Stiffness properties of the reticular lamina and the tectorial membrane as measured in the gerbil cochlea

Driving point stiffnesses of the reticular lamina with its Supporting structures and the tectorial membrane (TM) were determined with a piezoelectric sensor. Measurements were made at several radial positions and at four locations along the cochlea from base to apex. Furthermore, using a stiff probe, static images of the stepwise indentation of the reticular lamina (RL) were captured to monitor relative displacements of structures within the organ of Corti. Stiffness values at the RL approximately matched the stiffness values of the TM for each of the locations along the length of the cochlea. Reticular lamina moved like a rigid lever with its pivot point at the pillar cells' heads. Moreover, reticular lamina displacement was slightly greater than outer hair cell (OHC) or Deiters' cell cups displacement. While basilar membrane displecements were below the detection threshold of the system, the lower two thirds of the Deiters cells were compressed the most.