The caloric vestibular test in weightlessness.

Although the theoretical background for the caloric vestibular test was assumed to be known, recent studies in weightlessness have thrown doubts on the original theory of its mechanism. It is most likely that several mechanisms are involved in the generation of caloric nystagmus in addition to the convection current theory. Experiments with the caloric test in humans conducted during parabolic flight are described. These results are compared with the results of similar experiments performed in orbital missions.