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Results 301 - 350 of 1325
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Tychsen Lawrence - - 2008
Recent studies of human infants have described a spectrum of early-onset esotropia, from small angle to large heterotropias. We report here a similar spectrum of early-onset esotropia in infant monkeys, with emphasis on the relationship between visuomotor deficits, central nervous system circuitry, and orbital anatomy. Eye movements were recorded in ...
Pavani Sri Rama Prasanna - - 2008
Rotating point spread functions (PSFs) present invariant features that continuously rotate with defocus and are important in diverse applications such as computational imaging and atom/particle trapping. However, their transfer function efficiency is typically very low. We generate highly efficient rotating PSFs by tailoring the range of invariant rotation to the ...
Xu Kun - - 2008
This paper presents a novel basis function, called spherical piecewise constant basis function (SPCBF), for precomputed radiance transfer. SPCBFs have several desirable properties: rotatability, ability to represent all-frequency signals, and support for efficient multiple product. By smartly partitioning the illumination sphere into a set of subregions, and associating each subregion ...
Gong Shi Wei - - 2008
This paper presents an analysis of a human head response to impact by a foreign object. The analysis is accomplished via an integration of a head-striker contact force function with a 3-D finite-element (FE) head model. The contact force function developed by the authors is used to estimate the contact ...
Reynolds J S - - 2008
The head's inertia produces forces on the neck when the body moves. One collective function of the vestibulocollic and cervicocollic reflexes (VCR and CCR) is thought to be to stabilize the head with respect to the trunk during whole body movements. Little is known as to whether their head-movement kinematics ...
Bourke A K - - 2008
This study investigates distinguishing falls from normal Activities of Daily Living (ADL) by thresholding of the vertical velocity of the trunk. Also presented is the design and evaluation of a wearable inertial sensor, capable of accurately measuring these vertical velocity profiles, thus providing an alternative to optical motion capture systems. ...
Jaeger R - - 2008
The transformation of head-movements into neural signals represents a multi-stage process. It depends on orientation and movement of the head, the geometry and mechanics of the vestibular sensors, and the ensuing processing of the peripheral vestibular signals. While this process is well understood for the semicircular canals, where each canal ...
Angelaki Dora E - - 2008
Elegant sensory structures in the inner ear have evolved to measure head motion. These vestibular receptors consist of highly conserved semicircular canals and otolith organs. Unlike other senses, vestibular information in the central nervous system becomes immediately multisensory and multimodal. There is no overt, readily recognizable conscious sensation from these ...
Nooij Suzanne A E - - 2008
Adaptation to a novel gravitational state involves adaptation of vestibular mediated responses, in particular those mediated by the otolith organs. The present paper investigates whether the orientation of Listing's plane, which is under control of otolith signals, is affected by sustained exposure to hypergravity. Subjects were exposed to four G-loads ...
Gianna-Poulin Claire C - - 2008
High-velocity rotational stimuli have the potential to improve the diagnostic capabilities of clinical rotation testing by revealing nonlinear vestibulo-ocular reflex (VOR) responses that are indicative of asymmetric vestibular function. However, eye movements evoked by high-velocity rotations often are inconsistent over time and therefore do not yield reliable diagnostic measures. This ...
Garrick-Bethell Ian - - 2008
Out-of-plane head movements performed during fast rotation produce non-compensatory nystagmus, sensations of illusory motion, and often motion sickness. Adaptation to this cross-coupled Coriolis stimulus has previously been demonstrated for head turns made in the yaw (transverse) plane of motion, during supine head-on-axis rotation. An open question, however, is if adaptation ...
Laurens Jean - - 2008
During constant-velocity rotation about a tilted axis (OVAR), the VOR and the rotation perception last indefinitely, but show a striking dependency on tilt angle. We show that, during OVAR, a variety of motions can account for the head motion relative to gravity. Some of these are in conflict with canal ...
Jombik Peter - - 2008
Recently several studies have yielded evidence that impulses of bone-conducted (BC) sound can produce short-latency myogenic responses in the extraocular muscles, which are probably mediated by otolithic afferents. These responses, although miniscule, can be recorded with surface electrodes and are termed ocular vestibular evoked myogenic potentials (oVEMP). It is assumed ...
