Modeling potential distributions inside the cochlea caused by electrical stimulation

During the last decades the average speech intelligibility of cochlear-implant (CI) users has steadily been improved. Nevertheless, problems still occur especially in complex listening situations. One reason for that is the inaccurate signal transmission between CI electrodes and stimulated nerve cells. To develop new methods overcoming this problem, models are required that provide insight into the processes of electrical stimulation inside the complex geometry of the cochlea. This paper presents a detailed model of the electrically stimulated cochlea. The model consists of a virtual three-dimensional representation of the most important structures of the human cochlea. It serves as a basis for the volume conductor model, which was developed using finite element method. It allows for computation of the electrical potentials inside the modeled structures caused by current applied to the CI electrodes. The presented model was used to compare current spread for different electrode positions and configurations. The results show that the model can represent characteristic differences in spatial selectivity and hence be a help in realizing spatially more focused electrical stimulation.