Visual Occlusion Decreases Motion Sickness in a Flight Simulator.

Sensory conflict theories of motion sickness (MS) assert that symptoms may result when incoming sensory inputs (e.g., visual and vestibular) contradict each other. Logic suggests that attenuating input from one sense may reduce conflict and hence lessen MS symptoms. In the current study, it was hypothesized that attenuating visual input by blocking light entering the eye would reduce MS symptoms in a motion provocative environment. Participants sat inside an aircraft cockpit mounted onto a motion platform that simultaneously pitched, rolled, and heaved in two conditions. In the occluded condition, participants wore "blackout" goggles and closed their eyes to block light. In the control condition, participants opened their eyes and had full view of the cockpit's interior. Participants completed separate Simulator Sickness Questionnaires before and after each condition. The posttreatment total Simulator Sickness Questionnaires and subscores for nausea, oculomotor, and disorientation in the control condition were significantly higher than those in the occluded condition. These results suggest that under some conditions attenuating visual input may delay the onset of MS or weaken the severity of symptoms. Eliminating visual input may reduce visual/nonvisual sensory conflict by weakening the influence of the visual channel, which is consistent with the sensory conflict theory of MS.

The Effects of Training on Anxiety and Task Performance in Simulated Suborbital Spaceflight.

INTRODUCTION: In commercial spaceflight, anxiety could become mission-impacting, causing negative experiences or endangering the flight itself. We studied layperson response to four varied-length training programs (ranging from 1 h-2 d of preparation) prior to centrifuge simulation of launch and re-entry acceleration profiles expected during suborbital spaceflight. We examined subject task execution, evaluating performance in high-stress conditions. We sought to identify any trends in demographics, hemodynamics, or similar factors in subjects with the highest anxiety or poorest tolerance of the experience. METHODS: Volunteers participated in one of four centrifuge training programs of varied complexity and duration, culminating in two simulated suborbital spaceflights. At most, subjects underwent seven centrifuge runs over 2 d, including two +Gz runs (peak +3.5 Gz, Run 2) and two +Gx runs (peak +6.0 Gx, Run 4) followed by three runs approximating suborbital spaceflight profiles (combined +Gx and +Gz, peak +6.0 Gx and +4.0 Gz). Two cohorts also received dedicated anxiety-mitigation training. Subjects were evaluated on their performance on various tasks, including a simulated emergency. RESULTS: Participating in 2-7 centrifuge exposures were 148 subjects (105 men, 43 women, age range 19-72 yr, mean 39.4 ± 13.2 yr, body mass index range 17.3-38.1, mean 25.1 ± 3.7). There were 10 subjects who withdrew or limited their G exposure; history of motion sickness was associated with opting out. Shorter length training programs were associated with elevated hemodynamic responses. Single-directional G training did not significantly improve tolerance. DISCUSSION: Training programs appear best when high fidelity and sequential exposures may improve tolerance of physical/psychological flight stressors. The studied variables did not predict anxiety-related responses to these centrifuge profiles.Blue RS, Bonato F, Seaton K, Bubka A, Vardiman JL, Mathers C, Castleberry TL, Vanderploeg JM. The effects of training on anxiety and task performance in simulated suborbital spaceflight. Aerosp Med Hum Perform. 2017; 88(7):641-650.

A Wearable Device Providing a Visual Fixation Point for the Alleviation of Motion Sickness Symptoms.

OBJECTIVES: Motion sickness (MS) can be problematic for many military operations. Some pharmaceutical countermeasures are effective but can lead to side effects. Non-pharmaceutical countermeasures vary in effectiveness and can require time to be beneficial (e.g., desensitization). Previous research suggests that visual fixation can alleviate MS symptoms. In the current experiment we tested the effectiveness of a user-worn device that provides a visual fixation point that moves with the user. METHODS: Fourteen subjects viewed the interior of a rotating optokinetic drum (60°/s) through a visor that displayed either a clear view of the scene (control) or the scene with a fixation point (experimental). After 5 minutes of viewing, symptoms were assessed using (1) the Simulator Sickness Questionnaire that yields four scores (total, nausea, oculomotor, and disorientation) and (2) a 0 to 10 MS overall scale. RESULTS: Viewing the fixation point resulted in significantly lower scores for all measures. Control condition scores were as much as 400% higher than when the fixation point was viewed. CONCLUSIONS: A wearable device that presents a visual fixation point that moves with the user may reduce MS. The device's portability suggests that it may be suitable for some military operations, and additional research in the field is warranted.

