Long-duration head down bed rest as an analog of microgravity: Effects on the static perception of upright

Laurence Roy Harris, Michael Jenkin, Rainer Herpers
Journal of vestibular research: equilibrium & orientation, Volume Pre-press, page 1-16 - oct 2021

Abstract

Background: Humans demonstrate many physiological changes in microgravity for which long-duration head down bed rest (HDBR) is a reliable analog. However, information on how HDBR affects sensory processing is lacking.
Objective: We previously showed (25) that microgravity alters the weighting applied to visual cues in determining the perceptual upright (PU), an effect that lasts long after return. Does long-duration HDBR have comparable effects?
Methods: We assessed static spatial orientation using the luminous line test (subjective visual vertical, SVV) and the oriented character recognition test (PU) before, during and after 21 days of 6° HDBR in 10 participants. Methods were essentially identical as previously used in orbit (25).
Results: Overall, HDBR had no effect on the reliance on visual relative to body cues in determining the PU. However, when considering the three critical time points (pre-bed rest, end of bed rest, and 14 days post-bed rest) there was a significant decrease in reliance on visual relative to body cues, as found in microgravity. The ratio had an average time constant of 7.28 days and returned to pre-bed-rest levels within 14 days. The SVV was unaffected.
Conclusions: We conclude that bed rest can be a useful analog for the study of the perception of static self-orientation during long-term exposure to microgravity. More detailed work on the precise time course of our effects is needed in both bed rest and microgravity conditions.

BibTex references

@Article{HJH21,
  author       = {Harris, Laurence Roy and Jenkin, Michael and Herpers, Rainer},
  title        = {Long-duration head down bed rest as an analog of microgravity: Effects on the static perception of upright},
  journal      = {Journal of vestibular research: equilibrium \& orientation},
  volume       = {Pre-press},
  pages        = {1-16},
  month        = {oct},
  year         = {2021},
  keywords     = {HDBR; Human orientation perception; head down bed rest; perceptual upright; space flight analog; subjective visual vertical},
}

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» Laurence Roy Harris
» Michael Jenkin
» Rainer Herpers