The modulation of the sensitivity of the mammalian cochlea by low frequency tones. III. Basilar membrane motion.

The simultaneous presentation of an intense low frequency tone and a moderate intensity high frequency tone produced modulation of the high frequency motion of the cochlear partition in the first turn of the guinea pig cochlea. This modulation was in synchrony with the displacement caused by the low frequency tone. Maximum reduction in mechanical sensitivity was observed for peak displacements towards scala tympani, whereas a less pronounced reduction was observed for peak displacements towards scala vestibuli. Modulation was reduced or absent for high frequency tones more than an octave below the characteristic frequency of the mechanical tuning curve and was absent post mortem.