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Paradoxical long-term enhancement of distortion product otoacoustic emission amplitude after repeated exposure to moderate level, wide band noise in awake guinea pigs

Published online by Cambridge University Press:  16 July 2009

L Mei
Affiliation:
Department of Otolaryngology-Head and Neck Surgery, Renmin Hospital, Wuhan University, China
Z-W Huang
Affiliation:
Department of Otolaryngology-Head and Neck Surgery, Renmin Hospital, Wuhan University, China
Z-Z Tao*
Affiliation:
Department of Otolaryngology-Head and Neck Surgery, Renmin Hospital, Wuhan University, China
*
Address for correspondence: Dr Ze-Zhang Tao, Department of Otolaryngology-Head and Neck Surgery, Renmin Hospital, Wuhan University, Wuhan 430060, China. Fax: +86 27 88043958 E-mail: zezhangtao@hotmail.com

Abstract

Objective:

Hearing sensitivity usually diminishes with noise exposure. In the present study, we examined the effect of 93 dB(A) wide band noise on cochlear micromechanical sensitivity in awake guinea pigs.

Methods:

Animals were randomly assigned to groups receiving either single or repeated noise exposure. Distortion product otoacoustic emission amplitudes were recorded before, during and after noise exposure.

Results:

Ninety-three decibel(A) wide band noise reduced the distortion product otoacoustic emission amplitudes at all tested frequencies. The distortion product otoacoustic emission amplitudes for higher frequencies showed a permanent reduction, whereas those for lower frequencies showed a temporary reduction. Distortion product otoacoustic emission amplitudes for middle frequencies showed prolonged enhancement after repeated noise exposure.

Conclusion:

Our results suggest that (1) it is likely that there are intermediate stages between permanent threshold shift and temporary threshold shift, and (2) long-term enhancement of distortion product otoacoustic emission amplitudes may be an indication of tinnitus generation.

Information

Type
Main Articles
Copyright
Copyright © JLO (1984) Limited 2009

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