The effects of pressure in the middle ear.

Abstract

An increase in the air pressure of the middle ear cavity had a marked effect upon the electrical responses of the cochlea. For certain tones a small degree of pressure produced a slight improvement, but large pressures always caused a reduction of the responses. Generally, low tones were affected more than high tones, but the relation was not exactly in order of frequency. The introduction of pressure had no essential effect upon the form of the intensity function, for the reduction in sensitivity might be almost wholly compensated for by an increase in stimulus intensity. Effects were found for bone conduction as well as for air conduction, but the amount of effect differed greatly for these 2 forms of stimulation. When the ossicular chain was broken and bone conduction was used the effects of pressure were comparatively small. The conclusion is reached that middle ear pressure has its principal effect upon the eardrum, though minor effects evidently arise also in its action upon parts of the inner ear. The expts. were carried out on cats under Dial anesthesia and curarization.