bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Visual and Somatosensory Input on the Vestibulo-Oculomotor Reflex of Pigmented Rats
Authors: Niklasson M. , Tham R. , Larsby B. , Eriksson B.
Published: September 2021

Eye movements were recorded in the pigmented rat during vestibular, optokinetic and combined visual-vestibular stimulation. The dominant time constant in pigmented rats, tested during angular vestibular stimulation in darkness, is about two times longer than the cupular time constant. The gain and the duration of nystagmus, achieved by angular vestibular stimulation, can be enhanced by visual impulses. This is most evident during an optokinetic temporonasal stimulation, but is also seen with a nasotemporal stimulation. A mere optokinetic monocular stimulation without a synchronous vestibular excitation causes nystagmus only when the stimuli has a temporonasal direction. The duration of nystagmus, achieved by angular vestibular stimulation, is prolonged by disturbances of the neck proprioceptive system. This is more evident during a simultaneous visual input than in darkness. The ability to cancel nystagmus during conflicting vestibular and optokinetic impulses is well developed in the pigmented rat.
Asymmetric Optokinetic Afterresponse in Patients with Vestibular Neuritis
Authors: Brantberg Krister , Magnusson Måns
Published: September 2021

The symmetry of primary and secondary optokinetic afternystagmus (OKAN I and OKAN II, respectively) was studied in 14 patients with vestibular neuritis, as well as in 50 normals. The patients were examined at onset of symptoms and at follow-up 3 and 12 months later. At onset, OKAN was found mainly to reflect the spontaneous nystagmus. Although the spontaneous nystagmus disappeared in all patients within 3 months, both OKAN I and OKAN II was asymmetric at the 3- and 12-month check-ups. OKAN beating toward the lesioned ear was weaker than the OKAN beating toward the healthy ear. Thus, the asymmetric vestibular function was reflected not only in the OKAN I, but also by an asymmetry in OKAN II. Between the 3- and 12-month check-ups, asymmetry in OKAN declined, even among those patients who showed no improvement in caloric response during that time. The decreasing asymmetry in OKAN with time after lesion was, however, related to the disappearance of a positional nystagmus. Hence, the results may be interpreted as suggesting OKAN not only to be affected by vestibular side-difference, but also to be modified by the process responsible for vestibular compensation following a peripheral vestibular lesion.
A Comparison of the Latencies of Visually Induced Postural Change and Self-Motion Perception
Authors: Previc Fred H. , Mullen Thomas J.
Published: September 2021

This study compared the latencies of visually induced postural change and self-motion perception under identical visual conditions. The results showed that a visual roll stimulus elicits postural tilt in the direction of scene motion and an increase in postural instability several seconds before the subject begins to perceive illusory self-motion (vection) in the opposite direction. Postural and vection latencies correlate highly with one another, but bear little relationship with the magnitude of either sway or vection.
Guest Editorial
Authors: Igarashi Makoto
Published: September 2021

Note-Not infrequently, the “movers and shakers” in our field get together to present recent findings and new ideas, which invariably results in new or renewed vigor on the part of many others. Not so frequently, some insightful colleague finds the time and resources to bring together a small number of our most outstanding scientists to discuss and frame the foundation for a new initiative. Such a gathering was organised in April 1990, by Makoto Igarashi who, as then Director of Space Biomedical Division for the Universities Space Research Association, saw the importance of integrating the somewhat isolated studies relating human perception and disorientation in unusual environments. Because of the sophistication of the work represented, and its relevance to the theme of the Journal of Vestibular Research, the participants were invited to submit their work for publication, resulting in the first four papers in this issue. Dr. Igarashi has written an introduction, which follows as a guest editorial.
The Dynamics of Spatial Orientation During Complex and Changing Linear and Angular Acceleration1
Authors: Guedry F.E. , Rupert A.H. , McGrath B.J. , Qman C.M.
Published: September 2021

The dynamics of spatial orientation perception were examined in a series of experiments in which a total of 43 subjects were passively exposed to various combinations of linear and angular acceleration during centrifuge runs. Perceptual effects during deceleration were much stronger than effects during acceleration. The dynamics of spatial orientation perception differed substantially from changes in the vestibulo-ocular reflex (VOR). VOR was fairly well predicted by a current model, but our experiments revealed perceived change in attitude (roll, pitch, yaw tilt position in space) and perceived angular velocity in space that was not reflected by parallel changes in the plane or magnitude of the VOR. This series of experiments establishes several facts concerning spatial orientation perception beyond the predictive domain of any current model. New concepts are needed and several are suggested to deal with changing reactions to complex combinations of linear and angular accelerations.
Spatial Orientation and Posture During and Following Weightlessness: Human Experiments on Spacelab Life Sciences 1
Authors: Young Laurence R. , Oman Charles M. , Merfeld Daniel , Watt Douglas , Roy Serge , DeLuca Carlo , Balkwill David , Christie Jock , Groleau Nicolas , Jackson D. Keoki , Law Glenn , Modestino Sherry , Mayer William
Published: September 2021

