Model examines electrodynamics of cochlear implants

Cochlear implants, which work by electrically stimulating the auditory nerve in the brain, can help people with moderate to profound hearing loss regain the sense. The physics of why cochlear implants work, however, is not fully understood. Hauser and Verhey modified an algorithm to accurately simulate how the electric field around a cochlear implant evolves over time.

The study shows how electromagnetic parameters like phase duration, interphase gap, and pulse shape affect perceptions like loudness in a cochlear implant. The team replicated a little understood phenomenon with cochlear implants to reduce undesired facial nerve stimulation, which leads to painful muscle spasms, by using triphasic instead of biphasic pulses.

“This study is the first time a fully dynamical simulation of the electrical stimulation of an entire stimulation pulse has been done,” author Andreas Hauser said. “It shows the relation between percept and energy absorption by tissue. We also theoretically describe how hearing percepts can change depending on the stimulation of structural parts, like the facial nerve and bone tissue, and on a variety of pulse shape parameters.”

To simulate the electrodynamics of the cochlear nerve, the team used two models: a lattice-Boltzmann model to decrease computation times, and a composite of Debye relaxation models to take into account the highly dispersive nature of biological tissue. They then evaluated the polarization calculated in nerve tissue to draw a relation between hearing perception and various stimulus parameters.

The authors plan to verify their results using clinical data.

Source: “Simulation of cochlea implant stimulation considering dispersive properties of the environment,” by Andreas Hauser and Jesko Lars Verhey , Journal of Applied Physics (2021). The article can be accessed at https://doi.org/10.1063/5.0085776 .