bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the Torsional VOR in Weightlessness
Authors: Clarke Andrew H. , Teiwes Winfried , Scherer Hans
Published: September 2021

The experimental concept and findings from a recent manned orbital spaceflight are described. Together with ongoing terrestrial and parabolic studies, the present experiment is intended to further our knowledge of the sensory integrative processing of information from the semicircular canals and the otolithic receptors, and to quantify the presumed otolithic adaptation to altered gravito-inertial force environments in a more reliable manner than to date. The experiment included measurement of the basic vestibulo-oculomotor response during active head rotation about each of the three orthogonal axes. Priority was given to the recording of ocular torsion, as elicited by head oscillation about the roll axis, and thus due to the concomitant stimulation of the semicircular canals and otolith receptors. Videooculography was employed for the measurement of eye movements; head movement was measured by three orthogonally arranged angular rate sensors and a triaxial linear accelerometer device. All signals were recorded synchronously on a video/data recorder. Preliminary results indicate alterations in the torsional VOR under zero-g conditions, suggesting an adaptive modification of the torsional VOR gain over the course of the 6-day orbital flight. In addition, the inflight test findings yielded discrepancies between intended and performed head movement indicating impairment in sensorimotor coordination under prolonged microgravity conditions.
Vestibular Function and Sensory Interaction in Space Flight
Authors: Kornilova L.N. , Grigorova V. , Bodo G.
Published: September 2021

The vestibular system and vestibulo-visual interaction were examined in 11 astronauts by the electrooculographic (EOG) method during short- and long-term flights on days 2, 3, 5, 9, 22, 50, 164, and 169 (experiments OPTOKINES and LABYRINTH). In space (flight days 2 and 3), they showed enhanced spontaneous vertical nystagmus, and disorders of tracking of vertical and diagonal movements of the stimulus which improved after active head movements. Early increasing of the reactivity of the cupulo-endolymphatic system (flight days 2–3) was replaced after 5 days of flight with a reduction of the vestibular function and an increase of the significance of the visual input in the formation of oculomotor responses to combined vestibulo-optokinetic stimulation. The type of spontaneous ocular reaction and vestibular stimulation of oculomotor activity under the conditions of weightlessness represented, on one band, the general responses of sensory systems to weightlessness and, on the other hand, specificity of integrating and adaptive processes.
Vestibular Endorgan of the Frog After the Space Flight and Postural Alteration of the Neurectomized Frog – Its Morphological and Functional Resilience1
Authors: Suzuki Mamoru , Harada Yasuo , Sekitani Tooru
Published: September 2021

The vestibular organ of frogs returned from space were observed by SEM. Morphology of the sensory epithelia was normal, including ultrastructure, such as tip links and side links. The frogs’ behavior and vestibular morphology after various types of vestibular neurectomy were studied. Vestibular neurectomy resulted in tilting posture toward that side. This tilting gradually decreased to zero and the nerve regenerated. When the same nerve was cut again after postoral recovery, the tilting angle was smaller and recovery period was shorter than after the first neurectomy. When the bilateral nerves were cut and neural regeneration was inhibited on one side, tilting slowly developed toward that side. These results show that frogs’ postural change is modified by both central compensation and peripheral vestibular function.
Sensorimotor and Perceptual Function of Muscle Proprioception in Microgravity
Authors: Roll J.P. , Popov K. , Gurfinkel V. , Lipshits M. , André-Deshays C. , Gilhodes J.C. , Quoniam C.
Published: September 2021

Adaptive properties of the human proprioceptive systems were studied during the French-Soviet orbital flight (Aragatz mission, December 1988). The present space experiment investigated the hypothesis that the modifications of both biomechanical and physiological conditions occurring under microgravity involve considerable reorganization of body perception and postural control. The proprioceptive information originating in muscles is known to contribute, together with visual, vestibular, and sole cutaneous information to postural regulation. Moreover, by specifically activating the proprioceptive channel, muscle vibration is able to elicit both illusory movement sensations and postural responses. This experimental tool was used in microgravity in order to test various aspects of muscle sensory function. Ankle flexor and extensor vibration was applied under different experimental conditions. Quantitative analysis of motor responses was carried out on leg muscle EMG, goniometric, and kinesigraphic recordings. Joystick recordings and astronauts’ comments were used to describe the kinaesthetic sensations. The main results were as follows: 1) Under microgravity, the sensitivity of muscle receptors remains unchanged. 2) During the flight, the tonic vibration reflexes (TVR) increased significantly in flexor muscles, which exhibited a sustained tonic activity. 3) The whole-body postural responses normally induced by ankle flexor muscle vibration were suppressed, whereas they remained unchanged or were only reduced when vibrations were applied to the ankle extensor muscles. In all cases, the postural response velocity decreased. 4) A disfacilitation of the vibration-induced postural illusions was observed to occur during long-term exposure to microgravity. These illusions became atypical however. For example: body lift illusion could be induced by tibialis anterior muscle vibration, whereas it was never induced in the controls. The characteristics of the illusory body movements described under normal gravity can be restored by artificially increasing the axial foot support forces during the flight. In conclusion, these data suggest that a functional reorganization of the proprioceptive information processing occurs in microgravity, affecting both perceptual and motor aspects of behavior. It is possible that these proprioceptive adaptations may be partly attributable to the new whole-body propulsive foot functions imposed by exposure to weightlessness and to the adaptation of motor behavior to the third dimension of space.
Perceived Self-Orientation and Self-Motion in Microgravity, After Landing and During Preflight Adaptation Training
Authors: Harm Oeborah L. , Parker Donald E.
Published: September 2021