The 4 payload crew members of the Spacelab Life Sciences 9-day space flight in 1991 were subjected to limited vestibular testing in flight as well as pre and post flight. Major differences in individual “perceptual style” appeared in their reaction to the visual-vestibular stimuli in the rotating dome experiment, and especially in the extent to which nondirectional tactile cues served to anchor the subjective vertical and body postural reactions. The ability of subjects to point to remembered target positions was degraded in space, which produced a tendency to point low in some subjects in flight. The eye movements and subjective response to sudden stops and head pitching following continuous spinning (dumping) were measured both in space and on the ground. Although subjective duration of inflight rotation for the dumping tests was shorter than that for the preflight tests, the postrotatory nystagmus, with or without head pitch, was lengthened in time constant relative to preflight. Ground tests, in addition to the flight experiments, investigated the changes following in subjective and oculomotor reactions to whole body tilt, the ability to balance with eyes open and closed; leg muscle strength and stamina as related to posture; visual field dependence; and the perceptual and oculomotor reactions to horizontal linear acceleration. Several of these tests, as well as postflight measures of motion sickness susceptibility, revealed subtle evidence of neurovestibular alterations that lasted a week or more following the 10-day orbital exposure.
A Predictive Test for Space Motion Sickness
Authors: Markham Charles H. , Diamond Shirley G.
Published: September 2021

Eye torsion was examined in 13 astronaut subjects, tested during repeated episodes of 0 G and 1.8 G in parabolic flight aboard NASA’s KC-135. Four findings are included. 1) A strong relationship between previous history of SMS and ocular torsional disconjugacy in novel gravitational states. 2) Responses were unchanged in 4 subjects retested a year later. 3) Ocular torsional disconjugacy scores increased as exposure to 0 and 1.8 G increased. This was particularly evident in subjects who had had SMS. 4) Torsional studies during 10 to 20 parabolas are required to accurately predict SMS. The hypothesis of otolith asymmetry, compensated in 1 G but becoming unmasked in novel gravitational states, is proposed to explain the torsional disconjugacy and ensuing SMS.
Gaze Control in Microgravity: 2. Sequences of Saccades toward Memorized Visual Targets
Authors: Israël I. , André-Deshays C. , Charade O. , Berthoz A. , Popov K. , Lipshits M.
Published: September 2021

The reproduction, in complete darkness, of sequences of 5 horizontal saccades towards previously presented visual targets has been investigated in human subjects on the ground (control subjects) and one cosmonaut in microgravity. The incidence of corrective saccades during the execution of the memory-guided saccades in darkness has been examined. It was quite large for the control subjects (more than half of all saccades), and increased during the flight, while the corrective visually guided saccades incidence decreased. Direction errors occurred in about the third of all sequences on the ground, and this parameter also increased in microgravity. Memory-guided sequences were mostly hypermetric. Whereas the absolute error continuously increased with the target rank, it was not the case with the amplitude ratio, which presented a peak at the third rank, that is, at the middle of the sequence. The accuracy of the reproduction of the sequences did depend on the sequence pattern as much as on the subject. Some learning was observed in repeated reproduction of the same pattern. Although the average error did not change in microgravity, the linear regression coefficient between the visually guided and memory-guided saccades decreased.
Visual Hallucinations Evoked by Caloric Vestibular Stimulation in Normal Humans
Authors: Kolev Ognyan I.
Published: September 2021

This study describes a hitherto unknown phenomenon in healthy humans: visual hallucinations evoked by caloric vestibular stimulation. The hallucinations are of elementary type. The following quantitative and qualitative characteristics of the hallucinatory images were measured: latency, duration, location in the visual field, relation to the provoked vertigo, colour of the hallucinatory image and the background, number, size, shape, distance from the eyes, and motion. Two mechanisms are proposed to explain the genesis of these hallucinations. One mechanism is direct: change in the spontaneous activity of the visual system in several levels; the other mechanism is indirect: transient haemodynamic disturbance in the visual system.
The Vestibulocollic Reflex
Authors: Wilson V.J. , Boyle R. , Fukushima K. , Rose P.K. , Shinoda Y. , Sugiuchi Y. , Uchino Y.
Published: September 2021

Stabilization of the head is required not only for adequate motor performance, such as maintaining balance while standing or walking, but also for the adequate reception of sensory inputs such as visual and auditory information. The vestibular organs, which consist of three approximately orthogonal semicircular canals (anterior, horizontal, posterior) and two otolith organs (utriculus, sacculus), provide the most important input for the detection of head movement. Activation of afferents from these receptors evokes the vestibulocollic reflex (VCR), which stabilizes bead position in space. In this review, which is the outgrowth of a session of the vestibular symposium held in Hawaii in April, 1994, we discuss the neural substrate of this reflex and some aspects of the central processing involved in its production. Some topics are not considered, in particular the important interaction between the VCR and the cervicocollic reflex evoked by activation of neck afferents (70,119), and attempts to model the reflex (69).
Pharmacological Activity of the Ginkgo Biloba Extract (EGb 761) on Equilibrium Function Recovery in the Unilateral Vestibular Neurectomized CAT1
Authors: Tighilet Brahim , Lacour Michel
Published: September 2021

