Spontaneous otoacoustic emissions in tecta y1870c/+ mice reflect changes in cochlear amplification and how it is controlled by the tectorial membrane

Mary Ann Cheatham*, Yingjie Zhou, Richard J. Goodyear, Peter Dallos, Guy P. Richardson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Spontaneous otoacoustic emissions (SOAEs) recorded from the ear canal in the absence of sound reflect cochlear amplification, an outer hair cell (OHC) process required for the extraordinary sensitivity and frequency selectivity of mammalian hearing. Although wild-type mice rarely emit, those with mutations that influence the tectorial membrane (TM) show an incidence of SOAEs similar to that in humans. In this report, we characterized mice with a missense mutation in Tecta, a gene required for the formation of the striated-sheet matrix within the core of the TM. Mice heterozygous for the Y1870C mutation (Tecta Y1870C/+ ) are prolific emitters, despite a moderate hearing loss. Additionally, Kimura’s membrane, into which the OHC stereocilia insert, separates from the main body of the TM, except at apical cochlear locations. Multimodal SOAEs are also observed in Tecta Y1870C/+ mice where energy is present at frequencies that are integer multiples of a lower-frequency SOAE (the primary). Second-harmonic SOAEs, at twice the frequency of a lower-frequency primary, are the most frequently observed. These secondary SOAEs are found in spatial regions where stimulus-evoked OAEs are small or in the noise floor. Introduction of high-level suppressors just above the primary SOAE frequency reduce or eliminate both primary and second-harmonic SOAEs. In contrast, second-harmonic SOAEs are not affected by suppressors, either above or below the second-harmonic SOAE frequency, even when they are much larger in amplitude. Hence, second-harmonic SOAEs do not appear to be spatially separated from their primaries, a finding that has implications for cochlear mechanics and the consequences of changes to TM structure.

Original languageEnglish (US)
Article numbere0314
JournaleNeuro
Volume5
Issue number6
DOIs
StatePublished - Nov 1 2018

Keywords

  • Cochlear amplifier
  • Harmonic distortion
  • Outer hair cells
  • Spontaneous otoacoustic emissions
  • Tectorial membrane

ASJC Scopus subject areas

  • Neuroscience(all)

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