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Published on: January 12, 2018
Evaluation of commercially available electrodes and gels for recording of slow EEG potentials
P Tallgren1, S Vanhatalo, K Kaila
1Department of Biological and Environmental Sciences, University of Helsinki, P.O. Box 65, 00014 Helsinki, Finland.
Objective:
To test the applicability of different types of commercially available electrodes and electrode gels or pastes for recording of slow EEG potentials.
Methods:
Experiments were carried out on six types of reusable electrodes (silver, tin and gold cup electrodes, sintered silver-silver chloride (Ag|AgCl), platinum, stainless steel), six disposable Ag|AgCl electrode models, and nine gels or pastes. We studied the parameters, which are critical in slow-potential recording, such as polarization, initial and long-term stability and low-frequency noise.
Results:
The best results were obtained with the reusable sintered Ag|AgCl electrodes. The six disposable Ag|AgCl electrode models also proved to have appropriate electrical properties. Other types of reusable electrodes suffered from diverse degrees of polarization, baseline drift, low-frequency noise, high resistance, and changes in properties due to wear and tear. Seven out of nine gels or pastes contained a significant amount of chloride, which is a prerequisite for DC stability of Ag|AgCl electrodes, whereas the absolute concentration of chloride had little effect.
Conclusions:
Direct current (DC) coupled recording of EEG is critically dependent on the choice of electrode and gel.
Significance:
Our results provide rigorous criteria for choosing DC-stable electrodes and gels for DC-coupled or long time-constant AC-coupled recordings of slow EEG potentials.
