Modelling the action of caloric stimulation of vestibule. III. Caloric nystagmus induced by osmotic pressure variation.
The properties of the membranous wall of the semi-circular canal and of the labyrinthine fluids give as a result the inflating pressure of this inflatable structure. The difference of osmotic pressure between perilymph and endolymph, which is involved in this problem, depends on temperature. Therefore, a caloric stimulation leads to a change in the inflating pressure. A numerical model, similar to the model used to study the effects of relative volume variations, gives a quantitative estimation of the transcupular pressure arising in a horizontal semi-circular canal (i.e. without gravity dependent effects) during a caloric stimulation, according to the inflating pressure change. As a consequence, it appears that rotational and caloric stimulations are not quite similar. The caloric stimulation leads not only to a transcupular pressure difference but also to a change in inflating pressure. As a result of the change in inflating pressure, the stiffness of the cupula varies. This modifies the gain and the dynamics of the vestibulo-ocular reflex, and may explain the asymmetry between hot and cold stimulations.
Gentine
A
A
Clinique ORL, Université Louis Pasteur, Strasbourg, France.
Eichhorn
J L
JL
Kopp
C
C
Conraux
C
C
D002150:Caloric Tests; D003198:Computer Simulation; D004710:Endolymph / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D009760:Nystagmus, Physiologic / Q000502:physiology; D009997:Osmotic Pressure; D010498:Perilymph / Q000502:physiology; D012665:Semicircular Canals / Q000502:physiology*; D014722:Vestibule, Labyrinth / Q000502:physiology