NSF-SNSF Next generation of auditory brain stem implants. a translational program

About This Grant

The auditory brainstem implant (ABI) is the only option to improving hearing for individuals who are deaf from a devastating genetic syndrome called Neurofibromatosis Type 2 (NF2). Patients with NF2 develop multiple brain tumors including vestibular schwannomas in both ears that damage the hearing nerves, and hearing aids and cochlear implants are rarely helpful. Although most ABI users can hear sounds that help with lipreading, only few can understand speech (unlike the majority of cochlear implant patients). The design of the ABI has not changed in 30 years and the electrode system is stiff and does not follow the curvature of the brain. In this NSF-SNSF research proposal and in collaboration with the École Polytechnique Fédérale de Lausanne (Geneva, Switzerland), the researchers will develop an exciting new soft ABI technology that overcomes the problems of the clinical device in both mice and non-human primate. The goals of this collaborative proposal will focus on advancing the technology for soft ABIs that will enable minimally invasive surgical insertion, accurate positioning over the cochlear nucleus (CN) and spatially selective modulation of central auditory pathways. The U.S. researchers will deploy the soft ABI in rodent and nonhuman primate (NHP) models to gain complementary knowledge in electrical modulation of the CN and pursue the translation of the soft neurotechnology. Aim 1 of this project is to develop novel soft auditory brainstem implant (ABI) electrode arrays. The goal is to increase the conformability of the surface electrode array on the brainstem and miniaturize the electrodes to improve neuromodulation performance. Mechanically compliant soft ABI electrode arrays based on thin-film technology will be manufactured and systematically tested to determine the stability and integrity of the electrode implants, aiming for year-long function in vivo. Aim 2 of the project will test the soft ABI array for durability and performance in a chronic mouse model before the soft ABI is eventually used in valuable NHP models and in first studies in humans beyond the scope of this project. Performance of the mice will be assessed by behavioral tests to determine sensitivity to amplitude modulation (AM) of the electrical pulse train. This metric is chosen because, in human patients who use the ABI, it correlates best with speech comprehension. Aim 3 will test soft ABI arrays in nonhuman primate (NHP). The Boston and Swiss team will jointly implant 3 NHPs at the Swiss Non-Human Primates Competence Center for Research (SPCCR). The electrode array design will be tested and optimized, in biomimetic models prior to NHP surgery. Following chronic NHP implantation, the research team will perform assays of implant durability, record maps of activation by sound sequences on the CN and auditory cortex, and compare these activation maps to silence. Cortical maps activated by selective stimulation on the CN with the soft ABI will be collected and compared to auditory only stimulation. The introduction of soft, microfabricated ABIs has the potential to profoundly transform the landscape of neuroprosthetic interventions to enhance auditory perception. With their refined design, these advanced implants can achieve targeted stimulation of specific neural clusters within the cochlear nucleus, the target of the ABI. This precision can result in improved quality of perceived sound, increased speech intelligibility and reduced side effects. The resultant improvements will greatly elevate the overall quality of life among patients who have retrocochlear deafness. This collaborative U.S.-Swiss project is supported by the U.S. National Science Foundation (NSF) and the Swiss National Science Foundation (SNSF), where NSF funds the U.S. investigator and SNSF funds the partners in Switzerland. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.