Vection is the main contributor to motion sickness induced by visual yaw rotation: Implications for conflict and eye movement theories

Abstract

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 central and peripheral field of view (present/absent). In all conditions, head movements were minimized as much as possible. Measured parameters included vection strength, vection variability, OKN slow phase velocity, OKN frequency, the number of inadvertent head movements, and inadvertent head tilt. Results show that VIMS increases with vection strength, but that this relation varies among participants (R2 = 0.48). Regression parameters for vection variability, head and eye movement parameters were not significant. These results may seem to be in line with the Sensory Conflict theory on motion sickness, but we argue that a more detailed definition of the exact nature of the conflict is required to fully appreciate the relationship between vection and VIMS.

More vection means more velocity storage activity: a factor in visually induced motion sickness?

“…Nevertheless, the exact role of the VSM in VIMS remains to be defined. The results of Guo and colleagues are interesting with respect to our recent findings that VIMS induced by full-field optokinetic stimulation is also correlated to vection, that is, the visually induced illusion of self-motion (Nooij et al 2017 ). In that study, stationary participants were exposed to different full-field optokinetic rotational motion stimuli in yaw that evoked different levels of vection.…”

“…Curved black shields attached to both sides of the eye tracker goggle prevented the participant from seeing the screen edges. A rotary knob (SensoDrive GmbH, Germany) was attached to the right armrest for the continuous indication of vection strength (Nooij et al 2017 ). Brown noise presented through headphones masked any environmental noise.…”

“…As in our previous study (Nooij et al 2017 ), the visual stimulus consisted of a 360° panoramic image of a circular square lined with houses. Such a naturalistic scene has been shown to induce a compelling sense of vection (Riecke et al 2006 ).…”

“…Prolonged exposure to full-field visual motion, while being stationary, eventually evokes symptoms of visually induced motion sickness (VIMS, e.g., Crampton and Young 1953 ; Stern et al 1987 ; Hu et al 1989 ; Bonato et al 2004 ; Nooij et al 2017 ). In a previous study, we showed that the level of VIMS during visual yaw rotation was related to vection intensity: visual stimuli that induced strong vection induced higher levels of VIMS than visual stimuli that induced weak vection (Nooij et al 2017 ). Interestingly, as we will discuss later, susceptibility to motion sickness—including VIMS—has been associated with the so-called velocity storage mechanism (VSM, Raphan et al 1977 ), which is also involved in the generation of reflexive eye movements like the OKAN.…”

“…We found that stimuli inducing a high level of vection were more nauseogenic than stimuli that suppressed vection on an individual level. The observed relationships between VIMS and the VSM (Guo et al 2017 ) on the one hand, and VIMS and vection (Nooij et al 2017 ) on the other, suggests that also the VSM and vection are related.…”