Visual blur and motion sickness in an optokinetic drum.

BACKGROUND: The most commonly cited hypotheses for motion sickness (MS) focus on inconsistent sensory inputs. Visual/vestibular conflicts may lead to MS, but visual input from retinal regions/neural pathways that are sensitive to motion might bear more weight in MS etiology. We hypothesized that inducing blurred vision in an optokinetic drum would attenuate the influence of foveal (parvocellular) input, but not peripheral (magnocellular) input that is sensitive to motion. Increased relative influence of peripheral visual input was predicted to subsequently lead to more visual/vestibular conflict and subsequently more severe MS symptoms. METHODS: Through goggles that were either clear or frosted, 15 subjects (5 men, 10 women, mean age = 24.9 yr, range = 18-49) viewed the interior of a rotating (60° · s(-1)) optokinetic drum for 10 min. Subjects completed the Simulator Sickness Questionnaire (SSQ) before and after viewing. Overall subjective sickness ratings (0-10) and visually induced self-motion perception (vection) ratings (0-10) were also recorded. RESULTS: Postexposure SSQ scores obtained in the blur condition (total - 52.9, oculomotor - 38.9, disorientation - 69.6) were significantly higher than those obtained in the control condition (total - 30.4, oculomotor - 21.7, disorientation - 37.8). Overall sickness ratings and vection ratings were also significantly higher in the blur condition. CONCLUSIONS: These results suggest that visual blur can exacerbate MS, perhaps because of differential influences of visual pathways. Although these results were obtained with an optokinetic drum, possible effects of visual blurring in motion provocative environments such aircraft, watercraft, spacecraft, and land vehicles should be considered.

Motion sickness adaptation to Coriolis-inducing head movements in a sustained G flight simulator.

BACKGROUND: Technological advances have allowed centrifuges to become more than physiological testing and training devices; sustained G, fully interactive flight simulation is now possible. However, head movements under G can result in vestibular stimulation that can lead to motion sickness (MS) symptoms that are potentially distracting, nauseogenic, and unpleasant. In the current study an MS adaptation protocol was tested for head movements under +Gz. METHODS: Experienced pilots made 14 predetermined head movements in a sustained G flight simulator (at 3 +Gz) on 5 consecutive days and 17 d after training. Symptoms were measured after each head turn using a subjective 0-10 MS scale. The Simulator Sickness Questionnaire (SSQ) was also administered before and after each daily training session. RESULTS: After five daily training sessions, normalized mean MS scores were 58% lower than on Day 1. Mean total, nausea, and disorientation SSQ scores were 55%, 52%, and 78% lower, respectively. During retesting 17 d after training, nearly all scores indicated 90-100% retention of training benefits. DISCUSSION: The reduction of unpleasant effects associated with sustained G flight simulation using an adaptation training protocol may enhance the effectiveness of simulation. Practical use of sustained G simulators is also likely to be interspersed with other types of ground and in-flight training. Hence, it would be undesirable and unpleasant for trainees to lose adaptation benefits after a short gap in centrifuge use. However, current results suggest that training gaps in excess of 2 wk may be permissible with almost no loss of adaptation training benefits.

The sickening rug: a repeating static pattern that leads to motion-sickness-like symptoms.

The nauseogenic properties of a patterned rug that reputedly caused motion-sickness-like symptoms in those who viewed it was the topic of this study. Naive observers viewed a 1:1 scale image of the black-and-white patterned rug and a homogeneous gray region of equivalent luminance in a counterbalanced within-subjects design. After 5 min of viewing, symptoms were assessed with the simulator sickness questionnaire (SSQ), yielding a total SSQ score and sub-scores for nausea, oculomotor symptoms, and disorientation. All four scores were significantly higher in the rug condition. Observers also reported significantly more self-motion perception in the rug condition, even though they were seated during the experiment. Results are consistent with findings that suggest that neurologically normal individuals who view a repeating static pattern can experience unpleasant symptoms, some of which are similar to motion sickness.

Natural visual-field features enhance vection.

When a large optic-flow pattern is viewed, induced self-motion perception (vection) can result even for observers who are stationary relative to Earth. Vection is common in optokinetic drums, large-screen cinemas, vehicle simulators, and other virtual environments. However, not all optic-flow patterns are equally effective in producing vection. We hypothesized that visual-field characteristics that typically accompany self-motion are likely to facilitate vection. The two characteristics tested in the current study were color and global visual-field movement consistent with head bob and sway that occurs when a person walks or runs. Stationary observers viewed first-person perspective video clips on a rear-projection screen that depicted forward self-motion. Vection onset and magnitude were measured with a computer-interfaced slide device. In experiment 1, either a grayscale or color video was presented. In experiment 2, the video was shot either from a smooth rolling cart or with a hand-held camera that yielded gait information in addition to global expansion. Vection onset was found to be faster, and stronger in magnitude, when videos containing color and gait movements were viewed. These results suggest that visual-field features that are common during actual self-motion can enhance vection in a virtual environment, resulting in a more realistic experience for viewers.

