Transmission of Low Frequency Pressure Steps to the Perilymphatic Fluid

Abstract

The perilymphatic pressure was investigated in response to low frequency pressure changes in the ear canal and in the middle ear in the cat. the pressure transmission to the inner ear showed nonlinear characteristics with an asymmetry in the perilymphatic response to positive and negative pressure stimulation, respectively. a positive pressure stimulus in the ear canal and middle ear, respectively, caused a larger change in perilymphatic pressure than did a corresponding negative one. When the tympanic cavity was opened there was a substantial reduction in the amount of pressure transmitted to the inner ear from the ear canal. a shift in asymmetry was often also seen towards a greater change in perilymphatic pressure in response to a negative pressure stimulation than in response to a positive one. the stabilization process of the perilymphatic pressure in response to different input levels contained two different time constants indicating the pressure regulating mechanisms of the inner ear. the possibility of influencing the mean perilymphatic pressure during a period of alternating pressure changes in the ear canal or middle ear is discussed in the light of the nonlinear perilymphatic response to positive and negative pressures applied.