The research objective of this proposal is to test the hypothesis that intracochlear electrical stimulation with a polymeric high-density electrode array enables a more focused and selective activation of auditory neurons when compared with contemporary cochlear electrode arrays. To achieve the research objective we must develop a method for integrating a flexible high-density array with a silicone insertion platform (IP), and test the integrated device mechanically, electrically, in-vitro, and eventually in-vivo. We divide the proposed research into two phases. In Phase I we will focus on using an IP that has been validated in humans and (a) microfabricate and integrate a thin-film array with the IP, (b) using a 3D human cochlear model, validate the integrated array mechanically through bend tests and insertion studies, and electrically by impedance measurement, and (c) compare the efficacy of intracochlear electrical stimulation of the high-density array with a contemporary array in the cat model. In Phase II we leverage the methods established in Phase I to develop an array specifically sized for the cat model by integrating a thin-film array with a molded silicone insertion platform. INTELLECTUAL MERIT Over 180,000 individuals use cochlear implants worldwide and many achieve a high level of speech recognition. But there remains a group of patients achieving poor speech recognition and difficulty understanding speech in noisy environments. One potential means to overcome this challenge is to provide an enhanced coupling between the electrical to neural interface with a high-density array. Implementing such an array is impossible with contemporary fabrication methods where arrays are constructed by hand from bundles of wire encased in silicone. There simply is not enough room in the cochlea to scale up this method. This proposal is the first effort at integrating a thin-film based array with an IP. This is a transformative approach as it leverages the fine feature resolution (1ìm) offered by microfabricated thin-films and combines such arrays with an IP commanding the same mechanical flexibility, dimensions and features of contemporary arrays validated in humans. Furthermore, the introduction of integrated high-density arrays sized for the cat model will enable fundamental studies exploring and comparing novel electric fields shaping strategies, such as current steering and current focusing, employed to optimize the electrical-to-neural interface. BROADER IMPACTS Integrated thin-film arrays open a host of possibilities to further improve patient performance with cochlear implants. Recent studies have illustrated the benefit of combined electrical (high frequency) and acoustic (low frequency) stimulation for improving speech perception, especially in noisy environments. An important component is a short (10mm) array inserted into the base of the cochlea that preserves any remaining low frequency neural elements by minimizing trauma. By decoupling the mechanical design of the platform from the array, our approach enables continued development of less traumatic platforms while retaining the high-density electrode configuration. Furthermore, integrating a thin-film array with an insertion platform may enable such arrays to approach other structures such as stimulation of vestibular nerve fibers for a vestibular (balance) prosthesis and potentially deep brain stimulation to mitigate Parkinson's disease, epilepsy and depression. To broaden the participation of underrepresented groups, the PI maintains a strategy for integrating her research with outreach, mentoring, and teaching to engage students across the K-graduate continuum. This includes "Science Nights" at the Fernbank Science Center (Atlanta, GA) and codeveloping science modules with local middle/high schoolteachers. She guides undergraduate and graduate researchers in her BioSystems Interface Lab, mentors minority students, and is creating a graduate-level Hybrid Biosystems course addressing vestibular, cochlear and cardiac biosystems. The PI has developed a LabVIEW simulation of a cochlear implant signal processor as an IEEE Real World Engineering Project supporting free open-licensed educational materials thereby enabling her to reach an international student/teacher population. And finally, the PI is partnering with the local cochlear implant community to create undergraduate and graduate research opportunities for deaf students in her lab.
