Cochlear Microphonic Potential in Cats: Effects of Perilymphatic Pressure

Perilymphatic pressure variations were produced in cats and recordings made of cochlear potentials from the round window. A functional relationship between perilymphatic pressure and cochlear sensitivity with secondary dependence upon frequency and duration of pressure application was determined. Completely reversible changes in sensitivity were seen upon brief applications of pressure, while permanent damage was encountered when pressure was maintained. The short-term effects seem to bear the mark of a simple mechanical change in the inner ear. Specifically, the major consequence of brief pressure application appears to be increased overall stiffness of the inner ear conducting mechanism. This is indicated by the predominately low tone loss. Long-term effects result in irreversible losses which are approximately equal for all frequencies.