Locomotor balance recovery after unilateral vestibular neurectomy bas been found strongly accelerated in the cat when the animals received a postoperative treatment with Ginkgo biloba Extract (EGb 761: 50 mg/kg/d, i.p.), a result due to the improvement of plasticity mechanisms involved in vestibular compensation. The aim of this study was to determine which of the two main biochemical components (terpenes vs. flavonoids) contained in the extract was the most active in the recovery process, to test the influence of the route of administration, and to look for dose-dependent effects. Experiments were performed in six experimental groups of cats that were compared witb each other and with three control groups. Comparisons were done on the recovery profile and time course of equilibrium function restoration, as quantified by the rotating beam test. Four experimental groups were treated with the standardized extract EGb 761 given orally (p.o.: 2 groups; 40 mg and 80 mg/kg) or intraperitoneally (i.p.: 2 groups; 50 mg and 25 mg/kg), whereas the two others received only a special extract that did not contain the terpenes (i.p. administration: 25 mg and 10 mg/kg). Treatment was always given until complete recovery of locomotor balance function. The control groups received either no treatment (untreated cats), an oral vehicle (placebo cats), or a sham i.p. injection (sham cats). Results showed that locomotor balance recovery was significantly improved in all the experimental groups as compared to the control groups of cats, which recovered similarly and more slowly. Efficacy of the special extract without the terpenes was comparable to that of the total extract, indicating that the nonterpenic fraction was the most active biochemical constituent in this experimental model of central nervous system (CNS) plasticity. Pharmacological activity of the extract was also significantly better when given i.p. as compared to the p.o. route of administration, and dose-dependent effects were evidenced with the i.p. administration of the special extract without the terpenes, with a lower efficacy for the lowest dose (10 mg/kg). These data confirm that EGb 761 treatment serves as useful therapy in supporting brain functional recovery in this animal model of vestibular compensation and lead to a more precise understanding of the biochemical component that is active in this recovery process.
Recent Advances in Clinical Neurotology
Authors: Baloh Robert W. , Furman Joseph M.R. , Halmagyi G. Michael , Allum John H.J.
Published: September 2021

In recent years, owing to significant technological developments and an increased number of investigators entering the field, there have been spectacular advances in our understanding of the basic anatomy and physiology of the vestibular system. Unfortunately, these advances in basic science are slow to impact the clinical management of patients. We have selected a few important advances in clinical neurotology that have impacted the diagnosis and treatment of patients with vestibular disorders. This material was originally presented at the “Mechanisms of Vestibular Function and Dysfunction” symposium of the 1994 Neural Control of Movement meeting in Waikoloa, Hawaii.
Head-Only Rotational Testing: Influence of Volition and Vision1
Authors: Furman Joseph M. , Durrant John D.
Published: September 2021

Head-only rotational testing has been suggested as a method of assessing the vestibuloocular reflex in patients with reduced vestibular function as a result of ototoxicity. The purpose of this study was to investigate the influence of vision and volition on horizontal vestibuloocular reflex responses during head-only rotation in normal subjects to better define the test parameters for future clinical application. Ten asymptomatic, healthy subjects were tested using various combinations of volitional and visual conditions during head-only rotation. Results indicated that visual fixation enhanced responses slightly and that response dynamics were altered somewhat by volition. These findings provide motivation for future studies to further define head-only rotation test parameters for patients with suspected vestibular abnormalities.
Clinical Features of Mal de Debarquement: Adaptation and Habituation to Sea Conditions1
Authors: Gordon Carlos R. , Spitzer Orna , Doweck Ilana , Melamed Yehuda , Shupak Avi
Published: September 2021

A survey conducted among 116 crew members of seagoing vessels confirmed that mal de debarquement (M-D) is a transient feeling of swinging, swaying, unsteadiness, and disequilibrium. None of the subjects requested medical attention, although there were isolated cases in which a strong sensation of swinging and unsteadiness caused transient postural instability and impaired the ability to drive. In most cases, the sensation of M-D appeared immediately on disembarking and generally lasted a few hours. In addition, subjects usually described bouts or attacks of M-D associated with changes in body posture, head position, or with closing of the eyes. M-D was reported by 72% of our subjects. Sixty-six percent of subjects reported a high incidence following their first voyages. A significant positive correlation was found between M-D and seasickness susceptibility. The nature of M-D may be explained within the framework of multisensorimotor adaptation and habituation to a new or abnormal motion environment. It is suggested that M-D represents a dynamic, multisensorimotor form of CNS adaptive plasticity.
Vestibulo-Ocular Reflex Deficits to Rapid Head Turns Following Intratympanic Gentamicin Instillation
Authors: Allison R.S. , Eizenman M. , Tomlinson R.D. , Nedzelski J. , Sharpe J.A.
Published: September 2021