The research described in this paper is intended to support development and evaluation of preflight adaptation training (PAT) apparatus and procedures. Successful training depends on appropriate manipulation of visual and inertial stimuli that control perception of self-motion and self-orientation. For one part of this process, astronauts are trained to report their self-motion and self-orientation experiences. Before their space mission, they are exposed to the altered sensory environments produced by the PAT trainers. During and after the mission, they report their motion and orientation experiences. Subsequently, they are again exposed to the PAT trainers and are asked to describe relationships between their experiences in microgravity and following entry and their experiences in the trainers.
Gaze Control in Microgravity: 1. Saccades, Pursuit, Eye-Head Coordination
Authors: André-Deshays C. , Israël I. , Charade O. , Berthoz A. , Popov K. , Lipshits M.
Published: September 2021

During the long-duration spaceflight Aragatz on board the Mir station, an experiment exploring the different oculomotor subsystems involved in gaze control during orientation to a fixed target or when tracking a moving target was executed by two cosmonauts. Gaze orientation: with head fixed, the “main sequence” relationships of primary horizontal saccades were modified, peak velocity was higher and saccade duration was shorter in flight than on earth, latency was decreased and saccade accuracy was better in flight. With head free, gaze orientation toward the target was achieved by coordinated eye and head movements, their timing was maintained in the horizontal plane; when gaze was stabilized on the target, there was a trend of a larger eye than head contribution not seen in preflight tests. Pursuit: Horizontal pursuit at 0.25 and 0.5 Hz frequency remained smooth with a 0.98 gain and minor phase lag, on earth and in flight. In the vertical plane, the eye did not track the target with a pure smooth pursuit eye movement, but the saccadic system contributed to gaze control. Upward tracking was mainly achieved with a succession of saccades, whereas downward tracking was due to combined smooth pursuit and catch-up saccades. This asymmetry was maintained during flight in head fixed and head free situations. On earth head pea velocity was maxima upward, and in flight it was maximal downward.
The Effect of Head Tilt on Perception of Self-Orientation While in a Greater than One G Environment
Authors: Chelette Tamara L. , Martin Eric J. , Albery William B.
Published: September 2021

The effect of head tilt on the perception of self-orientation while in a greater than one G environment was studied in nine subjects using the Armstrong Laboratory Dynamic Environment Simulator. After a 12-s stabilization period at a constant head tilt and G level, subjects reported their perception of the horizon by placing their right hand in a position they believed to be horizontal. Head tilt conditions ranged from -30° to +45° pitch over each of three head yaw positions. G levels ranged from one to four and were in the longitudinal axis of the body (Gz). Hand position was recorded in both the pitch and roll body axes. A function of head tilt did improve the fit of a multiple regression model to the collected data in both the pitch and roll axes (P < .05). The best fit was accomplished with a nonlinear function of G and head pitch. When the head remained level but the environment tilted with respect to the G vector (at angles similar to those perceived during head tilt), subjects accurately reported the environmental tilt. Head tilt under G can result in vestibular-based illusionary perception of environmental tilt. Actual environmental tilt is accurately perceived due to added channels of haptic information.
Reliability of Psychophysiological Responses Across Multiple Motion Sickness Stimulation Tests
Authors: Stout Cynthia S. , Toscano William B. , Cowings Patricia S.
Published: September 2021

Although there is general agreement that a high degree of variability exists between subjects in their autonomic nervous system responses to motion sickness stimulation, very little evidence exists that examines the reproducibility of autonomic responses within subjects during motion sickness stimulation. Our objectives were to examine the reliability of autonomic responses and symptom levels across five testing occasions using the (1) final minute of testing, (2) change in autonomic response and the change in symptom level, and (3) strength of the relationship between the change in symptom level and the change in autonomic responses across the entire motion sickness test. The results indicate that, based on the final minute of testing, the autonomic responses of heart rate, blood volume pulse, and respiration rate are moderately stable across multiple tests. Changes in heart rate, blood volume pulse, respiration rate, and symptoms throughout the test duration are less stable across the tests. Finally, autonomic responses and symptom levels are significantly related across the entire motion sickness lest.
The Subjective Visual Vertical as a Clinical Parameter of Vestibular Function in Peripheral Vestibular Diseases
Authors: Böhmer Andreas , Rickenmann Jürg
Published: September 2021

