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Computational models provide critical insights into the mechanisms underlying electric–acoustic stimulation (EAS) of the auditory system. We present a substantially updated human cochlear model that now incorporates a detailed, population-based full-head representation, including the outer, middle, and inner ear as well as the brain. This extended model enables simulation of both intra- and extra-cochlear electrical stimulation alongside acoustic input.

Finite element method (FEM) simulations were performed under monopolar stimulation modes for intra- and non-invasive extra-cochlear electrodes. A novel computational framework was developed to predict acoustically and electrically evoked compound action potentials (aCAPs, eCAPs) and electrocochleography (ECochG), focusing on interactions at the hair cell and auditory nerve level during combined EAS. Key validation measures include transimpedance matrices (TIMs), voltage and current distributions, hair cell and neural activity, and resulting ECochG, eCAP and aCAP waveforms.

The model accurately reproduced TIMs and excitation spread patterns consistent with published human data and revealed distinct current pathways for intra- versus extra-cochlear stimulation. Simulated ECochG components (cochlear microphonics, auditory nerve neurophonics) and CAP morphology closely matched human recordings.

This full-head model offers a powerful tool for investigating electric–acoustic interactions as a novel diagnostic tool of low frequeny hearing.

Acknowledgements: These results is part of the project that received funding from the European Research Council (ERC) under the European Union's Horizon-ERC programme (Grant agreement READIHEAR No. 101044753, https://www.sciencedirect.com/science/article/pii/S0378595524001412#gs00001. PI: Waldo Nogueira).

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