bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertical and Horizontal Eye Displacement During Static Pitch and Roll Postures
Authors: Citek Karl , Ebenholtz Sheldon M.
Published: December 2019

The positions of both eyes were measured objectively in the dark following “look straight ahead” instructions for 16 subjects at 27 combinations of static pitch and roll postures over 360° of space, using an infrared video technique. Shifts in vertical version, or the doll reflex, varied sinusoidally with pitch and roll angle. At 0° roll, the average response has a peak-to-trough amplitude of 9.28° and is symmetric about a downward eye position of 4.63°. The proposed Dual Otolith Model (DOM), based on a combination of utricular and saccular inputs, provided excellent fits to the present data (R2=0.876) and to the data of previous studies (R2=0.916 to 0.994). Deviations in horizontal version varied sinusoidally with roll angle, with no significant effect of pitch angle. In general, clockwise (right-ear-down) rolls produced rightward eye movements, and counterclockwise (Ieft-ear-down) rolls produced leftward eye movements. The average versions were symmetric about a leftward eye position of 1.14°, with a peak-to-trough amplitude of 3.76°. The data were well represented by the proposed Horizontal Version Model (HVM; R2=0.796), which depended only on utricular input.
Quantitative Measurements of Eye Movements in a Patient with Tullio Phenomenon
Authors: Rottach Klaus G. , von Maydell Regina D. , DiScenna Alfred O. , Zivotofsky Ari Z. , Averbuch-Heller Lea , Leigh R. John
Published: December 2019

The Tullio phenomenon consists of vestibular symptoms on exposure to high-intensity acoustic stimuli, reflecting pathological stimulation of semicircular canals or otoliths. We report a patient with posttraumatic Tullio phenomenon to illustrate how precise measurement of eye movements during auditory stimulation, using the magnetic search coil technique, may characterize movements that are not clinically apparent or easily measured by other means. Such measurements in patients with surgically verified lesions may further elucidate the mechanisms responsible for this phenomenon.
Visual-Vestibular Interaction During Standing, Walking, and Running
Authors: Demer Joseph L. , Viirre Erik S.
Published: December 2019

In artificial laboratory situations where subjects undergo repetitive self-generated or externally imposed head rotations, visual-vestibular interaction during the wearing of telescopic spectacles can markedly augment gain of the vestibulo-ocular reflex (VOR). The present study was conducted to determine whether the wearing of these aids for the visually impaired is associated with similar visual-vestibular interaction during more natural activities. Angular eye and head movements of unrestrained normal volunteers were measured using magnetic search coils. In some subjects, head translations and rotations were also monitored by a flux gate magnetometer array. Measurements were performed of the VOR in darkness, and of the visually enhanced VOR (VVOR) in lit conditions, during three natural activities: 1) standing quietly; 2) walking in place; 3) running in place. These data were compared with similar measurements during repetitive voluntary head oscillations at 0.8 Hz in pitch or yaw. During VVOR, subjects viewed a target placed 6 to 10 m away and remembered this target during VOR trials in darkness. To assess the effects of altering visual-vestibular interactions, VVOR testing during normal vision was augmented by wearing of binocular telescopic spectacles of 2X, 4X, and 6X powers. Dorsoventral and mediolateral head translations were consistently phase-locked with pitch and yaw head rotations, respectively, such that head translation at least partially compensated for rotational disturbances of gaze. Angular velocity of the head was greater during walking than during standing, and was greater still during running, with a greater increase in each case for pitch as compared with yaw. Eye movements were phase compensatory for head movements. VOR gain (eye velocity divided by head velocity) was near 1.0 in both pitch and yaw during standing and during actively generated head rotation. During walking and running there was a significant decrease in angular VOR gain in pitch to approximately 0.75 (P < 0.0005). During ambulatory activities, normal and magnified vision were associated with VVOR gain enhancement in pitch and yaw that was statistically significant, but substantially less than was telescope magnification and markedly lower than was the corresponding VVOR gain measured during active head rotation. Measurements of unmagnified VOR and VVOR during walking and running showed that gain was lower than the “ideal” value of 1.0. However, since translational head perturbations during these activities partially offset the visual effects of angular disturbances, lower gains may nevertheless be associated with retinal image stability at typical indoor target distances. In contrast with performance during repetitive, uniplanar motion, vision has very limited influence on VOR gain during natural activities.
How to Construct and Move a Cat's Neck
Authors: Graf W. , Keshner E. , Richmond F.J.R. , Shinoda Y. , Statler K. , Uchino Y.
Published: December 2019