The subjective visual vertical, SV, was measured in the upright and side positions in 25 normal subjects and in 73 patients with various peripheral vestibular disorders. Significant deviations of SV (toward the affected ear) were found in 100% of the patients with vestibular nerve section and with Ramsay Hunt syndrome, in 89% of the patients with vestibular neuritis, and in 0% of the patients with benign paroxysmal positional vertigo. The deviation of SV gradually disappeared within a few weeks of the onset of the disease in all patients except in those with total VIIth nerve resection. SV is a parameter of tonic afferent differences between the two labyrinths similar to vestibular spontaneous nystagmus but is mediated by other parts of the inner ear (probably the otolith organs) and thus provides additional information on the labyrinthine function. SV measured in 90° side positions, however, did not reveal asymmetric vestibular sensitivity, which is in contrast to SV tested during eccentric rotation in patients after vestibular neurectomy.
Bilateral Loss of Eighth Nerve Function as the Only Clinical Sign of Vertebrobasilar Dollchoectasia1
Authors: Büttner U. , Ott M. , Helmchen Ch. , Yousry T.
Published: September 2021

The case of a 55-year-old female is presented, in whom first a loss of the vestibular and hearing function on the left side occurred with sudden onset, and 3 days later an additional loss of functions on the right side occurred. No other neurological symptoms were present. Angiography and MRI scan revealed vertebrobasilar dolichoectasia with a thrombus attached to the wall of the basilar artery. Anticoagulative therapy improved hearing function on the right side sufficiently to allow conversation. Vestibular organs remained unresponsive to caloric irrigation. This bilateral loss of eighth nerve function is discussed as a rare case of bilateral ischemia of the labyrinthine artery due to basilar dolichoectasia.
Vestibular Compensation: A Review of the Oculomotor, Neural, and Clinical Consequences of Unilateral Vestibular Loss
Authors: Curthoys Ian S. , Halmagyi G. Michael
Published: September 2021

Vestibular sensory input is just one sensory input involved in the control of functions such as gaze and posture. The recovery of gaze and posture control after partial or complete unilateral loss of vestibular input is reviewed. The relatively rapid and apparently complete behavioral recovery after unilateral vestibular loss was once regarded as justifying vestibular compensation being used as a text-book example of plasticity in the CNS. This review emphasizes how false that impression is: Detailed examination shows that vestibular compensation is not a single process that recovers completely at a rapid rate but is made up of a number of subprocesses that recover to different levels and at different rates. In some subprocesses there is very modest recovery; in other subprocesses there is probably substitution of other sensory input for the affected vestibular input. It also seems that in some instances new behavioral strategies appear to be learned to allow gaze and posture control to operate as if normal. Recent evidence concerning the physiological and pharmacological mechanisms underlying vestibular compensation is reviewed.
Arthrokinetic Information Affects Linear Self-Motion Perception
Authors: Bles Willem , Jelmorini Monique , Bekkering Harold , de Graaf Bernd
Published: September 2021

A sensation of linear self-motion can be induced in a blindfolded stationary sitting subject, who keeps contact with a linearly moving platform (acceleration 0.1 m/s2) in the frontoparallel plane by means of a hand-over-hand walking action. When discordant suprathreshold vestibular information from the otoliths is added by moving the subject laterally (acceleration 0.1 m/s2) in the same direction as the platform (acceleration of the platform 0.2 m/s2, so the arthrokinetic stimulus is also an acceleration of 0.1 m/s2, but into the opposite direction), the arthrokinetic information was found to have a predominant effect on the perceived direction of self-motion.
Does Posturography Differentiate Malingerers from Vertiginous Patients?
Authors: Uimonen Seija , Laitakari Kyösti , Kiukaanniemi Heikki , Sorri Martti
Published: September 2021

Voluntary, simulated vertigo and acute vertigo due to vestibular neuritis were examined by means of static posturography in 81 tests to evaluate the extent to which intentional malingering can be detected. Thirty healthy, normal subjects were first instructed to stand as still as possible on a static force platform and then to simulate dizziness. The true cases consisted of 21 patients with vestibular neuritis. The parameters analyzed included body sway velocity (BSV), body sway area of ellipse (BSE), and the Romberg quotient. Both the simulated and pathological posturographic BSV and BSE values differed from normal values under all test conditions, but they did not differ from each other, whereas the simulated values could be differentiated from the pathological ones with the Romberg quotient based on BSV. Five staff members of our audiological department were able to differentiate between the simulations and pathological cases quite well, with a median sensitivity of 0.77 and a specificity of 0.71 in a blinded test. A posturographic measurement, even performed once, can be useful to some extent for detecting simulation, but more investigation and development of the analysis system is required to obtain more specific results. For the present, the results obtained by trained observation of the subject in the test situation are at least as reliable as those obtained through the analysis of statistical measurements.
Effect of Gravito-Inertial Cues on the Coding of Orientation in Pre-Attentive Vision
Authors: Stivalet Philippe , Marendaz Christian , Barraclough Lorna , Mourareau Christian
Published: September 2021

