title: Selective Inner Hair Cell Dysfunction in Chinchillas Impairs Hearing-in-Noise in the Absence of Outer Hair Cell Loss.
abstract: Poorer hearing in the presence of background noise is a significant problem for the hearing impaired. Ototoxic drugs, ageing, and noise exposure can damage the sensory hair cells of the inner ear that are essential for normal hearing sensitivity. The relationship between outer hair cell (OHC) loss and progressively poorer hearing sensitivity in quiet or in competing background noise is supported by a number of human and animal studies. In contrast, the effect of moderate inner hair cell (IHC) loss or dysfunction shows almost no impact on behavioral measures of hearing sensitivity in quiet, when OHCs remain intact, but the relationship between selective IHC loss and hearing in noise remains relatively unknown. Here, a moderately high dose of carboplatin (75 mg/kg) that produced IHC loss in chinchillas ranging from 40 to 80 % had little effect on thresholds in quiet. However, when tested in the presence of competing broadband (BBN) or narrowband noise (NBN), thresholds increased significantly. IHC loss >60 % increased signal-to-noise ratios (SNRs) for tones (500-11,300 Hz) in competing BBN by 5-10 dB and broadened the masking function under NBN. These data suggest that IHC loss or dysfunction may play a significant role in listening in noise independent of OHC integrity and that these deficits may be present even when thresholds in quiet are within normal limits.
authors.affiliation: School of Behavioral and Brain Sciences, University of Texas at Dallas, Callier Center, 1966 Inwood Road, Dallas, TX, 75235, USA. Edward.Lobarinas@utdallas.edu.
authors.forename: Edward
authors.initials: E
authors.lastname: Lobarinas
authors.affiliation: Center for Hearing and Deafness, State University of New York at Buffalo, Buffalo, NY, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Salvi
authors.affiliation: Center for Hearing and Deafness, State University of New York at Buffalo, Buffalo, NY, USA.
authors.forename: Dalian
authors.initials: D
authors.lastname: Ding
mesh_terms: D000818:Animals; D001309:Auditory Threshold; D016190:Carboplatin / Q000633:toxicity; D002682:Chinchilla; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects / Q000502:physiology*; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D006317:Hearing Loss, Noise-Induced / Q000209:etiology*; D008297:Male; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D005680:gamma-Aminobutyric Acid; D016190:Carboplatin
keywords: carboplatin; chinchilla; hearing in noise; inner hair cell loss; masking