Basilar membrane mechanical responses were recorded from seven guinea pigs which had been treated with kanamycin sulphate (400 mg/kg for 8 to 10 days) and kept for different survival times so as to result in different levels of degeneration of the outer hair cells and organ of Corti. Following mechanical recording the cochleas were immediately prepared for scanning electron microscopy [D. Robertson and B. M. Johnstone, J. Acoust. Soc. Am. 66, 466–469 (1979)]. The mechanical responses to impulses differed from normal increasingly with the state of degeneration of the outer hair cells. Loss of the outer hair cells appear to correlate with loss of the vulnerable nonlinearity. The differences were pronounced in older animals in which the organ of Corti was totally missing, notably the impulse response continued to ring for longer. The cutoff frequency was raised and the phase curve lacked the rapid roll segment. These results indicate that, contrary to the widely held view, the structure of the organ of Corti exerts a significant influence on the motion of the basilar membrane on the apical end of the traveling wave envelope.

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