Extensive information has been accumulated over the past several years about the head-neck sensory-motor system, in particular that relating to cats. Using still x-ray and cineradiographic analysis, the skeletal geometry of head–neck posture in three dimensions—when an animal is resting, actively orienting, or locomoting—is described. From these descriptions, cervical, vertebral, and craniocervical joint biomechanics for all three rotational dimensions are quantified. These behavioral data on muscle and skeletal movements have been incorporated in a biomechanical, functional anatomical model of the head-neck movement system. Individual as well as groups of neck muscles have been measured in detail and their kinematics determined. The role of a number of these muscles will be described for several reflex and voluntary behavioral contexts, including muscle co-contractions. Having established how each movement is accomplished, the neuronal sensory-motor reflex basis of head–neck system stabilization in space is addressed. The vestibular system is largely responsible for acquisition and maintenance of upright posture. The bilateral semicircular canals (horizontal, anterior, posterior) and otoliths (sacculus, utriculus) feed information differentially to specific neck muscles: these connections are reviewed with regard to the origin of the reflex arc from each receptor to its destination of specific muscles. Behavioral data from normal animals, and from animals whose vestibular receptor systems are selectively lesioned, will be reviewed to complement the functional interpretation of the sensory–motor transformations. Finally, the requirements for space–time coordinated cat head-neck movements will be synthesized, based on biomechanics, muscle kinematics, canal/otolith connectivity, and selective lesion experiments.
A Review of Adaptive Change in Musculoskeletal Impedance during Space Flight and Associated Implications for Postflight Head Movement Control
Authors: McDonald P. Vernon , Bloomberg Jacob J. , Layne Charles S.
Published: December 2019

We present a review of converging sources of evidence which suggest that the differences between loading histories experienced in 1-g and weightlessness are sufficient to stimulate adaptation in mechanical impedance of the musculoskeletal system. As a consequence of this adaptive change we argue that we should observe changes in the ability to attenuate force transmission through the musculoskeletal system both during and after space flight. By focusing attention on the relation between human sensorimotor activity and support surfaces, the importance of controlling mechanical energy flow through the musculoskeletal system is demonstrated. The implications of such control are discussed in light of visual–vestibular function in the specific context of head and gaze control during postflight locomotion. Evidence from locomotory biomechanics, visual–vestibular function, ergonomic evaluations of human vibration, and specific investigations of locomotion and head and gaze control after space flight, is considered.
The Relative Roles of the Otolith Organs and Semicircular Canals in Producing Space Motion Sickness
Authors: Parker Donald E.
Published: December 2019

Inflight and post-landing “immunity” to the “coriolis sickness susceptibility test”, observed during the Skylab M131 experiment, suggests that the otolith organs play a major role in space motion sickness (SMS). This view is supported by the report that ocular counter-torsion asymmetries correlate with SMS incidence and severity. Further data indicate that sensory-motor adaptation to microgravity includes a process whereby central interpretation of otolith signals is biased from “tilt” toward translation. However, unexpected responses to linear acceleration suggest the importance of graviceptors distributed throughout the body in addition to the vestibular otolith organs. Research is needed to assess distributed graviceptor effects.
Human Heart Rate Variability Relation Is Unchanged During Motion Sickness
Authors: Mullen Thomas J. , Berger Ronald D. , Oman Charles M. , Cohen Richard J.
Published: December 2019

In a study of 18 human subjects, we applied a new technique, estimation of the transfer function between instantaneous lung volume (ILV) and instantaneous heart rate (HR), to assess autonomic activity during motion sickness. Two control recordings of ILV and electrocardiogram (ECG) were made prior to the development of motion sickness. During the first, subjects were seated motionless, and during the second they were seated rotating sinusoidally about an earth vertical axis. Subjects then wore prism goggles that reverse the left-right visual field and performed manual tasks until they developed moderate motion sickness. Finally, ILV and ECG were recorded while subjects maintained a relatively constant level of sickness by intermittent eye closure during rotation with the goggles. Based on analyses of ILV to HR transfer functions from the three conditions, we were unable to demonstrate a change in autonomic control of heart rate due to rotation alone or due to motion sickness. These findings do not support the notion that moderate motion sickness is manifested as a generalized autonomic response.
Immersed False Vertical Room
Authors: Coats Alfred C. , Norfleet William T.
Published: December 2019

