title: Localization of the cochlear amplifier in living sensitive ears.
abstract: BACKGROUND
  To detect soft sounds, the mammalian cochlea increases its sensitivity by amplifying incoming sounds up to one thousand times. Although the cochlear amplifier is thought to be a local cellular process at an area basal to the response peak on the spiral basilar membrane, its location has not been demonstrated experimentally.
  
  
  RESULTS
  Using a sensitive laser interferometer to measure sub-nanometer vibrations at two locations along the basilar membrane in sensitive gerbil cochleae, here we show that the cochlea can boost soft sound-induced vibrations as much as 50 dB/mm at an area proximal to the response peak on the basilar membrane. The observed amplification works maximally at low sound levels and at frequencies immediately below the peak-response frequency of the measured apical location. The amplification decreases more than 65 dB/mm as sound levels increases.
  
  
  CONCLUSIONS
  We conclude that the cochlea amplifier resides at a small longitudinal region basal to the response peak in the sensitive cochlea. These data provides critical information for advancing our knowledge on cochlear mechanisms responsible for the remarkable hearing sensitivity, frequency selectivity and dynamic range.
authors.affiliation: Oregon Hearing Research Center, Department of Otolaryngology and Head & Neck Surgery, Oregon Health & Science University, Portland, Oregon, United States of America. rent@ohsu.edu
authors.forename: Tianying
authors.initials: T
authors.lastname: Ren
authors.forename: Wenxuan
authors.initials: W
authors.lastname: He
authors.forename: Edward
authors.initials: E
authors.lastname: Porsov
mesh_terms: D000818:Animals; D001489:Basilar Membrane / Q000502:physiology; D003051:Cochlea / Q000503:physiopathology*; D005849:Gerbillinae; D006309:Hearing / Q000502:physiology*; D014732:Vibration