Affiliations: [a] RAF School of Aviation Medicine, Farnborough Hants, England, UK | [b] University of West Florida, and Naval Aerospace Medical Research Laboratory, Pensacola, Florida, USA | [c] Department of Otolaryngology – HNS, University of Washington, Seattle, Washington, USA | [d] Space Biomedical Research Institute, Johnson Space Center, Houston, Texas, USA
Note: [*] Reprint address: Donald E. Parker, Box 357923, Department of Otolaryngology-HNS, University of Washington, Seattle, Washington 98195-7923. Tel: (206) 285-7528; Fax: (206) 616-1828; E-mail: [email protected].
Abstract: 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.