The response of the vestibulo-ocular reflex following unilateral vestibular deafferentation by gentamicin ablation was studied using transient stimuli. The response to these rapid passive head turns showed a strong asymmetry with permanent, reduced gains toward the side of lesion. These gain reductions have large variation (gains of 0.26 to 0.83), which may result from preferential sparing of regularly firing afferent fibers following gentamicin ablation. Based on the size and nature of the nonlinearity, an explanation based on Ewald’s second law was discounted.
Objective and Subjective Time Courses of Recovery from Motion Sickness Assessed by Repeated Motion Challenges
Authors: Golding J.F. , Stott J.R.R.
Published: September 2021

The aim of this study was to determine whether the time course of recovery of tolerance, as assessed objectively by rechallenge with motion, paralleled the subjective recovery from motion sickness. Subjects (n = 20) were exposed to 5 pairs of nauseogenic motion challenges in which the time interval between the end of the first and the start of the second of each pair ranged from 15 min to 2 h. The cross-coupled motion challenge had an incrementing profile of rotational velocity from 4° to 92°.s-1 in steps of 4°.s-1 every 30 s, with 8 head movements per 30 s, of approximately 45°, and was continued to the point of moderate nausea. Objective loss of tolerance decreased from 15 min to 60 min after the first challenge, but increased again at 2 h. By contrast, most individuals reported subjective recovery by 15 min to 30 min. It was concluded that there is an underlying effect of motion sickness that sensitizes the response to subsequent motion for a period of at least 2 h. This underlying objective effect can occur in the absence of subjective symptoms, has a slower time course than the subjective recovery from symptoms and appears to be non-monotonic.
Orientation Illusions in Spaceflight
Authors: Kornilova L.N.
Published: September 2021

Investigations of spontaneous illusory reactions were carried out during spaceflights of various durations by ANKETA questionnaires (104 cosmonauts). From a total of 104 cosmonauts, 24, in addition, used a dictaphone to record a verbal description of the illusions and their sensations on tape. Analysis of data generated by ANKETA and the tapes thus recorded have shown that during adaptation to weightlessness, 98% of cosmonauts have noted the occurrence of various illusions of orientation (coordinate and kinetic): illusions pertaining to their position or illusions of self- and surround-motion. The development of spatial orientation illusions during and after flight is not limited to certain individuals, but is a general response of the sensory system to microgravity. These responses differ to some extent among individuals in severity, nature, time and duration of occurrence, and the dynamics of the process. Perceptual disorders may occur even if the cosmonaut feels well and experiences no anomalous autonomic reactions. The nature of spatial illusions was determined by the role and relative contribution of various types of sensory input to spatial orientation. After completion of the initial stage of adaptation to weightlessness, the perceptual disorders disappear. However, spontaneous illusory reactions were often observed after 50 days of exposure to weightlessness. The adaptation process during long-term spaceflight had an undulating course, in which adaptation and de-adaptation alternated. A classification of weightlessness illusions is proposed.
Microgravity Vestibular Investigations: Perception of Self-Orientation and Self-Motion
Authors: Benson Alan J. , Guedry Fred E. , Parker Donald E. , Reschke Millard F.
Published: September 2021

Four astronauts experienced passive whole-body rotation in a number of test sessions during a 7-day orbital mission. Pitch (Y-axis) and roll (X-axis) rotation required subject orientations on the rotator in which the otolith system was at radius of 0.5 m. Thus subjects experienced a constant -0.22 Gz stimulus to the otoliths during the 60 s constant-velocity segments of “pitch” and “roll” ramp profiles. The Gz stimulus, a radius-dependent vector ranging from -0.22 Gz at the otoliths to +0.36 Gz at the feet, generated sensory information that was not interpreted as inversion in any of the 16 tests carried out in flight (12 in pitch and 4 in roll orientation). None of the subjects was rotated with head off-center during the first 33 h of the mission. In the state of orbital adaptation of these subjects, a -0.22 Gz otolith stimulus did not provide a vertical reference in the presence of a gradient of -Gz stimuli to the trunk and legs.
Spatial performance of unilateral vestibular defective patients in nonvisual versus visual navigation
Authors: Péruch Patrick , Borel Liliane , Gaunet Florence , Thinus-Blanc Gatherine , Magnan Jacques , Lacour Michel
Published: September 2021

