Daniel Kipping1,2, Waldo Nogueira1,2
1 Department of Otolaryngology, Hannover Medical School (MHH), Hannover, Germany;Â 2 Cluster of Excellence Hearing4all, Germany
Background: Cochlear implant users with residual acoustic hearing in the implanted ear strongly benefit from combined electric-acoustic stimulation (EAS). However, EAS also introduces interferences between the two modalities that are not fully understood. The goal of this project is to provide a computational framework for the investigation of peripheral electric-acoustic interaction to allow for deeper insights into the underlying physiological mechanisms.
Methods: A computational model of a single auditory nerve fiber (ANF) excited by EAS was developed to study the interaction between electric and acoustic stimulation. Technically, two existing models of sole electric or acoustic stimulation were coupled to simulate responses to combined EAS. The model of acoustic stimulation is a phenomenological model of the auditory periphery (Bruce et al., 2018). The model of electric stimulation simulates direct electroneural stimulation of the ANF (Joshi et al., 2017). Different coupling methodologies between both models were investigated.
Results: The model was validated with single-ANF recordings from animal experiments. Simulated measures included threshold and dynamic range, spike rate, latency, jitter, and vector strength. The model reproduces the reported spike statistics including effects such as the lowering of electrical thresholds and dynamic ranges in deaf ANFs, or the reduction of phase locking by a second stimulus of the other modality. The refractoriness of the model leads to an inhibitory interaction between electrically and acoustically evoked spiking in accordance with published data.
Conclusion: We presented a model of an ANF responding to EAS that largely reproduces animal data. The presented model forms a basis for future investigations of EAS interaction.
 Acknowledgements
This work was supported by the DFG Cluster of Excellence EXC 2177/1 Hearing4all and funded by the German Research Foundation (DFG) – Project number: 396932747 (PI: Waldo Nogueira)
The model consists of a phenomenological model of acoustic stimulation (Bruce et al., 2018, green) and an integrate-and-fire model of electric stimulation (Joshi et al., 2017, orange). The model output are simulated spike times. Different coupling methods between both models were investigated (red).