To see if the spatial reference frame used by pre-attentive vision is specified in a retino-centered frame or in a reference frame integrating visual and nonvisual information (vestibular and somatosensory), subjects were centrifuged in a nonpendular cabin and were asked to search for a target distinguishable from distractors by difference in orientation (Treisman’s “pop-out” paradigm [1]). In a control condition, in which subjects were sitting Immobilized but not centrifuged, this task gave an asymmetric search pattern: Search was rapid and pre-attentional except when the target was aligned with the horizontal retinal/head axis, in which case search was slow and attentional (2). Results using a centrifuge showed that slow/serial search patterns were obtained when the target was aligned with the subjective horizontal axis (and not with the horizontal retinal/head axis). These data suggest that a multisensory reference frame is used in pre-attentive vision. The results are interpreted in terms of Riccio and Stoffregen’s “ecological theory” of orientation in which the vertical and horizontal axes constitute independent reference frames (3).
Neuronal Responses in Vestibular Nuclei to Dorsal Raphe Electrical Activation
Authors: Licata Flora , Li Volsi Guido , Maugeri Giuseppe , Santangelo Francesca
Published: September 2021

The effects of dorsal raphe (DR) electrical stimulation on the neuronal activity of vestibular nuclei were studied in anaesthetized rats. The aim was to establish whether the central systems classically involved in nociceptive functions are able to influence vestibular secondary neurons. DR activation induced modifications of the firing in 70% of the tested neurons, the percentage being similar in the lateral (LVN), superior (SVN), and spinal (SpVN) vestibular nuclei. Three different types of responses were recorded: long-lasting modifications (generally enhancements) of the mean firing rate (43%), short-latency response patterns (14%), both (43%). Short-latency response patterns were more numerous in LVN than in SVN. Iontophoretic applications of 5-HT antagonists Methysergide and Ketanserin blocked long-lasting effects but were scarcely effective on the short-latency response patterns evoked by DR stimulation. It is concluded that DR exerts a double control on secondary vestibular neurons: a generalised excitatory influence by serotoninergic fibers and a specific action mostly targeted on LVN, by nonserotoninergic pathways.
Investigation of the Horizontal, Vertical, and Oblique Optokinetic Nystagmus and Afternystagmus in Squirrel Monkeys
Authors: Kröller J. , Behrens F.
Published: September 2021

A moving random dot pattern was projected onto a tangent screen in front of awake untrained monkeys that were always placed in upright position. Eye movements were recorded in two dimensions to study the oblique optokinetic nystagmus (OKN) and compare it to the horizontal and vertical OKN. Any direction of pattern movement across the screen could be achieved. The angular velocity of pattern movement was varied between 6 and 180°/s. To display off-horizontal and off-vertical eye movements, the instantaneous direction and velocity of the eye movements were computed from the horizontal and vertical search coil voltages. At pattern velocities below 90°/s, stimulus-direction and direction of the OKN slow phase matched very precisely. Above 90°/s the slow-phase eye movement direction was systematically shifted toward the horizontal except for pure vertical stimulation. The slow-phase eye velocity at off-horizontal stimulation was inconstant, however; stable periods occurred repeatedly that were used to define the gain of OKN. Up to stimulus speeds of about 90°/s the OKN gain did not depend on the direction of stimulation and of OKN. At higher velocities the gain decreased with the increasing angle between stimulus direction and horizontal. Practically no vertical optokinetic afternystagmus (OKAN) could be observed, in either the up or down direction. At the onset of afternystagmus after oblique stimulation the direction of the OKAN slow phase immediately shifted over to the horizontal. The data indicate that the slow-phase direction and gain of oblique OKN with the monkey’s head upright can be described by the sum of a horizontal and a vertical velocity vector obtained during stimulation in these cardinal directions.
Body Orientation and Regulation of the Center of Gravity During Movement Under Water
Authors: Massion Jean , Fabre Jean-Claude , Mouchnino Laurence , Obadia Annie
Published: September 2021

Professional divers were instructed to adopt a vertical posture under water with their feet fixed to the ground and to perform a fast forward or backward upper trunk bending movement in response to a tone. Kinematic and EMG analyses were performed. It was first noted that the divers adopted a forward inclined, erect posture, suggesting that the verticality was misevaluated, although the effects of gravity were still exerted on the otoliths. Second, the upper trunk movements were still accompanied by opposite movements of lower segments and, as a result, the center of gravity displacement was still minimized, although not so accurately as on the ground. The EMG pattern consisting of early activation of a set of trunk, thigh, and shank muscles continued to occur under water. These results suggest that “axial synergies” associated with upper trunk movements are learned motor habits that regulate the center of gravity position regardless of the equilibrium constraints.
Horizontal Rotation Responses of Medullary Reticular Neurons in the Decerebrate Cat1
Authors: Schor Robert H. , Yates Bill J.
Published: September 2021

This study examines the response of neurons in the medullary reticular formation of the decerebrate cat to sinusoidal yaw rotations in the plane of the horizontal semicircular canals. Responsive neurons that could be antidromically activated from the spinal cord appeared to be less sensitive to the rotary stimulus than the rest of the population of responsive neurons. Most neurons had response dynamics similar to those of semicircular canal afferents.
Vestibularly Evoked Potentials (VESTEPs) of the Horizontal Semicircular Canals Under Different Body Positions in Space
Authors: Probst Thomas , Katterbach Tanja , Wist Eugene R.
Published: September 2021

