysteresis that differs between the eyes contra- (CE) and ipsilateral (IE) to head roll. Using a motorized turntable, healthy human subjects ( n = 8) were continuously rotated about the earth-horizontal naso-occipital axis. Starting from the upright position, a total of three full rotations at a constant velocity (2°/s) were completed (acceleration = 0.05°/s2, velocity plateau reached after 40 s). Subjects directed their gaze on a flashing laser dot straight ahead (switched on 20 ms every 2 s). Binocular three-dimensional eye movements were recorded with dual search coils that were modified (wires exiting inferiorly) to minimize torsional artifacts by the eyelids. A sinusoidal function with a first and second harmonic was fitted to torsional eye position as a function of torsional whole body position at constant turntable velocity. The amplitude and phase of the first harmonic differed significantly between the two eyes (paired t-test: P < 0.05): on average, counterroll amplitude of IE was larger [CE: 6.6 ± 1.6° (SD); IE: 8.1 ± 1.7°), whereas CE showed more position lag relative to the turntable (CE: 12.5 ± 10.7°; IE: 5.1 ± 8.7°). We conclude that cyclodivergence observed during static ocular counterroll is mainly a result of hysteresis that depends on whether eyes are contra- or ipsilateral to head roll. Static hysteresis also explains the phenomenon of residual torsion, i.e., an incomplete torsional return of the eyes when the first 360° whole body rotation was completed and subjects were back in upright position (extorsion of CE: 2.0 ± 0.10°; intorsion of IE: 1.4 ± 0.10°). A computer model that includes asymmetric backlash for each eye can explain dissociated torsional hysteresis during quasi-static binocular counterroll. We hypothesize that ocular torsional hysteresis is introduced at the level of the otolith pathways because the direction-dependent torsional position lag of the eyes is related to the head roll position and not the eye position.

Effects of Full-Field Visual Input on the Three-Dimensional Properties of the Human Vestibuloocular Reflex1

1995 ◽  
Vol 5 (3) ◽  
pp. 201-209
Author(s):  
Michael Fetter ◽  
Hubert Misslisch ◽  
Doris Sievering ◽  
Douglas Tweed
Keyword(s):  
Rotation Axis ◽  
Human Subjects ◽  
Three Dimensional ◽  
Head Rotation ◽  
Visual Input ◽  
Whole Body ◽  
Maximum Speed ◽  
Eye Position ◽  
Full Field ◽  
Straight Ahead

The three-dimensional (3-D) properties of the vestibuloocular reflex (VOR) were studied in six normal human subjects during passive whole-body rotations in darkness and with full-field visual input in light. Subjects were asked to fixate a point target stationary in space straight ahead or to imagine such a target in darkness. Using a 3-D rotating chair, subjects were rotated sinusoidally (frequency .3 Hz, maximum speed 37.5°/s) about an earth-vertical axis for horizontal stimulation and about an earth-horizontal axis for vertical and torsional stimulation. The subject faced forward for vertical stimulation, 90° to the side for torsional stimulation, or 15° to the right or left side for combined vertical and torsional stimulation. Left eye position was measured using 3-D search coils. The VOR response was quantified using the 3-D analogue of gain, a 3 × 3 matrix where each element describes the dependence of one component – torsional, vertical, or horizontal – of eye velocity on one component of head velocity. Average gain matrices were calculated for three cycles of rotation (10 s). Major findings were: (1) Gain values for the VOR were higher in light than in darkness for all directions. In light, vertical and horizontal responses were fully compensatory in both magnitude and direction, whereas the torsional responses were still weak. (2) Intersubject variability, large in the dark, was very small in the light for the vertical and horizontal responses but still considerable for the torsional. (3) Crosscoupling, in the form of partially horizontal eye movements in response to a torsional head rotation, was present in darkness but disappeared in light. (4) The VOR showed the same eye position dependence in darkness and in light; that is, if the eye is looking x° away from straight ahead, the eye rotation axis in response to a horizontal or vertical head rotation tilts about x°/4 in the same direction as the gaze line. These axis tilts are incompatible with perfect stabilization of the retinal image, but they are qualitatively appropriate for preserving Listing’s law.

