Issues regarding Skin Conductance measurement
The following reference book is recommended for Skin Conductance measurement.
"Electrodermal Activity" by Wolfram Boucsein , New York : Plenum Press, 1992
With regard to SC electrode paste:
"K-Y jelly is too hypertonic for electrodermal measurement. It should not be used if a paper is to be published on the experiment results. Recommended electrode paste is Unibase mixed with 0.05 mol/L Na Cl. A paste is available from Med Associates Med Associates which should meet the recommendations of Lykkens & Venables, Psychophysiology, Sept. 1971."
Customer's Comment:
I spent years mixing my own Unibase/saline paste. It was always full of air bubbles and difficult to use. Then I noticed that Peter Lang, one of the founders of psychophysiology, used K-Y, and he doesn't seem to have any problem publishing things. I'll stick with K-Y until someone demonstrates that it makes an empirical (not theoretical) difference.
Another useful reference is:
The Mind-Body perspective. Kenneth Hugdahl, Harvard University Press, Cambridge , MA . PP 101 to 130.
Basics of Skin Conductance Recording.
Taken from
1. Always wash your hands with soap and water before applying electrodes to someone else. If you have any breaks in the skin of your hands, or any “weeping” rashes or lesions, wear examination gloves.
2. Always have the subject wash his/her hands with soap and water and dry them thoroughly before applying electrodes. This helps to equate the degree of skin hydration across subjects.
3. If the subject has any breaks in the skin or weeping lesions on his/her hands near the recording sites, DO NOT RUN THAT SUBJECT.
Electrode Application
1. Select a pair of 8 mm pre-wired Ag/AgCl electrodes (dry them gently if necessary).
2. Apply the electrodes as follows:
- Strip the backing from one side of an electrode collar and stick it to the housing of the electrode, centering it carefully over the electrode disk. Place the electrode collar-down on the table and press to secure the collar to the housing.
- Use only Grass EC33 paste as an electrode medium. Keep the container closed between uses.
- Apply EC33 evenly to the surface of the electrode. Avoid creating air bubbles in the paste. Fill the electrode well to the top to insure contact between the entire electrode surface and the skin. Overfilling will cause paste to spread out under the collar when the electrode is applied to the subject, resulting in variation in the electrode contact area and poor adhesion of the collar. If you overfill the electrode, use the side of a toothpick to grade off the excess paste.
- Remove the backing paper from the electrode collar and press the electrode firmly in place on the subject with the lead wire running in an appropriate direction. Be careful not to move the electrode after contact with the skin. Smooth the electrode collar with your finger so that it adheres tightly to the skin.
- When using finger sites, it may be necessary to secure the electrode further by wrapping paper tape around the electrode and the subject's finger (not too tightly). For this reason, among others, the secondary sites on the thenar and hypothenar eminences may be preferable.
- Plug the electrode leads into the appropriate receptacles on the subject unit. It does not matter which plug goes into which receptacle (i.e., polarity is not an issue). Make sure that the calibration buttons on the unit are out and the associated status lights are off .
3. Reliable recording requires an adaptation period of at least 10 minutes (15-20 minutes is recommended for research in which within-session change in skin conductance level is an important variable). This period allows equilibration of hydration and sodium at the interface between the subject's skin and the electrode paste.
Cleanup Procedure
1. Always clean the electrodes immediately after use to prevent paste from hardening in the wells.
2.DO NOT USE TAP WATER to clean the Ag/AgCl electrodes. The trace metals in tap water can damage the electrode disk. Instead, fill the WaterPik reservoir with distilled water and use the jet to remove at the electrode disk. Try not to touch the electrode disk with the WaterPik nozzle. Closely examine the electrode and make sure that NO paste whatsoever remains on its surface .
3.Place the clean electrodes on a paper towel in the subject room to dry.
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