Objective: We examined motion sickness in an oscillating virtual environment presented via a video projector system. Background: Visible oscillation of the physical environment is known to induce both postural instability and motion sickness, but it cannot be assumed that the same phenomena will occur in a virtual simulation of such motion. Method: Standing participants (3 men and 9 women, 20—22 years of age) were exposed to oscillation of a virtual room. The stimulus was a computer-generated simulation of a laboratory device that is known to induce postural instability and motion sickness. Participants viewed the simulation for up to 40 min and were instructed to discontinue if they experienced symptoms of motion sickness. Results: Motion sickness incidence (42%) did not differ from that in studies using the corresponding physical moving room. Prior to motion sickness onset, the sick group exhibited changes in movement, relative to the well group, as predicted by the postural instability theory of motion sickness. Differences in movement between the sick and well groups developed over time, in contrast with previous studies using physical moving rooms, in which such movement differences have not evolved. Conclusion: The results indicate that changes in postural activity precede motion sickness that is induced by an oscillating virtual environment, but they also reveal differences in postural responses to virtual and physical motion environments. Application: Potential applications of this research include recommendations for the use of virtual environments as models for perception and action in physical environments.

We examined the influence of stance width (the distance between the feet) on postural sway and visually induced motion sickness. Stance width influences the magnitude of body sway, and changes in sway precede the subjective symptoms of motion sickness. Thus, manipulation of stance width may influence motion sickness incidence. Participants (healthy young adults) were exposed to complex, low-frequency oscillation of a moving room. Participants stood with their feet 5 cm, 17 cm, or 30 cm apart. During exposure to visual motion, the widest stance (30 cm) was associated with reduced incidence of motion sickness. For all stance widths, motion sickness was preceded by significant changes in motion of the head and torso. The results support the postural instability theory of motion sickness and suggest practical implications for the prevention of motion sickness. Adoption of wider stance may decrease the risk of motion sickness in operational situations.

Yu Y, Yank JR, Katsumata Y, Villard S, Kennedy RS, Stoffregen TA. Visual vigilance performance and standing posture at sea. Aviat Space Environ Med 2010; 81:375–82. Background: Research on land has demonstrated interactions between visual tasks and the control of stance. Variations in visual tasks can influence postural activity; conversely, changes in stance can influence quantitative measures of visual performance. At sea, crewmembers may alter their bodily movements to compensate for ship motion while simultaneously adjusting movements to optimize visual performance. Mutual influence of visual tasks on postural movements and of postural movements on visual tasks has not been demonstrated at sea. Methods: Crewmembers stood on a force plate, from which we obtained data on the positional variability of the center of pressure (COP). We varied stance width (5 cm, 17 cm, and 30 cm) and the difficulty of visual vigilance tasks (Easy vs. Hard). We collected data on visual performance and we assessed subjective mental workload. Results: Visual performance was better on the Easy task (mean d' = 4.28) than on the Hard task (mean d' = 3.55). Consistent with this result, subjective mental workload was greater for the Hard task than for the Easy task. The variability of postural activity was greater during the Easy task (mean = 2.0 cm · s⁻¹) than during the Hard task (mean = 1.9 cm · s⁻¹). Stance width influenced postural activity, but also (in 2-way and 3-way interactions) influenced visual performance. Both the magnitude and dynamics of postural activity changed over days at sea. Conclusions: In mild seas, variations in stance width modulate standing posture and influence the performance of computer-based visual tasks.

The authors asked whether standing posture could be controlled relative to audible oscillation of the environment. Blindfolded sighted adults were exposed to acoustic flow in a moving room, and were asked to move so as to maintain a constant distance between their head and the room. Acoustic flow had direct (source) and indirect (reflected) components. Participants exhibited strong coupling of postural motion with room motion, even when direct information about room motion was masked and was available only in reflected sound. Patterns of hip-ankle coordination closely resembled patterns observed in previous research involving coupling of sway with a visible moving room. The results demonstrate that blindfolded adults can control the dynamics of stance relative to motion of the audible environment.

Cognitive performance exhibits patterns of trial-to-trial variation that can be described as 1/f or pink noise, as do repeated measures of locomotor performance. Although cognitive and locomotor performances are known to interact when performed concurrently, it is not known whether concurrent performance affects the tasks' pink noise dynamical structure. In this study, participants performed a cognitive task (repeatedly producing a temporal interval) and a motor task (walking on a treadmill) in single- and dual-task conditions. In single-task conditions both tasks exhibited pink noise structure. For concurrent performance the dynamical structure of the cognitive task changed reliably in the direction of white (random) noise. The dynamical structure of locomotion remained pink noise. The change in cognitive dynamics occurred despite no reliable changes in mean or standard deviation measures for either task. The results suggest a functional reorganization of cognitive dynamics supporting successful task performance in dual-task conditions.