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.

scholarly journals Multimodal stimuli modulate rapid visual responses during reaching

2019 ◽  
Vol 122 (5) ◽  
pp. 1894-1908 ◽  
Author(s):  
Isabel S. Glover ◽  
Stuart N. Baker
Keyword(s):  
Median Nerve ◽  
Reticular Formation ◽  
Visual Target ◽  
Human Subjects ◽  
Vestibular Stimulation ◽  
Auditory Stimuli ◽  
Visual Responses ◽  
Healthy Human ◽  
Reaching Task ◽  
Upper Limb Function

The reticulospinal tract plays an important role in primate upper limb function, but methods for assessing its activity are limited. One promising approach is to measure rapid visual responses (RVRs) in arm muscle activity during a visually cued reaching task; these may arise from a tecto-reticulospinal pathway. We investigated whether changes in reticulospinal excitability can be assessed noninvasively using RVRs, by pairing the visual stimuli of the reaching task with electrical stimulation of the median nerve, galvanic vestibular stimulation, or loud sounds, all of which are known to activate the reticular formation. Surface electromyogram (EMG) recordings were made from the right deltoid of healthy human subjects as they performed fast reaching movements toward visual targets. Stimuli were delivered up to 200 ms before target appearance, and RVR was quantified as the EMG amplitude in a window 75–125 ms after visual target onset. Median nerve, vestibular, and auditory stimuli all consistently facilitated the RVRs, as well as reducing the latency of responses. We propose that this facilitation reflects modulation of tecto-reticulospinal excitability, which is consistent with the idea that the amplitude of RVRs can be used to assess changes in brain stem excitability noninvasively in humans. NEW & NOTEWORTHY Short-latency responses in arm muscles evoked during a visually driven reaching task have previously been proposed to be tecto-reticulospinal in origin. We demonstrate that these responses can be facilitated by pairing the appearance of a visual target with stimuli that activate the reticular formation: median nerve, vestibular, and auditory stimuli. We propose that this reflects noninvasive measurement and modulation of reticulospinal excitability.

Context Compensation in the Vestibuloocular Reflex During Active Head Rotations

2000 ◽  
Vol 84 (6) ◽  
pp. 2904-2917 ◽  
Author(s):  
W. P. Medendorp ◽  
J.A.M. Van Gisbergen ◽  
S. Van Pelt ◽  
C.C.A.M. Gielen
Keyword(s):  
Human Subjects ◽  
Linear Regression Analysis ◽  
Head Movements ◽  
Target Distance ◽  
General Context ◽  
Vestibuloocular Reflex ◽  
Gaze Stabilization ◽  
Retinal Slip ◽  
Eye Velocity ◽  
Head Rotations

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 (“default gain”). The slope of the fitted relationship, divided by the geometrically required slope, provided a measure for the quality of version context compensation (“context gain”). In both yaw and pitch experiments, we found default version gains close to one even for the remembered target condition, indicating that the active VOR for far targets is already close to ideal without visual support. In near target experiments, the presence of visual feedback yielded near unity context gains, indicating close to optimal performance (retinal slip <0.4°/s). For remembered targets, the context gain deteriorated but was still superior to performance in corresponding passive studies reported in the literature. In general, context compensation in the remembered target paradigm was better for vertical than for horizontal head rotations. The phase delay of version eye velocity relative to head velocity was small (∼2°) for both horizontal and vertical head movements. Analysis of the vergence data from the near target experiments showed that context compensation took into account that the two eyes require slightly different VORs. In thediscussion, comparison of the present default VOR gains and context gains with data from earlier passive studies has led us to propose a limited role for efference copies during self-generated movements. We also discuss how our analysis can provide a framework for evaluating two different hypotheses for the generation of binocular VOR eye movements.

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 Fractionation of muscle activity in rapid responses to startling cues

2017 ◽  
Vol 117 (4) ◽  
pp. 1713-1719 ◽  
Author(s):  
Lauren R. Dean ◽  
Stuart N. Baker
Keyword(s):  
Muscle Activity ◽  
Human Subjects ◽  
Activity Patterns ◽  
Reaction Times ◽  
Principal Component ◽  
Similar Proportion ◽  
Descending Pathways ◽  
Healthy Human ◽  
Wide Range ◽  
The Right

