Long-Duration Spaceflight Increases Depth Ambiguity of Reversible Perspective Figures.
Bottom Line: The reaction time decreased throughout the sessions, thus indicating a learning effect.However, the time to first percept reversal and the number of reversals were not different in orbit and after the flight compared to before the flight.These results indicate that the perception of "illusory" depth is altered in astronauts during spaceflight.
Affiliation: Lyon Neuroscience Research Center, Bron, France.
The objective of this study was to investigate depth perception in astronauts during and after spaceflight by studying their sensitivity to reversible perspective figures in which two-dimensional images could elicit two possible depth representations. Other ambiguous figures that did not give rise to a perception of illusory depth were used as controls. Six astronauts and 14 subjects were tested in the laboratory during three sessions for evaluating the variability of their responses in normal gravity. The six astronauts were then tested during four sessions while on board the International Space Station for 5-6 months. They were finally tested immediately after return to Earth and up to one week later. The reaction time decreased throughout the sessions, thus indicating a learning effect. However, the time to first percept reversal and the number of reversals were not different in orbit and after the flight compared to before the flight. On Earth, when watching depth-ambiguous perspective figures, all subjects reported seeing one three-dimensional interpretation more often than the other, i.e. a ratio of about 70-30%. In weightlessness this asymmetry gradually disappeared and after 3 months in orbit both interpretations were seen for the same duration. These results indicate that the perception of "illusory" depth is altered in astronauts during spaceflight. This increased depth ambiguity is attributed to the lack of the gravitational reference and the eye-ground elevation for interpreting perspective depth cues.
No MeSH data available.
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Mentions: On the ground the number of reversals was not significantly different between the control subjects and the astronauts for the silhouettes ([F (1,119) = 0.66, p = 0.418], but was significantly different for the perspective figures [F (1,239) = 7.07, p = 0.008]. The number of reversals was smaller for the perspective figures than for the silhouettes for both the control subjects [F (1,251) = 59.6, p < 0.001] and the astronauts [F (1,107) = 213, p < 0.001]. The number of reversals per minute averaged across all 20 subjects was 8.7 s (SD 5.4 s) for the perspectives figures and 20.5 s (SD 15.4 s) for the silhouettes. For the perspective figures, no significant difference in the number of reversals was found across pre-flight sessions and figures for both the astronauts and the control subjects (Fig 6). However, for the silhouettes, the ANOVA indicated a significant effect of session days [(F (2,35) = 4.48, p = 0.019].
No MeSH data available.