Bertolini G G Dip. Informatica e Sistemistica, Università degli Studi di Pavia, Via Ferrata, Pavia 1 - 27100, Italy. - - 2008
The rotational vestibulo-ocular reflex (rVOR) contributes to gaze stabilitization by compensating head rotational movements sensed by the semicircular canals (SCC). The CNS improves the performance of the horizontal rVOR through the so called velocity storage mechanism (VSM). However the properties of the VSM in response to pitch rotations are less ...
Ishida Masayuki - - 2008
Self-motion is known to be falsely perceived during exposure to the movement of visual surroundings. This illusory perception of visually-induced self-motion is known as "vection." The present study was conducted to examine the relative strengths of vection versus whole-body angular acceleration as they determine perceived self-rotation under conditions in which ...
Olasagasti I - - 2008
We present results of a study of torsional eye movements evoked by earth-vertical accelerations along the subject's longitudinal axis. The earth-vertical stimulus leads to a gravito-inertial acceleration vector that changes magnitude but not direction. It can therefore be viewed as a dynamic change of the gravity level. Up-down oscillations induced ...
Walker Mark F MF Department of Neurology, The Johns Hopkins University, Baltimore, MD, USA. - - 2008
We studied two rhesus monkeys before and after surgical ablation of the nodulus and uvula (Nod/Uv) of the cerebellum. Three-axis eye movements were recorded with the magnetic-field scleral search coil system during a variety of vestibular and ocular motor tasks. Here we describe the effects of the Nod/Uv lesions on ...
Sklavos S S Department of Physiology, School of Nursing, University of Athens, Goudi, Athens, - - 2008
Large gaze displacements are mediated by combined motion of the eye, head, trunk, and foot. We applied principal component analysis (PCA) to examine the degree of variability and linearity in the angular velocity pattern of the various segments involved that participate in this task. Ten normal subjects stood up and ...
Bertolini G - - 2008
To investigate the contribution of the vestibular velocity-storage mechanism (VSM) to the vertical rotational vestibulo-ocular reflex (rVOR) we recorded eye movements evoked by off-vertical axis rotation (OVAR) using whole-body constant-velocity pitch rotations about an earth-horizontal, interaural axis in four healthy human subjects. Subjects were tumbled forward, and backward, at 60 ...
Sheehan Scott E - - 2008
Short-radius centrifugation (SRC) provides a practical means of producing artificial gravity for long duration space flights, though perceptual side-effects could limit its operational feasibility. Head turns (HT) during SRC, other than those about the centrifugation axis, produce Cross-Coupled Stimulation (CCS), perceived as a tumbling sensation. CCS can be nauseagenic, though ...
Kessler Paul - - 2008
CONCLUSION: Testing of the horizontal vestibulo-ocular reflex (VOR) with head rotations (including head impulses) using the magnetic scleral search coil technique (SCT HHI) provides valuable additional diagnostic information in patients with persistent dizziness, oscillopsia or imbalance. It identifies high and low frequency/acceleration vestibular abnormalities that are frequently missed using other ...
Palla A - - 2008
Healthy human subjects, when roll tilted in darkness, make systematic errors in estimating subjective visual vertical (SVV). Typically, roll tilt underestimation occurs at angles beyond 60 degrees (A-effect). At smaller tilt angles, overestimation may occur (E-effect). At approximately 135 degrees whole-body roll tilt, Kaptein and Van Gisbergen (2004, 2005) found ...
Sinha N - - 2008
We investigated the perception of self-rotation using constant-velocity chair rotations. Subjects signalled self motion during three independent tasks (1) by pushing a button when rotation was first sensed, when velocity reached a peak, when velocity began to decrease, and when velocity reached zero, (2) by rotating a disc to match ...
Keshner E A - - 2008
Multiplanar environmental motion could generate head instability, particularly if the visual surround moves in planes orthogonal to a physical disturbance. We combined sagittal plane surface translations with visual field disturbances in 12 healthy (29-31 years) and 3 visually sensitive (27-57 years) adults. Center of pressure (COP), peak head angles, and ...
Darling Warren G WG Motor Control Laboratories, Department of Integrative Physiology, University of Iowa, Iowa City, IA 52242, USA. - - 2008
We studied possible frames of reference for kinesthetic perception of imposed hand motion direction in the frontal plane in ten young adult subjects with no history of neuromuscular disease. In one experiment, subjects were instructed to set unseen hand motion imposed by a motorized linear slide device parallel to the ...
