The two functions of the reticular lamina

The cell body of the outer hair cells connects the reticular lamina and the basilar membrane through supporting cells. According to the predominant view of cochlear mechanics, the outer hair cells enhance wave propagation in the scala media by dynamically expanding and contracting their body, thus providing an active driving force to the basilar membrane. In order to maximize the efficiency of such mechanism, the reticular lamina should behave like a rigid anchor; in this way the force associated with the length change of the outer hair cells body is efficiently transmitted to the basilar membrane. On the other hand, the motion of the reticular lamina provides a direct drive to the inner-hair cells through a fluid-cilia coupling mechanism. Therefore a free-to-move reticular lamina would be highly responsive to the activity of outer hair cells, thus locally enhancing the sensitivity of inner hair cells. Within this view, the reticular lamina should trade-off between the two conflicting requirements of 1) providing a firm attachment to the outer hair cells and 2) being sensitive to outer hair cells motility. A different thesis, partially supported by recent recordings of the intact organ of Corti, is that a longitudinal coupling of motion in the scala media (similar as in feed-forward cochlear models) allows for a simultaneous enhancement of basilar membrane and stereocilia vibrations without imposing contradicting requirements for the functioning of the reticular lamina. In this study, we discuss the recent experimental and theoretical findings under this perspective.