scholarly journals Inflight head stabilization associated with wingbeat cycle and sonar emissions in the Egyptian fruit bat

2020 ◽  
Author(s):  
Jackson Rossborough ◽  
Angeles Salles ◽  
Laura Stidsholt ◽  
Peter Madsen ◽  
Cynthia F. Moss ◽  
...  
Keyword(s):  
Target Identification ◽  
Vertical Axis ◽  
Head Movements ◽  
Temporal Association ◽  
Vertical Acceleration ◽  
Motion Sensors ◽  
Gaze Stabilization ◽  
Head Stabilization ◽  
Fruit Bat ◽  
Successful Execution

AbstractSensory processing of environmental stimuli during locomotion is critical for the successful execution of goal-directed behaviors and navigating around obstacles. The outcome of these sensorimotor processes can be challenged by head movements that perturb the sensory coordinate frames directing behaviors. In the case of visually-guided behaviors, visual gaze stabilization results from the integrated activity of the vestibuloocular reflex and motor efference copy originating within circuits driving locomotor behavior. A recent videographic study showed that echolocating bats exhibit inflight head stabilization during a target identification and landing task, though compensatory timing of the bats’ sonar signals was not reported. In the present investigation we tested hypotheses that head stabilization is more broadly implemented during epochs of exploratory flight, and is temporally associated with emitted sonar signals, which would optimize acoustic gaze. This was achieved by measuring head and body kinematics with motion sensors secured to the head and body of free-flying Egyptian fruit bats. These devices were integrated with ultrasonic microphones to record the bat’s sonar emissions and elucidate their temporal association with periods of head stabilization. Head accelerations in the Earth-vertical axis were asymmetric with respect to wing downbeat and upbeat relative to body accelerations. This indicated that inflight head and body accelerations were uncoupled, outcomes consistent with the implementation of head movements that limit vertical acceleration during wing downbeat. Furthermore, sonar emissions during stable flight occurred most often during wing downbeat and head stabilization, supporting the conclusion that head stabilization behavior optimized sonar gaze and environmental interrogation via echolocation.Summary statementDirect measurements of head and body kinematics from affixed motion sensors revealed head stabilization behaviors during exploratory flights in bats. Most sonar emissions were temporally correlated with this behavior, thereby contributing to the optimization of acoustic gaze.

Inactivation of Semicircular Canals Causes Adaptive Increases in Otolith-Driven Tilt Responses

2002 ◽  
Vol 87 (3) ◽  
pp. 1635-1640 ◽  
Author(s):  
Dora E. Angelaki ◽  
Shawn D. Newlands ◽  
J. David Dickman
Keyword(s):  
Eye Movements ◽  
Semicircular Canal ◽  
Translational Motion ◽  
Semicircular Canals ◽  
Vertical Axis ◽  
Lateral Motion ◽  
Functional Interaction ◽  
Gaze Stabilization ◽  
Theoretical Evidence ◽  
Ocular System

Growing experimental and theoretical evidence suggests a functional synergy in the processing of otolith and semicircular canal signals for the generation of the vestibulo-ocular reflexes (VORs). In this study we have further tested this functional interaction by quantifying the adaptive changes in the otolith-ocular system during both rotational and translational movements after surgical inactivation of the semicircular canals. For 0.1–0.5 Hz (stimuli for which there is no recovery of responses from the plugged canals), pitch and roll VOR gains recovered during earth-horizontal (but not earth-vertical) axis rotations. Corresponding changes were also observed in eye movements elicited by translational motion (0.1–5 Hz). Specifically, torsional eye movements increased during lateral motion, whereas vertical eye movements increased during fore-aft motion. The findings indicate that otolith signals can be adapted according to a compromised strategy that leads to improved gaze stabilization during motion. Because canal-plugged animals permanently lose the ability to discriminate gravitoinertial accelerations, adapted animals can use the presence of gravity through otolith-driven tilt responses to assist gaze stabilization during earth-horizontal axis rotations.

Inflight head stabilization associated with wingbeat cycle and sonar emissions in the lingual echolocating Egyptian fruit bat, Rousettus aegyptiacus

2021 ◽  
Author(s):  
Jackson Rossborough ◽  
Angeles Salles ◽  
Laura Stidsholt ◽  
Peter T. Madsen ◽  
Cynthia F. Moss ◽  
...  
Keyword(s):  
Head Stabilization ◽  
Fruit Bat

Viewing Target Distance Influences the Vestibulo-Ocular Reflex Gain when Assessed Using the Video Head Impulse Test

2018 ◽  
Vol 23 (5) ◽  
pp. 285-289 ◽  
Author(s):  
Patricia Castro ◽  
Sara Sena Esteves ◽  
Florencia Lerchundi ◽  
David Buckwell ◽  
Michael A. Gresty ◽  
...  
Keyword(s):  
Head Movements ◽  
Target Distance ◽  
Head Impulse Test ◽  
Video Head Impulse Test ◽  
Gaze Stabilization ◽  
Head Impulse ◽  
Ocular Reflex ◽  
Significant Difference ◽  
Vestibulo Ocular Reflex ◽  
Reflex Gain