Gianna-Poulin Claire C CC Neurological Sciences Institute, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA. - - 2008
Controversy remains about the linearity of the interaction between horizontal semicircular canal and otolith organ vestibulo-ocular reflexes (VORs) in the generation of horizontal eye movements during head movements including both rotational and translational components. We used three eccentric rotation techniques to investigate this interaction in human subjects: (1) the tangential ...
Maruta Jun J Department of Neurology, Mount Sinai School of Medicine, Box 1135, 1 Gustave L. Levy Place, New York, NY 10029, - - 2008
Whether ocular orientation to gravity is produced solely by linear acceleration in the horizontal plane of the head or depends on both horizontal and vertical components of the acceleration of gravity is controversial. Here, we compared orienting eye movements of rabbits during head tilt to those produced by centrifugation that ...
Schneider Erich E Department of Neurology, University Hospital of Munich - Grosshadern Ludwig-Maximilians University, Marchioninistr. 23, 81377, Munich, Germany. - - 2008
Locomotion control uses proprioceptive, visual, and vestibular signals. The vestibular contribution has been analyzed previously with galvanic vestibular stimulation (GVS), which constitutes mainly a virtual head-fixed rotation in the roll plane that causes polarity-specific deviations of gait. In this study we examined whether a visual disturbance has similar effects on ...
Wada Yoshiro Y Department of Physiology I, Nara Medical University, Nara, 634-8521, Japan. - - 2008
A major function of the otolith organ is to detect linear acceleration generated by two different head conditions, dynamic linear translation and static tilt relative to gravity. To investigate these sensory functions of the otolith organ, we analyzed vertical eye position in response to steady-state sinusoidal fore-aft translation over a ...
Jáuregui César - - 2007
In Brillouin-assisted slow-light the induced delay is always linked to a particular gain; i.e., the delay is directly proportional to the gain expressed in decibels. However, for certain applications this may be restrictive, and techniques to decouple gain and delay are thus of considerable practical interest. We propose a way ...
Allum John H J JH Department of ORL, University Hospital, Basel, Switzerland. - - 2008
One of the signatures of balance deficits observed in vestibular loss subjects is the greater instability in the roll compared to pitch planes. Directional differences in the timing and strengths of vestibular and proprioceptive sensory signals between roll and pitch may lead to a greater miscalculation of roll than pitch ...
Tanabe Satoru - - 2007
In this study, we examined the relationship between upper limb joint movements and horizontal racket head velocity to clarify joint movements for developing racket head speed during tennis serving. Sixty-six male tennis players were videotaped at 200 Hz using two high-speed video cameras while hitting high-speed serves. The contributions of ...
Duistermars Brian J - - 2007
Fruit flies respond to panoramic retinal patterns of visual expansion with robust steering maneuvers directed away from the focus of expansion to avoid collisions and maintain an upwind flight posture. Panoramic rotation elicits comparatively weak syndirectional steering maneuvers, which also maintain visual stability. Full-field optic flow patterns like expansion and ...
Bryan A S AS Ashton Graybiel Spatial Orientation Laboratory, Brandeis University, MS 033, Waltham, MA, 02454-9110, - - 2007
We tilted recumbent subjects at various angles about their yaw (foot to head) axis and had them indicate the direction of their subjective vertical and apparent head midline about the same axis. One set of tests was conducted during parabolic flight maneuvers where the background gravitoinertial acceleration varied from 0 ...
Grip Helena - - 2007
BACKGROUND: The ability to reproduce head position can be affected in patients after a neck injury. The repositioning error is commonly used as a measure of proprioception, but variations in the movement might provide additional information. METHODS: The axis of motion and target performance were analyzed during a head repositioning ...
Tomilovskaya E S - - 2007
The study was performed to explore effects of long-duration SF on the characteristics of horizontal gaze fixation reaction (hGFR). Changes in GFR observed in long-duration space flight (SF) point out to serious disturbances of the VOR system due to, apparently, altered vestibular activity. Two strategies of reaction adaptation to the ...
Yakusheva Tatyana A - - 2007
The ability to orient and navigate through the terrestrial environment represents a computational challenge common to all vertebrates. It arises because motion sensors in the inner ear, the otolith organs, and the semicircular canals transduce self-motion in an egocentric reference frame. As a result, vestibular afferent information reaching the brain ...