We recorded vestibularly evoked potentials (VESTEPs) using natural vestibular stimuli simulating the form of a normal head movement (“raised cosine”). Its smooth course was designed to minimize all possible sources of artifacts of mechanical, electrical, and physiological origin. This motion profile was applied to subjects (Ss) sitting upright, thus stimulating the horizontal semicircular canals alone, as well as when they were tilted in different positions in steps of 30° about the interaural y-axis, which had the effect of modulating the otolithic contribution to the horizontal VESTEP. The transient bell-shaped VESTEP recorded in the upright sitting S was more and more superimposed or replaced by a sustained negativity the more the S was tilted toward a horizontal position. Thus, the VESTEP gradually changes from a velocity response in the upright S (canals only) to a position response in the lying S (canals plus otoliths). Differences in the VESTEPs obtained for clockwise (cw) and counterclockwise (ccw) turns in the tilted S were found. The reason for this is not clear at present and requires further experimentation. However, the VESTEPs obtained under conditions involving backward tilts and cw turns corresponded to those obtained with forward tilts and ccw turns. A similar relationship was found for the VESTEPs obtained with backward tilts and ccw turns and those obtained with forward tilts and cw turns. The physiological basis of this is discussed.
Mediolateral Differential Projection to the Nodulus from the Inferior Olive in the Albino Rat: A Retrograde WGA-HRP Study
Authors: Umetani Takehiko
Published: September 2021

The mediolateral topographic organization of olivocerebellar projections to the nodulus in rats was investigated by a retrograde WGA-HRP method. The nodulus received olivary afferents from the contralateral dorsal cap, nucleus β, ventrolateral outgrowth, and dorsomedial cell column. The mediolateral extent of terminal areas of the olivocerebellar fibers arising from these subnuclei differed. The dorsal cap projected to the entire mediolateral area of the contralateral nodulus; the rostral and caudal parts of the dorsal cap projected to the lateral and medial parts of the nodulus, respectively. The nucleus β projected to the medial and intermediate parts of the nodulus. Differential projections from the nucleus β were observed in a rostrocaudal direction as those from the dorsal cap; the rostral and medial parts of the nucleus projected to the intermediate and medial parts of the nodulus, respectively. The ventrolateral outgrowth projected only to the intermediate part of the nodulus. The dorsomedial cell column projected to the lateral half of the nodulus, including its lateral tip. These and previous findings are compared with respect to this mediolateral topography.
Geometric Adjustments to Account for Eye Eccentricity in Processing Horizontal and Vertical Eye and Head Movement Data
Authors: Huebner William P. , Paloski William H. , Reschke Millard F. , Bloomberg Jacob J.
Published: September 2021

Neglecting the eccentric position of the eyes in the head can lead to erroneous interpretation of ocular motor data, particularly for near targets. We discuss the geometric effects that eye eccentricity has on the processing of target-directed eye and head movement data, and we highlight two approaches to processing and interpreting such data. The first approach involves determining the true position of the target with respect to the location of the eyes in space for evaluating the efficacy of gaze, and it allows calculation of retinal error directly from measured eye, head, and target data. The second approach effectively eliminates eye eccentricity effects by adjusting measured eye movement data to yield equivalent responses relative to a specified reference location (such as the center of head rotation). This latter technique can be used to standardize measured eye movement signals, enabling waveforms collected under different experimental conditions to be directly compared, both with the measured target signals and with each other. Mathematical relationships describing these approaches are presented for horizontal and vertical rotations, for both tangential and circumferential display screens, and efforts are made to describe the sensitivity of parameter variations on the calculated results.
Vestibulo-Ocular Response of Human Subjects Seated in a Pivoting Support System During 3 Gz Centrifuge Stimulation
Authors: McGrath B.J. , Guedry F.E. , Oman C.M. , Rupert A.H.
Published: September 2021

The vestibulo-ocular reflex (VOR) and spatial orientation perceptions were recorded in 15 subjects during 3 Gz centrifuge runs. These data were obtained to study two issues: (1) to gain insight into reports of asymmetrical disorientation and disturbance during acceleration and deceleration of centrifuge runs like those used to train pilots on the procedures to counteract G-induced loss of consciousness (G-LOC); (2) to study the effects of sustained vertical linear acceleration on the vestibular system. The centrifuge angular velocity profile consisted of a 19 s angular acceleration to 3 Gz that was sustained for 5 min during a period of constant angular velocity, and a 19 s deceleration to 1 Gz. The runs were repeated three times with the subject facing the motion and three times with the subject’s back to the motion. The VOR and spatial orientation perceptions from the eight subjects who completed all six runs were analyzed. The total VOR response during acceleration and deceleration was composed of interacting angular (AVOR) and linear components (LVOR). Asymmetries in pitch orientation perception between centrifuge acceleration and deceleration were not matched by asymmetries in the total VOR slow phase velocity. During the constant velocity high-G phase of the run, sustained up-beating LVOR (Lz nystagmus) was present in 14 of the 15 subjects. Significant individual differences in Lz nystagmus were found, but the maximum Lz response in our 15 subjects was probably of insufficient magnitude to degrade visual scan of cockpit instruments. Mean magnitudes ranged from 0 to 10 deg/s at 90 s from onset of centrifuge run.
Head Slippage During Broad-Frequency Rotational Chair Testing
Authors: Hanson Jason M. , Goebel Joel A.
Published: September 2021

