Conformally-mapped multielectrode arrays for in-vitro stimulation and recording of hippocampal acute slices

Multiple configurations of planar, conformally-mapped multielectrode arrays (cMEAs) are used to enable stimulation and recording of hippocampal acute slice activities. The configurations of the multielectrode arrays are conformal in that the designs incorporate the specific geometrical mapping of various sub-regions of the rat hippocampus (CA1-to-CA3, dentate gyrus-to-CA3, or individual regions). The high-density feature of the arrays also provides a high spatial resolution for current-source density (CSD) analysis, with 50 μm or 60 μm center-to-center distances. Fabrication of gold and ITO (indium tin oxide) based multielectrode arrays with up to sixty-four recording/stimulating elements has been achieved. Impedance measurements are taken for the multielectrode arrays, and a simple equivalent circuit has been employed to model the electrode-electrolyte interface; cyclic voltammetry and potential monitoring experiments are performed to set guidelines and to identify limitations of stimulation protocols, thus avoiding undesirable irreversible faradaic reactions due to excess stimulation. Evoked in-vitro electrophysiological experiments with acute slices of rat hippocampus have successfully been performed using the cMEAs.