Optokinetic drum tilt hastens the onset of vection-induced motion sickness.

Bubka A, Bonato F.

Department of Psychology, Saint Peter's College, Jersey City, NJ 07306, USA. bubka_a spc.edu

BACKGROUND: Under optokinetic drum conditions, a stationary participant views the patterned interior of a rotating drum. Quickly, most participants perceive illusory self-rotation in the direction opposite to the drum's true rotation (vection). It has been documented that up to 60% of participants experience motion sickness-like symptoms under optokinetic conditions perhaps because of conflicting sensory information from the visual and vestibular systems. METHODS: Keeping rotation speed constant (10 RPM), drum tilt relative to the axis of rotation was systematically manipulated (0 degrees, 5 degrees, 10 degrees), producing a wobble effect. Overall well-being and eight motion sickness symptoms were assessed every 2 min using subjective scales. RESULTS: Participants reported 1) a complex type of circular vection that included a "wobble" or "sway" component and 2) a quicker onset of motion sickness-like symptoms as tilt increased. CONCLUSION: In a tilted drum, the vestibular system correctly indicates that the participant is stationary while the visual system indicates a complex type of self-rotation. This type of sensory conflict is more severe than what takes place under typical optokinetic drum conditions (no tilt). Results suggest that as visual/vestibular sensory conflict increases, so does the speed at which motion sickness symptoms occur.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12688448&dopt=Abstract motion sickness




Rotation of subjective vertical is an important factor of visually-induced motion sickness.

Isu N, Matsumoto T, Aoki R.

Dept. of Information and Knowledge Engineer., Faculty of Engineer., Tottori University, Tottori, Japan.

Motion of visual scene (optokinetic stimulus) projected on a wide screen frequently induces motion sickness. Rotational movements of 3D visual images were analyzed to examine what factors are effective in visually-induced motion sickness and how the gravity contributes to its inducement. While an angle of a rotational axis of 3D visual image from the gravitational direction and its angle from the subjective vertical which was perceived by viewers through 3D visual image were varied, the severity of visually-induced motion sickness was measured.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12697561&dopt=Abstract motion sickness




Eye movement, vection, and motion sickness with foveal and peripheral vision.

Webb NA, Griffin MJ.

Human Factors Research Unit, Institute of Sound and Vibration Research, University of Southampton, Southampton, England.

BACKGROUND: Both motion sickness and the illusion of self-motion (i.e., vection) can be induced by moving visual scenes. The results of a previous study imply that motion sickness is primarily dependent on visual motion in foveal vision while vection is primarily dependent on motion in peripheral vision. HYPOTHESIS: It was hypothesized that similar motion sickness would be produced when tracking a single moving dot and a full screen of moving dots, but that vection would be greater when tracking multiple moving dots. METHOD: Sixteen subjects viewed moving images presented on a virtual reality head-mounted display. In one condition a single dot moved from left to right at 27 degrees x s(-1) over a distance of 18 degrees before returning instantly to its starting point. This motion was repeated continuously. In a second condition, five horizontal rows of dots, each 18 degrees apart, moved continuously across the screen at 27 degrees x s(-1); subjects were instructed to track each dot in the central row as it passed. RESULTS: In both conditions, there were nystagmic eye movements with an approximate amplitude of 18 degrees at 27 degrees x s(-1). Vection differed significantly between the two conditions, with more vection in the condition with five rows of dots. Subjects experienced motion sickness symptoms with both the single moving dot and the five rows of dots, with no significant difference in sickness between the two conditions. Subject ratings of motion sickness and vection were not correlated with each other in either of the two conditions. CONCLUSIONS: Motion sickness and vection can vary independently. Vection appears to be influenced by peripheral vision, as there was an increase in vection with full-field stimulation. Motion sickness induced by moving visual scenes may be influenced by foveal visual stimulation or by eye movements, as these were the same in both conditions.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12793532&dopt=Abstract motion sickness




Experimentally induced motion sickness in fish: possible role of the otolith organs.

