Caloric nystagmus decay during parabolic flight.
In human subjects the caloric test was conducted during parabolic flight. The slow-phase velocity (SPV) of the caloric nystagmus increased proportionally to the value of the g-force. The nystagmus disappeared in microgravity, after an exponential SPV decay that showed a specific time constant (Tc). The average Tc value of this SPV decay is on a lower level than the one found after a sudden stop-test in the laboratory in a 1-g condition. Because of the exponential characteristics of the SPV decays and their Tc values, evoked in both conditions, a common working mechanism of cupular stimulation is likely. Most probably a fluid movement, caused either by a sudden stop in a 1-g condition or by weightlessness after a calorization, provokes a cupula flexion followed by a reflexion. The results support the Bárány convection theory with regard to the endolymph movement following the caloric test.
De Jong
H A
HA
University of Amsterdam, The Netherlands.
Kortschot
H W
HW
Oosterveld
W J
WJ
D002150:Caloric Tests; D006112:Gravitation; D006801:Humans; D009760:Nystagmus, Physiologic / Q000502:physiology*; D013026:Space Flight; D014724:Vestibular Function Tests; D014722:Vestibule, Labyrinth / Q000502:physiology