We evaluated a new model of motion sickness—an enclosure decorated with visual cues to upright which was immersed either inverted or “front”-wall down, in Johnson Space Center's Weightless Environment Training Facility (WETF) pool. This “WETF False Vertical Room” (WFVR) was tested with 19 male and 3 female SCUBA diver subjects, aged 23 to 57, who alternately set clocks mounted near the room's 8 corners and made exaggerated pitch head movements. We found that (1) the WFVR test runs produced motion sickness symptoms in 56% and 36% of subjects in the room-inverted and room-front-down positions, respectively. (2) Pitch head movements were the most provocative acts, followed closely by setting the clocks—particularly when a clock face filled the visual field. (3) When measured with a self-ranking questionnaire, terrestrial motion sickness susceptibility correlated strongly (P < 0.005) with WFVR sickness susceptibility. (4) Standing instability, measured with a modified Fregly–Graybiel floor battery, also correlated strongly (P < 0.005) with WFVR sickness susceptibility. This result may reflect a relationship between visual dominance and WFVR sickness. (5) A control study demonstrated that the inverted and front-down positions produced WFVR sickness, but the upright position did not, and that adaptation may have occurred in some subjects with repeated exposure. The WFVR could become a useful terrestrial model of space motion sickness (SMS) because it duplicates the nature of the gravity-dependent sensory conflicts created by micro-gravity (visual and otolith inputs conflict while somatosensory gravity cues are minimized), and it also duplicates the nature of the provocative stimulus (sensory environment “rule change” versus application of motion to passive subject) more closely than any other proposed terrestrial SMS model. Also, unlike any other proposed terrestrial SMS model, the WFVR incorporates whole-body movement in all three spatial dimensions. However, the WFVR's sensory environment differs from that created by spaceflight in several respects, including the presence of frictional drag on limb movement, magnification at the face-mask-water interface, greater otolith conflict, exhaled bubbles, and the presence of some gravity-dependent somatosensory inputs.
Cogan's Syndrome
Authors: Helmchen C. , Jäger L. , Büttner U. , Reiser M. , Brandt T.
Published: December 2019

In the chronic-relapsing form of Cogan's syndrome, it can be difficult to evaluate the activity of the disease. In contrast to the initial stage, routine diagnostic techniques sometimes fail to indicate progression in the chronic stage. To determine whether high-resolution magnetic resonance imaging (HR-MRI) can be used to differentiate between active and inactive stages, we examined three patients with Cogan's syndrome (one during an acute relapse, two with chronic audiovestibular deficits), all of whom had antibodies to inner ear tissue (cochlea, vestibular labyrinth). Unenhanced T1-, T2, gadolinium-enhanced T1-weighted, and three-dimensional constructive interference in steady stage (CISS) images were used. Abnormal MRI signals of the inner ear were related to the activity of the disease. The patient studied during an acute exacerbation showed abnormal MRI signals in the vestibule, semicircular canals, vestibular nerve, and cochlea, which disappeared after the relapse. These abnormalities included high signal in the membranous labyrinth, the vestibule, and cochlea, with enhancement on T1-weighted images, indicating gadolinium leakage through the abnormal labyrinthine membrane into the perilymphatic spaces. In contrast, the other two patients with chronic audiovestibular deficits but no clinical signs of an acute relapse, had narrowing or occlusion of semicircular canals of the cochlea on the 3D-CISS images, but no high signal lesions (T1) and no enhancement. We conclude that sequential gadolinium-enhanced MRI can identify the active stage of Cogan's syndrome. The combination of HR-MRI and antibodies to inner ear antigens are helpful in the diagnosis of acute, sequential, bilateral audiovestibular impairment of autoimmune origin.
Direct Influence of Temperature on the Semicircular Canal Receptor
Authors: Suzuki Mamoru , Kadir Abdul , Hayashi Naoki , Takamoto Muneo
Published: December 2019

Effect of thermal stimulus on the vestibular receptor was studied using the isolated frog semicircular canal. The posterior (PSC) and lateral semicircular canals (LSC) were placed in the horizontal plane in frog Ringer's solution. The ampullary nerve was sucked into a glass suction electrode to record compound potentials. The steel thermal probe was positioned next to the ampullary surface to give thermal stimuli. When the PSC ampulla was cooled, the spontaneous discharge markedly increased. When the PSC ampulla was warmed, the discharge decreased. When the LSC ampulla was cooled, the discharge increased in the same manner as in the PSC. Also, warming of the LSC decreased the discharge in the same manner as in the PSC. The cupula was removed from the crista in order to eliminate the effect of volume change of the endolymph. The results were comparable to those with intact cupula in both the PSC and LSC. Cooling increased, while warming decreased the discharge. These responses are possibly due to a mechanism other than mechanical volume change, because the PSC and LSC yielded the same type of responses. Direct temperature reaction of the vestibular hair cell was suggested.
Central and Peripheral Components of Short Latency Vestibular Responses in the Chicken
Authors: Nazareth Andrea M. , Jones Timothy A.
Published: December 2019

Far-field recordings of short latency vestibular responses to pulsed cranial translation are composed of a series of positive and negative peaks occurring within 10 ms following stimulus onset. In the bird, these vestibular evoked potentials (VsEPs) can be recorded noninvasively and have been shown in the chicken and quail to depend strictly upon the activation of the vestibular component of the eighth nerve. The utility of the VsEP in the study of vestibular systems is dependent upon a clear understanding of the neural sources of response components. The primary aim of the current research in the chicken was to critically test the hypotheses that 1) responses are generated by both peripheral and central neurons and 2) peaks P1 and N1 originate from first order vestibular neurons, whereas later waves primarily depend on activity in higher order neurons. The principal strategy used here was to surgically isolate the eighth nerve as it enters the brainstem. Interruption of primary afferents of the eighth nerve in the brainstem substantially reduced or eliminated peaks beyond P2, whereas PI and N1 were generally spared. Surgical sections that spared vestibular pathways had little effect on responses. The degree of change in response components beyond N1 was correlated with the extent of damage to central vestibular relays. These findings support the conclusion that responses are produced by both peripheral and central elements of the vestibular system. Further, response peaks later than N1 appear to be dependent upon central relays, whereas PI and N1 reflect activity of the peripheral nerve. These findings clarify the roles of peripheral and central neurons in the generation of vestibular evoked potentials and provide the basis for a more useful and detailed interpretation of data from vestibular response testing.
Neck Influences on the Spatial Properties of Vestibulospinal Reflexes in Decerebrate Cats: Role of the Cerebellar Anterior Vermis
Authors: Manzoni D. , Pompeiano O. , Andre P.
Published: December 2019