Combined pitch and roll and cybersickness in a virtual environment.

BACKGROUND: Stationary subjects who perceive visually induced illusions of self-motion, or vection, in virtual reality (VR) often experience cybersickness, the symptoms of which are similar to those experienced during motion sickness. An experiment was conducted to test the effects of single and dual-axis rotation of a virtual environment on cybersickness. It was predicted that VR displays which induced illusory dual-axis (as opposed to single-axis) self-rotations in stationary subjects would generate more sensory conflict and subsequently more cybersickness. METHODS: There were 19 individuals (5 men, 14 women, mean age = 19.8 yr) who viewed the interior of a virtual cube that steadily rotated (at 60 degrees x s(-1)) about either the pitch axis or both the pitch and roll axes simultaneously. Subjects completed the Simulator Sickness Questionnaire (SSQ) before a trial and after 5 min of stimulus viewing. RESULTS: Post-treatment total SSQ scores and subscores for nausea, oculomotor, and disorientation were significantly higher in the dual-axis condition. CONCLUSIONS: These results support the hypothesis that a vection-inducing VR stimulus that rotates about two axes generates more cybersickness compared to aVR stimulus that rotates about only one. In the single-axis condition, sensory conflict and pseudo-Coriolis effects may have led to symptoms. However, in the dual-axis condition, not only was perceived self-motion more complex (two axes compared to one), the inducing stimulus was consistent with twice as much self-motion. Hence, the increased likelihood/magnitude of sensory conflict and pseudo-Coriolis effects may have subsequently resulted in a higher degree of cybersickness in the dual-axis condition.

Expanding and contracting optic-flow patterns and vection.

When stationary observers view an optic-flow pattern, visually induced self-motion perception (vection) and a form of motion sickness known as simulator sickness (SS), can result. Previous results suggest that an expanding flow pattern leads to more SS than a contracting pattern. Sensory conflict, a possible cause of SS, may be more salient when an expanding optic-flow pattern is viewed. An experiment was conducted to test if a more salient sensory conflict accompanying expanding flow patterns might inhibit vection. Participants (n = 15) viewed a pattern of blue squares, either steadily expanded or contracted, on a large rear-projection screen. Vection onset and magnitude were measured for 30 s with a computer-interfaced slide device. Vection onset was significantly faster, and vection magnitude stronger, when a contracting pattern was viewed. We propose that our extensive experience with forward self-motion may form a neural expectancy (exposure-history) about the sensory inputs which typically accompany expanding flow. However, since backward self-motion is less common, there may be a weaker exposure-history for contracting flow, and as a result these patterns generate less salient sensory conflict and subsequently less vection.

Vertical display oscillation effects on forward vection and simulator sickness.

BACKGROUND: The current study investigated the effects that vertical display oscillation had on the development of both vection and simulator sickness. METHODS: There were 16 subjects who were exposed to optic flow displays which simulated either: 1) constant velocity forward self-motion (pure radial flow); or 2) combined constant velocity forward and vertically oscillating self-motion (radial flow with vertical oscillation at one of three frequencies: 1.8, 3.7, or 7.4 Hz). During each 10-min display exposure, subjects rated the strength of their vection and eight symptoms listed on the Subjective Symptoms of Motion Sickness (SSMS) scale at 2-min intervals. Subjects also completed the Simulator Sickness Questionnaire (SSQ) designed by Kennedy and colleagues before and after each trial, which generated a total SSQ score and three SSQ subscores (nausea, oculomotor symptoms, and disorientation). RESULTS: Vertically oscillating displays (mean = 5.51; SD = 2.5) were found to produce significantly stronger vection ratings than non-oscillating displays (mean = 3.56; SD = 2.1). Vertically oscillating displays (mean = 58.18; SD = 32.2) were also found to produce significantly more severe sickness (as rated by total SSQ scores) than non-oscillating displays (mean = 29.67; SD = 24.7). Both vection and sickness symptoms increased in magnitude with prolonged exposure to optic flow. CONCLUSIONS: Our findings appear to represent a special case in visual self-motion perception where high-frequency vertical oscillation both enhances vection and increases simulator sickness when it is incorporated into an optic flow display simulating constant velocity self-motion in depth.

