A very stable electrode system for recording human scalp potentials with direct-coupled amplifiers.

Abstract Electrochemical factors involved in DC recordings are presented. Described is an electrode system which uses long flexible tubes to separate the metal-electrolyte interface of an electrode from the electrolyte-skin interface. Using commercially available Ag/AgCl skin potential electrodes, the system gave less than 0.5 μV/h drift occurring at each metal-electrolyte interface. The stability of the electrode bias potential is unaffected by connecting the bridge tubes to the subject or by other disturbances that occur during recording. In 1 h recordings from four subjects, the total measured potential changed at an average rate of 9 μV/min—a five fold improvement over previously described electrodes.