title: In vivo outer hair cell length changes expose the active process in the cochlea.
abstract: BACKGROUND
  Mammalian hearing is refined by amplification of the sound-evoked vibration of the cochlear partition. This amplification is at least partly due to forces produced by protein motors residing in the cylindrical body of the outer hair cell. To transmit power to the cochlear partition, it is required that the outer hair cells dynamically change their length, in addition to generating force. These length changes, which have not previously been measured in vivo, must be correctly timed with the acoustic stimulus to produce amplification.
  
  
  RESULTS
  Using in vivo optical coherence tomography, we demonstrate that outer hair cells in living guinea pigs have length changes with unexpected timing and magnitudes that depend on the stimulus level in the sensitive cochlea.
  
  
  CONCLUSIONS
  The level-dependent length change is a necessary condition for directly validating that power is expended by the active process presumed to underlie normal hearing.
authors.affiliation: Oregon Hearing Research Center, Oregon Health and Science University, Portland, Oregon, United States of America.
authors.forename: Dingjun
authors.initials: D
authors.lastname: Zha
authors.forename: Fangyi
authors.initials: F
authors.lastname: Chen
authors.forename: Sripriya
authors.initials: S
authors.lastname: Ramamoorthy
authors.forename: Anders
authors.initials: A
authors.lastname: Fridberger
authors.forename: Niloy
authors.initials: N
authors.lastname: Choudhury
authors.forename: Steven L
authors.initials: SL
authors.lastname: Jacques
authors.forename: Ruikang K
authors.initials: RK
authors.lastname: Wang
authors.forename: Alfred L
authors.initials: AL
authors.lastname: Nuttall
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D003051:Cochlea / Q000502:physiology*; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D006309:Hearing / Q000502:physiology*; D009925:Organ of Corti / Q000502:physiology; D041623:Tomography, Optical Coherence; D014732:Vibration