Cochlear models used in cochlear implant research

Over the past few decades, cochlear implants have undergone significant changes due to intensive research through experimental and computational analysis. However, obtaining an accurate and reliable cochlear model remains an open issue. Invasive measurements on the human ear are hardly possible, and the only alternative is animal models, but even this is not an ideal option, as animal cochleae are anatomically significantly different from the human cochleae. In this context, an ear model based on the latest knowledge of the physiology and molecular principles of hearing will allow the study of hearing disorders, whether they are caused by some genetic or external factors. It will also enable the experts to learn more about the detailed mechanisms of various forms of hearing impairment and open up avenues for the improvement of cochlear implants. With this in mind, the aim of this article is to explore different approaches to creating models of the human cochlea used in cochlear implant research. In the process of the study an individual emphasis is made on the variability of the human cochlea, sizes of its separate elements and shapes. Also considered are herein such methods of cochlea model creation as 3D-modeling, computer graphics and finite element method, as well as computational approaches. The results obtained allow us to state the fact that there are no ideal approaches and techniques to date available. The limitations of the models are related to difficulties in reproducing the microenvironment of the human cochlear apparatus, the need for clear validation and accurate parameterization of the main parameters of the cochlea. At the same time, we can expect that with a rapid increase in the available computational resources and development of effective computational methods, the models of the cochlea and cochlear implant will become more accurate and allow analyzing the cochlear micromechanics and the temporal response of the tissue to external stimulation.