Microgravity vestibular investigations: perception of self-orientation and self-motion.
Four astronauts experienced passive whole-body rotation in a number of test sessions during a 7-day orbital mission. Pitch (Y-axis) and roll (X-axis) rotation required subject orientations on the rotator in which the otolith system was at radius of 0.5 m. Thus subjects experienced a constant -0.22 Gz stimulus to the otoliths during the 60 s constant-velocity segments of "pitch" and "roll" ramp profiles. The Gz stimulus, a radius-dependent vector ranging from -0.22 Gz at the otoliths to +0.36 Gz at the feet, generated sensory information that was not interpreted as inversion in any of the 16 tests carried out in flight (12 in pitch and 4 in roll orientation). None of the subjects was rotated with head off-center during the first 33 h of the mission. In the state of orbital adaptation of these subjects, a -0.22 Gz otolith stimulus did not provide a vertical reference in the presence of a gradient of +Gz stimuli to the trunk and legs.
Benson
A J
AJ
RAF School of Aviation Medicine, Farnborough Hants, England, UK.
Guedry
F E
FE
Parker
D E
DE
Reschke
M F
MF
D018480:Astronauts; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D010037:Otolithic Membrane / Q000502:physiology; D012399:Rotation; D014722:Vestibule, Labyrinth / Q000502:physiology*; D014893:Weightlessness