A core goal of the BRAIN Initiative is to link neural activity to behavior which requires technology to acquire high-quality recordings of dynamic neural activity from different brain regions over time. To achieve this core goal, this optimization proposal will address the most pressing areas of technology development to enable the dissemination of polymer microelectrode arrays with such capability and promote their integration into neuroscience research practice. Polymer-based neural interfaces can achieve high-quality recordings over a year or more which is attributed to the greater stability of the device-tissue interface compared to more rigid metallic wire and silicon-based neural interfaces. Another distinct advantage is that the same microfabrication technology can be used to produce batches of surface and penetrating electrode arrays with carefully controlled features with micron and submicron dimensional precision. Microfabricated polymer probes are already available in limited designs having shank lengths of 10 mm or less and therefore predominantly used in rats. This technology needs to be extended for access to deeper brain regions in rodents and a wide range of brain targets in larger animals, including nonhuman primates, an important model in neuroscience and preclinical research. Existing device designs such as the prototype arrays previously developed for the rat hippocampus cannot simply be scale up or down to expand access to brain regions across different species. Instead, careful design is required in collaboration with users to meet space and weight requirements as well as workflow requirements to achieve precise placement at the desired depth. Therefore, this proposal tackles the necessary optimization of the previously developed technology to enable a library of designs that will enable their use in different animal models and to target different brain regions. Another goal is to develop the appropriate insertion methods for reliably placing electrodes at the desired depth and targeted region. Once the passive recording arrays and the matching surgical insertion methods are developed and optimized at the benchtop, these will be evaluated in mice, rats, and NHPs. Overall, this proposal not only addresses optimization but further advances in polymer microelectrode array technology for neural interfaces. This will enable early dissemination of polymer array systems for large-scale monitoring and manipulation of neural activity in collaboration with early adopters and demonstration of high-quality recordings obtained in multiple species over long periods that will attract additional users. Successful demonstration will facilitate our long-term goal of realizing the wide dissemination of reliable chronic neural interfaces across different neural tissues and species.

The objective of this technology optimization is to enable broad adoption of flexible polymer neural interface technology by engaging the neuroscience user community and developing designs that can be used across species from mouse to nonhuman primate. This work will result in library of different designs that target multiple brain regions from cortical to sub-cortical to deep brain as well as the specialized methods to enable accurate implantation to these targets. This collaborative effort advances polymer microelectrode array technologies to meet the large scale, high density goals of the BRAIN Initiative and establishes a dissemination path to make them widely available to the neuroscience and neuroengineering community.