Two Operating Modes for Outer Hair Cells and Implications for Cochlear Tuning

The role of cochlear outer hair cells (OHCs) in mammal hearing is compromised by the 'RC time constant problem'. The issue arises because if the cells are to operate at high acoustic frequencies conventional voltage driven 'electromotility' is low pass filtered by the cell membrane. By synthesising a description of the OHC as a piezoelectric actuator and its position between resonant basilar and tectorial membranes it is shown that sharp tuning can arise at high frequency if prestin/SLC26A5 is dynamically tensioned. The model predicts an imaginary (dissipative) component to the OHC capacitance as well as two distinct frequency tuning curve (ftc) shapes: a near symmetrical ftc at low CF, and a low frequency 'tail' on the more sharply tuned high CF ftcs