We studied the cervico-ocular reflex (COR) alone and in combination with the optokinetic (OKN) reflex in head-fixed pigeons. We analyzed these responses in two behavioral conditions: (1) animals were hung in a harness ("resting" condition); and (2) animals were additionally submitted to a frontal airflow that provoked a flight posture ...

To investigate the dynamic effects of external forces on the displacement of the otolith membrane and subsequent neuronal responses of otoliths, we performed numerical analyses of otolith membrane displacements. In these studies we included the full geometry of the human otolith maculae, including their 3D curvature. The first part focuses ...

Organizational structures intrinsic to nervous systems can be more precisely analyzed and compared with other logical structures once they are expressed in mathematical languages. A standard mathematical language for expressing organizational structure is that of groups. Groups are especially well suited to organizational structures involving multiple symmetries such as spatial ...

In conditions of slow passive transport without vision, even tenuous inertial signals from semi-circular canals and the haptic-kinaesthetic system should provide information about changes relative to the environment provided that it is possible to command the direction of the body's movements voluntarily. Without such control, spatial updating should be impaired ...

The subjective visual vertical was measured in 38 healthy subjects. The head was alternately roll-tilted to the right and to the left, and the start position of the light bar was alternately set clockwise and counterclockwise. When the head is tilted less than 60-70 degrees a deviation of the subjective ...

This study investigated the patterns of rotational mobility (> or =20 degrees ) and stability (< or =20 degrees ) of the head and trunk in wild Indian monkeys during natural locomotion on the ground and on the flat-topped surfaces of walls. Adult hanuman langurs (Semnopithecus entellus) and bonnet macaques ...

People naturally move their heads when they speak, and our study shows that this rhythmic head motion conveys linguistic information. Three-dimensional head and face motion and the acoustics of a talker producing Japanese sentences were recorded and analyzed. The head movement correlated strongly with the pitch (fundamental frequency) and amplitude ...

Path integration allows animals to navigate without landmarks by continuously processing signals generated through locomotion. Insects such as bees and ants have evolved an accurate path integration system, assessing and coding rotations with the help of a general directional reference, the sun azimuth. In mammals, by contrast, this process can ...

The aim of this study was to characterize the error pattern of continuously tracking the perceived earth-vertical during roll rotations from upright to right or left ear-down and from right or left ear-down to upright. We compared the tracking responses of two paradigms, which either continuously activated the otoliths organs ...

The big brown bat (Eptesicus fuscus) is an aerial-feeding insectivorous species that relies on echolocation to avoid obstacles and to detect flying insects. Spatial perception in the dark using echolocation challenges the vestibular system to function without substantial visual input for orientation. IR thermal video recordings show the complexity of ...

A method was developed to identify the linear, system level dynamics of the horizontal, angular vestibulo-ocular reflex (VOR) as it stabilized vision during head-free tracking of a visual target. Small amplitude, broad spectrum, stochastic torque perturbations were applied to the head while the subject tracked an unpredictable, moving target with ...

We investigated the nystagmus of a 12-year-old boy with suspected X-linked congenital nystagmus (CN) and exophoria to determine the underlying mechanisms and component signals in the 'dual-velocity' and other slow phases of his Asymmetric (a)Periodic Alternating Nystagmus (APAN). Fast Fourier transforms (FFT) were performed on the waveforms and residual data ...

BACKGROUND AND PURPOSE: Head stability is the dynamic process of maintaining an equilibrium position of the head-in-space. Individuals with vestibular deficits restrict head movements during dynamic activities in an effort to adapt to vestibular loss. However, this strategy does not provide them with a successful means for adaptation during dynamic ...

We compared the predictive behavior of smooth pursuit (SP) and suppression of the vestibuloocular reflex (VOR) in humans by examining anticipatory smooth eye movements, a phenomenon that arises after repeated presentations of sudden target movement preceded by an auditory warning cue. We investigated whether anticipatory smooth eye movements also occur ...

This paper presents an assessment tool for objective neck movement analysis of subjects suffering from chronic whiplash-associated disorders (WAD). Three-dimensional (3-D) motion data is collected by a commercially available motion analysis system. Head rotation, defined in this paper as the rotation angle around the instantaneous helical axis (IHA), is used ...

Rotational head motion in vertebrates is detected by the three semicircular canals of the vestibular system whose innervating primary afferent fibers encode movement information in specific head planes. In order to further investigate the nature of vestibular central processing of rotational motion in rhesus monkeys, it was first necessary to ...

The ability to simultaneously move in the world and maintain stable visual perception depends critically on the contribution of vestibulo-ocular reflexes (VORs) to gaze stabilization. It is traditionally believed that semicircular canal signals drive compensatory responses to rotational head disturbances (rotational VOR), whereas otolith signals compensate for translational movements [translational ...

