Contralateral-noise effects on cochlear responses in anesthetized mice are dominated by feedback from an unknown pathway

Stéphane F. Maison, Hajime Usubuchi, Douglas E. Vetter, A. Bélen Elgoyhen, Steven A. Thomas, M. Charles Liberman

Research output: Contribution to journalArticle

Abstract

Suppression of ipsilateral distortion product otoacoustic emissions (DPOAEs) by contralateral noise is used in humans and animals to assay the strength of soundevoked negative feedback from the medial olivocochlear (MOC) efferent pathway. However, depending on species and anesthesia, contributions of other feedback systems to the middle or inner ear can cloud the interpretation. Here, contributions of MOC and middle-ear muscle reflexes, as well as autonomic feedback, to contra-noise suppression in anesthetized mice are dissected by selectively eliminating each pathway by surgical transection, pharmacological blockade, or targeted gene deletion. When ipsilateral DPOAEs were evoked by low-level primaries, contra-noise suppression was typically ~1 dB with contra-noise levels around 95 dB SPL, and it always disappeared upon contralateral cochlear destruction. Lack of middle-ear muscle contribution was suggested by persistence of contra-noise suppression after paralysis with curare, tensor tympani cauterization, or section of the facial nerve. Contribution of cochlear sympathetics was ruled out by studying mutant mice lacking adrenergic signaling (dopamine β-hydroxylase knockouts). Surprisingly, contra-noise effects on lowlevel DPOAEs were also not diminished by eliminating the MOC system pharmacologically (strychnine), surgically, or by deletion of relevant cholinergic receptors (α9/α10). In contrast, when ipsilateral DPOAEs were evoked by high-level primaries, the contra-noise suppression, although comparable in magnitude, was largely eliminated by MOC blockade or section. Possible alternate pathways are discussed for the source of contra-noise-evoked effects at low ipsilateral levels.

Original languageEnglish (US)
Pages (from-to)491-500
Number of pages10
JournalJournal of Neurophysiology
Volume108
Issue number2
DOIs
StatePublished - Jul 15 2012
Externally publishedYes

Keywords

  • Efferent
  • Inner ear
  • Middle-ear muscles
  • Sympathetic nervous system

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)

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    Maison, S. F., Usubuchi, H., Vetter, D. E., Bélen Elgoyhen, A., Thomas, S. A., & Charles Liberman, M. (2012). Contralateral-noise effects on cochlear responses in anesthetized mice are dominated by feedback from an unknown pathway. Journal of Neurophysiology, 108(2), 491-500. https://doi.org/10.1152/jn.01050.2011