A new technique for implanting a fine-wire microelectrode for chronic recording of unit activity from freely-moving...

We report here a newly developed chronic implantation technique using an epoxy-coated fine-stainless steel wire (33 microm in diameter) to record single unit activity from the brain of freely-moving mice with as little tissue injury as possible. Since the fine-wire electrode is not capable of staying straight by itself or of penetrating into the brain, a pair of permanent neodymium magnets placed on a micromanipulator as well as below the animal's head was used for stereotaxic implantation to keep the fine-wire straight and strong by the magnetic fields. With those implanted electrodes recording of single units from the hippocampal CA1 of freely-moving mice was performed during sleep and wakefulness.