PROJECT SUMMARY Examining how behavior arises from the complex interconnected activity of the brain is a cornerstone of neuroscience research. A recent technological advance in neurotechnology is enabling studies where the parallel activity of thousands of neurons can be studied in rodent brains. The Neuropixels probe, allowing 384 channels of electrophysiological data to be observed from the brain, is now a valuable tool for next-generation experiments. One goal of this project is to provide a commercial alternative to the Neuropixels probe and associated electronics that will enable feature parity in recording capability, but also be usable in scientific applications currently unaddressed by the existing Neuropixels probe. Our proposed solution is partially enabled by the makers of the Neuropixles probes—IMEC has recently made commercially available the electronics of the probes as a standalone 384 channel chip without the silicon electrodes attached. By connecting this proven technology to a new type of electrode array—flexible polyimide-based probes—we outline a strategy to offer technology with similar channel density that is 1) is resistant to breakage upon insertion, 2) enables closely-spaced implantation sites, and 3) has a significant reduction in glial scarring compared to silicon probes, enabling extremely stable recordings for months. Furthermore, by coupling this probe to powerful datalogging electronics, we will offer a way to scale channel counts to above 3000 without the need for cables between the animal and a computer.