Visually induced symptoms questionnaire (VISQ): A subjective evaluation method for biomedical effects induced by stereoscopic 3D video.

The purpose of this paper is to establish an easy-to-use questionnaire for subjective evaluations of visually induced motion sickness (VIMS) and visual fatigue caused by stereoscopic 3D (s3D) images. We reviewed previously used questionnaires and extracted 51 important subjective evaluation items from them. We then recruited 251 participants to observe 3D images designed to easily induce sickness or visual fatigue, and we asked them to respond to the 51 items. As a result of exploratory factor analysis, four factors were extracted according to their factor loadings, and the number of items was reduced to 21. Further processing by confirmatory factor analysis led to the selection of 15 items. Comparing mean ratings for each factor before and after item reduction indicated that item reduction did not significantly affect the participant responses. Therefore, the 15-item Visually Induced Symptoms Questionnaire (VISQ), can be used to evaluate VIMS and s3D visual fatigue.

Spatial presence depends on 'coupling' between body sway and visual motion presented on head-mounted displays (HMDs).

This study investigated the effects of simulating self-motion via a head-mounted display (HMD) on standing postural sway and spatial presence. Standing HMD users viewed simulated oscillatory self-motion in depth. On a particular trial, this naso-occipital visual oscillation had one of four different amplitudes (either 4, 8, 12 or 16 m peak-to-peak) and one of four different frequencies (either 0.125, 0.25, 0.5 or 1 Hz). We found that simulated high amplitude self-oscillation (approximately 16 m peak-to-peak) at either 0.25 Hz or 0.5 Hz: 1) generated the strongest effects on postural sway; and 2) made participants feel more spatially present in the virtual environment. Our findings provide insight into the parameters of simulated self-motion that generate the strongest postural responses within virtual environments. These postural constraints have valuable implications for improving our understanding of sensory processes underlying the ergonomic experience of virtual environments simulated using HMDs.

Effects of auditory information on self-motion perception during simultaneous presentation of visual shearing motion.

Recent studies have found that self-motion perception induced by simultaneous presentation of visual and auditory motion is facilitated when the directions of visual and auditory motion stimuli are identical. They did not, however, examine possible contributions of auditory motion information for determining direction of self-motion perception. To examine this, a visual stimulus projected on a hemisphere screen and an auditory stimulus presented through headphones were presented separately or simultaneously, depending on experimental conditions. The participant continuously indicated the direction and strength of self-motion during the 130-s experimental trial. When the visual stimulus with a horizontal shearing rotation and the auditory stimulus with a horizontal one-directional rotation were presented simultaneously, the duration and strength of self-motion perceived in the opposite direction of the auditory rotation stimulus were significantly longer and stronger than those perceived in the same direction of the auditory rotation stimulus. However, the auditory stimulus alone could not sufficiently induce self-motion perception, and if it did, its direction was not consistent within each experimental trial. We concluded that auditory motion information can determine perceived direction of self-motion during simultaneous presentation of visual and auditory motion information, at least when visual stimuli moved in opposing directions (around the yaw-axis). We speculate that the contribution of auditory information depends on the plausibility and information balance of visual and auditory information.

Visual rotation axis and body position relative to the gravitational direction: Effects on circular vection.

The visual-vestibular conflict theory asserts that visual-vestibular conflicts reduce vection and that vection strength is reduced with an increasing discrepancy between actual and expected vestibular activity. Most studies support this theory, although researchers have not always accepted them. To ascertain the conditions under which the theory of the visual-vestibular conflict can be applied, we measured circular vection strength accompanied by manipulation of the visual-otolith conflict by setting the axes of visual global motion (pitch, roll, and yaw) as either earth-horizontal or earth-vertical, using three different body positions (supine, left-lateral recumbent, and sitting upright). When the smaller stimulus was used, roll vection strength was greater with the visual-otolith conflict than without it, which contradicts the visual-vestibular conflict theory. We confirmed this result, as observers were able to distinguish circular vection from an illusory body tilt. Moreover, with observers in an upright position, the strength of yaw vection, which does not involve the visual-otolith conflict, increased and was almost equal to that of roll vection, which involves the visual-otolith conflict. This suggests that if the visual stimulus covers the entire visual field, the strength of circular vection around the earth-vertical axis exceeds that around the earth-horizontal axis, which is a finding consistent with the visual-vestibular conflict theory.

