On ground, the perception of self-motion is a multi-sensory task predominantly determined by the vestibular and visual systems. The vestibular system transduces both external forces and gravity. However, in a microgravity environment the vestibular system is no longer affected by gravity, which may disrupt astronauts’ perception of distance, self-motion, and interpretation of tilt and translation. Given that astronauts are routinely required to estimate their motion in order to complete mission requirements, understanding how self-motion is estimated under microgravity conditions is key to mission safety.

The VECTION project will develop a model to examine how human visual self-motion perception is altered during long-duration microgravity conditions. Visual motion cues will be presented on a virtual reality head-mounted display to elicit a sense of self-motion. The subject’s ability to give spatial updates based on visual motion cues will be assessed by measuring how far the participant needs to virtually “travel” through the simulated environment to reach a visual target. Perceived tilt and translation will be evaluated by measuring perceived orientation following the simulation. After “traveling” through the simulated environment, subjects will indicate their perceived orientation relative to the recollection of the external environment. An additional test will use virtual reality to measure perception of distance and evaluate the influence of microgravity on perceived distance.

The objectives of this experiment are to:

1. Assess the effectivity of visual cues for motion before, during, and after long-duration exposure to microgravity
   1. Assess the perceived travel distance evoked by visual motion alone under microgravity compared to the effect of comparable simulations on ground
   2. Assess whether distances in the visual scene in general are misperceived in microgravity
2. Assess whether visual motion cues might be subject to ambiguity in terms of tilt and translation before, during, and after long duration exposure to microgravity
3. Generate a model that examines how long-duration exposure to microgravity may affect the processing of optic information to evoke self-motion and how this processing changes upon return to ground conditions

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