The vestibulospinal (VS) reflexes elicited by animal rotation modify the activity of limb musculature, thus preserving balance and postural stability. We investigated whether the orientation of these postural responses is strictly dependent upon the direction of head displacement or else can be modified by extralabyrinthine inputs to the goal of stabilizing body position. The experiments were performed in decerebrate cats, in which the effects of static body-to-head displacements were tested on the multiunit EMG responses of the medial head of the triceps brachii to wobble of the whole animal at 0.15 Hz, 10°, both in the clockwise (CW) and counterclockwise (CCW) direction. These stimuli allowed us to determine the muscle response vector, whose orientation component corresponds to the direction of head displacement giving rise to the maximal EMG response. When the animal body was kept straight with respect to the head, the triceps response vector was always oriented close to the transverse axis, pointing to the side-down direction. Following 30° of body-to-head displacement around a vertical axis passing through the first-second cervical joints, the response vectors of both the left and the right muscles shifted in the same direction of body rotation, thus remaining approximately perpendicular to the body axis. The change in muscle vector orientation corresponded on the average to the angle of body-to-head displacement. Only slight changes in amplitude of the muscle responses were observed. These findings imply that the maximal activation of the triceps brachii always occurred for the same direction of body displacement, irrespective of the pattern of discharge of vestibular afferents, which is determined by the direction of head displacement. The rotation of the triceps response vector induced by body-to-head displacement was reduced or suppressed by inactivation of the ipsilateral cerebellar anterior vermis, following local microinjection of the GABAA agonist muscimol. These findings indicate that 1) the sensory input which results from changing the body position with respect to the head, probably originating from neck receptors, is able to modify the pattern of the VS reflexes, which appear to be organized in a body-centered reference frame, and 2) the cerebellar vermis is required for the proper execution of this sensorimotor transformation.
Spatial Updating During Rotation: The Role of Vestibular Information and Mental Activity
Authors: Yardley Lucy , Higgins Marsha
Published: December 2019

The remarkable accuracy with which healthy subjects can monitor their orientation while walking in darkness has been attributed to a process whereby awareness of orientation is automatically updated by information derived from active locomotion. The aim of this study was, first, to determine the contribution of vestibular information to the perception of orientation without vision, by comparing the accuracy of judgments of orientation following passive (seated) rotation about an earth-vertical axis with those following active (locomotor) rotation. The second aim was to assess whether monitoring orientation is indeed automatic, or whether it requires some degree of mental effort. This was evaluated by assessing whether accuracy in monitoring multiple passive or active rotations was affected by asking subjects to perform a mental task (that is, counting backwards) during rotation. The results indicated that although reliance on the primarily vestibular information available during passive rotation enabled subjects to accurately monitor single turns of up to 180°, subjects were able to judge orientation after multiple turns more accurately after active rotation than after passive rotation, owing to the additional sensorimotor feedback gained from active locomotion. Accuracy in judging orientation was substantially impaired by backwards counting during both passive and active locomotion. This finding confirms that monitoring orientation during multiple turns in darkness necessitates central processing and adds to the growing body of evidence for the influence of mental activity on the perception and control of orientation.
Unilateral Vestibular Deafferentation Induces Brain-Derived Neurotrophic Factor (BDNF) Protein Expression in the Guinea Pig Lateral but not Medial Vestibular Nuclei
Authors: Smith Paul F. , Darlington Cynthia L. , Yan Qiao , Dragunow Michael
Published: December 2019

The aim of the present study was to investigate the expression of the neurotrophin, brain-derived neurotrophic factor (BDNF), in the vestibular nucleus complex (VNC) following unilateral vestibular deafferentation (UVD). Using immunohistochemistry, BDNF expression was analyzed in the bilateral VNC of the guinea pig in sham animals, and immediately, 10 h, and 50 h post-UVD. No BDNF expression was seen in the VNC in sham animals or immediately or 10 h post-UVD. However, at 50 h post-UVD, clear BDNF expression was seen in the bilateral lateral vestibular nuclei (LVN) and in the bilateral abducens nuclei, but not in the medial vestibular nuclei (MVN). The significance of this late BDNF expression is unclear.
Integration of nonlabyrinthine inputs by the vestibular system: Role in compensation following bilateral damage to the inner ear
Authors: Yates Bill J. , Miller Derek M.
Published: December 2019

