The rubber hand illusion in microgravity and water immersion (original) (raw)

npj Microgravity

Our body has evolved in terrestrial gravity and altered gravitational conditions may affect the sense of body ownership (SBO). By means of the rubber hand illusion (RHI), we investigated the SBO during water immersion and parabolic flights, where unconventional gravity is experienced. Our results show that unconventional gravity conditions remodulate the relative weights of visual, proprioceptive, and vestibular inputs favoring vision, thus inducing an increased RHI susceptibility.

Perceived Body Orientation in Microgravity: Effects of Prior Experience and Pressure Under the Feet

Human activities often involve sensing body orientation using cues from gravity. Astronauts in microgravity are deprived of those cues and may have difficulty with certain tasks. We theorized that experience in microgravity combined with mechanically induced pressure under the feet(footpressure)wouldimprovetheaccuracyofasubject’sperception of the body’s z-axis as indicated by pointing to the subjective horizon (SH). Method: Experiments were conducted during parabolic flights using five experienced subjects and five novices. Subjects were required to raise their arm to point to their SH with eyes closed. Measurements were made on Earth and in microgravity, with or without foot pressure. Both pointing accuracy and the kinetics of the movement were analyzed. Results: Performance by experts was stable under all conditions. However, novices in microgravity pointed to a significantly lower SH (16.5°] below the 1-G SH) and slowed their movements (mean angular velocity of movement: 16.8°  s1 less than in 1 G). Foot pressure improved the performance of the novices so that it was closer to that observed at 1 G (8.9° below the 1-G SH). Discussion: These results suggest that pressure cues under the feet activated the internal model of gravity in the novices, and thus improved the accuracy of their perception of their z-axis. Subjects with prior experience in microgravity correctly perceived their z-axis without the supplementary input.

Quantifying body ownership information processing and perceptual bias in the rubber hand illusion

Bodily illusions have fascinated humankind for centuries, and researchers have studied them to learn about the perceptual and neural processes that underpin multisensory channels of bodily awareness. The influential rubber hand illusion (RHI) has been used to study changes in the sense of body ownership: how a limb is perceived to belong to one’s body, which is a fundamental building block in many theories of bodily awareness, self-consciousness, embodiment, and self-representation. However, the methods used to quantify perceptual changes in bodily illusions — including the RHI — have mainly relied on subjective questionnaires and rating scales, and the degree to which such illusory sensations depend on sensory information processing has been difficult to test directly. Here we introduce a signal detection theory (SDT) framework to study the sense of body ownership in the RHI. We provide evidence that the illusion is associated with changes in body ownership sensitivity that depend ...

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