Neutral buoyancy and the static perception of upright

Area of Science:

• Neuroscience
• Human Physiology
• Space Biology

Background:

• Perceptual upright relies on integrating visual, graviceptive, and somatosensory cues, alongside a headward prior.
• The vestibular system (otoliths) and somatosensation are primary gravity detectors.
• Understanding these cues is vital for spaceflight and terrestrial orientation challenges.

Purpose of the Study:

• To investigate the role of somatosensation in determining perceptual upright using neutral buoyancy.
• To assess the impact of removing somatosensory input on spatial orientation.
• To evaluate neutral buoyancy as a microgravity analogue for perceptual studies.

Main Methods:

• Utilized neutral buoyancy to eliminate somatosensory information, isolating vestibular gravity cues.
• Employed the oriented character recognition test (OChaRT) to measure perceptual upright (PU).
• Compared spatial orientation under neutrally buoyant and terrestrial conditions.

Main Results:

• Reduced influence of visual cues on perceived upright under neutral buoyancy.
• Unaffected influence of gravity cues despite removal of somatosensation.
• No significant alteration in the weighting of vision, gravity, or body cues.

Conclusions:

• Somatosensation has a minimal role in establishing perceptual upright when vestibular cues are present.
• Short-duration neutral buoyancy is a limited analogue for microgravity's perceptual effects compared to bed rest.
• Vestibular input is crucial for maintaining spatial orientation in the absence of somatosensory information.