Inputs from the skin and muscles of the limbs and trunk as well as the viscera are relayed to the medial, inferior, and lateral vestibular nuclei. Vestibular nucleus neurons very quickly regain spontaneous activity following a bilateral vestibular neurectomy, presumably due to the presence of such nonlabyrinthine inputs. The firing of a small fraction of vestibular nucleus neurons in animals lacking labyrinthine inputs can be modulated by whole-body tilts; these responses are eliminated by a spinal transection, showing that they are predominantly elicited by inputs from the trunk and limbs. The ability to adjust blood distribution in the body and maintain stable blood pressure during movement is diminished following a bilateral vestibular neurectomy, but compensation occurs within a week. However, bilateral lesions of the caudal portions of the vestibular nuclei produce severe and long-lasting cardiovascular disturbances during postural alterations, suggesting that the presence of nonlabyrinthine signals to the vestibular nuclei is essential for compensation of posturally-related autonomic responses to occur. Despite these observations, the functional significance of nonlabyrinthine inputs to the central vestibular system remains unclear, either in modulating the processing of vestibular inputs or compensating for their loss.
International survey of vestibular rehabilitation therapists by the Barany Society Ad Hoc Committee on Vestibular Rehabilitation Therapy
Authors: Cohen Helen S. , Gottshall Kim R. , Graziano Mariella , Malmstrom Eva-Maj , Sharpe Margaret H.
Published: December 2019

The goal of this study was to determine how occupational and physical therapists learn about vestibular rehabilitation therapy, their educational backgrounds, referral patterns, and their ideas about entry-level and advanced continuing education in vestibular rehabilitation therapy. The Barany Society Ad Hoc Committee for Vestibular Rehabilitation Therapy invited therapists around the world to complete an E-mail survey. Participants were either known to committee members or other Barany Society members, known to other participants, identified from their self-listings on the Internet, or volunteered after reading notices published in publications read by therapists. Responses were received from 133 therapists in 19 countries. They had a range of educational backgrounds, practice settings, and referral patterns. Few respondents had had any training about vestibular rehabilitation during their professional entry-level education. Most respondents learned about vestibular rehabilitation from continuing education courses, interactions with their colleagues, and reading. All of them endorsed the concept of developing standards and educating therapists about vestibular anatomy and physiology, vestibular diagnostic testing, vestibular disorders and current intervention strategies. Therefore, the Committee recommends the development of international standards for education and practice in vestibular rehabilitation therapy.
Increased vestibular contribution to posture control in individuals with chronic headache
Authors: Wei-Lynn So Christina , Bent Leah R.
Published: December 2019

Objective: Numerous studies have identified an association between headache disorders and vestibular symptoms, such as dizziness, vertigo, and motion sensitivity. Using bipolar, binaural galvanic vestibular stimulation (GVS), our objectives were to (1) determine the degree of vestibular sensitivity in borderline headache sufferers, and (2) characterize the postural response to vestibular perturbation in these individuals. Methods: Fourteen volunteers participated in this study: 8 individuals with chronic headache (6 with migraine and 2 with tension type headache (TTH)), and 6 healthy control subjects. Thirty trials of 15-second duration were conducted across 6 conditions (GVS left (L) or right (R), or no stimulation (No GVS) with either eyes open (EO) or eyes closed (EC)). Peak medial-lateral (M-L) centre of pressure (CoP) was calculated during quiet stance. Results: Headache subjects demonstrated significantly higher peak displacement of the M-L CoP than control subjects (p=0.0461). Although peak M-L CoP in both the EO (p = 0.0753) and EC (p=0.09623) visual conditions were not significantly different between headache sufferers compared to healthy controls, there is some suggestion that people with chronic headache may use vestibular information to a greater extent and that the presence of vision may not sufficiently compensate for vestibular induced instability. The initial push M-L CoP was not significantly different between groups, suggesting different sensory contributions for the initial and latter response to GVS. Conclusions: People with chronic headache exhibit increased postural sway, which may reflect the re-weighting of sensory information with an increased vestibular and a reduced visual contribution to postural control. Significance: These results support existing research on vestibular abnormalities in chronic headache sufferers that may provide a basis for future treatment therapies.
Mechanical properties and motion of the cupula of the human semicircular canal
Authors: Selva Pierre , Oman Charles M. , Stone Howard A.
Published: December 2019

