The auditory nerve implant-concept and device description of a novel electrical auditory prosthesis

The cochlear implant (CI) is considered one of the most successful neural prostheses, enabling deaf individuals to achieve intelligible speech perception. However, CI performance remains limited in noise and with complex acoustic scenes, including music and multi-talker speech. One major issue for CIs is the poor electrode-neural interface where electrodes are positioned within the bony cochlea and distant from the auditory nerve fibers. Due to recent advances with microelectrode technologies designed for peripheral nerves, there has been rekindled interest in the auditory nerve implant (ANI), in which a novel prosthesis with a microelectrode array has been developed for direct stimulation of the auditory nerve. Animal studies demonstrate that the ANI achieves substantially lower thresholds and more selective neural activation compared to CI stimulation, which could lead to greater hearing performance. To successfully translate the ANI to patients, the ANI device components need to be further designed for safe and reliable implantation in humans through development of alternative surgical techniques, and validated in chronic animal studies. New stimulation strategies also need to be developed, especially with the potential to insert tens to hundreds of microelectrodes across the spiraling tonotopy of the auditory nerve to activate more spatially and temporally distinct nerve fiber patterns than is possible with the CI. Once in humans, extensive perceptual experiments can be performed with the ANI to characterize thresholds, loudness growth functions, pitch patterns, temporal coding properties, and spectral selectivity, as well as evaluating novel stimulation strategies that will guide the development of the next generation ANI system.