Half-Octave Shift in Mammalian Hearing Is an Epiphenomenon of the Cochlear Amplifier

Sripriya Ramamoorthy, Alfred L. Nuttall

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


The cochlear amplifier is a hypothesized positive feedback process responsible for our exquisite hearing sensitivity. Experimental evidence for or against the positive feedback hypothesis is still lacking. Here we apply linear control theory to determine the open-loop gain and the closed-loop sensitivity of the cochlear amplifier from available measurements of basilar membrane vibration in sensitive mammalian cochleae. We show that the frequency of peak closed-loop sensitivity is independent of the stimulus level and close to the characteristic frequency. This implies that the half-octave shift in mammalian hearing is an epiphenomenon of the cochlear amplifier. The open-loop gain is consistent with positive feedback and suggests that the high-frequency cut-off of the outer hair cell transmembrane potential in vivo may be necessary for cochlear amplification.

Original languageEnglish (US)
Article numbere45640
JournalPloS one
Issue number9
StatePublished - Sep 25 2012

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences
  • General


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