The Effect of Gravitational Force on the Vestibular Caloric Test

Abstract

Vestibulary caloric tests were carried out on four subjects at 1 g, 1.25 g, 1.5 g and 1.8 g in a large centrifuge. The experiments showed that (1) vestibular caloric tests are influenced by the strength of the gravitational field; (2) the maximum intensity of nystagmus increases with higher values of g; (3) this increase is in direct proportion to the increase in the gravitational field strength; (4) the latency period decreases with higher values of g; (5) the results are the same with cold and hot water irrigation. It is also shown that the duration increases with higher g-values hut the material relating to this factor is not complete. An extrapolation of the result towards values of g less than 1 tends to show that there is no nystagmus in conditions of weightlessness and that the liminal value for nystagmus is about 0.1 g. An investigation involving the caloric test and preponderance at higher g-loads is planned.