Electrodermal Activity

Much of this information was gleaned from the following sources: sdfasd sdfasdf asdfasd

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

Useful links

Introduction to electrodermal activity

A Guide for Analysing Electrodermal Activity (EDA) & Skin Conductance Responses (SCRs) for Psychological Experiments

Electrodermal activity measurements

Biopac Electrodermal Response Basics

EDA (GSR) subject preparation

Guidelines for GSR, EDA, EDR, SCL, and SCR

Initial Setup

Power on the MP150

Ensure that the EDA100C (Electrodermal Activity) amplifier is attached and set to channel #3

Electrode Setup

Connect two LEAD110A leads into the EDA100C

Plug one lead into the Vin+ port and the other into the Vin- port

Use electrode prep swab to clean the index and middle fingers of the participant's non-dominant hand

Remove two EL507 electrodes. el507

Put extra GEL101 on them 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 http://www.bem.fi/book/27/27.htm

Attach the pinch connector of one LEAD110A to the EL507 electrode on the middle finger, and the other to the EL507 electrode on the pointer finger.

Wait at least five minutes before recording. The electrolyte gel will continue to penetrate into the stratum corneum, which will cause a drift in the ECL (specifically, increased conductivity).