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====== Electrodermal Activity ======

====== Useful links ======
  * From a Biopac Webinar Series on EDA
    * [[https://www.biopac.com/webinars/eda-faq/?utm_medium=email&sslid=MzM0MjE0MjW0MDECAA&sseid=MzY1MTG1NDM1AAA&jobid=ea326d6e-ec92-409b-b3af-85f85f3a982c|Biopac EDA FAQ]]
    * [[https://attendee.gotowebinar.com/register/2317784079198741762|Webinar I: How to acquire EDA data]]
    * {{:kpnl:biopac:biopac-how-to-get-great-eda-data-pt-1-eur-slides.pdf|Webinar I slides}}
    * {{:kpnl:biopac:biopac-eda-webinar-pt-1-eur-q-and-a.pdf|Webinar I Q&A}}
    * [[https://attendee.gotowebinar.com/register/6047847590080923137|Webinar II: How to analyze EDA data]]
    * {{:kpnl:biopac:how-to-get-great-eda-data-analysis-and-scripting-webinar-slides.pdf|Webinar II slides}}

  * [[http://blog.biopac.com/electrodermal-activity-eda/|Introduction to electrodermal activity]]
  * [[http://www.biopac.com/manuals/EDA%20SCR%20Analysis.pdf|A Guide for Analysing Electrodermal Activity
(EDA) & Skin Conductance Responses (SCRs)
for Psychological Experiments ]] \\
  * [[http://www.biopac.com/FAQPage.ASP?id=25&Src=Research|Electrodermal activity measurements]] \\
  * [[http://www.biopac.com/Manuals/app_pdf/app187.pdf|Biopac Electrodermal Response Basics ]] \\
  * [[http://www.biopac.com/FAQPage.ASP?id=190&Src=Research|EDA (GSR) subject preparation]] \\
  * [[http://www.biopac.com/FAQPage.ASP?id=199&Src=Research|Guidelines for GSR, EDA, EDR, SCL, and SCR]]

<note tip>Much of this information was gleaned from the following sources:
  * Critchley, H.D. (2002). Electrodermal Responses: What Happens in the Brain. //The Neuroscientist, 8//(2), 132-142
  * Boucsein, W., Fowles, D.C., Grimnes, S., Ben-Shakhar, G., Roth, W.T., Dawson, M.E., & Filion, D.L. (2012). Publication recommendations for electrodermal measurements. //Psychophysiology, 49//, 1017-1034.
  * Braithwaite, J.J., Watson, D.G., Jones, R., Rowe, M. (2013). A Guide for Analysing Electrodermal Activity (EDA) and Skin Conductance Responses (SCRs) from Psychological Experiments.
</note>

There are several aspects of the EDA that one can measure:
  * **SC** = Skin conductance. Measured in microsiemens or micromhos (the reciprocal of resistance, ohm)
  * **SCL** = tonic changes in SC
    * note: we will generally not focus on SCL for a number of reasons. These include the fact that SCL will drift over time due to both physiological (SCRs can raise SCL) and non-physiological (polarization of electrodes in DC recording) factors.
  * **SCR** = phasic changes in SC
  * **NS-SCR** = SCRs that occur without any identifiable eliciting stimulus
  * **ER-SCR** = SCR that is evoked by a specific eliciting stimulus

The onset of an ER-SCR will occur 1 to 3 seconds after the event and will have a rise-time (i.e. from initial deflection to peak amplitude) of 0.5 to 5 seconds.

10% of participants will be non-responders.  That is, these individuals will not show an appreciable SCR.

Moreover, there are several ways to evaluate these responses. With regard to SCRs, one can
  * evaluate the peak amplitude of the SCR
  * evaluate the rise-time of the SCR
  * evaluate the recovery time of the SCR
    * note: generally this is measured to 67% or 50% recovery because after an SCR there will likely be an increase in SCL. That is, the response will not completely recover to pre-SCR baseline.
  * evaluate the frequency of NS-SCRs within a given epoch
  * evaluate the rate of SCR habituation 
====== Recording Electrodermal Responses =======


===== Initial Setup =====

  * Power on the [[http://www.biopac.com/data-acquisition-analysis-system-mp150-system-mac|MP150]]
  * Ensure that the [[http://www.biopac.com/gsr-eda-galvanic-skin-response-amplifier-electrodermal-activity|EDA100C]] (Electrodermal Activity) amplifier is attached and set to channel #3

{{:kpnl:biopac:mp150_eda100c.png?0x250|}}     {{:kpnl:biopac:mp150_eda100c_ch.png?100}}

===== Electrode Setup =====

  - Connect two [[http://www.biopac.com/clip-lead-black-3m-unshielded|LEAD110A]] leads into the EDA100C
    - Plug one lead into the ''Vin+'' port and the other into the ''Vin-'' port
{{:kpnl:biopac:scr_lead110a.jpg?0x250|}}  {{:kpnl:biopac:mp150_eda100c_vin.png?0x250|}}
  - Use electrode prep swab to clean the __index and middle__ fingers of the participant's non-dominant hand (**//or not!?//**)
  - Remove two [[http://www.biopac.com/disposable-electrodermal-electrode-100-education|EL507]] electrodes. {{:kpnl:biopac:scr_el507.jpg?150|el507}}
    - Put extra [[http://www.biopac.com/electrode-gel-isotonic-education|GEL101]] on them {{:kpnl:biopac:scr_gel101.jpg?0x75|gel101}}
    - **You must use the specific SCR GEL101**. Other conductive gels (e.g. the EEG gel) are not appropriate.
  - Place them on the middle phalanx of the participant's index and middle fingers. Refer to the image below{{  :kpnl:biopac:scr_middle_phalanx.jpg?100  |http://www.bem.fi/book/27/27.htm}}
  - Attach the pinch connector of one [[http://www.biopac.com/clip-lead-black-3m-unshielded|LEAD110A]] to the [[http://www.biopac.com/disposable-electrodermal-electrode-100-education|EL507 electrode]] on the middle finger, and the other to the [[http://www.biopac.com/disposable-electrodermal-electrode-100-education|EL507 electrode]] on the pointer finger.
  - Wait at least five minutes before recording. The electrolyte gel will continue to penetrate into the [[https://en.wikipedia.org/wiki/Stratum_corneum|stratum corneum]], which will cause a drift in the ECL (specifically, increased conductivity).