Illusory self-motion often provokes motion sickness, which is commonly explained in terms of an i... more Illusory self-motion often provokes motion sickness, which is commonly explained in terms of an inter-sensory conflict that is not in accordance with previous experience. Here we address the influence of cognition in motion sickness and show that such a conflict is not provocative when the observer believes that the motion illusion is indeed actually occurring. Illusory self-motion and motion sickness were elicited in healthy human participants who were seated on a stationary rotary chair inside a rotating optokinetic drum. Participants knew that both chair and drum could rotate but were unaware of the actual motion stimulus. Results showed that motion sickness was correlated with the discrepancy between participants’ perceived self-motion and participants’ beliefs about the actual motion. Together with the general motion sickness susceptibility, this discrepancy accounted for 51% of the variance in motion sickness intensity. This finding sheds a new light on the causes of visually ...
Full-field visual rotation around the vertical axis induces a sense of self-motion (vection), opt... more Full-field visual rotation around the vertical axis induces a sense of self-motion (vection), optokinetic nystagmus (OKN), and, eventually, also motion sickness (MS). If the lights are then suddenly switched off, optokinetic afternystagmus (OKAN) occurs. This is due to the discharge of the velocity storage mechanism (VSM), a central integrative network that has been suggested to be involved in motion sickness. We previously showed that visually induced motion sickness (VIMS) following optokinetic stimulation is dependent on vection intensity. To shed light on this relationship, the current study investigated whether vection intensity is related to VSM activity, and thus, to the OKAN. In repetitive trials (eight per condition), 15 stationary participants were exposed to 120 s of visual yaw rotation (60°/s), followed by 90 s in darkness. The visual stimulus either induced strong vection (i.e., scene rotating normally) or weak vection (central and peripheral part moving in opposite directions). Eye movements and subjective vection intensity were continuously measured. Results showed that OKAN occurred less frequently and with lower initial magnitude in the weak-vection condition compared to the strong-vection condition. OKAN decay time constants were not significantly different. The results suggest that the stimuli that produced strong vection also enhanced the charging of the VSM. As VSM activity presumably is a factor in motion sickness, the enhanced VSM activity in our strong-vection condition hints at an involvement of the VSM in VIMS, and could explain why visual stimuli producing a strong sense of vection also elicit high levels of VIMS.
This study investigated the role of vection (i.e., a visually induced sense of self-motion), opto... more This study investigated the role of vection (i.e., a visually induced sense of self-motion), optokinetic nystagmus (OKN), and inadvertent head movements in visually induced motion sickness (VIMS), evoked by yaw rotation of the visual surround. These three elements have all been proposed as contributing factors in VIMS, as they can be linked to different motion sickness theories. However, a full understanding of the role of each factor is still lacking because independent manipulation has proven difficult in the past. We adopted an integrative approach to the problem by obtaining measures of potentially relevant parameters in four experimental conditions and subsequently combining them in a linear mixed regression model. To that end, participants were exposed to visual yaw rotation in four separate sessions. Using a full factorial design, the OKN was manipulated by a fixation target (present/absent), and vection strength by introducing a conflict in the motion direction of the centra...
When in darkness, humans can perceive the direction and magnitude of rotations and of linear tran... more When in darkness, humans can perceive the direction and magnitude of rotations and of linear translations in the horizontal plane. The current paper addresses the integrated perception of combined translational and rotational motion, as it occurs when moving along a curved trajectory. We questioned whether the perceived motion through the environment follows the predictions of a self-motion perception model (e.g., Merfeld et al. in J Vestib Res 3:141-161, 1993; Newman in A multisensory observer model for human spatial orientation perception, 2009), which assume linear addition of rotational and translational components. For curved motion in darkness, such models predict a non-veridical motion percept, consisting of an underestimation of the perceived rotation, a distortion of the perceived travelled path, and a bias in the perceived heading (i.e., the perceived instantaneous direction of motion with respect to the body). These model predictions were evaluated in two experiments. In ...
