Timing of the reticular lamina and basilar membrane vibration in living gerbil cochleae

• Main Authors: Wenxuan He, David Kemp, Tianying Ren
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2018-09-01
• Series: eLife
• Subjects: cochlea; cochlear amplifier; outer hair cells; low-coherence interferometer; reticular lamina; basilar membrane
• Online Access: https://elifesciences.org/articles/37625

Auditory sensory outer hair cells are thought to amplify sound-induced basilar membrane vibration through a feedback mechanism to enhance hearing sensitivity. For optimal amplification, the outer hair cell-generated force must act on the basilar membrane at an appropriate time at every cycle. However, the temporal relationship between the outer hair cell-driven reticular lamina vibration and the basilar membrane vibration remains unclear. By measuring sub-nanometer vibrations directly from outer hair cells using a custom-built heterodyne low-coherence interferometer, we demonstrate in living gerbil cochleae that the reticular lamina vibration occurs after, not before, the basilar membrane vibration. Both tone- and click-induced responses indicate that the reticular lamina and basilar membrane vibrate in opposite directions at the cochlear base and they oscillate in phase near the best-frequency location. Our results suggest that outer hair cells enhance hearing sensitivity through a global hydromechanical mechanism, rather than through a local mechanical feedback as commonly supposed.