The mathematical model for the dynamics of the cupula-endolymph system of the inner ear semicircular canal, as elaborated by numerous investigators, remains a foundational tool in all of vestibular physiology. Most models represent the cupula as a linear spring-like element of stiffness K=ΔP/ΔV, where ΔV is the volume displaced upon application of a pressure difference ΔP. The parameter K directly influences the long time constant of the cupula-endolymph system. Given estimates of K based on experiments, we use thick and thin bending membrane theory, and also finite-element simulations based on more realistic cupula morphologies, to estimate the human cupula's Young's modulus E ≈ 5.4 Pa. We show that for a model morphology, thick bending membrane theory and finite-element predictions are in good agreement, and conclude that the morphology of the attachment of the cupula to the slope of the crista should not greatly influence the volume displacement. We note, however, that other biological materials with very low E are hydrogels that have significant viscoelastic properties. Experiments to directly measure E and investigate potential viscoelastic behavior ultimately may be needed. In addition, based on experimental images we study two other different shapes for the cupula and quantify their impact on the deflection of the cupula. We also use a three-dimensional finite-element model to analyze both the shear strain distribution and its time evolution near the sensory epithelium. We conclude that stimulation of sensory hair cells probably begins at the centre of the crista and spreads toward the periphery of the cupula and down the sides of the crista. Thus, spatio-temporal variations in the shearing stimulus are predicted to impact subsequent transduction and encoding. Finally, modeling the fluid-filled vertical channels believed to lie within the cupula, we investigate the impact of different tube diameters on the transverse displacement field. We show that, for the assumed diameters and grid spacing, cupula displacements should be highly sensitive to the diameter of the tubes. Experiments to verify the existence of cupular channels and accurately measure their diameter and spacing are needed.
Effects of microgravity on cognition: The case of mental imagery
Authors: Grabherr Luzia , Mast Fred W.
Published: December 2019

Human cognitive performance is an important factor for the successful and safe outcome of commercial and non-commercial manned space missions. This article aims to provide a systematic review of studies investigating the effects of microgravity on the cognitive abilities of parabolic or space flight participants due to the absence of the gravito-inertial force. We will focus on mental imagery: one of the best studied cognitive functions. Mental imagery is closely connected to perception and motor behavior. It aids important processes such as perceptual anticipation, problem solving and motor simulation, all of which are critical for space travel. Thirteen studies were identified and classified into the following topics: spatial representations, mental image transformations and motor imagery. While research on spatial representation and mental image transformation continues to grow and specific differences in cognitive functioning between 1 g and 0 g have been observed, motor imagery has thus far received little attention.
Age effect on the Gaze Stabilization test
Authors: Honaker Julie A. , Shepard Neil T.
Published: December 2019

Impairments of the vestibular-ocular reflex (VOR) lead to a decline in visual acuity during head movements. Dynamic visual acuity (DVA) testing is a sensitive assessment tool for detecting VOR impairments. DVA evaluates accuracy of visual acuity during fixed velocity head movements. In contrast, the Gaze Stabilization test (GST) is a new functional evaluation of the VOR that identifies a person's maximum head velocity (in degrees per second) a person can maintain with stable vision of a target (i.e. optotype). The objective of this study was to evaluate the effect of age on the GST in participants without vestibular disease. The study was conducted in a vestibular and balance laboratory at a tertiary medical center. A total of 87 healthy adult volunteers were included in this study. The main outcome measure was the association between age and both GST maximum head velocity in the yaw (right/left) plane and velocity symmetry. A significant negative correlation was found between age and maximum head velocity (r =−0.469, p< 0.001). Our results suggest that age should be considered when interpreting GST results in the yaw plane, however standardization of testing methods should be established as variation in results has been reported in the literature.
The reliability, stability, and concurrent validity of a test of gaze stabilization
Authors: Ward Bryan K. , Mohammad Maha T. , Whitney Susan L. , Marchetti Gregory F. , Furman Joseph M.
Published: December 2019

The gaze stabilization test (GST) is a computerized test of the vestibulo-ocular reflex that reports maximum head velocity while maintaining fixed visual acuity. The GST thus assesses the vestibulo-ocular reflex differently from the dynamic visual acuity test (DVAT). The purpose of this study was to assess the reliability, stability, and validity of the GST in a healthy young and older population. Forty subjects (20 older adults with mean (SD) age of 76.3 (5.3) and 20 young controls with mean (SD) age of 25.2 (3.2)) performed the GST and DVAT assessments. The version of the GST used in this study has a tunneled mirror system to ensure a consistent participant distance of 4 m from the computer screen. All subjects repeated trials within 30 minutes of initial testing. Twenty subjects (10 from each age group) returned 7–10 days later to repeat the GST and DVAT assessments. Vestibular symptoms were assessed before and after GST and DVAT assessments. The mean (SD) GST scores for the older group were 123 (33) deg/s in the yaw plane and 108 (27) deg/s in the pitch plane. For the young group, mean (SD) GST scores were 157 (34) deg/s in the yaw plane and 141(25) deg/s in the pitch plane. There was a significant between-group difference for GST scores in both yaw and pitch planes (p< 0.01). The intraclass correlation coefficient (ICC) for GST scores performed on the same day was 0.75 in the yaw plane and 0.69 in the pitch plane. The ICC including the 20 subjects who repeated the GST within 7–10 days was 0.59 in the yaw plane and 0.54 in the pitch plane. In general, GST was more stable than DVAT. GST was more stable in younger vs. older subjects whereas DVAT was more stable in older vs. younger subjects. Concurrent validity, determined by Spearman correlation coefficients between GST and DVAT loss results were −0.62 in the yaw plane and −0.38 in the pitch plane (p< 0.02). These results suggest that the gaze stabilization test (GST) has good same-day test-retest reliability and stability in healthy young and older adults. The moderate correlation between same-day GST and DVAT loss scores suggest the two tests may be measuring similar, but different constructs.
Head tilt response: A complementary test to the Subjective Visual Vertical
Authors: Geisinger Dario , Ferreira Enrique , Suarez Alejo , Suarez Hamlet
Published: December 2019