Vertical Divergence and Counterroll Eye Movements Evoked by Whole-Body Position Steps About the Roll Axis of the Head in Humans

2001 ◽  
Vol 85 (2) ◽  
pp. 671-678 ◽  
Author(s):  
A. A. Kori ◽  
A. Schmid-Priscoveanu ◽  
D. Straumann
Keyword(s):  
Eye Movements ◽  
Human Subjects ◽  
Body Position ◽  
Semicircular Canals ◽  
Whole Body ◽  
Healthy Human ◽  
Vertical Divergence ◽  
Roll Axis ◽  
Otolith Stimulation ◽  
Dynamic Gain

In healthy human subjects, a head tilt about its roll axis evokes a dynamic counterroll that is mediated by both semicircular canal and otolith stimulation, and a static counterroll that is mediated by otolith stimulation only. The vertical ocular divergence associated with the static counterroll too is otolith-mediated. A previous study has shown that, in humans, there is also a vertical divergence during dynamic head roll, but this report was not conclusive on whether this response was mediated by the semicircular canals only or whether the otoliths made a significant contribution. To clarify this issue, we applied torsional whole-body position steps (amplitude 10°, peak acceleration of 90°/s2, duration 650 ms) about the earth-vertical (supine body position) and earth-horizontal (upright body position) axis to healthy human subjects who were monocularly fixating a straight-ahead target. Eye movements were recorded binocularly with dual search coils in three dimensions. The dynamic parameters were determined 120 ms after the beginning of the turntable movement, i.e., before the first fast phase of nystagmus. The static parameters were measured 4 s after the beginning of the turntable movement. The dynamic gain of the counterroll was larger in upright (average gain: 0.48 ± 0.10 SD) than in supine (0.36 ± 0.10) position. The static gain of the counterroll in the upright position (0.21 ± 0.06) was smaller than the dynamic gain. Divergent eye movements (intorting eye hypertropic) evoked during the dynamic phase were not significantly different between supine (average vergence velocity: 0.87 ± 0.51°/s) and upright (0.84 ± 0.64°/s) positions. The static vertical divergence in upright position was 0.32 ± 0.14°. The results indicate that the dynamic vertical divergence in contrast to the dynamic ocular counterroll is not enhanced by otolith input. These results can be explained through the different patterns of connectivity between semicircular canals and utricles to the eye muscles. Alternatively, we hypothesize that the small dynamic vertical divergence represents the remaining vertical error necessary to drive an adaptive control mechanism that normally maintains a vertical eye alignment.

Spatial Alignment of Rotational and Static Tilt Responses of Vestibulospinal Neurons in the Cat

1999 ◽  
Vol 82 (2) ◽  
pp. 855-862 ◽  
Author(s):  
S. I. Perlmutter ◽  
Y. Iwamoto ◽  
J. F. Baker ◽  
B. W. Peterson
Keyword(s):  
Horizontal Plane ◽  
Dimensional Space ◽  
Body Position ◽  
Three Dimensional ◽  
Whole Body ◽  
Angular Difference ◽  
Spatial Alignment ◽  
Minimum Sensitivity ◽  
Alert Cats ◽  
Vestibulospinal Neurons

The responses of vestibulospinal neurons to 0.5-Hz, whole-body rotations in three-dimensional space and static tilts of whole-body position were studied in decerebrate and alert cats. The neurons’ spatial properties for earth-vertical rotations were characterized by maximum and minimum sensitivity vectors ( R max and R min) in the cat’s horizontal plane. The orientation of a neuron’s R max was not consistently related to the orientation of its maximum sensitivity vector for static tilts ( T max). The angular difference between R max and T max was widely distributed between 0° and 150°, and R max and T max were aligned (i.e., within 45° of each other) for only 44% (14/32) of the neurons. The alignment of R max and T max was not correlated with the neuron’s sensitivity to earth-horizontal rotations, or to the orientation of R max in the horizontal plane. In addition, the extent to which a neuron exhibited spatiotemporal convergent (STC) behavior in response to vertical rotations was independent of the angular difference between R max and T max. This suggests that the high incidence of STC responses in our sample (56%) reflects not only canal-otolith convergence, but also the presence of static and dynamic otolith inputs with misaligned directionality. The responses of vestibulospinal neurons reflect a complex combination of static and dynamic vestibular inputs that may be required by postural reflexes that vary depending on head, trunk, and limb orientation, or on the frequency of stimulation.

