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Reverse transduction measured in the isolated cochlea by laser Michelson interferometry
1Department of Physiology, School of Medical Sciences, University Walk, Bristol, UK.
Nature
|October 28, 1993
Summary
Mammalian hearing sensitivity relies on outer hair cells amplifying sound in the cochlea. This study provides direct evidence that outer hair cell length changes mechanically amplify basilar membrane vibrations, confirming their role in hearing.
Area of Science:
- Auditory Neuroscience
- Cellular Biophysics
Background:
- Mammalian hearing sensitivity is linked to sound amplification within the cochlea.
- Outer hair cells (OHCs) are hypothesized to enhance basilar membrane motion by reducing damping.
- OHCs exhibit membrane-potential-induced length changes at acoustic rates, a process called 'reverse transduction'.
Purpose of the Study:
- To investigate the mechanical feedback mechanism of outer hair cells in cochlear amplification.
- To determine if OHC length changes generate forces sufficient to move the basilar membrane.
Main Methods:
- Utilized a displacement-sensitive interferometer to measure cochlear partition motion.
- Stimulated OHCs with electrical current across the partition in an isolated cochlea.
Main Results:
- Electrically driven OHC length changes caused measurable distortion of the cochlear partition.
- Produced place-specific basilar membrane vibrations of approximately 1 nm, similar to auditory threshold levels.
Conclusions:
- Demonstrated that outer hair cell activity directly drives mechanical vibrations of the basilar membrane.
- Provided direct evidence that the outer hair cell population is the source of cochlear amplification.