This paper studies the phenomenon of the perceived vertical by means of a novel dynamic experiment. This task is inspired in the Subjective Visual Vertical test and can be regarded as complementary in terms of how the information involved varies (visual, otolithic and neck proprioception). The experiment consists in presenting a white stripe in a pair of virtual reality goggles and adjusting the roll angle of the head until the stripe is aligned with the gravitational vertical. The roll angle of the head is measured and recorded along each trial where the white stripe changes position four times, after a specific amount of time. The task was run on a group of 28 normal subjects and a small sample of 5 patients with vestibular hypofunction. Six parameters derived from Control Theory were extracted from the data to characterize the subject transient response. All parameters for normal subjects were found to be normally distributed. Experimental results show that discrimination is possible between normal subjects and patients using just one or two of the parameters studied.
Short and long-term postural learning to withstand galvanic vestibular perturbations
Authors: Tjernström Fredrik , Bagher Ali , Fransson Per-Anders , Magnusson Måns
Published: December 2019

We investigated changes of postural responses to repeated bipolar galvanic vestibular stimulation on 5 consecutive days and once again after 3 months. Subjects consisted of 21 healthy volunteers. Except for the first day did the induced torque variance in response to galvanic vestibular stimulation not decrease {within} each test session, but there was a major reduction {from day to day} (p< 0.001) reflecting a continued processing of the postural experience gained during the stimulation. The decreased end level magnitude of postural responses after 5 days was retained after 3 months. The galvanic stimulation failed to induce larger torque variance compared to quiet stance toward the end of the 5 days as well as after 3 months, indicating a down-regulation of a repeated erroneous vestibular stimulation by the postural control system – i.e. sensory reweighting. This argues that a major adaptation effect to galvanic vestibular perturbation takes place after the exposure to the stimulation – similar to the concept of the consolidation process involved in motor learning. This should be considered when repeatedly assessing vestibular function both clinically and in studies. It implies that sensory training involved in rehabilitation from vestibular diseases/deficiencies should be executed with spaced intervals in order to procure more efficient learning processes and in the end, a better function.
Does tilt/translation ratio affect perception of deceleration in driving simulators?
Authors: Stratulat Anca M. , Roussarie Vincent , Vercher Jean-Louis , Bourdin Christophe
Published: December 2019

Tilt-coordination is a technique which uses the tilt-translation ambiguity of the vestibular system to simulate linear accelerations on dynamic driving simulators, in combination with real linear accelerations. However, the tilt/translation ratio is chosen empirically. We experimentally determine the most realistic tilt/translation ratio to simulate a given value of deceleration. Under specific conditions of driving simulation, five tilt/translation ratios were applied, with an inverse-proportional quantity of tilt and translation, so that the sum of the two (the proportion of the deceleration simulated by translational motion and the proportion simulated by tilt) was always equal to the same overall value (0.8 m/s2). We find that different ratios lead to different perceptions, depending on the quantity of tilt and translation. With a higher tilt ratio, the braking is perceived as being stronger than when there is a higher translation ratio and the most realistic tilt/translation ratio found is neither pure tilt, nor pure translation, but 35/65% tilt/translation. The way these different ratios are perceived during braking is discussed from vestibular and non-vestibular points of view.
The 2D modified head impulse test: A 2D technique for measuring function in all six semi-circular canals
Authors: Migliaccio Americo A. , Cremer Phillip D.
Published: December 2019

The head impulse test can be used to measure peripheral vestibular function of all six semicircular canals. Traditionally, vertical canal function is measured by rotating the head from a starting neutral position (forward facing) about a diagonal plane that bisects the sagittal and coronal planes. These types of head rotations elicit eye movements with large vertical and torsional (about the line of sight) angular velocity components. Three-dimensional (3D: horizontal, vertical and torsional) eye measurement techniques are needed to measure these velocity components. We wanted to determine whether 2D measurements coupled to a modified head impulse test are sufficient to measure function of all six canals. In this study we measured individual canal function in patients (n = 5) with peripheral unilateral hypofunction and control subjects (n = 4) using the traditional head impulse test and the 'gold standard' 3D (dual-coil) scleral search coil technique. We compared these results with those from our 2D modified head impulse test using the 2D coil technique (single-coil). We show that both techniques detect similar levels of asymmetrical function in patients and are equally accurate in isolating canals with hypofunction. We conclude that 2D eye measurement techniques, such as video pupil-tracking, can be used to test all six canals.
Migraine, vertigo and migrainous vertigo: Links between vestibular and pain mechanisms
Authors: Balaban Carey D.
Published: December 2019