Aviation Space and Environmental Medicine, Jun 1, 2007
Introduction: In motion sickness desensitization programs, the motion sickness provocative stimul... more Introduction: In motion sickness desensitization programs, the motion sickness provocative stimulus is often a forward bending of the trunk on a rotating chair, inducing Coriolis effects. Since respiratory relaxation techniques are applied successfully in these courses, we investigated whether these repetitive trunk movements by themselves may induce hyperventilation and consequently add to the motion sickness. Methods: There were 12 healthy subjects who participated in our study. In the Baseline condition, subjects sat relaxed on the stationary chair. In the Hypervent condition, subjects performed voluntary hyperventilation (the level was prescribed). In two other conditions subjects rhythmically bent their trunk on a stationary chair (Tilt-Stat condition) and on a rotating chair (Tilt-Rot condition). In all conditions we measured respiratory and cardiovascular activity (heart frequency, tidal volume, end-tidal CO 2 , and respiration frequency). Results: Of the 12 subjects, 9 had to stop prematurely in the Tilt-Rot condition because of moderate nausea. Except for heart rate in the Tilt-Rot condition, the measured physiological parameters in these subjects in the Tilt-Stat and Tilt-Rot conditions were not statistically different from the Baseline condition. Only in the Hypervent condition were significant differences observed, but no nausea. Discussion: The findings show that hyperventilation is not the main cause of nausea during the Coriolis effects. We conclude that during the pilot desensitization program with Coriolis stimuli, measurement of cardiovascular and respiratory parameters is not necessary; however, in those cases that do not respond to the intervention, we recommend paying attention to respiratory parameters because hyperventilation does occur on an individual basis.
Journal of vestibular research : equilibrium & orientation, 2007
It has been found that sustained centrifugation on Earth may evoke sickness symptoms that are sim... more It has been found that sustained centrifugation on Earth may evoke sickness symptoms that are similar to those of the Space Adaptation Syndrome (SAS). As in SAS, incidence of this 'Sickness Induced by Centrifugation' (SIC) is about 50% and the symptoms are particularly evoked by head movements. By systematically varying the G-load and duration of centrifugation, the current study investigated the characteristics of the gravitational stimulus that is required for SIC to occur. Subjects were exposed to centrifugation at 2 and 3Gx, for a duration of 45 and 90 minutes. A standardized head movement protocol was used to evoke SIC after centrifugation. The results show that in six out of 12 subjects (50%) no serious symptoms were elicited. In the remaining subjects, the effects of the 3G runs exceeded those of the 2G runs, and within each G-level symptom intensity was higher for the 90 min than for the 45 min exposure. An exponential fit on this data showed that the time constant o...
Adaptation to a novel gravitational state involves adaptation of vestibular mediated responses, i... more 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 differing in duration (45 or 90 min) and magnitude (2 or 3G). During centrifugation subjects were in a supine position, directing the gravito-inertial acceleration along the naso-occipetal axis. We determined the orientation of Listing's plane before and after each centrifuge run, with the head erect and tilted in pitch. Head tilt in pitch induced a counter-pitch of Listing's plane, which was found to be less pronounced after centrifugation. In addition, exposure to 3G for 90 min induced a small backward tilt of Listing's plane compared to the pretest orientation (head erect). In order to explain these results a hypothesis is discussed, proposing that the orientation of Listing's plane in the head is governed by a head fixed orientation vector that is modulated by the direction of gravity relative to the head. Sustained centrifugation is proposed to decrease this gravitational modulation, leading to the effects observed. This could reflect a shift towards a more body centered frame of reference.
Background / Purpose: In this study, we investigated for the first time in the same experiment, t... more Background / Purpose: In this study, we investigated for the first time in the same experiment, the effect of visual information, simulator motion in additional directions and active vehicle control on the perception of simulator motion (roll-rate) during curve driving. Main conclusion: Mean detection threshold for roll-rate increased in active driving conditions. However, large differences between participants were observed. Results suggest that this is related to the level of immersion in the simulation.
Journal of vestibular research : equilibrium & orientation, 2011
During the first days of spaceflight, about 50-70% of the astronauts experience symptoms of Space... more During the first days of spaceflight, about 50-70% of the astronauts experience symptoms of Space Motion Sickness (SMS). It has been proposed that an asymmetry between the left and right otolith organs contributes to an astronaut's individual susceptibility. A recently developed test to measure unilateral utricular function enabled us to re-investigate this so-called otolith asymmetry hypothesis, while using the paradigm of sustained centrifugation as a ground based model for SMS. This latter paradigm has been shown to elicit symptoms similar to those of SMS and is referred to as Sickness Induced by Centrifugation (SIC). In 15 healthy subjects unilateral utricular function was assessed by recording ocular counter rolling during a unilateral centrifugation paradigm. In addition, saccular function was assessed by recording Vestibular Evoked Myogenic Potentials (VEMPs), and horizontal semicircular canal function was assessed using bithermal caloric stimulation. SIC-susceptible subj...