Gaze stabilization during head movements is provided by the vestibulo-ocular reflex (VOR). Clinical assessment of this reflex is performed using the video Head Impulse Test (vHIT). To date, the influence of different fixation distances on VOR gain using the vHIT has not been explored. We assessed the effect of target proximity on the horizontal VOR using the vHIT. Firstly, we assessed the VOR gain in 18 healthy subjects with 5 viewing target distances (150, 40, 30, 20, and 10 cm). The gain increased significantly as the viewing target distance decreased. A second experiment on 10 subjects was performed in darkness whilst the subjects were imagining targets at different distances. There were significant inverse relationships between gain and distance for both the real and the imaginary targets. There was a statistically significant difference between light and dark gains for the 20- and 40-cm distances, but not for the 150-cm distance. Theoretical VOR gains for different target distances were calculated and compared with those found in light and darkness. The increase in gain observed for near targets was lower than predicted by geometrical calculations, implying a physiological ceiling effect on the VOR. The VOR gain in the dark, as assessed with the vHIT, demonstrates an enhancement associated with a reduced target distance.

Rapid horizontal gaze movement in the monkey

1995 ◽  
Vol 73 (4) ◽  
pp. 1632-1652 ◽  
Author(s):  
J. O. Phillips ◽  
L. Ling ◽  
A. F. Fuchs ◽  
C. Siebold ◽  
J. J. Plorde
Keyword(s):  
Eye Movement ◽  
Head Movement ◽  
Vertical Axis ◽  
Head Position ◽  
Head Movements ◽  
Gaze Shifts ◽  
Gaze Shift ◽  
The Gaze ◽  
Small Correction ◽  
Horizontal Gaze

1. We studied horizontal eye and head movements in three monkeys that were trained to direct their gaze (eye position in space) toward jumping targets while their heads were both fixed and free to rotate about a vertical axis. We considered all gaze movements that traveled > or = 80% of the distance to the new visual target. 2. The relative contributions and metrics of eye and head movements to the gaze shift varied considerably from animal to animal and even within animals. Head movements could be initiated early or late and could be large or small. The eye movements of some monkeys showed a consistent decrease in velocity as the head accelerated, whereas others did not. Although all gaze shifts were hypometric, they were more hypometric in some monkeys than in others. Nevertheless, certain features of the gaze shift were identifiable in all monkeys. To identify those we analyzed gaze, eye in head position, and head position, and their velocities at three points in time during the gaze shift: 1) when the eye had completed its initial rotation toward the target, 2) when the initial gaze shift had landed, and 3) when the head movement was finished. 3. For small gaze shifts (< 20 degrees) the initial gaze movement consisted entirely of an eye movement because the head did not move. As gaze shifts became larger, the eye movement contribution saturated at approximately 30 degrees and the head movement contributed increasingly to the initial gaze movement. For the largest gaze shifts, the eye usually began counterrolling or remained stable in the orbit before gaze landed. During the interval between eye and gaze end, the head alone carried gaze to completion. Finally, when the head movement landed, it was almost aimed at the target and the eye had returned to within 10 +/- 7 degrees, mean +/- SD, of straight ahead. Between the end of the gaze shift and the end of the head movement, gaze remained stable in space or a small correction saccade occurred. 4. Gaze movements < 20 degrees landed accurately on target whether the head was fixed or free. For larger target movements, both head-free and head-fixed gaze shifts became increasingly hypometric. Head-free gaze shifts were more accurate, on average, but also more variable. This suggests that gaze is controlled in a different way with the head free. For target amplitudes < 60 degrees, head position was hypometric but the error was rather constant at approximately 10 degrees.(ABSTRACT TRUNCATED AT 400 WORDS)

Changes in temporal binding related to decreased vestibular input

2012 ◽  
Vol 25 (0) ◽  
pp. 107
Author(s):  
Nai-Yuan Nicholas Chang ◽  
Alex K. Malone ◽  
Timothy E. Hullar
Keyword(s):  
Vertical Axis ◽  
Normal Subjects ◽  
Head Movements ◽  
Whole Body ◽  
The Novel ◽  
Vestibular Input ◽  
Temporal Binding ◽  
Sensory Stimuli ◽  
Vestibular Hypofunction ◽  
Temporal Binding Window