When tilted subjects are asked to set a luminous line to the perceived earth-vertical in a dark surrounding, they systematically underestimate the true direction of earth-vertical at large tilt angles, a phenomenon first described by Aubert (A-phenomenon). At small tilt angles, subjects usually overestimate the direction of earth-vertical. Overestimation has ...

We studied short-term (30 min) adaptation of the vestibulo-ocular reflex (VOR) in five normal humans using a "position error" stimulus without retinal image motion. Both before and after adaptation a velocity gain (peak slow-phase eye velocity/peak head velocity) and a position gain (total eye movement during chair rotation/amplitude of chair ...

The eye movement component that rotates around the line of sight, i.e., the ocular torsion, is in many aspects different from horizontal and vertical eye movements. While ocular torsion is mediated only by reflexive pathways like the torsional vestibulo-ocular and optokinetic reflexes (TVOR and OKN, respectively), horizontal and vertical components ...

Otolithic influence on optokinetic eye-movements (visual-vestibular interaction) was investigated using oscillation of a lateral linear acceleration-step combined with optokinetic stimulation. According to our preliminary study using a 40-deg/s optokinetic stimulus speed at 0.3 and 0.5 G acceleration-steps, the interaction was characterized by a linear addition during the agonistic stimulus condition, ...

Alterations in the gain of the vertical angular vestibulo-ocular reflex (VOR) are dependent on the head position in which the gain changes were produced. We determined how long gravity-dependent gain changes last in monkeys after four hours of adaptation, and whether the adaptation is mediated through the nodulus and uvula ...

The mechanisms for adaptation to visual rotation were investigated by exposing subjects to different rotation angles in a stepwise fashion. We found that response direction continuously changed to compensate for the imposed rotation, but this change was limited to 90 deg. Larger changes were accomplished by inverting both spatial axes ...

The cervico-ocular reflex (COR) is an ocular stabilization reflex that is elicited by rotation of the neck. It works in conjunction with the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) in order to prevent visual slip over the retina due to self-motion. The gains of the VOR and OKR ...

When seated subjects are submitted to a linear acceleration, reports indicate that the kinematic and electromyographic (EMG) responses of the head-neck system can be modulated with the magnitude of the linear acceleration. There is no evidence, however, that head kinematics or neck EMG activity can be modulated when specific knowledge ...

We analyze velocity fluctuations in turbulent Rayleigh-Bénard convection. The velocity measurements were taken at the center of an aspect-ratio-one convection cell filled with water. The measured probability density functions of the velocity difference over a time interval tau are found to change with tau, indicating that the velocity fluctuations are ...

This study provides the first systematic examination of the effects of intratympanic gentamicin instillation on vestibulo-ocular responses of guinea pigs during both Earth-vertical yaw axis and off-vertical axis rotation. A scleral search coil was sutured to the right eye of pigmented female guinea pigs prior to trans-bullar instillation of a ...

The perception of body position is mainly mediated by otolith information and visual cues. It has been shown, however, that proprioceptive sources are also involved. To distinguish between the contributions of the vestibular and nonvisual extra-vestibular information to graviception, we tested the effects of a stimulus that leaves the vestibular ...

The gain of the vestibulo-ocular reflex (VOR) normally depends on the distance between the subject and the visual target, but it remains uncertain whether vergence angle can be linked to changes in VOR gain through a process of context-dependent adaptation. In this study, we examined this question with an adaptation ...

We determined the spatial dependence of adaptive gain changes of the vertical angular vestibulo-ocular reflex (aVOR) on gravity in five human subjects. The gain was decreased for 1 h by sinusoidal oscillation in pitch about a spatial vertical axis in a subject-stationary surround with the head oriented left-side down. Gains ...

This study used visual-vestibular conflict to effect short-term torsional and horizontal adaptation of the vestibulo-ocular reflex (VOR). Seven normal subjects underwent sinusoidal whole-body rotation about the earth-vertical axis for 40 min (+/- 37 degrees/s, 0.3 Hz) while viewing a stationary radial pattern fixed to the chair (x0 viewing). During adaptation ...

Measurements of the subjective visual horizontal (SVH) were made in a large swing-out gondola centrifuge. Rotation of the centrifuge was anti-clockwise, as seen from above. Test subjects were seated upright in the gondola, facing forwards. In front of the subject, at a straight-ahead eye-level position, there was a narrow luminous ...

The low frequency oscillatory flow in a rotating curved pipe was studied by using the method of biparameter perturbation. Perturbation solutions up to the second order were obtained and the effects of rotation on the low frequency oscillatory flow were examined in detail. The results indicated that there exists evident ...

Labyrinthine defective subjects (LDS) experience oscillopsia during head movements due to the absence of the vestibulo-ocular reflex (VOR). The purpose of this study was to compare horizontal and vertical visual motion detection in LDS during (i) body-stationary and (ii) horizontal whole-body oscillation conditions. Twelve LDS and controls detected the onset ...

