Abstract
In all commercial cochlear implant (CI) devices, the electric stimulation is performed with a rectangular pulse that generally has two phases of opposite polarity. To date, developing new stimulation strategies has relied on the efficacy of this shape. Here, we investigate the potential of a novel stimulation paradigm that uses biophysically-inspired electrical ramped pulses. Using electrically-evoked auditory brainstem response (eABR) recordings in mice, we found that less charge, but higher current level amplitude, is needed to evoke responses with ramped shapes that are similar in amplitude to responses obtained with rectangular shapes. The most charge-efficient pulse shape had a rising ramp over both phases, supporting findings from previous in vitro studies. This was also true for longer phase durations. Our study presents the first physiological data on CI-stimulation with ramped pulse shapes. By reducing charge consumption ramped pulses have the potential to produce more battery-efficient CIs and may open new perspectives for designing other efficient neural implants in the future.
Highlights
In all commercial cochlear implant (CI) devices, the electric stimulation is performed with a rectangular pulse that generally has two phases of opposite polarity
Our study presents the first physiological data on CI-stimulation with ramped pulse shapes
The smaller evoked auditory brainstem response (eABR) amplitude observed with more basal electrode-stimulation is likely due to the slightly longer distance from the basal electrodes to the modulus relative to the apical electrodes, as was recently indicated in a x-ray image of a CI-implanted mouse cochlea[18]
Summary
In all commercial cochlear implant (CI) devices, the electric stimulation is performed with a rectangular pulse that generally has two phases of opposite polarity. CI users can perceive speech in quiet settings fairly well, they face challenges when it comes to more complex sound environments, such as understanding a friend speaking in a noisy restaurant or perception of music These limitations are in particular caused by the spread of current induced by each electrode and by the poor efficiency between the electrical pulse and auditory-nerve responses. In all commercial CI devices, the electrical pulse has a rectangular shape and usually consists of two phases of opposite polarity to ensure charge-balanced stimulation. This configuration renders them safe for long-term usage by CI users. With the standard rectangular pulse shape, the current level amplitude decreases with distance from the stimulated electrode and the rectangular shape is maintained
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