[A new approach to the mechanism of vestibular response to caloric stimulation]

Barany's classical hydrodynamic theory has been called into question by the zero-gravity Spacelab experiments, and several new hypotheses are put forth to explain the vestibular response to caloric stimulation. We have developed a mathematic model based on the analysis of an experimental model of the semicircular canal, incorporating observations done with zero-gravity and with gravity. Two purely mechanical phenomena are involved: one one hand, the modification of the hydrostatic pressure on both sides of the cupula due to a temperature variation if the semicircular canal is not in the horizontal plane in normal gravity conditions; on the other hand, local changes in endolymph pressure and volume due to the mechanical and osmotic properties of the canal, which are independent from gravity and from the position of the canal. These mechanical processes, though not exclusive, are predominant and therefore sufficient to explain the caloric response of the vestibulum in all cases.