Perception of body angular displacement while free-floating in microgravity during parabolic flight.

purposeAccurate perception of self-motion perception is critical for spatial orientation, especially in environments lacking visual or gravitational cues, such as during spaceflight. This study investigated how humans perceive passive whole-body rotation while free-floating in microgravity during parabolic flight.

methodsSix study participants were passively rotated about their yaw, pitch, and roll axes by an operator. The rotation angles ranged from 30 degrees to 420 degrees, and participants reported their perceived angular displacement after each trial. Visual and auditory cues were eliminated, and motion was recorded using inertial sensors.

resultsErrors between perceived and actual amplitudes were generally larger for pitch and roll rotations than yaw. Participants tended to inaccurately estimate the amplitude of both pitch and yaw rotations, with errors becoming more pronounced at larger angular displacements. Perception gain (the ratio of perceived to actual rotation) showed greater variability for pitch and roll than yaw. Overall, perception gain was higher for roll than for pitch or yaw, although this may have been influenced by the slower average angular velocities of these roll rotations.

conclusionThese findings suggest axis-dependent differences in motion perception in microgravity, likely due to the absence of otolith input and changes in tactile feedback, which underscores the role gravity plays in perceiving pitch and roll motion. Errors in estimating rotations could pose operational challenges for astronauts performing orientation-dependent tasks in low-gravity environments. These findings may also inform rehabilitation strategies for vestibular patients by determining the roles of cues from the semicircular canals and tactile feedback when compensating for impaired sense of gravity.