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Richard T. Dyde, James E. Zacher, Michael R. Jenkin, Heather L. Jenkin, Laurence R. Harris; Perceptual orientation judgements in astronauts: pre-flight results. Journal of Vision 2010;10(7):869. doi: 10.1167/10.7.869.
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Introduction: Bodies in the Space Environment (BISE) is a Canadian Space Agency sponsored experiment currently running onboard the International Space Station. The project examines the effect of long-term exposure to microgravity on perceived object orientation. Methods: Thirteen astronauts were tested using the Oriented Character Recognition Test (OCHART) as part of the pre-flight data collection process. OCHART measures the orientation at which a letter probe is “perceptually upright” (PU) (Dyde et al. 2006 Exp. Brain Res. 173: 612). OCHART was performed while upright and lying right-side-down (rsd). By varying the background orientation and the orientation of the subjects the relative contribution of vision, gravity and the body can be determined. Data from 49 undergraduate students were collected for comparison. Students' data variance was computed and a second pool of 24 student subjects was constructed to match variance in the astronaut subject pool. Results: When in an upright posture the direction of PU was more influenced by a tilted visual background for the complete student group compared to astronauts. Astronauts' PUs had significantly smaller variances than those of the complete student group. Comparing the astronauts with a group of 24 students (matched for variance) showed that there was no difference in the influence of the tilted background on PU between these two groups. When these two groups' data was compared in the rsd posture, the direction of PU was reliably closer to the axis of gravity (and further away from the body centre-line) for the students compared to astronauts. Discussion: Initial data suggest that astronauts rely less on the axis of gravity when performing an orientation measure compared to a student-group matched for variance. Experiments are ongoing with a subject pool age-matched to the astronaut group.
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