Helling K, Hausmann S, Clarke A, Scherer H.

Department of Otorhinolaryngology, University Hospital Benjamin Franklin, Free University of Berlin, Berlin, Germany. kai.helling medizin.fu-berlin.de

OBJECTIVE: Although the occurrence of motion sickness is largely attributed to sensory conflict, the reasons for the highly variable inter-individual susceptibility to motion sickness remain unclear. One cause may be asymmetry between otoconial masses in the right and left inner ear. This hypothesis has been supported by experiments in fish under conditions of prolonged weightlessness and parabolic flight. In swordtail fish (Xiphophorus helleri) we examined the extent to which a Coriolis force environment, which has a strong motion sickness-triggering effect, disturbs swimming behaviour or produces motion sickness. MATERIAL AND METHODS: In a sealed aquarium, fish (n = 22) were subjected to Coriolis stimulation by constant vertical axis rotation, combined with pendular oscillation around a horizontal axis. RESULTS: Initially, at low stimulus intensity, all fish showed active compensatory swimming behaviour. However, while the majority (n = 19) maintained active compensation movements at higher stimulus levels, the others (n = 3) entered a passive uncoordinated state, from which they recovered again after reduction of stimulus intensity. On examination of the otoconial mass, we found asymmetries between the right and left utricles in all three cases and between the saccules in one case. CONCLUSION: We conclude that a lateral preponderance of the otoconial masses in the utricle or saccule promotes motion sickness under experimental conditions. The utricle appears to play a more important role in this than the saccule.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12797583&dopt=Abstract motion sickness




Vestibular testing abnormalities in individuals with motion sickness.

Hoffer ME, Gottshall K, Kopke RD, Weisskopf P, Moore R, Allen KA, Wester D.

Department of Defense, Spatial Orientation Center, Department of Otolaryngology, Naval Medical Center San Diego, San Diego, CA 92134-2200, USA. mehoffer nmcsd.med.navy.mil

HYPOTHESIS: The goal of this study was to compare the results of vestibular testing in individuals with motion sickness to a group of control subjects. BACKGROUND: Studying motion sickness is difficult, because no animal model has been developed and symptoms rarely occur outside motion environments. Tests that can be performed in normal laboratory settings, which help to identify individuals with motion sickness, may be valuable in characterizing this disorder. METHODS: Twenty active duty military individuals with well-documented motion sickness were tested. The test battery included sinusoidal rotational chair testing to calculate vestibulo-ocular reflex function, step-velocity testing to calculate vestibular time constants, and posturography testing to assess vestibulo-spinal reflex status. The results of this test battery were compared with a set of age- and sex-matched controls without motion sickness. RESULTS: Vestibular test abnormalities were demonstrated in individuals with motion sickness. Vestibulo-spinal reflex function on posturography was normal in the control group but abnormal in 70% of the individuals with motion sickness. In addition, 5% of the control group demonstrated a minimal shortening of the absolute time constant, whereas 60% of the individuals with motion sickness had abnormal absolute time constants. CONCLUSION: A significant percentage of individuals with motion sickness demonstrate abnormalities in their time constant or vestibulo-spinal reflex function. These abnormalities can be detected using standard, land-based vestibular tests. These preliminary results have implications in understanding the etiology of motion sickness and may provide outcome measures to be used in treating motion sickness.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12851557&dopt=Abstract motion sickness




Fos induction in the amygdala by vestibular information during hypergravity stimulation.

Nakagawa A, Uno A, Horii A, Kitahara T, Kawamoto M, Uno Y, Fukushima M, Nishiike S, Takeda N, Kubo T.

Department of Otolaryngology, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.

