Differentiation of cochlear pathophysiology in ears damaged by salicylate or a pure tone using a nonlinear systems identification technique.
Mongolian gerbils were exposed to either alpha-ketoglutarate, salicylate, or an 8-kHz pure tone. Cochlear microphonic (CM) was recorded from the round window in response to 68 and 88 dB SPL Gaussian noise. A nonlinear systems identification technique provided the frequency-domain parameters of a third-order polynomial model characterizing cochlear mechano-electric transduction (MET). A series of physiologic indices were derived from further exploration of the model. Exposure to the 8-kHz pure tone and round window application of salicylate resulted in different changes in the polynomial parameters and physiologic indices even though the threshold shifts were similar. A general reduction of CM magnitude was found after the tone exposure, and an increase at low-mid frequencies was demonstrated in the salicylate group especially at the lower signal level. The slope of the MET curve was reduced by the acoustic overstimulation. The root or the operating point of the MET was shifted in opposite directions after the two treatments. Sound-pressure levels that saturate MET expanded in the tone exposure group and narrowed in the salicylate group. The signal level also had effects on these indices.
Bian
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Hearing and Speech Department, University of Kansas Medical Center, Kansas City 66160, USA.
Chertoff
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ME
D000818:Animals; D001305:Auditory Fatigue / Q000187:drug effects / Q000502:physiology; D003051:Cochlea / Q000187:drug effects / Q000503:physiopathology*; D003055:Cochlear Microphonic Potentials / Q000187:drug effects / Q000502:physiology*; D005849:Gerbillinae; D006316:Hearing Loss, High-Frequency / Q000139:chemically induced / Q000503:physiopathology; D006317:Hearing Loss, Noise-Induced / Q000139:chemically induced / Q000503:physiopathology*; D007656:Ketoglutaric Acids / Q000494:pharmacology; D011837:Radiation-Protective Agents / Q000494:pharmacology; D012459:Salicylates / Q000633:toxicity*
D007656:Ketoglutaric Acids; D011837:Radiation-Protective Agents; D012459:Salicylates