[Suprathreshold alternating vestibular stimuli in orbiting spacecrafts].

The actual knowledge of the thresholds of stimulation of the otolith organ is reviewed. A vestibular stimulus unknown until now with a value transgressing the threshold has been found. This gravitational force is due to the gravitation of the sun and is caused by the fact that the spacecraft is moving at a different speed with respect to the sun on one side of the orbit than on the other. The problems of vestibular experiments in space and the connection with space motion sickness due to a field of microgravitation in orbiting spacecrafts is discussed.