Wood Scott J SJ Universities Space Research Association, Houston, TX, USA. - - 2007
The effect of stimulus frequency on tilt and translation motion perception was studied during constant velocity off-vertical axis rotation (OVAR), and compared to the effect of stimulus frequency on eye movements. Fourteen healthy subjects were rotated in darkness about their longitudinal axis 10 degrees and 20 degrees off-vertical at 45 ...
Bockisch Christopher J CJ Department of Neurology, University Hospital Zürich, Frauenklinikstrasse 26, Zurich, Switzerland. - - 2007
Reaching for an object while simultaneously rotating induces Coriolis and centrifugal inertial forces on the arm that require compensatory actions to maintain accuracy. We investigated whether the nervous system uses vestibular signals of head rotation to predict inertial forces. Human subjects reached in darkness to a remembered target 33 cm ...
Beer Jeremy - - 2007
INTRODUCTION: Experiments measured the optokinetic cervical reflex (OKCR), wherein the banking pilot aligns the head with the horizon. In a synthetic cockpit, the flight display was manipulated to test whether changing the visual reference frame would alter OKCR. METHODS: Eight subjects (five rated pilots) flew a route in simulated visual ...
Olberg R M - - 2007
The capture of flying insects by foraging dragonflies is a highly accurate, visually guided behavior. Rather than simply aiming at the prey's position, the dragonfly aims at a point in front of the prey, so that the prey is intercepted with a relatively straight flight trajectory. To better understand the ...
Cowsik R - - 2007
The rotations around the vertical axis associated with the normal mode oscillations of the Earth and those induced by the seismic and other disturbances have been very difficult to observe directly. Such observations will provide additional information for 3D modeling of the Earth and for understanding earthquakes and other underground ...
Vingerhoets R A A - - 2007
During prolonged rotation about a tilted yaw axis, often referred to as off-vertical axis rotation (OVAR), a percept of being translated along a conical path slowly emerges as the sense of rotation subsides. Recently, we found that these perceptual changes are consistent with a canal-otolith interaction model that attributes the ...
Chen S C - - 2007
In most current vision prosthesis designs, head movement is the sole director of visual gaze and scanning due to the head-mounted nature of the camera. Study of this unnatural behaviour may provide insight into improved prosthesis designs and rehabilitation procedures. In this paper, we conducted a psychophysical study to investigate ...
Rajguru Suhrud M SM Department of Bioengineering, University of Utah, 20 South 2030 East, Rm. 506, Salt Lake City, UT 84112, - - 2007
Benign paroxysmal positional vertigo (BPPV) is a common vestibular disorder that results in brief periods of vertigo and nystagmus, when the head is tipped relative to gravity. Symptoms are commonly attributed to the pathological presence of heavy calcium carbonate particles within the lumen of the semicircular canal(s)-a condition termed canalithiasis. ...
Fetsch Christopher R CR Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, - - 2007
Heading perception is a complex task that generally requires the integration of visual and vestibular cues. This sensory integration is complicated by the fact that these two modalities encode motion in distinct spatial reference frames (visual, eye-centered; vestibular, head-centered). Visual and vestibular heading signals converge in the primate dorsal subdivision ...
Cheung Carol C - - 2007
Prior experiments have demonstrated that people are able to adapt to cross-coupled accelerations associated with head movements while spinning at high rotation rates (e.g., 23 rpm or 138 degrees/s). However, while adapting, subjects commonly experience serious side effects, such as motion sickness, non-compensatory eye movements, and strong and potentially disorienting ...
Green Andrea M - - 2007
An accurate internal representation of our current motion and orientation in space is critical to navigate in the world and execute appropriate action. The force of gravity provides an allocentric frame of reference that defines one's motion relative to inertial (i.e., world-centered) space. However, movement in this environment also introduces ...
Maes L - - 2007
OBJECTIVES: The aim of this study was to construct a rotational test protocol after exploring the stimulus parameters of the rotatory vestibular test. METHODOLOGY: Twenty-four normal subjects were submitted to three different rotational paradigms: the sinusoidal harmonic acceleration test (SHAT), the pseudorandom rotation test (PRRT), and the velocity step test ...
Sanderson Jeffrey - - 2007
We demonstrate a new method for measuring the time constant of head-movement-contingent oscillopsia (HMCO) produced by vestibular Coriolis stimulation. Subjects briskly rotated their heads around pitch or roll axes whilst seated on a platform rotating at constant velocity. This induced a cross-coupled vestibular Coriolis illusion. Simultaneous with the head movement, ...
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