Self-motion perception is a multi-sensory process that involves visual, vestibular, and other cues. When perception of self-motion is induced using only visual motion, vestibular cues indicate that the body remains stationary, which may bias an observer’s perception. When lowering the precision of the vestibular cue by for example, lying down or by adapting to microgravity, these biases may decrease, accompanied by a decrease in precision. To test this hypothesis, we used a move-to-target task in virtual reality. Astronauts and Earth-based controls were shown a target at a range of simulated distances. After the target disappeared, forward self-motion was induced by optic flow. Participants indicated when they thought they had arrived at the target’s previously seen location. Astronauts completed the task on Earth (supine and sitting upright) prior to space travel, early and late in space, and early and late after landing. Controls completed the experiment on Earth using a similar regime with a supine posture used to simulate being in space. While variability was similar across all conditions, the supine posture led to significantly higher gains (target distance/perceived travel distance) than the sitting posture for the astronauts pre-flight and early post-flight but not late post-flight. No difference was detected between the astronauts’ performance on Earth and onboard the ISS, indicating that judgments of traveled distance were largely unaffected by long-term exposure to microgravity. Overall, this constitutes mixed evidence as to whether non-visual cues to travel distance are integrated with relevant visual cues when self-motion is simulated using optic flow alone.

自我运动感知是一个多感官过程，涉及视觉、前庭和其他线索。当仅使用视觉运动诱导自我运动的感知时，前庭线索表明身体保持静止，这可能会偏差观察者的感知。当通过躺下或适应微重力等方式降低前庭提示的精度时，这些偏差可能会减少，同时精度也会降低。为了检验这个假设，我们在虚拟现实中使用了移动到目标任务。宇航员和地球上的控制人员看到了一系列模拟距离内的目标。目标消失后，光流诱导向前自运动。参与者表示他们认为自己已经到达目标先前看到的位置。宇航员在太空旅行之前、太空中的早期和晚期以及着陆后的早期和晚期完成了地球上的任务（仰卧和直立）。对照组在地球上完成了实验，使用类似的方式，采用仰卧姿势来模拟在太空中的情况。虽然所有条件下的变异性相似，但对于宇航员来说，仰卧姿势带来的增益（目标距离/感知旅行距离）明显高于宇航员在飞行前和飞行后早期但在飞行后后期的坐姿。宇航员在地球上和在国际空间站上的表现没有发现差异，这表明对旅行距离的判断在很大程度上不受长期暴露于微重力的影响。总体而言，这构成了关于当仅使用光流模拟自运动时，行进距离的非视觉线索是否与相关视觉线索整合的混合证据。