Broad-frequency rotational chair testing is employed in clinical and research settings to evaluate the response of the vestibulo-ocular reflex (VOR) over a range of frequencies. Accurate computation of the gain and phase of the VOR is dependent upon the assumption that the subject’s head is rigidly coupled to the rotating chair over the range of frequencies employed. We tested this assumption by examining head slippage in 20 normal subjects using a standard rotational chair over the frequency range 0.025 to 2 Hz. Measurements were made with the subjects’ head optimally restrained according to our standard clinical protocol and with the head minimally restrained. Head slippage was expressed as gain and phase of the head with respect to the chair. Computation of these parameters was made by comparing the signal received from a biteblock-mounted rate sensor rigidly coupled to the skull with that of the chair’s tachometer. We found highly significant slippage of the head with respect to the chair occurred at 0.5, 1 and 2 Hz, even with the head optimally restrained, leading to increased gain and a phase lag. Gain and phase were highly variable for both conditions at 2 Hz indicating inadequate head fixation using our methods. Below 0.5 Hz, minimal head slippage occurred whether the head was restrained or simply rested against a contoured headrest. Consideration of these results may lead to changing some practices currently employed in broad-frequency rotational chair testing at frequencies of 0.5 Hz and above.
Assessment of Vestibular Function by Videonystagmoscopy
Authors: Vitte E. , Sémont A.
Published: September 2021

Videonystagmoscopy has been used to subjectively observe the responses of the vestibular system in a population of patients with vestibular deficits. These results were compared with those of a control group of healthy, age-matched volunteers. The videonystagmoscopy device is made of one or two CCD cameras mounted on lightproof goggles, allowing a subjective observation of ocular movements on a video monitor. The eye movements, as well as the position of the head in space, can be recorded on videotape. The eyes are illuminated by infrared light emitting diodes placed on each side of the camera lens. The subjects are seated on a manually driven Barany chair. Subjects went through a protocol of passive roll head tilt on each side, followed by a slow, whole body rotation of 180° amplitude, clockwise and counterclockwise, and then a head shaking test (HST). The eyes were subjectively observed, and we focussed on: torsional eye movements during head tilt, nystagmus when the rotation had stopped, and nystagmus induced by HST. With this simple and noninvasive examining procedure, screening of vestibular function at the bedside or during E.N.T. clinical investigations is possible.
Vestibular-Neck Interaction and Transformation of Sensory Coordinates
Authors: Mergner T. , Huber W. , Becker W.
Published: September 2021

The article considers findings and concepts on vestibular-proprioceptive interaction for self-motion perception and postural control under the form of simple describing models. It points out that vestibular-neck interaction is only a small fraction of an extended mechanism of coordinate transformations. This links together the different parts of our bodies, so that sensory information arising in one part of the body can be used for perceptual or motor tasks in other parts. Particular emphasis is put on the problems that arise from imperfect signal transduction in the vestibular semicircular canal systems at low stimulus frequencies/velocities. Also, a “down-and-up-channeling” principle is suggested, by which the body support is linked via coordinate transformations to the internal notion of physical space provided by the vestibular system. Furthermore, the following question is addressed: how does the brain use visual input to overcome the vestibular deficiencies, at the risk of visual self-motion illusions? Finally, a conceptual model of postural control is presented in which a proprioceptive feedback that links the body to its support surface is merged with a loop for postural stabilization in space.
Combined Influences of Gravitoinertial Force Level and Visual Field Pitch on Visually Perceived Eye Level
Authors: DiZio Paul , Li Wenxun , Lackner James R. , Matin Leonard
Published: September 2021