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)

scholarly journals Three-Dimensional Binocular Kinematics of Torsional Vestibular Nystagmus During Convergence on Head-Fixed Targets in Humans

2001 ◽  
Vol 86 (1) ◽  
pp. 113-122 ◽  
Author(s):  
O. Bergamin ◽  
D. Straumann
Keyword(s):  
Human Subjects ◽  
Three Dimensional ◽  
Vertical Component ◽  
Vestibular Stimulation ◽  
Fixed Target ◽  
Healthy Human ◽  
Retinal Slip ◽  
Gain Reduction ◽  
The Right ◽  
Eye Velocity

When a human subject is oscillated about the nasooccipital axis and fixes upon targets along the horizontal head-fixed meridian, angular eye velocity includes a vertical component that increases with the horizontal eccentricity of the line-of-sight. This vertical eye movement component is necessary to prevent retinal slip. We asked whether fixation on a near head-fixed target during the same torsional vestibular stimulation would lead to differences of vertical eye movements between the right and the left eye, as the directions of the two lines-of-sight are not parallel during convergence. Healthy human subjects ( n = 6) were oscillated (0.3 Hz, ±30°) about the nasooccipital axis on a three-dimensional motor-driven turntable. Binocular movements were recorded using the dual search coil technique. A head-fixed laser dot was presented 1.4 m (far head-fixed target) or 0.25 m (near head-fixed target) in front of the right eye. We found highly significant ( P < 0.01) correlations (R binocular = 0.8, monocular = 0.59) between the convergence angle and the difference of the vertical eye velocity between the two eyes. The slope of the fitted linear regression between the two parameters ( s = 0.45) was close to the theoretical slope necessary to prevent vertical retinal slippage (predicted s = 0.5). Covering the left eye did not significantly change the slope ( s = 0.52). In addition, there was a marked gain reduction (∼35%) of the torsional vestibuloocular reflex (VOR) between viewing the far and the near targets, confirming earlier results by others. There was no difference in torsional gain reduction between the two eyes. Lenses of +3 dpt positioned in front of both eyes to decrease the amount of accommodation did not further change the gain of the torsional VOR. In conclusion, ocular convergence on a near head-fixed target during torsional vestibular stimulation leads to deviations in vertical angular velocity between the two eyes necessary to prevent vertical double vision. The vertical deviation velocity is mainly linked to the amount of convergence, since it also occurs during monocular viewing of the near head-fixed target. This suggests that convergence during vestibular stimulation automatically leads to an alignment of binocular rotation axes with the visual axes independent of retinal slip.

Eyelid Movements: Behavioral Studies of Blinking in Humans Under Different Stimulus Conditions

2003 ◽  
Vol 89 (5) ◽  
pp. 2784-2796 ◽  
Author(s):  
Frans VanderWerf ◽  
Peter Brassinga ◽  
Dik Reits ◽  
Majid Aramideh ◽  
Bram Ongerboer de Visser
Keyword(s):  
Human Subjects ◽  
Total Duration ◽  
Eye Position ◽  
Healthy Human ◽  
Phase Duration ◽  
Upper Eyelid ◽  
Search Coil ◽  
Behavioral Studies ◽  
Zero Position ◽  
Phase Amplitude

The kinematics and neurophysiological aspects of eyelid movements were examined during spontaneous, voluntary, air puff, and electrically induced blinking in healthy human subjects, using the direct magnetic search coil technique simultaneously with electromyographic recording of the orbicularis oculi muscles (OO-EMG). For OO-EMG recordings, surface electrodes were attached to the lower eyelids. To measure the vertical lid displacement, a search coil with a diameter of 3 mm was placed 1 mm from the rim on the upper eyelid on a marked position. Blink registrations were performed from the zero position and from 28 randomly chosen positions. Blinks elicited by electrical stimulation of the supraorbital nerve had shortest duration and were least variable. In contrast, spontaneous blinks had longer duration and greater variability. Blinks induced by air puff had a slightly longer duration and similar variability as electrically induced blinks. There was a correlation between the maximal down phase amplitude and the integrated OO-EMG. Blink duration and maximal down phase amplitude were affected by eye position. Eyes positioned 30° above horizontal displayed the shortest down phase duration and the largest maximal down phase amplitude and velocity. At 30° below horizontal, blinks had the longest total duration, the longest down phase duration, and the lowest maximal down phase amplitude and velocity. The simultaneously recorded integrated OO-EMG was largest in the 30° downward position. In four subjects, the average blinking data showed a linear relation between eye position and OO-EMG, maximal down phase amplitude, and maximal downward velocity.

scholarly journals Intense light as anticoagulant therapy in humans

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244792
Author(s):  
Yoshimasa Oyama ◽  
Sydney Shuff ◽  
Pavel Davizon-Castillo ◽  
Nathan Clendenen ◽  
Tobias Eckle
Keyword(s):  
Myocardial Ischemia ◽  
Human Subjects ◽  
Light Therapy ◽  
Whole Body ◽  
Ischemia And Reperfusion ◽  
Ischemia And Reperfusion Injury ◽  
Novel Therapy ◽  
Healthy Human ◽  
Myocardial Ischemia And Reperfusion ◽  
Intense Light

