Using new techniques to visualize and measure sound-induced vibration deep inside the moving organ of Corti, we found that two functionally crucial structures, the basilar membrane and the reticular lamina, have different centers of rotation, leading to shearing motion and rapid deformation for the mechano-receptive outer hair cells. Structural relations within the hearing organ are much more dynamic than previously thought.

Sound-evoked movement of an outer hair cell inside the intact guinea pig hearing organ. Note the small sideways motion of the stereocilia bundle at the top. This small motion makes it possible to hear!