Transient abnormalities in masking tuning curve in early progressive hearing loss mouse model
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Universidade Federal de Minas Gerais
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Artigo de periódico
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Resumo
Damage to cochlear outer hair cells (OHCs) usually affects frequency selectivity in proportion to hearing threshold increase.
However, the current clinical heuristics that attributes poor hearing performance despite near-normal auditory sensitivity to
auditory neuropathy or “hidden” synaptopathy overlooks possible underlying OHC impairment. Here, we document the part
played by OHCs in influencing suprathreshold auditory performance in the presence of noise in a mouse model of progressive hair
cell degeneration, the CD1 strain, at postnatal day 18–30 stages when high-frequency auditory thresholds remained near-normal.
Nonetheless, total loss of high-frequency distortion product otoacoustic emissions pointed to nonfunctioning basal OHCs. This
“discordant profile” came with a huge low-frequency shift of masking tuning curves that plot the level of interfering sound necessary
to mask the response to a probe tone, against interfering frequency. Histology revealed intense OHC hair bundle abnormalities in
the basal cochlea uncharacteristically associated with OHC survival and preserved coupling with the tectorial membrane. This
pattern dismisses the superficial diagnosis of “hidden” neuropathy while underpinning a disorganization of cochlear frequency
mapping with optimistic high-frequency auditory thresholds perhaps because responses to high frequencies are apically shifted.
The audiometric advantage of frequency transposition is offset by enhanced masking by low-frequency sounds, a finding essential
for guiding rehabilitation.
Abstract
Assunto
Perda Auditiva Condutiva-Neurossensorial Mista, Células Ciliadas Auditivas Externas
Palavras-chave
Sensorineural hearing losses, Cochlear outer hair cells
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Endereço externo
https://www.hindawi.com/journals/bmri/2018/6280969/