The electrical properties of metal microelectrodes

The electrical properties of metal microelectrodes for single-unit recording are reviewed. An equivalent circuit is presented, the elements of which are discussed. The most important element is the electrolytic capacitor formed by the metal-electrolyte interface. Its value is about 0.2 pF/µ
²
at 1 kHz. The effects of exposed metallic area at the tip and platinization are described, and some consideration is given to problems peculiar to the operation of these electrodes in neural tissue.