RESUMO
BACKGROUND: The importance of cognitive processing of orientation cues in visually induced motion sickness and vection is often overlooked. Upright versus inverted visual scenes containing cues of different levels of salience were compared. METHODS: Panoramic scenes of 360 degrees were projected in the visual equivalent to the nauseogenic situation of rotating about an axis tilted from the vertical with a field of view of 84 degrees rotating at 0.2 Hz (72 degrees x s(-1)). Exposures were for 10 min or until moderate nausea developed. The design was counterbalanced repeated measures. Pilot Study: Subjects (N = 12) viewed visual conditions: a distant bland coastline scene as from an aircraft, tilted 30 degrees (Up); the same scene but inverted (Invert); and the scene morphed with no obvious orientation cues (Abstract). Main Experiment: Subjects (N = 22) viewed a city street scene containing numerous unambiguous and strong verticality cues under two conditions: upright (Up) and inverted (Invert), with 18 degrees tilt of rotational axis. RESULTS: Pilot Study: there were no significant differences between conditions in time (mean +/- SD min) to nausea endpoint (Up: 7.4 +/- 3.1; Invert: 7.1 +/- 3.1;Abstract: 7.8 +/- 2.4), nor for total symptom scores, nor for vection. Main Experiment: the upright scene was significantly more nauseogenic than the inverted, with shorter times to nausea endpoint (Up: 8.7 +/- 2.3; Invert: 9.2 +/- 2.2) and greater total symptom scores. Vection was marginally greater for Up than Invert. CONCLUSIONS: Salient and unambiguous higher order cognitive cues may modulate the development of motion sickness induced by optokinetic stimuli. There was no one-to-one correspondence between vection and motion sickness.
