Whether it’s for EEG, ECG, or ECT, electrodes have a myriad of electrophysiological techniques in the field of biomedical research. As far as electrode positioning and selection, decisions about which type to use are best made via literature and discussions with colleagues. Here are some general considerations to observe when determining preferences; most electrodes used for biopotential recording are Ag/Ag-Cl.
Electrode property preference such as gel type must also be taken into account when conducting tests. Electrodes are generally grouped between disposable and reusable types. Typically, either solid or wet gels are used to complement electrodes in gathering test data. Solid gels are easier on the skin than wet gels due to superior water content in wet gels that react aggressively on the skin. The choice between electrodes should then be determined based off of testing criteria and duration. For instance, if there are two electrodes with 4% salt, one wet gel and one solid gel, the wet gel would be more reactive. Reusable and disposable EDA/GSR electrodes both use isotonic gel, however they do not yield different results and will be almost identical during use with the exception of a few feature based discrepancies. The researcher should compare one electrode setup to the other during a measurement with a single EDA/GSR series amplifier.
When the electrodes are functional, chemical reactions at the face of the electrodes occur to permit electrical currents to flow between the subject and equipment. These reactions force the electrode surface to gradually degrade. With appropriate cleaning and storage, reusable electrodes may well last several years, however, the electrode surface deteriorates. Disposable electrodes efficiently eliminate this source of variance as each subject uses electrodes with unsullied surfaces. Inevitably, researchers will cycle through more disposable models over time and duration of use.
Silver-silver chloride (Ag-AgCl) electrodes provide accurate and clear transmission of surface biopotentials and are useful for recording all surface biopotentials on animals and human EEG. BIOPAC offers reusable Ag/AgCl electrodes for recording biopotentials with surface, snap, or post connection. BIOPAC EL250 series and EL650 series reusable electrodes incorporate a variety of features for high-stability recordings: non-polarizable, sintered to increase electrode/electrolyte contact area, reusable via resurfacing, and high stability recordings.
Post electrodes can be used for improved contact through fur or hair. BIOPAC’s EL120 posts have 12 posts in a 10 mm contact area; the posts are 2 mm deep to push through the fur/hair to provide good contact with the skin surface.
BIOPAC’s wide range of reusable electrodes and disposable electrodes provides researchers the chance to best achieve research objectives while maintaining subject comfort and budget requirments. Serving disciplines from Human, Animal, and MRI physiology to Biomedical Engineering, proper electrode selection can lead to a greater success rate at reaching targeted lab/test results.