Relation between changes in compound action potential tuning curves and the pathology of cochlear hair cells stereocilia]

Relations of the changes of compound action potential tuning curve (AP-TC) and AP(N1) threshold to the pathology of the cochlear hair cells stereocilia were examined in acoustic-traumatized guinea pigs. The results showed that all animals with hair cell stereocilia damaged showed deteriorations of AP-TC. It supports the suggestion that mechanical properties of hair cell stereocilia contribute to the frequency selectivity of cochlea. After exposure, the characteristic frequency (CF) shift of AP-TC was observed. The mechanism of CF shift may be related to the lesion of hair cell stereocilia which may change normal tono-topic on cochlear level. Correlation between the damages of inner/outer hair cell stereocilia and changes of AP-TC and AP threshold suggested that the threshold and tuning properties of the cochlea are dependent upon the integrity of the inner and outer hair cells and their inter-relationship.