This thesis combines computational modelling with cadaveric and clinical data to deepen our understanding of cochlear implants (CIs). For the past two or three decades, improvements in CI performance have been limited due to gaps in our understanding of how CI interacts with auditory nerves. Persistent questions, such as the unexplained polarity effect and the impact of CI-modiolus distance, have remained unclear. This research aims to improve our knowledge of CI principles. It introduces a hypothesis, based on precise computational models, that explains these unclear phenomena, suggesting the internal auditory meatus (IAM) as a key factor in neural activations by CI. This work also involves validating these computational models through physical experiments on cochleae and CIs. It compares clinical measurements from patients and from simulations like extra-cochlear electrodes and scalp voltages. Additionally, it proposes a proof-of-concept in-vitro cell culture model based on these simulations.

In detail, Chapter 2 focuses on validating these models against human temporal bone specimens for evaluating the accuracy of computational methods. Chapter 3 develops a comprehensive head model that sheds light on how CIs affect neural pathways and electric field intensities, with a special focus on the IAM. This leads to the proposed hypothesis. Chapter 4 explores clinical applications, studying extra-cochlear electrodes and simulating CI-induced scalp voltages, supported by cadaveric and clinical data. Chapter 5 introduces a novel in-vitro model for studying responses of spiral ganglion neurons (SGNs) to CIs. Overall, this thesis aims to advance our understanding of CI principles and opens up new possibilities for research in the field of auditory prosthetics.