The role of middle ear muscles in the development of resistance to noise induced hearing loss.
The role of middle ear muscles (MEMs) in the development of increased resistance to noise induced hearing loss (NIHL) was studied using monaural chinchillas. Animals with severed MEMs as well as those with intact MEMs were exposed to an octave band noise (OBN) centered at 0.5 kHz at 95 dB for six hours/day for ten consecutive days. Results indicated that animals with severed MEMs showed greater initial threshold shifts (TS) than the animals with intact MEMs. Both the groups showed a decrease in TS over the ten days of exposure. The subjects were given five days of recovery and then re-exposed to the same noise at 106 dB for 48 h. Permanent threshold shifts (PTS) in each group was compared against those in a control group exposed to the noise only at the higher level. Interestingly, both the 'conditioned' groups incurred substantially less PTS than the control group exposed only to the higher level.
Department of Communicative Disorders and Sciences, State University of New York, Buffalo 14214.
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D
Henderson
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M
Subramaniam
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M
Papazian
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VP
Spongr
D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D002682:Chinchilla; D003051:Cochlea / Q000473:pathology; D004432:Ear, Middle / Q000502:physiology* / Q000601:surgery; D018072:Hair Cells, Auditory, Outer / Q000473:pathology; D006317:Hearing Loss, Noise-Induced / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D009132:Muscles / Q000502:physiology* / Q000601:surgery; D013997:Time Factors