What is it about?
The paper shows how piezoelectric-like outer hair cells (OHCs) amplify cochlear mechanical responses to sound thereby making mammalian hearing more sensitive. Recent measurements of nanometer vibrational motions in response to sound show that OHC motions are at the wrong phase too produce cochlear amplification by the classic mechanism of forces acting on the basilar membrane (BM). The largest sound-evoked motions within the cochlea are at the Reticular Lamina (RL) and this RL motion acts to increase the amplitude of the fluid traveling wave, which, in turn, increases BM motion as the traveling wave moves apically.
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Why is it important?
This paper describes a major advance in understanding how the cochlea works. Such understanding is important for basic science and for clinical uses, e.g., for understanding the results of clinical tests and deciding on interventions. Also, for the goal of cochlear regeneration, understanding the role of each cell type is essential.
Perspectives
Since the early 1990’s we have known the basic properties of many elements of the cochlea: that OHCs have somatic motility controlled by current flowing through OHC-stereocilia mechano-electric-transduction channels, and that BM mechanical responses to sound are amplified. However, until a few years ago, the only motion measurements in healthy cochleae were of the BM. With this BM-centric orientation, cochlear amplification was thought to be by OHCs pushing/pulling on the BM at the right phase to increase BM motion. New measurements using optical coherent tomography (OCT) have shown that structures above the BM move much more than the BM and that OHC motion is not at the right phase to directly amplify BM motion. The mechanism proposed by this paper is that OHCs amplify RL motion, which increases the fluid traveling wave, and the increased fluid traveling wave then increases BM motion. This new mechanism for cochlear amplification fits the data and shows how the various elements of the cochlea work together to produce BM amplification.
John Guinan
Mass Eye & Ear; Harvard Medical School
Read the Original
This page is a summary of: Outer hair cells can amplify the fluid traveling wave by changing organ-of-Corti area in the short-wave region, January 2024, American Institute of Physics,
DOI: 10.1063/5.0189698.
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