Modelling Cochlear Micromechanics

The cochlea is an organ of the hearing system, whose basic function is to map sounds of different frequencies onto corresponding characteristic positions along the basilar membrane (BM). Sound-induced BM vibration is transformed into deflection of stereocilia on the hair cells, which then encodes the sound as neural signals for perception. Most cochlear models used to describe the BM vibration patterns or the pressure distributions along the cochlea are concerned with macromechanics, which often assumes the organ of Corti moves as a single unit and ignores individual motion of different components. New technologies provide the opportunity to measure the dynamic behaviour of different components within the organ of Corti. However, it is still difficult to measure every aspect of cochlear dynamics. The present work studies the behaviour of a radial slice of the cochlea at the microscopic level using finite element method. The individual motion of each component within the organ of Corti is calculated with static pressure loading on the BM and the motions of the experimentally accessible parts are compared with experiments. The elastic components are modelled with plate/beam element and perilymph and endolymph are modelled with fluid element. The reticular lamina moves as a stiff plate without much bending and is pivoting around a point close to the region of the inner hair cells and the basilar membrane shows an asymmetric mode shape with maximum displacement occurring between the second-row and the thirdrow of the outer hair cells, in agreement with experimental observations.