Hearing research
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The effects of chronic intracochlear electrical stimulation on the cochlear nucleus (CN) were studied in eight cats that were neonatally deafened by daily intramuscular injections of neomycin. Profound hearing loss was confirmed in each animal by auditory brainstem response (ABR) and frequency following response (500 Hz) testing. Five of the kittens were implanted unilaterally with a scala tympani electrode array at ages 8-16 weeks. ⋯ The CN in animals that received electrical stimulation showed significant bilateral degenerative changes in all three measured parameters. Total nuclear volume was reduced by 35-36%, spherical cell size was reduced by 20-26%, and spherical cell density decreased by 36-42%, as compared to the normal cat CN. Comparisons were also made in the stimulated animals between CN ipsilateral to the stimulated cochlea and the contralateral, unstimulated CN.(ABSTRACT TRUNCATED AT 250 WORDS)
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This paper describes the course and morphology of efferent fibres in an avian cochlea. Horseradish peroxidase stained efferent fibres in the pigeon papilla basilaris were identified by Nomarski optics and camera lucida drawings. ⋯ Small thin fibres contact short or intermediate hair cells over the free basilar membrane or tall hair cells over the neural limbus. A physiological consequence of the findings is that efferent activity will concomitantly lead to a contraction of hyaline cells and a hyperpolarization of hair cells.