The purpose of this study was to investigate the effects of unilateral vestibular neurotomy on humans ability to perform navigation tasks. These tasks provided self-motion feedback by way of either locomotor activity only (nonvisual navigation or “locomotor task”) or visual motion cues only (visually simulated navigation or “visual task”). After exploration of an environment in which 4 locations were marked by different objects, subjects attempted to navigate to those locations either by reproducing the same paths as those followed during exploration, by reversing routes, or by making spatial inferences (shortcuts). Vestibular defective patients were tested one day before surgical treatment and during the recovery time course following unilateral vestibular nerve lesion (1 week, 1 month, and 3 months later). Their performance was assessed by measuring turn error and distance error in both navigation tasks and was compared to that of control subjects tested 4 times at similar time intervals. Turn error in the reproduction of previously explored routes in the locomotor task was lower in patients before surgery than in controls, suggesting the existence of compensatory processes. In the acute stage (1 week) after unilateral vestibular lesion, turn error was greater in patients than in controls for the highest level of mental representation (spatial inferences or reversing routes); impairment at making accurate rotations had disappeared by 1 month after vestibular lesion in both navigation tasks. These results point to the role of vestibular cues, in interaction with other sensory modalities, in the elaboraion of an accurate internal representation of the environment. In addition, they suggest that unilateral suppression of vestibular information would induce transitory spatial memory disorganization at a high level of information processing.
Does habitual, vigorous optokinetic stimulation alter optokinetic nystagmus and sensitivity to circularvection?
Authors: McDermott Kate H. , Matheson Anna J. , Titov Nikoli , Darlington Cynthia L. , Smith Paul F.
Published: September 2021

Previous studies have shown that experience with optokinetic stimulation can alter a subject's sensitivity to illusions such as circularvection (CV). The aim of the present experiment was to compare optokinetic nystagmus (OKN), optokinetic afternystagmus (OKAN), and sensitivity to CV between 2 groups of sportspeople: 1) squash players (n=16), who regularly experience vigorous optokinetic stimulation while engaging in their sporting activity, and 2) weightlifters (n=16), whose sport does not involve the same degree of optokinetic stimulation as squash, but who nevertheless have to achieve a high degree of physical skill. OKN, OKAN (frequency, slow phase velocity, and timeconstant), and latency to CV (Stage 2 and Stage 3) were measured using electro-oculographic recording inside an optokinetic drum. Contrary to predictions,there were no significant differences in OKN, OKAN, or latency to CV between the 2 groups. These results suggest that 1) the practice effects that alter the sensitivity to CV may decay relatively quickly, and 2) differences in recreational sporting activities between subjects may not be a significant confounding factor in visual-vestibular interaction experiments.
A factor analytic study of the dizziness handicap inventory: does it assess phobic avoidance in vestibular referrals?
Authors: Asmundson Gordon J.G. , Stein Murray B. , Ireland Desmond
Published: September 2021

Panic disorder and agoraphobia have been associated with increased functional disability in individuals who have vestibular problems. The Dizziness Handicap Inventory (DHI), a 25-item self-report questionnaire with three rationally derived subscales, was designed to measure functional, emotional, and physical disability associated with vestibular disturbance. Despite the apparent usefulness of the DHI, there have been few studies of its psychometric properties. The primary purpose of the present study was to assess the factor structure of the DHI. A principal components analysis with oblique rotation was conducted on data collected from 95 patients referred to a tertiary-care vestibular disorders clinic for assessment of vestibular disturbance. Both 2-factor and 3-factor solutions are reported. The 2-factor solution was indicative of General Functional Limitations and Postural Difficulties. In the 3-factor solution, General Functional Limitations was split into factors indicative of Disability in Activities of Daily Living and Phobic Avoidance, while the Postural Difficulties factor remained stable. We also characterized the 3-factor solution by assessing the correlation of factor scores with measures of vestibular symptoms, mood, and anxiety. The general pattern of results does not support the validity of the original subscale structure of the DHI. Implications for revising the DHI to provide a more comprehensive and factorially valid assessment of disability associated with vestibular disturbance are discussed.
The subdivisions of the guinea pig vestibular complex revealed by acetylcholinesterase staining
Authors: Ris Laurence , Saussez Sven , Gerrits Nicolaas , Godaux Emile , Pochet Roland
Published: September 2021

A detailed map of the vestibular nuclear complex of the guinea pig has been established by Gstoettner and Burian (1987), using cytoarchitectonic (cresyl violet staining) and fiberarchitectonic criteria. However, the exact borders between the different subdivisions are not always evident in Nissl stained sections. In the present study, serial sections of the vestibular nuclei of the guinea pig were stained to visualize acetylcholinesterase (AChE) activity, and compared with corresponding sections stained with cresyl violet. All of the subdivisions of the vestibular nuclear complex previously described are more readily distinguished in AChE than in Nissl preparations. The AChE reactivity also shows that the medial vestibular nucleus extends more rostrally than previously described. Furthermore, it questions whether the area classically referred to as the rostral pole of the descending vestibular nucleus belongs to the descending vestibular nucleus or to the lateral vestibular nucleus (LV). Finally, a morphometric analysis performed on cresyl violet stained sections shows that (1) in the caudal LV, the neurons of the ventromedial extension are smaller than those of the dorsolateral extension and that (2) in the rostral LV, the ventromedial division contains a larger ratio of smaller neurons than the dorsolateral one.
The effect of d-amphetamine on optokinetic nystagmus in the guinea pig
Authors: Marlinsky V.V. , Reber M. , Kröller J.
Published: September 2021

