Background: Both motion sickness and the illusion of self-motion (i.e., vection) can be induced by moving visual scenes. The results of a previous study imply that motion sickness is primarily dependent on visual motion in foveal vision while vection is primarily dependent on motion in peripheral vision.
Hypothesis: It was hypothesized that similar motion sickness would be produced when tracking a single moving dot and a full screen of moving dots, but that vection would be greater when tracking multiple moving dots.
Method: Sixteen subjects viewed moving images presented on a virtual reality head-mounted display. In one condition a single dot moved from left to right at 27 degrees x s(-1) over a distance of 18 degrees before returning instantly to its starting point. This motion was repeated continuously. In a second condition, five horizontal rows of dots, each 18 degrees apart, moved continuously across the screen at 27 degrees x s(-1); subjects were instructed to track each dot in the central row as it passed.
Results: In both conditions, there were nystagmic eye movements with an approximate amplitude of 18 degrees at 27 degrees x s(-1). Vection differed significantly between the two conditions, with more vection in the condition with five rows of dots. Subjects experienced motion sickness symptoms with both the single moving dot and the five rows of dots, with no significant difference in sickness between the two conditions. Subject ratings of motion sickness and vection were not correlated with each other in either of the two conditions.
Conclusions: Motion sickness and vection can vary independently. Vection appears to be influenced by peripheral vision, as there was an increase in vection with full-field stimulation. Motion sickness induced by moving visual scenes may be influenced by foveal visual stimulation or by eye movements, as these were the same in both conditions.