Gapless man: machine interface in the inner ear

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Over 5% of the world population, 360 Million people, suffer from disabling hearing loss. In severe forms, the auditory function can be restored by a neuroprostheses called a cochlear implant (CI), which functionally replaces lost inner ear sensory cells by directly stimulating the auditory nerve fibers. Despite the success of these devices, some limitations remain, including suboptimal auditory resolution and high energy consumption, which are mainly due to the anatomical gap between the implanted electrode array in the cochlea and the auditory neurons nearby. Within a recently completed, multinational EU FP7 project coordinated by the main applicant (www.nanoci.org), proof of principle for overcoming the anatomical gap by guided growth of auditory nerve fibers towards the electrode array has been obtained in vivo. In addition, in vitro experiments have shown a potential reduction of the stimulus energy by a factor of 5, if the distance of the auditory neurons from the electrode was eliminated. Within the proposed project, we intend to improve the gapless interface through optimized growth factor guidance in combination with chronic electrical stimulation and detailed morphological, biochemical and electrophysiological characterization of regrown auditory neurons in vitro and in vivo. Native and stem cell generated, donated human auditory neurons will be used in vitro for validation. The ultimate goal of the proposed project is to assess the potential of the gapless interface between auditory neurons and the cochlear implant electrodes through chronic electrical stimulation in vivo. If successful, the proposed project may lead to more energy efficient cochlear implant systems with higher auditory resolution and improved sound quality.