EXPERIMENTAL STUDY ON FATIGUE OF INNER EAR BY COCHLEAR MICROPHONICS

Abstract

1. Experiments were done on the development and recovery of fatigue of the inner ear of guinea pig. Continuous pure tone stimuli were given and the change in the cochlear microphonics was traced and recorded from different parts of cochlea using an intra-cochlear microelectrode.2. Fatigue which was not observed by relatively low tone stimuli with the electrode placed around the round window or into the basal turn, observed in cases of recording from the second or the third turn.3. The region of cochlea which showed fatigue most remarkably was dependent on the frequency of sound applied, being the third turn for 125, 250 and 500cps., the second turn for 1000 and 2000cps, the basal turn for 4000cps. respectively.4. The intensity of the stimulus to induce the fatigue in one minute was dependent on the frequency, being 115db_??_120db at 125cps., 110db_??_115db at 250cps., 107db_??_112db at 500cps., 96db_??_101.db at 1000cps., 104db_??_109db at 2000cps. and 96db at 4000cps. (sound pressure level) respectively, and no fatigue was recognized by the stimuli below this level even when the rstimuli were' given continuously for five minutes.5. Development of the fatigue was influenced by intensity of the stimulir ather than duration of the stimuli, while in its recovery process the reverse relationship was observed.6. The region of cochlea which was most responsive for certain pure tone stimuli was found to coincide with the region which showed sign of fatigue most easily for the same tone stimuli.