Movements in response to acoustically startling cues have shorter reaction times than those following less intense sounds; this is known as the StartReact effect. The neural underpinnings for StartReact are unclear. One possibility is that startling cues preferentially invoke the reticulospinal tract to convey motor commands to spinal motoneurons. Reticulospinal outputs are highly divergent, controlling large groups of muscles in synergistic patterns. By contrast the dominant pathway in primate voluntary movement is the corticospinal tract, which can access small groups of muscles selectively. We therefore hypothesized that StartReact responses would be less fractionated than standard voluntary reactions. Electromyogram recordings were made from 15 muscles in 10 healthy human subjects as they carried out 32 varied movements with the right forelimb in response to startling and nonstartling auditory cues. Movements were chosen to elicit a wide range of muscle activations. Multidimensional muscle activity patterns were calculated at delays from 0 to 100 ms after the onset of muscle activity and subjected to principal component analysis to assess fractionation. In all cases, a similar proportion of the total variance could be explained by a reduced number of principal components for the startling and the nonstartling cue. Muscle activity patterns for a given task were very similar in response to startling and nonstartling cues. This suggests that movements produced in the StartReact paradigm rely on similar contributions from different descending pathways as those following voluntary responses to nonstartling cues. NEW & NOTEWORTHY We demonstrate that the ability to activate muscles selectively is preserved during the very rapid reactions produced following a startling cue. This suggests that the contributions from different descending pathways are comparable between these rapid reactions and more typical voluntary movements.

Reductions in phenomenological, physiological and attentional indices of depressive mood after 2 Hz rTMS over the right parietal cortex in healthy human subjects

2003 ◽  
Vol 120 (1) ◽  
pp. 95-101 ◽  
Author(s):  
Jack van Honk ◽  
Dennis J.L.G. Schutter ◽  
Peter Putman ◽  
Edward H.F de Haan ◽  
Alfredo A.L d'Alfonso
Keyword(s):  
Parietal Cortex ◽  
Human Subjects ◽  
Depressive Mood ◽  
Healthy Human ◽  
Healthy Human Subjects ◽  
The Right

scholarly journals Disentangling reward processes underlying payoff maximization from individual differences in gain frequency bias and reinforcement learning

2021 ◽  
Author(s):  
Pragathi Priyadharsini Balasubramani ◽  
Juan Diaz-Delgado ◽  
Gillian Grennan ◽  
Mariam Zafar-Khan ◽  
Fahad Alim ◽  
...  
Keyword(s):  
Reinforcement Learning ◽  
Individual Differences ◽  
Human Subjects ◽  
Reward Processing ◽  
Anterior Cingulate ◽  
Beta Activity ◽  
Neural Basis ◽  
Healthy Human ◽  
Specific Symptom ◽  
The Right

Humans make choices based on both reward magnitude and reward frequency. Probabilistic decision making is popularly tested using multi-choice gambling paradigms that require participants to maximize task payoff. However, research shows that performance in such paradigms suffers from individual bias towards the frequency of gains as well as individual differences that mediate reinforcement learning, including attention to stimuli, sensitivity to rewards and risks, learning rate, and exploration vs. exploitation based executive policies. Here, we developed a two-choice reward task, implemented in 186 healthy human subjects across the adult lifespan, to understand the cognitive and neural basis of payoff-based performance. We controlled for individual gain frequency biases using experimental block manipulations and modeled individual differences in reinforcement learning parameters. Simultaneously recorded electroencephalography (EEG)-based cortical activations showed that diminished theta activity in the right rostral anterior cingulate cortex (ACC) as well as diminished beta activity in the right parsorbitalis region of the inferior frontal cortex (IFC) during cumulative reward presentation correspond to better payoff performance. These neural activations further associated with specific symptom self-reports for depression (greater ACC theta) and inattention (greater IFC beta), suggestive of reward processing markers of clinical utility.

scholarly journals State-dependent differences in the frequency of TMS-evoked potentials

2019 ◽  
Author(s):  
Candice T. Stanfield ◽  
Martin Wiener
Keyword(s):  
Resting State ◽  
Right Hemisphere ◽  
Human Subjects ◽  
Dominant Frequency ◽  
Healthy Human ◽  
Cortical Areas ◽  
State Dependent ◽  
Concurrent Use ◽  
Cortical Regions ◽  
The Right

AbstractPrevious evidence suggests different cortical areas naturally oscillate at distinct frequencies, reflecting tuning properties of each region. The concurrent use of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) has been used to perturb cortical regions, resulting in an observed post-stimulation response that is maximal at the natural frequency of that region. However, little is known about the spatial extent of TMS-induced activation differences in cortical regions when comparing resting state (passive) versus active task performance. Here, we employed TMS-EEG to directly perturb three cortical areas in the right hemisphere while measuring the resultant changes in maximal evoked frequency in healthy human subjects during a resting state (N=12) and during an active sensorimotor task (N=12). Our results revealed that the brain engages a higher dominant frequency mode when actively engaged in a task, such that the frequency evoked during a task is consistently higher across cortical regions, regardless of the region stimulated. These findings suggest that a distinct characteristic of active performance versus resting state is a higher state of natural cortical frequencies.