This review develops the hypothesis that co-morbid balance disorders and migraine can be understood as additive effects of processing afferent vestibular and pain information in pre-parabrachial and pre-thalamic pathways, that have consequences on cortical mechanisms influencing perception, interoception and affect. There are remarkable parallel neurochemical phenotypes for inner ear and trigeminal ganglion cells and these afferent channels appear to converge in shared central pathways for vestibular and nociceptive information processing. These pathways share expression of receptors targeted by anti-migraine drugs. New evidence is also presented regarding the distribution of serotonin receptors in the planum semilunatum of the primate cristae ampullaris, which may indicate involvement of inner ear ionic homeostatic mechanisms in audiovestibular symptoms that can accompany migraine.
Vestibular dysfunction and compensation after removal of acoustic neuroma
Authors: Uehara Natsumi , Tanimoto Hitoshi , Nishikawa Tasuku , Doi Kiyoshi , Katsunuma Sayaka , Kimura Hidehito , Kohmura Eiji , Nibu Ken-ichi
Published: December 2019

Objective: To evaluate vestibular function after unilateral acoustic neuroma surgery via a retrosigmoid approach. Methods: Thirty-eight patients were tested using caloric irrigation, static posturography, and the Dizziness Handicap Inventory (DHI) before, and one week to nine months after surgery. Results: Twenty-six patients were categorized as a response group and 12 as a no-response group on the basis of preoperative caloric irrigation findings. The posturographic parameters and DHI scores at one week after surgery showed significant deterioration in the response group, but not in the no-response group. However, they recovered to the preoperative baseline at 3 months after surgery. The posturographic parameters and DHI scores for older patients tended to be worse than those for younger patients at 6 and 9 months after surgery. Conclusion: Patients in whom caloric responses are retained preoperatively show a temporary disturbance of balance after removal of acoustic neuroma. Disequilibrium after surgery ameliorates to the preoperative baseline within three months due to vestibular compensation, regardless of preoperative vestibular function. It is possible that poorer vestibular compensation may facilitate incomplete recovery in older patients after surgery.
The reliability and response stability of dynamic testing of the vestibulo-ocular reflex in patients with vestibular disease
Authors: Mohammad Maha T. , Whitney Susan L. , Marchetti Gregory F. , Sparto Patrick J. , Ward Bryan K. , Furman Joseph M.
Published: December 2019

The purpose of the study was to investigate the test-retest reliability and response stability of the Dynamic Visual Acuity (DVA) and Gaze Stabilization Test (GST) in patients with vestibular disorders. Twenty-nine patients with vestibular disease (16–78 years) participated. Subjects performed the GST and DVA in pitch and yaw planes, twice in one session and once after 7–10 days. The GST output is the maximum head velocity at which the patient was able to identify orientation of the letter E. The DVA output is the change in visual acuity when moving the head compared to static acuity. Subjects indicated their level of dizziness and visual blurring using a visual analog scale. Within- and between-sessions intraclass correlation coefficients ranged between 0–0.5 for the DVA and GST measures, with better correlations for within-session assessments. Response stability (standard error of measurement / mean) of the GST ranged between 21–32% and the DVA ranged between 25–69% with vertical DVA being most influenced by measurement error. Subjects' symptoms did not correlate with performance on either test. The current test protocol needs refinement to enhance reliability and stability in persons with vestibular disorders.
Experimental measurement of utricle dynamic response1
Authors: Dunlap M.D. , Spoon C.E. , Grant J.W.
Published: December 2019

The utricle of the red-eared turtle was subjected to forced sinusoidal oscillations across various frequencies (10–125 Hz) and amplitudes (5–9 μm) to determine dynamic characteristics of the utricle under natural inertial stimulation. The utricle was maintained in physiologic solution during the entire experiment. Utricular specimens were prepared so that the Otoconial Layer (OL) crystals were exposed yet undisturbed, and the neuroepithelium was secured to a glass slide with dental floss strands. A piezoelectric-actuated platform, fitted to the stage of the microscope, created controlled sinusoidal displacement along the utricle's medial-lateral direction. The OL surface displacement was measured through the microscope with high-speed video at 1500 fps. A sub-pixel image registration algorithm was used to achieve displacement resolution ⩽ 15 nm. The Membranous Shelf (MS), that overlies the macula, was recorded with high-speed video under identical amplitude and frequency inputs and was used as a reference point. Maximum displacement amplitudes of the OL and MS were used to determine the Amplitude Ratio (AR) of the OL relative to the MS. ARs at various frequencies were fit to a single degree of freedom model of the utricle to determine the utricle's natural frequency of 363 Hz (95% confidence intervals: 328, 397) with a damping ratio of 0.96 (0.8, 1.12).