PURPOSE: Vertically skewed eye movements are induced by head tilt toward the shoulder (roll). Because vertical and torsional eye movements are tightly coupled both mechanically and neuronally, the purpose of the present study was to investigate the conjugacy of torsional eye movements during the Bielschowsky head tilt test (BHTT). Furthermore, ...

We investigated gaze-stabilizing reflexes in the chameleon using the three-dimensional search-coil technique. Animals were rotated sinusoidally around an earth-vertical axis under head-fixed and head-free conditions, in the dark and in the light. Gain, phase and the influence of eye position on vestibulo-ocular reflex rotation axes were studied. During head-restrained stimulation ...

The accuracy with which the vestibular system anticipates and compensates for the visual consequences of translation during forward and backward movements was investigated with transient motion profiles in rhesus monkeys trained to fixate targets on an isovergence screen. Early during motion when visuomotor reflexes remain relatively ineffective and vestibular-driven mechanisms ...

We ask how vestibular and optokinetic information is combined ("fused") when human subjects who are being passively rotated while viewing a stationary optokinetic pattern try to tell when they have reached a previously instructed angular displacement ("targeting task"). Inevitably such a task entices subjects to also draw on cognitive mechanisms ...

It has been suggested that, after a passive linear acceleration of a seated subject which resembles a small, rear-end car impact, sensory information from proprioceptive, vestibular, and visual systems elicit stabilizing neck muscular responses. These neck muscular responses are presumably reflex based and are modified with the magnitude of the ...

Head controls provide an alternative means of computer access. This study determined whether neck movement limitations are associated with reduced performance with such head controls. This study also identified features of the cursor movement path that could aid in assessing computer access limitations. Fifteen subjects without disabilities and ten subjects ...

The vestibular system has often been studied by perturbing the position of the head. This study was conducted to identify the dynamic properties of the head-neck system in response to horizontal plane perturbations. A quasilinear approach was used to quantify the dynamics of the head-neck system at different levels of ...

Proceeding from recent evidence for a sensory involvement in the pathophysiology of idiopathic spasmodic torticollis (ST), we asked whether the abnormal head posture of these patients is associated with distortions of their internal spatial reference frames due to abnormal processing of neck proprioceptive and/or vestibular input. Twelve ST patients were ...

Human capabilities in manipulating many different tools with dexterity suggest modular neural organization at functional levels, but anatomical modularity underlying the capabilities has yet to be demonstrated. Although modularity in phylogenetically older parts of the cerebellum is well known, comparable modularity in the lateral cerebellum for cognitive functions remains unknown. ...

We characterized the interaural translational vestibulo-ocular reflex (tVOR) in 6 normal humans to brief (approximately 200 ms), high-acceleration (0.4-1.4g) stimuli, while they fixed targets at 15 or 30 cm. The latency was 19 +/- 5 ms at 15-cm and 20 +/- 12 ms at 30-cm viewing. The gain was quantified ...

The purpose of this study was to evaluate the relative contributions of inputs from the vestibular system and the trunk to head-trunk coordination. Twelve healthy adults and 6 adults with diminished bilateral labyrinthine input (LD) were seated with their trunk either fixed to the seat or free to move. Subjects ...

This study investigated the reciprocal relation between estimation of body tilt and visual vertical by using self-controlled passive body tilts at constant velocity (slow tilts with no semicircular canal activation) or constant acceleration (rapid tilts with canal activation). In both conditions, the visual vertical was overestimated in the luminous line ...

PURPOSE: To compare responses to vertical and horizontal optokinetic (OK) stimulation in patients with disorders of ocular alignment. METHODS: Using the magnetic search coil technique, we measured horizontal and vertical rotations of both eyes in six patients with strabismus since childhood and eight normal subjects. The OK stimulus subtended 72 ...

The vestibulo-ocular reflex (VOR) serves to keep images relatively stable on the retina. To maintain appropriate performance and minimize image slip throughout life, VOR is subjected to long-term adaptive regulation by visual input. It has been reported that adaptive changes in VOR gain (eye velocity/head velocity) are evoked either by ...

OBJECTIVE: To study the characteristics of human body dynamic responses to landing impact. METHOD: Five healthy young men were exposed to 4-10 G for 50-80 ms half-sine acceleration pulse at 20 degrees supine angle and 10 G for 50 ms impact at 30 degrees to 60 degrees supine angles. The ...

Sensory systems often provide ambiguous information. For example, otolith organs measure gravito-inertial force (GIF), the sum of gravitational force and inertial force due to linear acceleration. However, according to Einstein's equivalence principle, a change in gravitational force due to tilt is indistinguishable from a change in inertial force due to ...