Physiological masking functions in normal and acoustically traumatized cats

Abstract

In cats that have undergone acoustic traumatization, it has been observed that several characteristics in the shape of single auditory nerve fiber tuning curves correspond to histological changes in the hair cells of the cochlea [N. Y. S. Kiang, M. C. Liberman, and R. A. Levine, Ann. Otol. Rhinol. Laryngol. 85, 752–768 (1976)]. Dallos and Cheatham (J. Acoust. Soc. Am. 59, 591–597 (1976)] using the whole‐nerve action potential as a response have demonstrated masking curves in normal animals similar in shape to single‐fiber tuning curves. We have measured whole‐nerve action potential tuning curves (AP tuning curve) in both normal and acoustically traumatized cats to investigate the sensitivity of such a measure in reflecting changes in single‐fiber tuning curves. A tonal masker in a forward‐masking paradigm was used to elicit the measured responses. AP tuning curves were generated at several signal frequencies in order to measure the physiological changes at different places along the cochlea. A preliminary review of the data indicate that the AP tuning curves in acoustically traumatized animals can show a broadening of the tip region relative to normals.