Effects of visually simulated roll motion on vection and postural stabilization.

BACKGROUND: Visual motion often provokes vection (the induced perception of self-motion) and postural movement. Postural movement is known to increase during vection, suggesting the same visual motion signal underlies vection and postural control. However, self-motion does not need to be consciously perceived to influence postural control. Therefore, visual motion itself may affect postural control mechanisms. The purpose of the present study was to investigate the effects of visual motion and vection on postural movements during and after exposure to a visual stimulus motion. METHODS: Eighteen observers completed four experimental conditions, the order of which was counterbalanced across observers. Conditions corresponded to the four possible combinations of rotation direction of the visually simulated roll motion stimulus and the two different visual stimulus patterns. The velocity of the roll motion was held constant in all conditions at 60 deg/s. Observers assumed the standard Romberg stance, and postural movements were measured using a force platform and a head position sensor affixed to a helmet they wore. Observers pressed a button when they perceived vection. Postural responses and psychophysical parameters related to vection were analyzed. RESULTS: During exposure to the moving stimulus, body sway and head position of all observers moved in the same direction as the stimulus. Moreover, they deviated more during vection perception than no-vection-perception, and during no-vection-perception than no-visual-stimulus-motion. The postural movements also fluctuated more during vection-perception than no-vection-perception, and during no-vection-perception than no-visual-stimulus-motion, both in the left/right and anterior/posterior directions. There was no clear habituation for vection and posture, and no effect of stimulus type. CONCLUSION: Our results suggested that visual stimulus motion itself affects postural control, and supported the idea that the same visual motion signal is used for vection and postural control. We speculated that the mechanisms underlying the processing of visual motion signals for postural control and vection perception operate using different thresholds, and that a frame of reference for body orientation perception changed along with vection perception induced further increment of postural sway.

Motion parallax driven by head movements: conditions for visual stability, perceived depth, and perceived concomitant motion.

Yoking the movement of the stimulus on the screen to the movement of the head, we examined visual stability and depth perception as a function of head-movement velocity and parallax. In experiment 1, for different head velocities, observers adjusted the parallax to find (a) the depth threshold and (b) the concomitant-motion threshold. Between these thresholds, depth was seen with no perceived motion. In experiment 2, for different head velocities, observers adjusted the parallax to produce the same perceived depth. A slower head movement required a greater parallax to produce the same perceived depth as faster head movements. In experiment 3, observers reported the perceived depth for different parallax magnitudes. Perceived depth covaried with smaller parallax without motion perception, but began to decrease with larger parallax and concomitant motion was seen. Only motion was seen with the larger parallax.

Relative distance cues contribute to scaling depth from motion parallax.

The visual system scales motion parallax signals with information about absolute distance (M. E. Ono, Rivest, & H. Ono, 1986). The present study was designed to determine whether relative distance cues, which intrinsically provide information about relative distance, contribute to this scaling. In two experiments, two test stimuli, containing an equal extent of motion parallax, were presented simultaneously at a fixed viewing distance. The relative distance cues of dynamic occlusion and motion parallax in the areas surrounding the test stimuli (background motion parallax) and/or relative size were manipulated. The observers reported which of the two parallactic test stimuli appeared to have greater depth, and which appeared to be more distant. The results showed that the test stimulus specified, by the relative distance cues, as being more distant was perceived as having more depth and as being more distant. This indicates that relative distance cues contribute to scaling depth from motion parallax by modifying the information about the absolute distance of objects.