Altered gravity environments including both hypo- and hypergravity can elicit motion sickness. Vestibular information is known to be essential for motion sickness, but its other neural substrates are poorly understood. We previously showed that bilateral lesions of the amygdala suppressed hypergravity-induced motion sickness in rats, using pica behavior as an emetic index. We show in the present study that during hypergravity stimulation, vestibular information activated the central nucleus of the amygdala (CeA), as determined by the induction of Fos expression, in comparison between normal and bilaterally labyrinthectomized rats. The finding that Fos expression was confined to the CeA and almost completely absent in other subnuclei of the amygdala contrasted with many previous studies that used other stressful stimuli such as foot shock, restraint and forced swimming, suggesting a specific vestibular effects on the amygdala. Prolongation of hypergravity resulted in reduction of Fos expression in the CeA, suggesting a process of habituation. Such decreases appeared earlier than in the vestibular nucleus, suggesting that adaptive changes in the CeA to hypergravity were independent of changes in the vestibular input. Our results suggest the amygdala is a neural substrate involved in the development of and habituation to motion sickness.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12965235&dopt=Abstract motion sickness




The critical role of velocity storage in production of motion sickness.

Cohen B, Dai M, Raphan T.

Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029, USA. bernard.cohen mssm.edu

We propose that motion sickness is mediated through the orientation properties of velocity storage in the vestibular system that tend to align eye velocity produced by the angular vestibulo-ocular reflex (aVOR) with gravito-inertial acceleration (GIA). (GIA is the sum of the linear accelerations acting on the head. In the absence of translational accelerations, gravity is the GIA.) We further postulate that motion sickness produced by cross-coupled vestibular stimulation can be characterized by a metric composed of the disparity between the axis of eye rotation and the GIA, the strength of the response to angular motion, and the response duration, as determined by the central vestibular time constant, that is, by the time constant of velocity storage. The nodulus and uvula of the vestibulocerebellum are likely to be the central sites where the disparity is sensed, where the vestibular time constants are habituated, and where links are made to the autonomic system to produce the symptoms and signs.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14662476&dopt=Abstract motion sickness




Facial pain increases nausea and headache during motion sickness in migraine sufferers.

Drummond PD, Granston A.

School of Psychology, Murdoch University, 6150 Western Australia, Australia. drummond central.murdoch.edu.au

The aim of this study was to determine whether trigeminal nerve discharge associated with painful stimulation of the temple would intensify symptoms of motion sickness in migraine sufferers. If so, this would support the notion that symptoms such as nausea and headache interact with each other during attacks of migraine. Symptoms of motion sickness were rated at 2 min intervals during 15 min of optokinetic stimulation in 27 migraine sufferers and 23 age- and sex-matched controls. To document changes in frontotemporal blood flow, pulse amplitude was monitored with photoelectric pulse transducers. To induce facial pain, ice was applied to the temple for 30 s, three times at 4 min intervals during optokinetic stimulation. On another occasion, pain was induced during optokinetic stimulation by immersing the non-dominant hand in 2 degrees C ice water for 30 s, three times at 4 min intervals. On a third occasion, measures were obtained during optokinetic stimulation alone. Migraine sufferers rated themselves as being generally more susceptible to motion sickness than controls. In addition, symptoms of motion sickness provoked by optokinetic stimulation were greater in migraine sufferers than in controls. Painful stimulation of the temple intensified nausea and headache during optokinetic stimulation, whereas painful stimulation of the hand did not. Since nausea also intensifies facial pain during motion sickness, nausea and headache may reinforce each other in a vicious circle. In the absence of painful stimulation, increases in pulse amplitude during optokinetic stimulation were greater in migraine sufferers than controls, possibly because the discomfort associated with motion sickness triggered extracranial vasodilatation in migraine sufferers as part of a fight-or-flight (defense) response. Extracranial vasodilatation did not differ between migraine sufferers and controls when ice was applied to the temple or hand during optokinetic stimulation, implying that the additional discomfort associated with painful stimulation of the head and hand evoked a defense response in controls. These findings suggest that a mechanism which boosts extracranial neurovascular reflexes to stress and which heightens symptoms of motion sickness, increases susceptibility to migraine.

Online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14749288&dopt=Abstract motion sickness