Cochlear Outer-Hair-Cell Power Generation and Viscous Fluid Loss

Area of Science:

• Auditory Neuroscience
• Bioacoustics
• Mechanobiology

Background:

• The role of outer hair cells (OHCs) in cochlear mechanical power generation remains debated.
• Understanding cochlear mechanics is crucial for diagnosing and treating hearing loss.

Purpose of the Study:

• To directly calculate the power generated by OHCs and lost to fluid viscosity in the cochlea.
• To quantify the cochlear mechanical power output in response to varying sound pressure levels (SPL).

Main Methods:

• A 3D computational model of the mouse cochlea was developed, incorporating organ of Corti cytoarchitecture.
• The model was validated against in vivo basilar membrane motion data.
• Power loss due to viscosity and OHC power generation were directly calculated.

Main Results:

• OHC power output can exceed acoustic input power by over three orders of magnitude at 10 dB SPL.
• OHC power output increases with SPL and saturates at higher levels.
• Total OHC power output reaches approximately 2 pW at 80 dB SPL, with individual OHCs generating up to 10 fW.

Conclusions:

• The cochlea actively generates substantial mechanical power, primarily through OHC activity.
• OHC power generation is intensity-dependent, increasing and then saturating with SPL.
• These findings resolve the controversy regarding cochlear power production and highlight the OHCs' critical role.