Weightlessness and the ontogeny of vestibular function: evidence for persistent vestibular threshold shifts in chicks incubated in space.

The effect of microgravity on the embryonic development of the vestibular function was investigated by comparing the vestibular function parameters measured in 21-old chicks incubated as embryos aboard the Space Shuttle Discovery with those of age-matched synchronous controls incubated on earth. Measurements of the electrophysiological responses in both groups of chicks indicated that the exposure of embryos to weightlessness resulted in altered sensitivity of embryonic vestibular sensors. Moreover, the effect of space flight was persistent: it was still present one month after the spacecraft landed on earth.