Blood coagulation is central to myocardial ischemia and reperfusion (IR) injury. Studies on the light elicited circadian rhythm protein Period 2 (PER2) using whole body Per2-/- mice found deficient platelet function and reduced clotting which would be expected to protect from myocardial IR-injury. In contrast, intense light induction of PER2 protected from myocardial IR-injury while Per2 deficiency was detrimental. Based on these conflicting data, we sought to evaluate the role of platelet specific PER2 in coagulation and myocardial ischemia and reperfusion injury. We demonstrated that platelets from mice with tissue-specific deletion of Per2 in the megakaryocyte lineage (Per2loxP/loxP-PF4-CRE) significantly clot faster than platelets from control mice. We further found increases in infarct sizes or plasma troponin levels in Per2loxP/loxP-PF4-CRE mice when compared to controls. As intense light increases PER2 protein in human tissues, we also performed translational studies and tested the effects of intense light therapy on coagulation in healthy human subjects. Our human studies revealed that intense light therapy repressed procoagulant pathways in human plasma samples and significantly reduced the clot rate. Based on these results we conclude that intense light elicited PER2 has an inhibitory function on platelet aggregation in mice. Further, we suggest intense light as a novel therapy to prevent or treat clotting in a clinical setting.

scholarly journals Cardiovascular responses to antigravity muscle loading during head-down tilt at rest and after dynamic exercises

2018 ◽  
Author(s):  
Cristiano Alessandro ◽  
Amirehsan Sarabadani Tafreshi ◽  
Robert Riener
Keyword(s):  
Muscle Activity ◽  
Human Subjects ◽  
Cardiovascular Responses ◽  
Bed Rest ◽  
Cardiovascular Regulation ◽  
Upright Position ◽  
The Body ◽  
Healthy Human ◽  
Arterial Blood ◽  
Muscle Loading

AbstractThe physiological processes underlying hemodynamic homeostasis can be modulated by muscle activity and gravitational loading. The effects of antigravity muscle activity on cardiovascular regulation has been observed during orthostatic stress. Here, we evaluated such effects during head-down tilt (HDT). In this posture, the gravitational gradient along the body is different than in upright position, leading to increased central blood volume and reduced venous pooling. We compared the cardiovascular signals obtained with and without antigravity muscle loading during HDT in healthy human subjects, both at rest and during recovery from leg-press exercises. Further, we compared such cardiovascular responses to those obtained during upright position. We found that loading the antigravity muscles during HDT at rest led to significantly higher values of arterial blood pressure than without muscle loading, and restored systolic values to those observed during upright posture. Maintaining muscle loading post-exercise altered the short-term cardiovascular responses, but not the values of the signals five minutes after the exercise. These results demonstrate that antigravity muscle activity modulates cardiovascular regulation during HDT. This modulation should therefore be considered when interpreting cardiovascular responses to conditions that affect both gravity loading and muscle activity, for example bed rest or microgravity.

scholarly journals Oscillatory neural responses evoked by natural vestibular stimuli in humans

2016 ◽  
Vol 115 (3) ◽  
pp. 1228-1242 ◽  
Author(s):  
Steven Gale ◽  
Mario Prsa ◽  
Aaron Schurger ◽  
Annietta Gay ◽  
Aurore Paillard ◽  
...  
Keyword(s):  
Constant Velocity ◽  
Human Subjects ◽  
Whole Body ◽  
Alpha Power ◽  
Alpha Band ◽  
Experimental Conditions ◽  
Healthy Human ◽  
Vestibular Loss ◽  
Bilateral Vestibular Loss ◽  
Cortical Oscillations

While there have been numerous studies of the vestibular system in mammals, less is known about the brain mechanisms of vestibular processing in humans. In particular, of the studies that have been carried out in humans over the last 30 years, none has investigated how vestibular stimulation (VS) affects cortical oscillations. Here we recorded high-density electroencephalography (EEG) in healthy human subjects and a group of bilateral vestibular loss patients (BVPs) undergoing transient and constant-velocity passive whole body yaw rotations, focusing our analyses on the modulation of cortical oscillations in response to natural VS. The present approach overcame significant technical challenges associated with combining natural VS with human electrophysiology and reveals that both transient and constant-velocity VS are associated with a prominent suppression of alpha power (8–13 Hz). Alpha band suppression was localized over bilateral temporo-parietal scalp regions, and these alpha modulations were significantly smaller in BVPs. We propose that suppression of oscillations in the alpha band over temporo-parietal scalp regions reflects cortical vestibular processing, potentially comparable with alpha and mu oscillations in the visual and sensorimotor systems, respectively, opening the door to the investigation of human cortical processing under various experimental conditions during natural VS.

Sign in / Sign up

Export Citation Format

Share Document