[Space motion sickness]

This review describes symptoms of space motion sickness (SMS) observed in many cosmonauts during the first day in orbit. It also discusses similar symptoms detected in them upon return to the Earth which constitute the readaptation syndrome. The paper gives a detailed discussion of different theories that explain the etiology and pathogenesis of SMS and the post-flight readaptation syndrome, viz, sensory conflict or sensory mismatch, disorders in the labyrinthine paired function, and blood and cerebrospinal fluid (CSF) circulation. It is emphasized that none of the theories used separately can clarify all aspects of the origin and development of SMS. The authors main tain that the mechanisms underlying the above changes are not contradictory but rather interrelated and complementary. Each of them having a larger or smaller specific weight may be involved in the development of SMS. In some people marked vestibular asymmetry may become the leading factor, in others inadequate adaptive capabilities to fluid redistribution may result in blood and CSF disorders, and in still others sensory conflict may play the crucial role. A correlation between SMS and vestibular adaptation is discussed. Results of studying the vestibular function during and after real space flights are presented.