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.

scholarly journals The Effect of lumbar lordosis on the distance between preemptive nail position of lumbar pedicle screw and prevertebral large vessels

2020 ◽  
Author(s):  
Li Zhao ◽  
Chenguang Wan ◽  
Chao Feng ◽  
Hongshi Zhang ◽  
He Sun
Keyword(s):  
Pedicle Screw ◽  
Lumbar Lordosis ◽  
Human Subjects ◽  
Healthy People ◽  
Healthy Human ◽  
Lumbar Intervertebral Disc ◽  
Scan Data ◽  
The Right ◽  
Large Vessels ◽  
Lumbar Pedicle

Abstract Objective: To study the effect of lumbar lordosis on the distance between preemptive nail position of lumbar pedicle screw and anterior large vessels In imaging.Methods: With the lumbar intervertebral disc plain CT scan data of 107 healthy human subjects, we had measured the lumbar lordosis angle, the distance between preemptive nail position of lumbar pedicle screw and anterior large vessels of each patient, and statistical analysis was performed by SPSS (v25.0).Results: 1. No correlation was found between lumbar lordosis and the distance between preemptive nail position of lumbar pedicle screw and anterior large vessels in healthy people, but there was a weak positive correlation between lumbar lordosis and age. 2. In healthy people, the distance between L1-2 right preemptive nail position of lumbar pedicle screw and anterior large vessel was larger than that on left side, while the distance between L3-5 right preemptive nail position of lumbar pedicle screw was smaller than that on left side.Conclusion: lumbar lordosis does not affect the distance between preemptive nail position of lumbar pedicle screw and anterior large vessels. Placing pedicle screw on the right side of L1-2 is more safe than placing it on the left side, and placing pedicle screw on the left side of L3-5 is more safe than on the right side.

Visually induced cross-axis postsaccadic eye drift

1993 ◽  
Vol 69 (4) ◽  
pp. 1031-1043 ◽  
Author(s):  
Z. Kapoula ◽  
D. A. Robinson ◽  
L. M. Optican
Keyword(s):  
Magnetic Field ◽  
Human Subjects ◽  
Vertical Component ◽  
Field Method ◽  
Full Field ◽  
Vertical Saccades ◽  
Before And After ◽  
Cross Axis ◽  
The Right ◽  
Random Dot Pattern

1. It has been previously shown that, if a visual pattern is transiently moved just after every saccade, it is possible to induce horizontal, postsaccadic, ocular drift after horizontal saccades that persists in the dark. In this study we show that horizontal ocular drift can also be created after vertical saccades. Five human subjects viewed binocularly the interior of a full-field hemisphere filled with a random-dot pattern. They were encouraged to make frequent vertical saccades. During training, eye movements were recorded by the electrooculogram. A computer detected the end of every saccade and immediately moved the pattern to the left after up saccades and right after down saccades. The motion was exponential, its amplitude was 25% of the vertical component of the antecedent saccade, its time constant was 50 ms. Before and after 2-3 h of training, movements of both eyes were measured by the eye-coil/magnetic-field method while subjects were instructed to make vertical saccades in the dark, in the presence of the movable adapting pattern, and between stationary targets for calibration. 2. After training (approximately 20,000 saccades) all subjects developed a zero-latency, exponential ocular drift to the left after up saccades and to the right after down saccades. The amplitude of the horizontal drift, expressed as a percentage of the vertical component of the preceding saccade, was 2.7% in the dark. This rose to 10.2% in the presence of the movable adapting stimulus. The latter rise is not due to visual following systems but to a zero-latency increase in initial drift velocity. 3. The horizontal drifts were usually unequal between the two eyes, indicating the presence of disconjugate movements. We measured intrasaccadic disconjugate horizontal movements of all subjects. In agreement with studies by others of saccades in the light, we measured a divergence during up saccades (1.3 degrees) and a convergence for down (0.4 degrees), but in this case for spontaneous saccades in the dark. After training, these values increased for saccades in the dark but decreased in the light in the presence of the adapting stimulus. These changes were largely idiosyncratic and statistically significant in only a few subjects. 4. The cross-axis postsaccadic drifts were separated into their conjugate and disconjugate components. The disconjugate components were small and idiosyncratic, and the means were small for saccades in the dark. The only consistent trend was in the presence of the adapting stimulus where up saccades were often followed by convergence.(ABSTRACT TRUNCATED AT 400 WORDS)

Sign in / Sign up

Export Citation Format

Share Document