Perception of smooth and perturbed vection in short-duration microgravity

Successful adaptation to the microgravity environment

of space and readaptation to gravity on earth

requires recalibration of visual and vestibular signals.

Recently, we have shown that adding simulated viewpoint

oscillation to visual self-motion displays produces more

compelling vection (despite the expected increase in visualvestibular

conflict experienced by stationary observers).

Currently, it is unclear what role adaptation to gravity might

play in this oscillation-based vection advantage. The vection

elicited by optic flow displays simulating either smooth

forward motion or forward motion perturbed by viewpoint

oscillation was assessed before, during and after microgravity

exposure in parabolic flight. During normal 1-g

conditions subjects experienced significantly stronger

vection for oscillating compared to smooth radial optic flow.

The magnitude of this oscillation enhancement was reduced

during short-term microgravity exposure, more so for simulated

interaural (as opposed to spinal) axis viewpoint

oscillation. We also noted a small overall reduction in vection

sensitivity post-flight. A supplementary experiment

found that 1-g vection responses did not vary significantly

across multiple testing sessions. These findings: (i) demonstrate

that the oscillation advantage for vection is very

stable and repeatable during 1-g conditions and (ii) imply

that adaptation or conditioned responses played a role in the

post-flight vection reductions. The effects observed in

microgravity are discussed in terms of the ecology of terrestrial

locomotion and the nature of movement in

microgravity.