Hearing research
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Ten newborn kittens were deafened by systemic administration of neomycin sulfate. Profound hearing losses were documented by ABR and FFR (500 Hz) testing. At 9-17 weeks of age, the young deafened cats were unilaterally implanted with a multichannel scala tympani electrode. ⋯ In more apical regions there was no significant difference between the stimulated and control cochleas. The mechanisms underlying this selective conservation of spiral ganglion neurons induced by chronic intracochlear electrical stimulation are uncertain. Since no comparable chronic stimulation studies have been conducted in adults, it is not known whether similar conservation effects could be induced in mature animals.
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Four newborn kittens were deafened by daily intramuscular injections of neomycin sulfate, beginning the day after birth and continuing for 14-16 days. At 10-16 weeks of age the deaf kittens were implanted unilaterally with a four wire intracochlear electrode array. The animals were stimulated daily (starting at 13-18 weeks of age), for a period of one hour, at 6 dB above the electrically evoked auditory brainstem response threshold. ⋯ These changes were observed in both cochlear nuclei (ipsilateral to both stimulated and unstimulated ears) of the deafened animals. With the measures employed, no significant difference was demonstrated in comparisons between the deafened/unstimulated and the deafened/stimulated cochlear nuclei. That is, no reversal of the profound effects of deafening was observed in the cochlear nuclei as a consequence of chronic intracochlear electrical stimulation which was begun 11 to 16 weeks after deafening.