Human Orientation Perception during Transitions in the Presence of Visual Cues

Vestibular cues are critical for human perception of self-motion and when available visual cues influence these perceptions. However, it is poorly understood how perception of self-motion is affected by transitions in the presence of visual cues (e.g., when visual cues become present, such as when a pilot flies out of the clouds). To investigate this, 11 subjects (3 female, mean 25 +/- 4 years) were seated and rotated about an Earth-vertical yaw axis, while asked to report their perception of angular rotation by pressing a left/right button every time they felt like they had rotated 90 degrees to the left/right. A head mounted display provided visual rotation cues (specifically angular velocity cues only). When present, visual cues were always congruent with inertial rotation. We used 4 different visual cue conditions: no visual cues, visual angular velocity cues, visual angular velocity cues transitioning to no visual cues, and no visual cues transitioning to visual angular velocity cues. We experimented with 2 different rotation profiles per visual cue condition. Based on the timing between subject button press inputs, we inferred their perception of angular velocity. During and immediately after a sudden loss of visual cues, we found a transition in perception of angular velocity on the order of 30 seconds. When visual cues appeared after vestibular cues had deviated from reality, there was a 10 second delay before angular velocity perception converged to that associated with the provided visual angular velocity cues. Both these time periods are long than expected and longer than the time delay associated with the psychophysical task. Our results indicate that the brain does not discard the influence of past visual motion cues immediately after suddenly losing visual cues. Suddenly gaining visual cues is also associated with some time delay in integrating the cues into a central perception of motion. By quantifying the time course of self-motion perception following transitions in the presence of visual cues, we can better understand pilot spatial disorientation. For example, a terrestrial pilot flying out of clouds or an astronaut in the final stages of landing on the moon with dust blowback, each experience a transition in the presence of visual cues affecting spatial orientation perception.