Open-Source, Three-Dimensional Polymer Microelectrode Array for Multi-Region Hippocampal Recording

A three-dimensional (3D) multi-shank polymer microelectrode array (pMEA) was developed for simultaneous multi-region hippocampus recording with a conformal electrode layout informed by cell body locations derived from rat brain atlas. To access the cornu ammonis 1 (CA1), cornu ammonis 3 (CA3), and dentate gyrus (DG) subregions, two linear 4-shank arrays ($2 \times 4$), separated by 1.5 mm, were combined to form a 3D implant and accurately placed deep in rat brain (4.5 mm depth) using a novel laser micromachined polyimide shuttle ($40 \mu \mathrm{m}$thick) which allowed the pia mater to remain intact. The complete designs and fabrication protocols are freely available under a permissive open-source license (CC BY 4.0).