Lecture 2 - Skin Conductance Measurement

Question 1

What are the three main pathways influencing EDA?

Answer 1

1. Hypothalamus
2. Basal ganglia and cortex
3. Recticular formation

Question 2

What does ipsilateral mean?

Answer 2

Activity in the one side of the brain is reflected on the same side of the body

Question 3

What does contralateral mean?

Answer 3

Activity in one side of the brain gets reflected on the other side of the body

Question 4

Why is skin conductance so interesting?

Answer 4

Skin conductance is / sweat glands are only controlled by the sympathetic nervous system
Uses only the neurotransmitter acetylcholine (mostly represented in the parasympathetic nervous system)

Question 5

Of the three pathways, what systems are ipsilateral and contralateral?

Answer 5

• Hypothalamus and the limbic system is ipsilateral
• Basal ganglia and the cortex contralateral
• (reticular formation / brainstem)

Question 6

Give Ohm’s law and the formula for conductance

Answer 6

V = I * R

C = 1 / R —> C = I / V
C in microSiemens

Question 7

What types of sweatglands are there and where are they located?

Answer 7

1. