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Biomedical subjects

W Bles

Publications and source records attributed to W Bles.

At least 19 recordsLinked to original sources
PubMed2001

Cognitive suppression of tilt sensations during linear horizontal self-motion in the dark.

On the basis of models of otolith functioning, one would expect that, during sinusoidal linear self-motion in darkness, percepts of body tilt are experienced. However, this is normally not the case, which suggests that the otoliths are not responsive to small deviations from the vertical of the gravito-inertial force vector acting on them. Here we show that this is incorrect. Subjects usually know on what kind of linear motion device they are (going to be) moved, having seen it prior to experimentation. This may result in a cognitive suppression of such otolith responses. In the present study, subjects were kept completely unaware of how they were moved and were asked to report on how they thought they moved. About 50% of the reports included tilt percepts almost immediately. It is concluded that this reveals the presence of otolith responsiveness to even small and short-lived deviations of the gravito-inertial force vector from verticality, a responsiveness which is suppressed when (prior) cognitions exist that the motion path is purely in the horizontal plane.

Adult↗
PubMed2000

Motion sickness.

The number of recently published papers on motion sickness may convey the impression that motion sickness is far from being understood. The current review focusses on a concept which tends to unify the different manifestations and theories of motion sickness. The paper highlights the relations between ergonomic principles to minimise motion sickness and the concept predictions. The clinical management of sufferers from motion sickness in terms of selection, pharmacological measures and desensitisation courses is treated as well.

Humans↗
PubMed1998

Modelling motion sickness and subjective vertical mismatch detailed for vertical motions.

In an attempt to predict the amount of motion sickness given any kind of motion stimulus, we describe a model using explicit knowledge of the vestibular system. First, the generally accepted conflict theory is restated in terms of a conflict between a vertical as perceived by the sense organs like the vestibular system and the subjective vertical as determined on the basis of previous experience. Second, this concept is integrated with optimal estimation theory by the use of an internal model. If detailed for vertical motions only, the model does predict typical observed motion sickness characteristics, irrespective the parameter setting. By adjusting the nonvestibular parameters, the model can also quantitatively be adapted to seasickness data from the literature. With this concept, sickness severity hypothetically can also be predicted for other motions, irrespective of their origin and complexity.

Conflict, Psychological↗
PubMed1998

Coriolis effects and motion sickness modelling.

Coriolis effects are notorious in relation to disorientation and motion sickness in aircrew. A review is provided of experimental data on these Coriolis effects, including the modulatory effects of adding visual or somatosensory rotatory motion information. A vector analysis of the consequences of head movements during somatosensory, visual and/or vestibular rotatory motion stimulation revealed that the more the sensed angular velocity vector after the head movements is aligned with the gravitoinertial force vector, the less nauseating effects are experienced. It is demonstrated that this is a special case of the subjective vertical conflict theory on motion sickness that assumes that motion sickness may be provoked if a discrepancy is detected between the subjective vertical and the sensed vertical as determined on the basis of incoming sensory information.

Coriolis Force↗
PubMed1998

Contributions of roll and pitch to sea sickness.

The purpose of this study was to test the traditional assumption that sea sickness is uniquely provoked by heave motion characteristics, with pitch and roll movements being ineffective. In an experiment with a ship motion simulator, subjects were exposed to pitch and roll motions in combination with rather weak heave motions that have no motion sickness-inducing potential. Very high levels of motion sickness were observed (with a motion sickness rating scale) in almost 50% of our subjects. In three control experiments, it was shown that these heave motions, when presented separately, indeed have no motion sickness-inducing potential and that pitch and roll motions presented alone or in combination with each other have only a very small motion sickness-inducing potential. These results indicate that pitch and roll when combined with small heave motions, which in themselves are not sickness provoking, produce more motion sickness than claimed by the classic models. This suggests that in models on motion sickness, pitch and roll should be combined in a nonlinear fashion with heave and that such models will remain rather crude if they do not include a description of the vestibular contribution to motion sickness.

Adaptation, Physiological↗
PubMed1998

Motion sickness: only one provocative conflict?

In reviewing the various forms of motion sickness, the classic sensory rearrangement theory has been redefined by demonstrating that only one type of conflict is necessary and sufficient to explain all different kinds of motion sickness. A mathematical description is provided from the summarizing statement that "All situations which provoke motion sickness are characterised by a condition in which the sensed vertical as determined on the basis of integrated information from the eyes, the vestibular system and the nonvestibular proprioceptors is at variance with the subjective vertical as expected from previous experience."

Computer Simulation↗
PubMed1998

Roll motion stimuli: sensory conflict, perceptual weighting and motion sickness.

In an experiment with 17 subjects, interactions of visual roll motion stimuli and vestibular body tilt stimuli were examined in determining the subjective vertical. Interindividual differences in weighting the visual information were observed, but in general, visual and vestibular responses added in setting the vertical. Despite the conflicting sensory information, motion sickness was not reported apart from one subject on one single occasion. This is in conflict with the sensory mismatch theory on motion sickness, but in agreement with the subjective vertical conflict theory.

Conflict, Psychological↗
PubMed1998

Cervically induced ocular torsion: physiological and clinical aspects.

Ocular torsion was measured in five subjects during sinusoidal lateral tilt (amplitude 25 degrees, 0.2 Hz). The cervical contribution to ocular torsion was best visible as the difference between the signals obtained in conditions with only head tilt and conditions with whole body tilt. Contribution of the neck did not affect the slow component, but produced an anticompensatory modulation of the beating field offset by means of saccades (analogous to gaze shift). Static tilt conditions (25 degrees tilt) of the trunk only, the head only or the whole body showed similar data, although of smaller amplitude. The results from patients suffering from post-whiplash syndrome were similar to those of healthy subjects, showing large intersubject variability. The reduced tolerance to head tilt of whiplash patients restricts useful implementation of this sort of test in the clinic.

Adult↗
PubMed1997

A sustained hyper-g load as a tool to simulate space sickness.

In April 1989 the three European scientist astronauts of the D1 Spacelab Mission were exposed to a 1.5 hours +3G centrifuge run in supine position, resulting in a linear acceleration along the subjects' x-axis. Afterwards, severe motion sickness symptoms were provoked by head movements (Sickness Induced by Centrifugation: SIC). The astronauts mentioned close similarities with what they experienced in space during the D1-Spacelab Mission in 1985, where head movements also provoked motion sickness symptoms (Space Adaptation Syndrome: SAS). Moreover, the astronauts agreed that the rank order of their susceptibility to SAS was the same as for SIC. It was therefore postulated that with this method SAS could be simulated on earth. Additionally, in otolith function tests following the centrifuge run, changes in visual-vestibular interaction were observed, which replicated objective findings obtained with the same astronauts immediately after the D1 Spacelab Mission. During the last couple of years a series of experiments has been carried out to determine the nature of the stimulus causing SIC, the incidence of SIC, and the underlying cardio-vascular and/or vestibular mechanisms. These experiments were carried out on several astronauts and some 50 'normal' healthy subjects. In the next sections the main findings of all these experiments and the implications are summarized.

Acceleration↗
PubMed1996

Ocular torsion before and after 1 hour centrifugation.

To assess a possible otolith contribution to effects observed following prolonged exposure to hypergravity, we used video oculography to measure ocular torsion during static and dynamic conditions of lateral body tilt (roll) before and after 1 h of centrifugation with a Gx-load of 3 G. Static tilt (from 0 to 57 degrees to either side) showed a 10% decrease in otolith-induced ocular torsion after centrifugation. This implies a reduced gain of the otolith function. The dynamic condition consisted of sinusoidal body roll (frequency 0.25 Hz, amplitude 45 degrees) about an earth horizontal and about an earth vertical axis (respectively, "with" and "without" otolith stimulation). Before centrifugation the gain of the slow component velocity (SCV) was significantly lower "with" otolith stimulation than "without" otolith stimulation. Apparently, the contribution of the otoliths counteracts the ocular torsion response generated by the semicircular canals. Therefore, the observed increase in SCV gain in the condition "with" otolith stimulation after centrifugation, seems in correspondence with the decreased otolith gain in the static condition.

Adult↗
PubMed1994

Arthrokinetic and vestibular information enhance smooth ocular tracking during linear (self-)motion.

We studied the gain of smooth ocular tracking for visual, vestibular and arthrokinetic cues, in combination as well as separately, in order to examine how these multisensory cues influence tracking performance. By use of motion along a linear track (besides the self-evident visual influence) evidence was found for arthrokinetic and vestibular enhancement of smooth ocular tracking. These results were in close correspondence with the results of our former study about arthrokinetic influence on linear self-motion perception. Therefore, we conclude that information from the limbs about linear (self-)movement has analogous characteristics and generates analogous responses to the information about angular (self-)movement.

Analysis of Variance↗
PubMed1993

Postural consequences of long duration centrifugation.

In the present paper a series of experiments will be described in which the postural consequences of long (up to 1.5 h) duration 3G-centrifugation have been subject to investigation. A vestibular model is presented in order to explain for the postural imbalance found in specific conditions after the centrifuge run, and for the often concomitant feelings of motion sickness (50% of the subjects suffer from Sickness Induced by long duration Centrifugation). Finally, the possible relation between SIC and the Space Adaptation Syndrome is discussed.

Adaptation, Physiological↗
PubMed1992

A new autosomal dominant syndrome of idiopathic progressive vestibulo-cochlear dysfunction with middle-age onset.

A kindred is described with progressive autosomal dominant vestibulo-cochlear dysfunction resulting in instability in the dark, head movement dependent oscillopsia and hearing loss. The first symptoms appeared in the 4th decade and progressed to vestibular areflexia, presumably in the 5th decade and to almost total deafness in the 6th-7th decade of life. The history was negative for other neurological, otological or infectious diseases, or the use of neuro-ototoxic drugs. The affected subjects showed remarkable compensation for the loss of vestibular function.

Aged↗
PubMed1992

Influence of visual, vestibular, cervical, and somatosensory tilt information on ocular rotation and perception of the horizontal.

By combining a tilting chair and a tilting room we investigated the subjective horizontal (SH) and ocular counterrotation (OCR) as a function of body tilt, trunk tilt, and tilt of a visual frame. Significant influences of (isolated or combined) vestibular and visual information were found, but no influence of neck proprioception. A second and similar experiment, however, now conducted with subjects devoid of labyrinthine function, suggested a contribution of the neck as well as of somatosensory origin. This made a reinterpretation of our data for normal subjects possible.

Adult↗
PubMed1991

The Aubert-Fleischl paradox does appear in visually induced self-motion.

An experiment was set up to investigate the possible influence of oculomotor activity on experienced speed of circular vection. With the standard lined inner wall of an optokinetic drum as stimulus, we found that subjects, sequentially exposed to periods with or without fixation point, experienced an increment in speed of circular vection when the eyes were kept stationary as compared to when optokinetic nystagmus occurred. In a control condition, however, where the influence of optokinetic nystagmus vs fixed gaze on the speed of circular vection was measured separately, the effect was not significant. These findings might explain a discrepancy found in the literature.

Adult↗
PubMed1991

Ocular rotation and perception of the horizontal under static tilt conditions in patients without labyrinthine function.

In a previous study (1) it was found that in healthy subjects Ocular (Counter) Rotation is mainly due to otolith stimulation and only to a minor extent induced by slanted visual structures. Stimulation of the neck by tilting the trunk laterally upwards did not result in a systematic rotation of the eyes. In the present study it was found that subjects with bilateral loss of vestibular function showed a higher visually induced ocular rotation. Tilting the head (cervical stimulation) or the whole body (somatosensory stimulation) also led to a considerable OCR, demonstrating substitution of other sensory modalities for the loss of vestibular function. Estimates of the subjective horizontal were noisy, demonstrating the lack of an adequate gravitational reference signal.

Ear, Inner↗
PubMed1991

The tilting room and posturography.

The tilting room examination technique is detailed. The advantages of posturography with the tilting room as an additional tool in the clinical vestibular examination are described for patients with uni- and bilateral loss of vestibular function, for patients with an acoustic neurinoma and for patients suffering from cervical ataxia. Some illustrations are also given of other applications of the tilting room.

Ataxia↗