Dual contribution to amplification in the mammalian inner ear.
The inner ear achieves a wide dynamic range of responsiveness by mechanically amplifying weak sounds. The enormous mechanical gain reported for the mammalian cochlea, which exceeds a factor of 4000, poses a challenge for theory. Here we show how such a large gain can result from an interaction between amplification by low-gain hair bundles and a pressure wave: hair bundles can amplify both their displacement per locally applied pressure and the pressure wave itself. A recently proposed ratchet mechanism, in which hair-bundle forces do not feed back on the pressure wave, delineates the two effects. Our analytical calculations with a WKB approximation agree with numerical solutions.
Reichenbach
Tobias
T
Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, 1230 York Avenue, New York, New York 10065-6399, USA.
Hudspeth
A J
AJ
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D003051:Cochlea / Q000166:cytology / Q000502:physiology; D007758:Ear, Inner / Q000166:cytology / Q000502:physiology*; D006199:Hair Cells, Auditory, Inner / Q000166:cytology / Q000378:metabolism; D008322:Mammals / Q000502:physiology*; D008954:Models, Biological; D009068:Movement; D011312:Pressure