Journal of vestibular research : equilibrium & orientation, 2008
Adaptation to a novel gravitational state involves adaptation of vestibular mediated responses, i... more 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 differing in duration (45 or 90 min) and magnitude (2 or 3G). During centrifugation subjects were in a supine position, directing the gravito-inertial acceleration along the naso-occipetal axis. We determined the orientation of Listing's plane before and after each centrifuge run, with the head erect and tilted in pitch. Head tilt in pitch induced a counter-pitch of Listing's plane, which was found to be less pronounced after centrifugation. In addition, exposure to 3G for 90 min induced a small backward tilt of Listing's plane compared to the pretest orientation (head erect). In order to explain these results a hypoth...
In motion sickness desensitization programs, the motion sickness provocative stimulus is often a ... more In motion sickness desensitization programs, the motion sickness provocative stimulus is often a forward bending of the trunk on a rotating chair, inducing Coriolis effects. Since respiratory relaxation techniques are applied successfully in these courses, we investigated whether these repetitive trunk movements by themselves may induce hyperventilation and consequently add to the motion sickness. There were 12 healthy subjects who participated in our study. In the Baseline condition, subjects sat relaxed on the stationary chair. In the Hypervent condition, subjects performed voluntary hyperventilation (the level was prescribed). In two other conditions subjects rhythmically bent their trunk on a stationary chair (Tilt-Stat condition) and on a rotating chair (Tilt-Rot condition). In all conditions we measured respiratory and cardiovascular activity (heart frequency, tidal volume, end-tidal CO2, and respiration frequency). Of the 12 subjects, 9 had to stop prematurely in the Tilt-Rot...
Illusory self-motion often provokes motion sickness, which is commonly explained in terms of an i... more Illusory self-motion often provokes motion sickness, which is commonly explained in terms of an inter-sensory conflict that is not in accordance with previous experience. Here we address the influence of cognition in motion sickness and show that such a conflict is not provocative when the observer believes that the motion illusion is indeed actually occurring. Illusory self-motion and motion sickness were elicited in healthy human participants who were seated on a stationary rotary chair inside a rotating optokinetic drum. Participants knew that both chair and drum could rotate but were unaware of the actual motion stimulus. Results showed that motion sickness was correlated with the discrepancy between participants’ perceived self-motion and participants’ beliefs about the actual motion. Together with the general motion sickness susceptibility, this discrepancy accounted for 51% of the variance in motion sickness intensity. This finding sheds a new light on the causes of visually ...
Full-field visual rotation around the vertical axis induces a sense of self-motion (vection), opt... more Full-field visual rotation around the vertical axis induces a sense of self-motion (vection), optokinetic nystagmus (OKN), and, eventually, also motion sickness (MS). If the lights are then suddenly switched off, optokinetic afternystagmus (OKAN) occurs. This is due to the discharge of the velocity storage mechanism (VSM), a central integrative network that has been suggested to be involved in motion sickness. We previously showed that visually induced motion sickness (VIMS) following optokinetic stimulation is dependent on vection intensity. To shed light on this relationship, the current study investigated whether vection intensity is related to VSM activity, and thus, to the OKAN. In repetitive trials (eight per condition), 15 stationary participants were exposed to 120 s of visual yaw rotation (60°/s), followed by 90 s in darkness. The visual stimulus either induced strong vection (i.e., scene rotating normally) or weak vection (central and peripheral part moving in opposite directions). Eye movements and subjective vection intensity were continuously measured. Results showed that OKAN occurred less frequently and with lower initial magnitude in the weak-vection condition compared to the strong-vection condition. OKAN decay time constants were not significantly different. The results suggest that the stimuli that produced strong vection also enhanced the charging of the VSM. As VSM activity presumably is a factor in motion sickness, the enhanced VSM activity in our strong-vection condition hints at an involvement of the VSM in VIMS, and could explain why visual stimuli producing a strong sense of vection also elicit high levels of VIMS.