Imbalance among patients with vestibular hypofunction has been related to inadequate compensatory eye movements in response to head movements. However, symptoms of imbalance might also occur due a temporal mismatch between vestibular and other balance-related sensory cues. This temporal mismatch could be reflected in a widened temporal binding window (TBW), or the length of time over which simultaneous sensory stimuli may be offset and still perceived as simultaneous. We hypothesized that decreased vestibular input would lead to a widening of the temporal binding window. We performed whole-body rotations about the earth-vertical axis following a sinusoidal trajectory at 0.5 Hz with a peak velocity of 60°/s in four normal subjects. Dichotic auditory clicks were presented through headphones at various phases relative to the rotations. Subjects were asked to indicate whether the cues were synchronous or asynchronous and the TBW was calculated. We then simulated decreased vestibular input by rotating at diminished peak velocities of 48, 24 and 12°/s in four normal subjects. TBW was calculated between ±1 SD away from the mean on the psychometric curve. We found that the TBW increases as amplitude of rotation decreases. Average TBW of 251 ms at 60°/s increased to 309 ms at 12°/s. This result leads to the novel conclusion that changes in temporal processing may be a mechanism for imbalance in patients with vestibular hypofunction.

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.

scholarly journals Sit-To-Stand Movement Evaluated Using an Inertial Measurement Unit Embedded in Smart Glasses—A Validation Study

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5019
Author(s):  
Justine Hellec ◽  
Frédéric Chorin ◽  
Andrea Castagnetti ◽  
Serge S. Colson
Keyword(s):  
Concurrent Validity ◽  
Inertial Measurement Unit ◽  
Vertical Axis ◽  
Measurement Unit ◽  
Vertical Acceleration ◽  
Optoelectronic System ◽  
Inertial Measurement ◽  
Sit To Stand ◽  
Smart Glasses ◽  
Absolute Reliability

Wearable sensors have recently been used to evaluate biomechanical parameters of everyday movements, but few have been located at the head level. This study investigated the relative and absolute reliability (intra- and inter-session) and concurrent validity of an inertial measurement unit (IMU) embedded in smart eyeglasses during sit-to-stand (STS) movements for the measurement of maximal acceleration of the head. Reliability and concurrent validity were investigated in nineteen young and healthy participants by comparing the acceleration values of the glasses’ IMU to an optoelectronic system. Sit-to-stand movements were performed in laboratory conditions using standardized tests. Participants wore the smart glasses and completed two testing sessions with STS movements performed at two speeds (slow and comfortable) under two different conditions (with and without a cervical collar). Both the vertical and anteroposterior acceleration values were collected and analyzed. The use of the cervical collar did not significantly influence the results obtained. The relative reliability intra- and inter-session was good to excellent (i.e., intraclass correlation coefficients were between 0.78 and 0.91) and excellent absolute reliability (i.e., standard error of the measurement lower than 10% of the average test or retest value) was observed for the glasses, especially for the vertical axis. Whatever the testing sessions in all conditions, significant correlations (p < 0.001) were found for the acceleration values recorded either in the vertical axis and in the anteroposterior axis between the glasses and the optoelectronic system. Concurrent validity between the glasses and the optoelectronic system was observed. Our observations indicate that the IMU embedded in smart glasses is accurate to measure vertical acceleration during STS movements. Further studies should investigate the use of these smart glasses to assess the STS movement in unstandardized settings (i.e., clinical and/or home) and to report vertical acceleration values in an elderly population of fallers and non-fallers.

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)

Adaptation of the vestibulo-ocular reflex, subjective tilt, and motion sickness to head movements during short-radius centrifugation

2003 ◽  
Vol 13 (2-3) ◽  
pp. 65-77
Author(s):  
Laurence R. Young ◽  
Kathleen H. Sienko ◽  
Lisette E. Lyne ◽  
Heiko Hecht ◽  
Alan Natapoff
Keyword(s):  
Motion Sickness ◽  
Body Position ◽  
Rest Period ◽  
Vertical Axis ◽  
Head Movements ◽  
Whole Body ◽  
Slow Phase ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Angular Velocities

Head movements made while the whole body is rotating at unusually high angular velocities (here with supine body position about an earth-vertical axis) result in inappropriate eye movements, sensory illusions, disorientation, and frequently motion sickness. We investigated the acquisition and retention of sensory adaptation to cross-coupled components of the vestibulo-ocular reflex (VOR) by asking eight subjects to make headturns while being rotated at 23 rpm on two consecutive days, and again a week later. The dependent measures were inappropriate vertical VOR, subjective tilt, and motion sickness in response to 90° yaw out-of-plane head movements. Motion sickness was evaluated during and following exposure to rotation. Significant adaptation effects were found for the slow phase velocity of vertical nystagmus, the reported magnitude of the subjective tilt experienced during head turns, and motion-sickness scores. Retention of adaptation over a six-day rest period without rotation occurred, but was not complete for all measures. Adaptation of VOR was fully maintained while subjective tilt was only partially maintained and motion-sickness scores continued to decrease. Practical implications of these findings are discussed with particular emphasis on artificial gravity, which could be produced in weightlessness by means of a short-radius (2 m) rotator.

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