The effect of d-amphetamine oral administration in doses of 1–2.5 mg/kg on horizontal optokinetic nystagmus (OKN) and afternystagmus (OKAN) was investigated in the guinea pig. Eye movements were recorded by means of the electromagnetic search-coil technique. After amphetamine administration the range of stimulus velocities effective for eliciting OKN was 10–20 deg/s higher than before treatment. The mean values and the fluctuations of the eye velocity during slow nystagmus phases before and after treatment did not differ. Aministration of amphetamine led to 2–8 s increase in OKAN duration. The OKAN prolongation did not depend on stimulation velocity. The dependency of OKAN duration on stimulation velocity was well approximated by a linear regression. The slope of the regression line was 0.160 ± 0.022 before and 0.177 ± 0.028 after treatment. Similarity in the coefficients indicates that amphetamine did not alter the relationship between the velocity of optokinetic stimulus and the duration of afternystagmus. Constant prolongation of OKAN over the whole range of stimulation velocities could reflect a constant shift in activity of neurons representing the velocity storage. The effects observed on OKN gain curves and the increase in OKAN duration did not display a clear dependency on the dosages of d-amphetamine used in the experiments. We assume that the effects of treatment reflected a general increase in attentiveness and motility of animals resulting from the arousal action of amphetamine.
3D eye movements-basics and clinical applications
Authors: Fetter Michael , Haslwanter Thomas
Published: September 2021

The eye muscles in humans are arranged such that they allow rotations of the globe about any axis in three-dimensional space. Only 3D analysis techniques will suffice to describe the sometimes complex dependencies between the elicited eye movements and the stimulation conditions. With the recent availability of modern 3D eye movement measurement techniques and the further development of appropriate mathematical descriptions, we are now able to study eye movements in all three degrees of freedom. This article describes the basic mathematical tools for 3D eye movement analysis like rotation vectors, reference frames, coordinate systems, and the concept of Listing's law. In a second part some clinical applications are presented. The close coupling between the vestibular and the oculomotor system suggests that by observing spontaneous and elicited eye movements in the case of an acute unilateral vestibular pathology we might be able to find out which parts of the vestibular system (that is, which of the semicircular canals or which of the otoliths) are affected. The rationale of such an analysis is based on the observation that electrical stimulation of single semicircular canal afferents in animals induces eye movements that lie roughly in the plane of the canal. It is, therefore, possible to deduce which canals cause the eye movements observed when only some parts of the vestibular system are defective. Thus, the analysis of 3D movements not only provides an improved understanding of how the brain organizes movement in 3D space, but also has the potential to significantly improve our diagnostic capabilities.
Surface height effects on postural control: A hypothesis for a stiffness strategy for stance*
Authors: Carpenter Mark G. , Frank James S. , Silcher Cathy P.
Published: September 2021

One possible factor influencing the control of upright stance is the perceived threat to one's personal safety, i.e. balance confidence. We explored this factor by examining the control of stationary stance when standing on an elevated platform under various conditions of reduced visual and vestibular inputs. Twenty-eight adults (14 male and 14 female, mean age = 23.5 years) participated in the experiment. Postural control was examined by recording the amplitude variability (RMS) and mean power frequency (MPF) of center of pressure excursions (COP) over a 2-minute interval while participants stood in a normal stance on a low (0.19 m) and a high (0.81 m) platform with toes positioned either at or away from the edge of the platform. Vision was manipulated through eyes open and eyes closed trials. Vestibular input was reduced by tilting the head into extension [1]. Anterior-posterior RMS and MPF of COP were significantly influenced by an interaction between surface height and vision. When vision was available, a significant decrease in RMS was observed during quiet standing on a high surface compared to a low surface independent of step restriction. When vision was available MPF increased when subjects were raised from a low to a high surface. The mean position of the COP was significantly influenced by an interaction between height and step restriction. Differences in RMS and MPF responses to height manipulation were observed between genders in eyes closed conditions. Vestibular input influenced postural control at both low and high levels with significant increases in RMS when vestibular input was reduced. The reciprocal changes observed in RMS and MPF suggest modifications to postural control through changes in ankle stiffness. Vision appears to play a role in increasing ankle stiffness when balance confidence is compromised.
Model-based study of the human cupular time constant
Authors: Dai Mingjia , Klein Avniel , Cohen Bernard , Raphan Theodore
Published: September 2021

The time constant of the angular vestibulo-ocular reflex (aVOR), measured from the response to steps of rotation about a yaw axis, has frequently been estimated as a single exponential. However, the slow phase velocity envelope during per- or post-rotatory nystagmus is more accurately represented by two exponential modes. One represents activity in the vestibular nerve induced by deflection of the cupula, the other by activation that the input from the canals produces in the central velocity storage integrator. The sum of the cupula and the integrator responses describes the overall response of slow phase eye velocity and can be approximated by a double exponential. Frequently, there is a plateau in the initial portion of eye velocity response, but this may be masked by habituation, making the cupula contribution unobservable and impossible to estimate. Using a model-based technique to analyze responses with a clear plateau, we estimated peripheral and central vestibular time constants by double exponential fits to slow phase eye velocity. Cupular time constants were varied from 1 to 10 s to identify values that gave optimal fits of the data according to a Chi-square criterion. The mean cupular time constant for 10 human subjects was 4.2 ± 0.6 s. Fits of the data were also good for time constants between 3.5 to 7 s, but not for 1 to 3 or 7.5 to 10 s. The estimated cupular time constants also fit responses where there was no plateau. In 8 monkeys, cupular time constants were estimated as 3.9 ± 0.5 s, which agreed with those derived from activity in the vestibular nerve. There was no difference between monkey and human cupular time constants from these estimates. It is likely that the human cupular time constant is similar to that of the monkey and shorter than previously thought.
Sensory and motor interdependence in postural adjustments
Authors: McCollum Gin
Published: September 2021

