Suppression of Low-Frequency Tones in the Organ of Corti Vibrations of the Basal Turn in the Mongolian Gerbil Cochlea

Both active gain and nonlinearity in cochlear mechanics originate in the organ of Corti at a location that extends far basal to the place of the probe tone and not in the BM. Together with the previous reports by others, we conclude that the nonlinear acoustic interaction in the ear canal between a probe tone and tones much higher than the probe frequency is caused by the reduction (suppression) of mechanical gain actively generated by outer hair cells (OHC) in the organ of Corti. There was no indication that the suppressor generated a response at the probe frequency that was not already present in the response to the probe tone presented alone. Our results support the hypothesis that stimulus-frequency otoacoustic emissions (SFOAEs) measured in the ear canal sound pressure originate in a large region extending basal to the place of the probe tone. The BM does not appear to be the site of either generation or propagation of SFOAEs.