[The effect of weightlessness on vestibular function].

During and after space missions crew members showed significant vestibular changes. The cosmonaut-researcher of the orbital complex Soyuz T-7--Salyut-7 developed inhibition of compensatory and enhancement of nystagmic eye movements in response to active head movements in the frontal plane. During an acute stage of readaptation crew members of the orbital complex Soyuz T-4--Salyut-6 displayed attenuation of the oculomotor reaction to optokinetic stimulation. One of them exhibited overt asymmetry of this oculomotor reaction. This cosmonaut also developed distinct spontaneous nystagmus in the dark and floating eye movements when he tried to fix his gaze at a stationary object. These findings give evidence that space flight may induce vestibular asymmetry and disorders of mechanisms of opto-vestibular interaction.