Time constants of the vestibular thermal reaction.

For the thermal test, adaptation time constants of about 100 s are described in the literature. By automatically alternating hot-cold irrigation, as designed by us, precision of stimulus application of different temperatures was considerably improved. Furthermore, temperature was registered with a thermocouple device. The actually effective thermal stimulus on the horizontal canal was calculated by a mathematical model. Nystagmus analysis was carried out automatically with the Kiel-program. With 15 radical cavities (where stimulus intensity is very strong) non-linearities were especially distinct. After switching to the 44 degrees C stimulus, there was an extremely steep rise in the reaction in the form of a so-called "on-effect" or "post-inhibitory overshoot". After reaching maxima of up to 150 degrees/s, the reaction decreased quickly with time constants of 22-45 s.