Psychophysical measurements of the level at which observers set a small visual target so as to appear at eye level (VPEL) were made on 13 subjects in 1.0 g and 1.5 g environments in the Graybiel Laboratory rotating room while they viewed a pitched visual field or while in total darkness. The gravitoinertial force was parallel to the z-axis of the head and body during the measurements. The visual field consisted of two 58° high, luminous, pitched-from-vertical, bilaterally symmetric, parallel lines, viewed in otherwise total darkness. The lines were horizontally separated by 53° and presented at each of 7 angles of pitch ranging from 30° with the top of the visual field turned away from the subject (top backward) to 30° with the top turned toward the subject (top forward). At 1.5 g, VPEL changed linearly with the pitch of the 2-line stimulus and was depressed with top hackward pitch and elevated with top forward pitch as had been reported previously at 1.0 g (1.2): however, the slopes of the VPEL-vs-pitch functions at 1.0 g and 1.5 g were indistinguishable. As reported previously also (3,4), the VPEL in darkness was considerably lower at 1.5 g than at 1.0 g: however, although the y-intercept of the VPEL-vs-pitch function in the presence of the 2-line visual field (visual field erect) was also lower at 1.5 g than at 1.0 g as it was in darkness, the G-related difference was significantly attenuated by the presence of the visual field. The quantitative characteristics of the results are consistent with a model in which VPEL is treated as a consequence of an algebraic weighted average or a vector sum of visual and nonvisual influences although the two combining rules lead to fits that are equally good.
Vestibular Type I and Type II Hair Cells. 2: Morphometric Comparisons of Dissociated Pigeon Hair Cells
Authors: Ricci Anthony J. , Cochran Stephen L. , Rennie Katherine J. , Correia Manning J.
Published: September 2021

Morphometric properties of solitary hair cells dissociated from the semicircular canals (SCC), utricles (UTR), and lagenas (LAG) of adult white king pigeons, Columba livia, were compared. Measurements were made of the cell body, cuticular plate and hair bundle. Cells were divided into two groups: type 1 (group 1) was predominantly type I hair cells, and type 2 (group 3) was primarily type II hair cells. Comparisons are made initially between end organs for each group. A subpopulation of short otolith hair cells was identified. Quantitative comparisons between isolated type 1 and type 2 hair cells demonstrated that type 1 hair cells were more homogeneous both within and between vestibular end organs; while they had shorter, thinner neck regions, narrower apical surfaces, with longer and thinner bodies than did type 2 hair cells. Generally, for both type 1 and type 2 hair cells, two different hair bundle shapes were present, those (unimodal) with a single sharp taper from longest to shortest stereocilia, and those (bimodal) with an initial steep tape-followed by a less steep taper. An additional subtype of type 1 hair cells with short hair bundles was identified. SCC hair cells have fewer hair bundles with bimodal tapers across all cell groups when compared to UTR or LAG. All cell subtypes identified for dissociated hair cells were corroborated using histologic sections.
The Velocity Storage Mechanism of the Optokinetic Nystagmus Under Apparent Stimulus Movements in Squirrel Monkeys
Authors: Kröller J. , Behrens F. , Marlinsky V.V.
Published: September 2021

Experiments in two awake untrained squirrel monkeys were performed to study the velocity storage mechanism during fast rise of OKN slow phase velocity. This was done by testing the monkey’s capability to perform OKN in response to a stationary-appearing stroboscopically illuminated stripe pattern of a horizontally rotating drum. Nystagmus was initially elicited during constant illumination lasting between 0.6 and 25 s. The periodicity of the stripe pattern was 2.37°. When after the constant light the flash illumination was switched on again, two types of behavior could occur, depending on the length of the constant light interval (CLI): 1) when the CLI was shorter than a threshold value of 6.2 seconds, the OKN ceased under the flash stimulation. Then a “post-OKN” occurred that increased with the length of the CLIs, indicating that the intermittently illuminated pattern did not provoke fixation suppression of OKN aftereffects. 2) when the CLI was above threshold, the OKN continued under the flash light: it will he called “apparent movement OKN.” The threshold CLI between the type 1 and the type 2 response did not depend on drum velocities between 21.5°/s and 71.3°/s. The average gain of the apparent movement OKN was 0.83 ± 0.04; gain and stability of slow phase eye movement velocity did not deviate systematically from the usually elicited OKN. OKAN after apparent movement OKN did not deviate from OKAN after constantly illuminated moving patterns. In response to the OKN initiation by a constantly illuminated pattern up to pattern velocities of 100°/s, the OKN steady state gain was reached within the first 2 or 3 nystagmus beats. We ascribe the increase of the post-OKN with CLI and the existence of a threshold constant light interval to activity-accumulation in the common velocity-to-position integrator (velocity storage) of the brain stem. Loading of the velocity storage takes place after the OKN gain has already reached the steady-state value. Apparent movement OKN could also be elicited in guinea pigs that lack an effective smooth pursuit system. We suggest that apparent movement OKN is produced by mechanisms located in the brain stem.
Effects of body orientation and rotation axis on pitch visual-vestibular interaction
Authors: Clément Gilles , Wood Scott J. , Lathan Corinna E. , Peterka Robert J. , Reschke Millard F.
Published: September 2021