Expanding and contracting optical flow patterns and simulator sickness.

BACKGROUND: Sensory conflict may be a factor in simulator sickness (SS) given that visual input is often inconsistent with other sensory inputs. It was predicted that an expanding optical flow pattern would lead to more sensory conflict, and subsequently more SS than a contracting pattern. METHODS: There were 16 individuals who participated in the experiment (6 men, 10 women, mean age = 24.4 yrs). Subjects viewed a steadily expanding pattern of blue squares displayed on a computer monitor. In a second condition the pattern steadily contracted. Subjects completed the Simulator Sickness Questionnaire (SSQ) designed by Kennedy and colleagues both before and after a trial (5 min exposure to optic flow). A total SSQ score and three SSQ sub-scores (nausea, oculomotor, and disorientation) were obtained. RESULTS: Mean post-treatment total SSQ scores (mean=28) in the expanding condition were higher than those obtained in the contracting condition (mean=17). Nausea and oculomotor SSQ sub-scores were also higher in the expanding condition compared with the contracting condition. CONCLUSIONS: Experience with expanding flow patterns that result during forward self-motion, and the sensory inputs that usually accompany them, have resulted in a central nervous system expectancy about what the appropriate inputs should be during forward self-motion. Less experience with backwards self-motion (and contracting patterns) may result in a lower level of expectation regarding what the appropriate sensory inputs should be for contracting flow patterns. This lower level of neural expectancy may subsequently lead to less sensory conflict and less SS generated by contracting flow patterns.

Rotation velocity change and motion sickness in an optokinetic drum.

BACKGROUND: Stationary subjects who view the interior of an optokinetic drum often experience motion sickness (MS) symptoms, perhaps because visual and vestibular sensory inputs are in conflict. It was predicted that intermittently changing drum rotation velocity would cause an increase in sensory conflict, and subsequently lead to more MS. Visual input indicating frequent changes in self-motion would not be consistent with vestibular input indicating no self-motion. When drum rotation is steady, visual and vestibular inputs are more likely to agree given that the vestibular organs only respond to change. METHODS: There were 12 individuals who participated in the experiment (7 men, 5 women, mean age = 24.0 yr). In two conditions subjects viewed the interior of an optokinetic drum that steadily rotated at either 5 RPM or 10 RPM. In a third condition drum velocity alternated every 30 s between 5 RPM and 10 RPM (5/10 RPM condition). In all conditions the subject's head was immobilized in the center of the drum that rotated on an Earth-vertical axis. Subjects completed the Simulator Sickness Questionnaire (SSQ) designed by Kennedy and colleagues both before a trial and after 4 min of drum viewing. A total SSQ score and three SSQ sub-scores (nausea, oculomotor, and disorientation) were obtained. RESULTS: Mean post-treatment total SSQ scores (mean = 41) were significantly the highest in the 5/10 RPM condition followed by the conditions of steady rotation velocity at 10 RPM (mean = 36) and 5 RPM (mean = 24). Likewise, mean nausea sub-scores were also the highest (mean = 24) in the 5/10 RPM condition followed by the 10 RPM condition (mean = 19) and the 5 RPM condition (mean = 11). CONCLUSIONS: These results support the hypothesis that a conflict between sensed and expected effects of self-motion alone can lead to MS. Changing rotation velocity increases sensory conflict that in turn leads to more MS.

Chromaticity, spatial complexity, and self-motion perception.

The effects of visual field color and spatial complexity on self-motion perception were investigated by placing observers inside a large rotating cylinder (optokinetic drum). Under optokinetic-drum conditions visually induced self-motion (vection) is typically perceived within 30 s, even though all forms of sensory input (eg vestibular, proprioceptive, auditory), except vision, indicate that the observer is stationary. It was hypothesized that vection would be hastened and vection magnitude increased by adding chromatic colors and spatial complexity to the lining of an optokinetic drum. Addition of these visual-field characteristics results in an array that shares more visual-field characteristics with our typical environment that usually serves as a stable frame of reference regarding self-motion perception. In the color experiment, participants viewed vertical stripes that were: (i) black and white, (ii) various gray shades, or (iii) chromatic. In the spatial complexity experiment, participants were presented with: (i) black-and-white vertical stripes, or (ii) a black-and-white checkerboard pattern. Drum rotation velocity was 5 rev. min(-1) (30 degrees s(-1)), and both vection onset and magnitude were measured for 60 s trials. Results indicate that chromaticity and spatial complexity hasten the onset of vection and increase its perceived magnitude. Chromaticity and spatial complexity are common characteristics of the environments in which our visual system evolved. The presence of these visual-field features in an optic flow pattern may be treated as an indicator that the scene being viewed is stationary and that the observer is moving.

