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One of the biggest obstacles to chronic single unit recording is how to move electrodes into or through the desired brain area while maintaining sufficient stability to allow recording of the same cell over hours or days. Our microdrives are based around a precision screw, machined to a pitch of 200 µm, which advances the electrodes in 25 µm steps (1/8th turns). A spring tensions the screw and prevents it from moving spontaneously. The microdrives carry between one and 16 electrodes. They are hand-machined and assembled and are thus expensive - they are, however, reusable many times if treated with care, and are very stable.
The photograph on the right shows a microdrive that has been wired up for 4-tetrode recording. The electrode wires are wire-wrapped onto wires connected to the recording pins and coated in nail lacquer (red, for visibility). During recording, the black cap is removed and the headstage plugged on in its place. At the end of the experiment, the drive is removed, the nail lacquer washed off with acetone and the drive re-wired.
Features:
▪ Lightweight (~1.5 g)
▪ Custom-built connectors made from long Lemo pins allow easy connection and disconnection, combined with electro-mechanical stability
▪ Compression spring maintains tension on the screw and prevents slippage
▪ Robust, stainless-steel construction
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