On the electrical responses of the cochlea and the auditory tract of the cat to a phase reversal produced in a continuous musical tone

Abstract

The audible phase change beat occurring under certain conditions when the phase of a pure musical tone is changed by [PI] (180[degree]) is due to the phase change itself. The electrical effects accompanying such a change were recorded from the auditory tract and cochlea of decerebrate eats, using amplification, recording and monitoring apparatus previously described, and a new photoelectric siren for the production of phase changes in continuous tones with good wave form. With frequencies between 256 and 1024 cycles, and sound intensities from 40 1o SO phons, the tract responded to phase change with a silent period of 2 to 3 cycles. The cochlear response reproduced the impressed phase change with considerable accuracy. The well-marked silent period is a typical response of resonant structures*, probably the fibres of the basilar membrane. The cochlear response recorded from the round window was of 11011-Tesonant type, supporting the membrane potential theory of cochlear response, and excluding the action potential and hair-cell theories. The gap in the tract response might not represent complete physiological inactivity, but might correspond to a burst of unsynchronised impulses from out of tune elements, beyond the resolving powers of the apparatus, which could constitute the physiological counterpart of the phase change beat.