Measurement of basilar membrane vibrations and evaluation of the cochlear condition

The experimental procedure for measuring basilar membrane responses to acoustic signals is described. The surgical procedure developed for opening the cochlea with minimal trauma is presented. Each experiment included sound pressure level measurements to define the input signal, cochlear microphonic (CM) measurements to monitor the cochlear condition, interferometric measurements and histological evaluation of the cochleas. The characteristic frequency (CF) and the sensitivity at CF for the basilar membrane response is correlated with the change of CM response observed in six animals. It is demonstrated that both tuning characteristics are extremely sensitive to cochlear trauma as evidenced by changes of CM.