Skin conductance response

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Joined: 13 Jan 2012, 16:27
Location: NSCR

Skin conductance response

Postby Liza » 13 Mar 2012, 15:43

Recently we discussed the measurement of SCL with hand palm stickers. It was suggested that the hand should not be cleaned with alcohol before attaching the SCL stickers, while the skin should be cleaned with alcohol before attaching the ECG/ICG stickers. The question is; is this true, and if so, why shouldn't the handpalm be cleaned with alcohol?

Furthermore, I was wondering whether temperature and humidity of the testing room should taken into account when measuring SCL?

Posts: 9
Joined: 20 Jan 2012, 21:03

Re: Skin conductance response

Postby jcndegeus » 19 Mar 2012, 17:10

Alcohol cleaning: I have absolutely no idea. Firt time I hear this. What does the Boucsein book say about this?

Temperature: ideally we control the temperature and humidity as much as possible. That being impractical in some setups the next best thing is to carefully measure them throughout the experiment. Most experimental rooms will not show huge fluctuations but if measurement suggests otherwise subject-specific temperature and humidity could be tested as potential confounders by regressing them on SCL measures (and adding them as covariates if significant correlation is found).

Eco

Posts: 9
Joined: 20 Jan 2012, 21:03

Re: Skin conductance response

Postby jcndegeus » 13 Jul 2012, 09:12

I have been reading up on this and found this in an excellent recent Handbook by Jim Blascovich,
Wendy Berry Mendes, Eric Vanman, and Sally Dickerson:
"Preparation of the skin includes washing with a mild, nonabrasive soap. Use of
alcohol-based hand sanitizer or anti-bacterial soap prior to sensor placement is not
recommended because the chemicals in them may excessively dry out the skin,
resulting in lower levels of EDA and obscure sensitive changes. An electrolyte
(either KCL, NaCL) or commercially available conductance cream is then applied
in a thin film on the two sensor sites and also in the wells of the sensors. Once the
sensors are attached, it is advisable to wait several minutes (typically 5 to 15
minutes) prior to beginning the recording session to allow for the conductance
gel to adhere to the skin."

Agrees with my broader reading save that other sources argue against NaCL/KCL paste.
A brief summary of what I extracted as to do /not todo's follows:

-Never abrade the skin
-Washing with soap and water
-Electrodes *always* Ag-AgCl (they cost but resist polarization)
-Conductive Paste:
OK: Unibase + physiological saline; K-Y jelly ; Biopac ;
not OK: gels with high NaCl content will migrate to skin tissue over time, inflating SCL
- Keep the surface area exposed to the electrode constant across subjects and sessions

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