This study investigated the role of vection (i.e., a visually induced sense of self-motion), opto... more This study investigated the role of vection (i.e., a visually induced sense of self-motion), optokinetic nystagmus (OKN), and inadvertent head movements in visually induced motion sickness (VIMS), evoked by yaw rotation of the visual surround. These three elements have all been proposed as contributing factors in VIMS, as they can be linked to different motion sickness theories. However, a full understanding of the role of each factor is still lacking because independent manipulation has proven difficult in the past. We adopted an integrative approach to the problem by obtaining measures of potentially relevant parameters in four experimental conditions and subsequently combining them in a linear mixed regression model. To that end, participants were exposed to visual yaw rotation in four separate sessions. Using a full factorial design, the OKN was manipulated by a fixation target (present/absent), and vection strength by introducing a conflict in the motion direction of the centra...
When in darkness, humans can perceive the direction and magnitude of rotations and of linear tran... more When in darkness, humans can perceive the direction and magnitude of rotations and of linear translations in the horizontal plane. The current paper addresses the integrated perception of combined translational and rotational motion, as it occurs when moving along a curved trajectory. We questioned whether the perceived motion through the environment follows the predictions of a self-motion perception model (e.g., Merfeld et al. in J Vestib Res 3:141-161, 1993; Newman in A multisensory observer model for human spatial orientation perception, 2009), which assume linear addition of rotational and translational components. For curved motion in darkness, such models predict a non-veridical motion percept, consisting of an underestimation of the perceived rotation, a distortion of the perceived travelled path, and a bias in the perceived heading (i.e., the perceived instantaneous direction of motion with respect to the body). These model predictions were evaluated in two experiments. In ...
Aviation Space and Environmental Medicine, Jun 1, 2007
Introduction: In motion sickness desensitization programs, the motion sickness provocative stimul... more Introduction: In motion sickness desensitization programs, the motion sickness provocative stimulus is often a forward bending of the trunk on a rotating chair, inducing Coriolis effects. Since respiratory relaxation techniques are applied successfully in these courses, we investigated whether these repetitive trunk movements by themselves may induce hyperventilation and consequently add to the motion sickness. Methods: There were 12 healthy subjects who participated in our study. In the Baseline condition, subjects sat relaxed on the stationary chair. In the Hypervent condition, subjects performed voluntary hyperventilation (the level was prescribed). In two other conditions subjects rhythmically bent their trunk on a stationary chair (Tilt-Stat condition) and on a rotating chair (Tilt-Rot condition). In all conditions we measured respiratory and cardiovascular activity (heart frequency, tidal volume, end-tidal CO 2 , and respiration frequency). Results: Of the 12 subjects, 9 had to stop prematurely in the Tilt-Rot condition because of moderate nausea. Except for heart rate in the Tilt-Rot condition, the measured physiological parameters in these subjects in the Tilt-Stat and Tilt-Rot conditions were not statistically different from the Baseline condition. Only in the Hypervent condition were significant differences observed, but no nausea. Discussion: The findings show that hyperventilation is not the main cause of nausea during the Coriolis effects. We conclude that during the pilot desensitization program with Coriolis stimuli, measurement of cardiovascular and respiratory parameters is not necessary; however, in those cases that do not respond to the intervention, we recommend paying attention to respiratory parameters because hyperventilation does occur on an individual basis.
Journal of vestibular research : equilibrium & orientation, 2007
It has been found that sustained centrifugation on Earth may evoke sickness symptoms that are sim... more It has been found that sustained centrifugation on Earth may evoke sickness symptoms that are similar to those of the Space Adaptation Syndrome (SAS). As in SAS, incidence of this 'Sickness Induced by Centrifugation' (SIC) is about 50% and the symptoms are particularly evoked by head movements. By systematically varying the G-load and duration of centrifugation, the current study investigated the characteristics of the gravitational stimulus that is required for SIC to occur. Subjects were exposed to centrifugation at 2 and 3Gx, for a duration of 45 and 90 minutes. A standardized head movement protocol was used to evoke SIC after centrifugation. The results show that in six out of 12 subjects (50%) no serious symptoms were elicited. In the remaining subjects, the effects of the 3G runs exceeded those of the 2G runs, and within each G-level symptom intensity was higher for the 90 min than for the 45 min exposure. An exponential fit on this data showed that the time constant o...