Spatial transformations of the vestibular-optokinetic system must account for changes in head position with respect to gravity in order to produce compensatory oculomotor responses. The purpose of this experiment was to study the influence of gravity on the vestibulo-ocular reflex (VOR) in darkness and on visual-vestibular interaction in the pitch plane in human subjects using two different comparisons: (1) Earth-horizontal axis (EHA) rotation about an upright versus a supine body orientation, and (2) Earth-horizontal versus Earth-vertical (EVA) rotation axes. Visual-vestibular responses (VVR) were evaluated by measuring the slow phase velocity of nystagmus induced during sinusoidal motion of the body in the pitch plane (at 0.2 Hz and 0.8 Hz) combined with a constant-velocity vertical optokinetic stimulation (at ±36°/s). The results showed no significant effect on the gain or phase of the VOR in darkness or on the VVR responses at 0.8 Hz between EHA upright and EHA supine body orientations. However, there was a downward shift in the VOR bias in darkness in the supine orientation. There were systematic changes in VOR and VVR between EHA and EVA for 0.2 Hz, including a reduced modulation gain, increased phase lead, and decreased bias during EVA rotation. The same trend was also observed at 0.8 Hz, but at a lesser extent, presumably due to the effects of eccentric rotation in our EVA condition and/or to the different canal input across frequencies. The change in the bias at 0.2 Hz between rotation in darkness and rotation with an optokinetic stimulus was greater than the optokinetic responses without rotation. During EHA, changes in head position relative to gravity preserve graviceptor input to the VVR regardless of body orientation. However, the modifications in VVR gain and phase when the rotation axis is aligned with gravity indicate that this graviceptive information is important for providing compensatory eye movements during visual-vestibular interaction in the pitch plane.
Behaviour of adult hamsters subjected to hypergravity
Authors: Sondag H.N.P.M. , de Jong H.A.A. , Oosterveld W.J.
Published: September 2021

We studied vestibular function in 20 adult hamsters (3 months old) subjected to either prolonged hypergravity (n=10) or normal gravity (n=10) for 2 months. Locomotion and swimming of the hypergravity hamsters under light conditions were normal. Equilibrium maintenance was severely disturbed; only 6 of 10 hypergravity hamsters managed to walk on the small tube after 2 months, whereas all 10 controls were able to walk on the tube. The air-righting reflex was severely disturbed; the hypergravity hamsters made 30% correct responses. Finally, 5 of 8 hypergravity hamsters had to be saved from drowning when swimming in total darkness. Histological examination of the utricular otoconial layers afterwards, using energy dispersive X-ray element (EDAX) analysis and scanning electron microscopy, did not reveal any differences in calcium content, shape and size distribution of the otoconia between hypergravity hamsters and controls. We suggest that adult hamsters adapt to hypergravity, leading to problems in normal functioning when tested in 1 G, especially in tasks in which sensory input of the vestibular system is important for spatial orientation. These disturbances were more severe in adult hamsters than in young ones, tested in previous experiments. Therefore, we assume that age is a factor for adaptation to altered gravity conditions.
Postural compensation after intratympanic gentamicin treatment of Meniere's disease
Authors: Pyykkö Ilmari , Eklund Susanna , Ishizaki Hisayoshi , Aalto Heikki
Published: September 2021

We have treated 93 patients with severe Meniere's disease with gentamicin (GM) applied with 1 to 4 or intratympanic injections in a prospective study. The patients were tested at frequent intervals and followed up for two years. Postural stability was evaluated on posturography. Unsteadiness and gait between attacks, working capacity and vertigo were scored. Before commencing the treatment 47 of the patients complained from moderate to severe postural instability. After treatment moderate to severe postural instability was met in 19 patients. Initially the sway velocity was 27 mm/s on average being significantly worse than in referents. Two weeks after treatment the sway velocity increased to 33 mm/s. Thereafter the sway velocity slowly started to decline to 31 mm/s after two years. Patients with severe attacks of rotatory vertigo had a good postural outcome with GM treatment. In logistic regression analysis the most significant risk factor for poor recovery after GM treatment was severely reduced gait before commencing the treatment with odds ratio of 2.0. Subjectively, after two years, the patients rated their postural stability significantly improved when compared to pretreatment values. The good subjective rating of postural stability is related to postural training program where in the absence of attacks, the patients have learned to cope with daily tasks.
Postural sway with earth-fixed and body-referenced finger contact in young and older adults
Authors: Reginella Reginald L. , Redfern Mark S. , Furman Joseph M.
Published: September 2021

Sensory information from lightly touching a reference with the hand is known to influence postural sway in young adults. The primary aim of this study was to compare the influence of finger contact (FC) with an earth-fixed reference to the influence of FC with a body-fixed reference. A second goal of this study was to determine if FC is used differently by older adults compared to younger adults. Using a force plate, center of pressure at the feet was recorded from blindfolded young and older subjects during several conditions. Subjects either did or did not lightly touch a force-sensitive plate that was either earth-fixed or moved forward and backward in synchrony with body sway (that is, sway-referenced). In addition, support surface conditions were also varied, including a fixed floor and a sway-referenced floor using an EquitestTM. Results showed that the type of FC, floor condition, and age each had an effect on postural sway. Touching an earth-fixed plate decreased postural sway as compared to no touching, while touching a sway-referenced plate incresased sway. This influence of FC was enhanced when the floor was sway-referenced. Although older subjects swayed more than young subjects overall, no age-FC interactions occurred, indicating that FC was not utilized differently between the age groups. This study suggests that FC cannot be disregarded as erroneous, especially when proprioceptive information from the legs is distorted. Further, FC is integrated with other sensory information by the postural control system similarly in young and older persons.