Recording electrodes transfer electrical potentials at the recording site to the input of the recording machine. Electrode materials should be those, which do not interact chemically with the electrolytes of the scalp. Electrodes coated with tin, silver chloride, gold etc. are satisfactory.
Experimental evidence suggests that silver-silver chloride or gold disc electrodes held on by collodion provide best results.
Electrode types most commonly used in clinical EEG are metal discs or cups attached to the scalp and other recording sites. They usually have diameters of 4-10 mm. Before electrodes are applied, the application site is prepared by wiping with alcohol or abrasive electrolyte gels . Electrodes are applied over the scalp, using a paste (such as Ten20) that can both hold the electrode in place and provide good electrical contact.
Clip electrodes are sometimes used for recording from the earlobes. The clips should contain cups or discs made from the same materials as the scalp electrodes .
References:
- Recording techniques: montages, electrodes, amplifiers and filters. In: Halliday et al. A Textbook of Clinical Neurophysiology. Wiley, Chichester
- Guideline One: Minimum Technical Requirements for Performing Clinical Electroencephalography. J. Clin. Neurophysiol. 11 (1) 2-5, Raven Press Ltd. New York
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