Adaptation to a novel gravitational state involves adaptation of vestibular mediated responses, i... more 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 differing in duration (45 or 90 min) and magnitude (2 or 3G). During centrifugation subjects were in a supine position, directing the gravito-inertial acceleration along the naso-occipetal axis. We determined the orientation of Listing's plane before and after each centrifuge run, with the head erect and tilted in pitch. Head tilt in pitch induced a counter-pitch of Listing's plane, which was found to be less pronounced after centrifugation. In addition, exposure to 3G for 90 min induced a small backward tilt of Listing's plane compared to the pretest orientation (head erect). In order to explain these results a hypothesis is discussed, proposing that the orientation of Listing's plane in the head is governed by a head fixed orientation vector that is modulated by the direction of gravity relative to the head. Sustained centrifugation is proposed to decrease this gravitational modulation, leading to the effects observed. This could reflect a shift towards a more body centered frame of reference.
Background / Purpose: In this study, we investigated for the first time in the same experiment, t... more Background / Purpose: In this study, we investigated for the first time in the same experiment, the effect of visual information, simulator motion in additional directions and active vehicle control on the perception of simulator motion (roll-rate) during curve driving. Main conclusion: Mean detection threshold for roll-rate increased in active driving conditions. However, large differences between participants were observed. Results suggest that this is related to the level of immersion in the simulation.
Journal of vestibular research : equilibrium & orientation, 2011
During the first days of spaceflight, about 50-70% of the astronauts experience symptoms of Space... more During the first days of spaceflight, about 50-70% of the astronauts experience symptoms of Space Motion Sickness (SMS). It has been proposed that an asymmetry between the left and right otolith organs contributes to an astronaut's individual susceptibility. A recently developed test to measure unilateral utricular function enabled us to re-investigate this so-called otolith asymmetry hypothesis, while using the paradigm of sustained centrifugation as a ground based model for SMS. This latter paradigm has been shown to elicit symptoms similar to those of SMS and is referred to as Sickness Induced by Centrifugation (SIC). In 15 healthy subjects unilateral utricular function was assessed by recording ocular counter rolling during a unilateral centrifugation paradigm. In addition, saccular function was assessed by recording Vestibular Evoked Myogenic Potentials (VEMPs), and horizontal semicircular canal function was assessed using bithermal caloric stimulation. SIC-susceptible subj...
Journal of vestibular research : equilibrium & orientation, 2008
Adaptation to a novel gravitational state involves adaptation of vestibular mediated responses, i... more 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 differing in duration (45 or 90 min) and magnitude (2 or 3G). During centrifugation subjects were in a supine position, directing the gravito-inertial acceleration along the naso-occipetal axis. We determined the orientation of Listing's plane before and after each centrifuge run, with the head erect and tilted in pitch. Head tilt in pitch induced a counter-pitch of Listing's plane, which was found to be less pronounced after centrifugation. In addition, exposure to 3G for 90 min induced a small backward tilt of Listing's plane compared to the pretest orientation (head erect). In order to explain these results a hypoth...
In motion sickness desensitization programs, the motion sickness provocative stimulus is often a ... more In motion sickness desensitization programs, the motion sickness provocative stimulus is often a forward bending of the trunk on a rotating chair, inducing Coriolis effects. Since respiratory relaxation techniques are applied successfully in these courses, we investigated whether these repetitive trunk movements by themselves may induce hyperventilation and consequently add to the motion sickness. There were 12 healthy subjects who participated in our study. In the Baseline condition, subjects sat relaxed on the stationary chair. In the Hypervent condition, subjects performed voluntary hyperventilation (the level was prescribed). In two other conditions subjects rhythmically bent their trunk on a stationary chair (Tilt-Stat condition) and on a rotating chair (Tilt-Rot condition). In all conditions we measured respiratory and cardiovascular activity (heart frequency, tidal volume, end-tidal CO2, and respiration frequency). Of the 12 subjects, 9 had to stop prematurely in the Tilt-Rot...
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Papers by Suzanne Nooij