The Development and Testing of a Multi-Depth Microwire Electrode Array

We describe a method by which a single shaft multi-microwire electrode can be easily and efficiently fabricated. The constructed electrode can then be used for multi-depth neuronal unit recording from one or more tracks in deep brain structures of anesthetized or awake animals. The electrode consists of multiple strands of 50 μm Teflon insulated tungsten microwires threaded through a 25 gauge stainless steel cannula. The individual microwires are then cut to specified offsets, depending on which layers the researcher is interested in. In this case the three wires present are cut to 1 mm, 600 μm, and 250 μm from the tip of the distal end of the cannula. These distances correspond to the II, III, and V layer of the rat sensorimotor cortex. At the base of the electrode, the wires are soldered to individual pins of a miniature connector that plugs into preamplifier that is part of a TDT (Tucker-Davis Technologies) modular signal processing system. Although in vivo data has yet to be attained and analyzed for this type of an electrode, EIS (Electrochemical Impedance Spectroscopy) analysis has shown that the electrode design is well suited for brain tissue recordings.