Tungsten ball microelectrode for extracellular single-unit recording

Abstract

An electrolytic method is described for manufacturing ball-tipped tungsten microelectrodes. The tungsten ball is produced by slowly withdrawing the electrode from the etching solution until the wire mells and tungsten metal forms a ball at the end of the shaft. The size of the ball is related to both the size of the wire shaft and the amount of current being passed. Smaller balled tips are produced when wire of smaller shaft diameter is induced to spark and melt. Higher voltages and larger shaft diameters at sparking yield larger balled tips. Ball-tipped electrodes are produced easily and reliably by this method and require little training. Such electrodes are sturdy and capable of stably recording activity of either single cells or multiple-units with good signal-to-noise ratio. They can record extracellular perikaryal responses from neurons at several levels of the nervous system. Responses of single nerve fibers are not isolated by these electrodes.