The sensory reafference from a movement depends upon the movement, and the movement chosen depends upon the available senses, as demonstrated by vestibular patients who abandon certain movements. Often, one variable is assumed to be dependent whereas the other is independent; however, sensory and motor dynamics in posture are interdependent as conditions upon each other. This paper applies conditional dynamics to characterize the global structure of interdependence between sensory states and motor strategies in fast postural adjustments. The mathematical formalism incorporates rich but disparate experimental, clinical, and theoretical results about sensory and motor control of posture. The control structures presented include relatively stable anatomical, physiological, and functional structures, both continuous and discrete, leading to a composite functional logic for the coordination of these structures in sensorimotor control. Results include sensorimotor control structures for postural adjustments for healthy subjects and certain types of vestibular patients. The sensorimotor control structures for patients with absent vestibular function suggest implications for management of the deficit.
Subregional analysis of amino acid levels in the guinea pig hippocampus following unilateral vestibular deafferentation
Authors: Zheng Yiwen , Smith Paul F. , Darlington Cynthia L.
Published: September 2021

Recent behavioural and neurophysiological studies suggest that the hippocampus uses vestibular information, along with information from other sensory systems, to accomplish its spatial computational processing. By contrast, there is a dearth of neurochemical data on the interactions between the vestibular system and hippocampus. The aim of the present study was to examine levels of glutamine, glutamate, gamma-amino-butyric acid (GABA), glycine, serine, threonine and taurine in the CA1, CA2, CA3 and dentate gyrus (DG) subregions of the hippocampus at 10 hs following UVD in guinea pig, using high-performance liquid chromatography (HPLC) with electrochemical detection (ECD). Glutamine levels were not significantly different between the UVD and control conditions, except in the bilateral DG where they were significantly lower ( p < 0.05). However, no significant differences in glutamate levels were observed. Although there were no significant differences in GABA levels in the DG, CA1 and CA2 regions following UVD, there was a significant increase in GABA levels in the contralateral CA3 region in the sham group compared to intact anesthetic controls. Glycine levels were significantly higher in the contralateral DG and ipsilateral CA1 in the sham groups compared to intact anesthetic controls ( p < 0.05). However, in contralateral CA2 and ipsilateral CA3, glycine levels were significantly higher for both the sham and UVD groups compared to anesthetic controls ( p < 0.05). Threonine levels were not significantly different in CA1; however, in ipsilateral DG and ipsilateral CA3, they were significantly higher in the sham groups compared to anesthetic controls and the UVD groups ( p < 0.05). In ipsilateral CA2, threonine levels were significantly higher in the UVD group compared to anesthetic controls ( p < 0.05). Taurine levels did not differ significantly in the DG, CA1 or CA3 following UVD; however, they were significantly higher in ipsilateral CA2 following UVD ( p < 0.05). Finally, serine levels were not significantly different in any area of the hippocampus following UVD or sham surgery. This study provides the first data on amino acid levels in the hippocampus following UVD and sham temporal bone surgery and suggests that peripheral vestibular damage may particularly affect glutamine, glycine, threonine and taurine levels in various subregions of the hippocampus.
Disruption of postural readaptation by inertial stimuli following space flight*
Authors: Black F. Owen , Paloski William H. , Reschke Millard F. , Igarashi Makoto , Guedry Fred , Anderson David J.
Published: September 2021

Postural instability (relative to pre-flight) has been observed in all shuttle astronauts studied upon return from orbital missions. Postural stability was more closely examined in four shuttle astronaut subjects before and after an 8 day orbital mission. Results of the pre- and post- flight postural stability studies were compared with a larger ( n = 34) study of astronauts returning from shuttle missions of similar duration. Results from both studies indicated that inadequate vestibular feedback was the most significant sensory deficit contributing to the postural instability observed post flight. For two of the four IML-1 astronauts, post-flight postural instability and rate of recovery toward their earth-normal performance matched the performance of the larger sample. However, post-flight postural control in one returning astronaut was substantially below mean performance. This individual, who was within normal limits with respect to postural control before the mission, indicated that recovery to pre-flight postural stability was also interrupted by a post-flight pitch plane rotation test. A similar, though less extreme departure from the mean recovery trajectory was present in another astronaut following the same post-flight rotation test. The pitch plane rotation stimuli included otolith stimuli in the form of both transient tangential and constant centripetal linear acceleration components. We inferred from these findings that adaptation on orbit and re-adaptation on earth involved a change in sensorimotor integration of vestibular signals most likely from the otolith organs.
Human soleus H-reflex excitability is decreased by dynamic head-and-body tilts
Authors: Paquet Nicole , Hui-Chan Christina W.Y.
Published: September 2021

