[Direct observation of the vibration and the traveling wave on the basilar membrane of the guinea pig].

Basilar membrane vibration was investigated in guinea pigs by using a laser Doppler velocimeter. To monitor the physiological condition of the cochlea, compound action potentials and distortion product otoacoustic emissions were measured before and after each experiment. Sharply tuned (Q10dB : 4.6-7.0) mechanical vibrations were successfully observed in 190 preparations of 15 animals. In these animals, strong compressive nonlinearity of the basilar membrane response and steep phase lag above the characteristic frequency were observed clearly. These findings strongly support the existence of active mechanical elements that play important roles behind the auditory transduction in the cochlea.