Finite-element model of the active organ of Corti

Abstract

The cochlear amplifier that provides our hearing with its extraordinary sensitivity and selectivity is thought to be the result of an active biomechanical process within the sensory auditory organ, the organ of Corti. Although imaging techniques are developing rapidly, it is not currently possible, in a fully active cochlea, to obtain detailed measurements of the motion of individual elements within a cross section of the organ of Corti. This motion is predicted using a two-dimensional finite-element model. The various solid components are modelled using elastic elements, the outer hair cells (OHCs) as piezoelectric elements and the perilymph and endolymph as viscous and nearly incompressible fluid elements. The model is validated by comparison with existing measurements of the motions within the passive organ of Corti, calculated when it is driven either acoustically, by the fluid pressure or electrically, by excitation of the OHCs. The transverse basilar membrane (BM) motion and the shearing motion between the tectorial membrane and the reticular lamina are calculated for these two excitation modes. The fully active response of the BM to acoustic excitation is predicted using a linear superposition of the calculated responses and an assumed frequency response for the OHC feedback.

Finite element modelling of cochlear electrical coupling

“…The first and second rows of OHCs move in-phase with both acoustical and electrical excitations, as shown in Figs. 4 and 8 of Ni et al (2016) and also observed by Karavitaki and Mountain (2007) in the excised cochlea with electrical stimuli. The third row moves not strictly in-phase with the other two rows when excited electrically, due to greater influence from the Hensen cells, as shown in Fig.…”

“…The third row moves not strictly in-phase with the other two rows when excited electrically, due to greater influence from the Hensen cells, as shown in Fig. 4 of Ni et al (2016) and Fig. 12 of Karavitaki and Mountain (2007).…”

“…12 of Karavitaki and Mountain (2007). Figure 4 of Ni et al (2016) suggests that the phase variation is for combined mechanical and electrical stimulation is almost undetectable for frequencies below 1 kHz, but the variation between OHC row 1 and row 3 rises to about 15 at 5 kHz. The results for the 19 and 24 mm slices are qualitatively similar to those for the 12 mm slice.…”

“…The great advantage of finite element methods (FEMs) over many other modelling techniques is that they are capable of modelling structures of high complexity, such as the cochlea. This ability has, for example, permitted accurate modelling of cochlear micro-mechanics (Ni et al, 2016). Electrical FEMs have been used to study the behaviour of cochlear implants (Briaire and Frijns, 2000;Choi and Wang, 2014;Saba, 2012;Sue et al, 2013;Tran et al, 2011;Tran et al, 2013).…”

Description of Cochlear Morphology and Hair Cell Variation in the Beluga Whale

“…Thus, having information on hair cell morphometrics is necessary for understanding how morphology relates to hearing function specific to each species. Mechanics of the organ of Corti are relatively well described (Chen et al 2011;Liu et al 2015;Soons et al 2015;Lee et al 2016;Ni et al 2016). However, if the morphometrics of the reticular lamina are consistent among species, this may have some biomechanical implications.…”