The modulation of soleus (SO) H-reflex excitability during dynamic whole head-and-body tilts (WHBT) was investigated in normal healthy subjects. Between 30 and 70 ms, and 151 and 190 ms after head acceleration onset, the H-reflex amplitude was smaller than during quiet standing by 7.6% ( p < 0.01) and 15.4% ( p = 0.06) respectively. This finding suggested that dynamic WHBT reduced the excitability of the predominantly monosynaptic stretch reflex arc in the majority of the subjects studied.
Incomplete segregation of endorgan-specific vestibular ganglion cells in mice and rats
Authors: Maklad Adel , Fritzsch Bernd
Published: September 2021

The endorgan-specific distribution of vestibular ganglion cells was studied in neonatal and postnatal rats and mice using indocarbocyanine dye (DiI) and dextran amines for retrograde and anterograde labeling. Retrograde DiI tracing from the anterior vertical canal labeled neurons scattered throughout the whole superior vestibular ganglion, with denser labeling at the dorsal and central regions. Horizontal canal neurons were scattered along the dorsoventral axis with more clustering toward the dorsal and ventral poles of this axis. Utricular ganglion cells occupied predominantly the central region of the superior vestibular ganglion. This utricular population overlapped with both the anterior vertical and horizontal canals' ganglion cells. Posterior vertical canal neurons were clustered in the posterior part of the inferior vestibular ganglion. The saccular neurons were distributed in the two parts of the vestibular ganglion, the superior and inferior ganglia. Within the inferior ganglion, the saccular neurons were clustered in the anterior part. In the superior ganglion, the saccular neurons were widely scattered throughout the whole ganglion with more numerous neurons at the posterior half. Small and large neurons were labeled from all endorgans. Examination of the fiber trajectory within the superior division of the vestibular nerve showed no clear lamination of the fibers innervating the different endorgans. These results demonstrate an overlapping pattern between the different populations within the superior ganglion, while in the inferior ganglion, the posterior canal and saccular neurons show tighter clustering but incomplete segregation. This distribution implies that the ganglion cells are assigned for their target during development in a stochastic rather than topographical fashion.
Predicting control mechanisms for human head stabilization by altering the passive mechanics
Authors: Keshner E.A. , Hain T.C. , Chen K.J.
Published: September 2021

The purpose of this study was to clarify the mechanisms controlling head and neck stabilization in the horizontal (yaw) and vertical (pitch) planes by changing the passive mechanics of the head-neck motor system. Angular velocities of the head and trunk in space were recorded in seated subjects during external perturbations of the trunk with pseudorandom sum-of-sines (SSN) stimuli. Four subjects in yaw and nine subjects in pitch actively stabilized their heads in the dark, and performed a mental distraction task in the dark both with and without a weight atop the head. In yaw, the behavior of the head was found to change relatively little with added inertia. As adding inertia to a passive mechanical system should cause substantial changes in dynamics, we inferred that neural mechanisms were invoked to maintain the constant response dynamics. A mathematical model of head-neck control [11] was applied to predict the relative influence of the vestibulocollic and cervicocollic reflexes, and of inertia, stiffness, and viscosity. Using optimization methods to fit the model to experimental data, we identified stiffness and vestibulocollic reflex gain as the primary contributors to the control of head stabilization in space. In pitch, increasing inertia accentuated phase shifts at higher frequencies. Because our pitch model was insufficiently constrained, we only simulated responses due to passive mechanics. Model simulation predicted unstable head motion at all test frequencies. Subjects were able to compensate for trunk motion at most frequencies, however, suggesting that neural components were modulated to exert compensatory responses both with and without additional weight.
The role of vision on postural strategy evaluated in patients affected by congenital nystagmus as an experimental model
Authors: Di Girolamo S. , Di Nardo W. , Cosenza A. , Ottaviani F. , Dickmann A. , Savino G.
Published: September 2021

The role of vision in postural control is crucial and is strictly related to the characteristics of the visual stimulus and to the performance of the visual system. The purpose of this investigation was to evaluate the effects of chronically reduced visual cues upon postural control in patients affected by Congenital Nystagmus (CN). These patients have developed since birth a postural strategy mainly based on vestibular and somatosensorial cues. Fifteen patients affected by CN and 15 normal controls (NC) were enrolled in the study and evaluated by means of dynamic posturography. The overall postural control in CN patients was impaired as demonstrated by the equilibrium score and by the changes of the postural strategy. This impairment was even more enhanced in CN than in NC group when somatosensorial cues were experimentally reduced. An aspecific pattern of visual impairment and a pathological composite score were also present. Our data outline that in patients affected by CN an impairment of the postural balance is present especially when the postural control relies mainly on visual cues. Moreover, a decrease in accuracy of the somatosensory cues has a proportionally greater effect on balance than it has on normal subjects.