Rotation direction change hastens motion sickness onset in an optokinetic drum.

BACKGROUND: Many stationary subjects who view the patterned interior of a rotating cylinder (optokinetic drum) experience motion sickness (MS) symptoms. An experiment was conducted to investigate the effects of rotation direction change on MS onset and severity. It was predicted that intermittently changing rotation direction would hasten MS onset due to an increased degree of visual/vestibular sensory conflict. METHODS: There were 12 individuals who participated in the experiment (4 men, 8 women, mean age = 24.4 yr). Subjects viewed the interior of an optokinetic drum that rotated at 5 rpm (30 degrees x s(-1)). Drum rotation was either consistently in the same direction or rotation direction changed every 30 s. Eight MS symptoms were assessed at 2-min intervals using a subjective scale (0 = none, 1 = slight, 2 = moderate, 3 = severe). RESULTS: Overall, MS onset was fastest when drum rotation direction changed. Specific MS symptoms significantly affected were dizziness, stomach awareness, and nausea. CONCLUSIONS: These results suggest that a lack of correlation between the sensed and expected effects of motion alone can lead to MS. These results cannot be accounted for by a lack of correlation between sensed and expected gravitational vertical given that these were held constant across conditions.

Infertility practice management. I. Leadership and management style: results from the 2002 survey of 374 Society for Assisted Reproductive Technology member centers.

OBJECTIVES: To identify current trends in management and leadership styles in Society for Assisted Reproductive Technology (SART) member infertility centers; and to understand the similarities and disparities that exist in physicians', administrators', and staff perceptions of management and leadership styles in these centers. MATERIALS AND METHODS: Questionnaires were developed to collect information on the leadership and management styles in place in SART member infertility centers. Survey instruments were distributed to the 374 SART centers. Survey instruments for one physician, the center administrator, and six staff members (two each in nursing, laboratory, and administration) were issued to the SART liaison in each of the SART member centers. Respondents included physicians, practice administrators, nurses, technicians, patient services, billing, and support staff. RESULTS AND DISCUSSION: Analysis of respondents' answers revealed that surveyed staff members reported a fairly high degree of job satisfaction. Physician and administrator management styles seemed to fall between interactive and directive styles; however, physicians and administrators perceived themselves as being more interactive than other staff members viewed them. Overall, extreme differences were unlikely, given the reported high degree of job satisfaction. Finally, survey outcome data were compared with responding centers' ART outcome rates as published by the Centers for Disease Control and Prevention (CDC). CONCLUSIONS: Overall, although employee job satisfaction seemed to be high, there were statistical differences between groups for several questions; the disparities in responses for these questions are indicators for potential management and leadership consideration. In addition, statistical correlations were found between the responses for several questions and the centers' respective CDC-published ART outcome rates.

Display color affects motion sickness symptoms in an optokinetic drum.

BACKGROUND: Many stationary participants who view the patterned interior of a rotating cylinder (optokinetic drum) experience motion sickness (MS) symptoms. Most drum interiors have consisted of black and white patterns. An experiment was conducted to investigate the effects of chromaticity on MS onset and severity. METHODS: There were 12 individuals who participated in the experiment (4 men, 8 women, mean age = 25). Keeping rotation speed constant (5 RPM), the color of vertical stripes in an optokinetic drum was manipulated. There were three conditions used: 1) alternating black and white stripes; 2) gray stripes having different luminance values; and 3) chromatic stripes (white, red, yellow, black, green, and blue) that approximately matched the luminance values of the stripes in the gray condition. Every 2 min, eight motion sickness symptoms were assessed (for up to 16 min) using a subjective scale (0 = none, 1 = slight, 2 = moderate, 3 = severe). RESULTS: Overall, MS onset was fastest, and symptoms the most severe, in the chromatic condition. The two major MS symptoms that were significantly affected were headache and dizziness. CONCLUSIONS: Chromaticity may affect how much an observer's visual environment appears to be stationary, perhaps because chromaticity is such a common feature of the stationary environment in which our visual system evolved. In an optokinetic drum, the addition of chromaticity may increase the disparity between visual and vestibular inputs, a factor thought by many to contribute to MS onset and severity.

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

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.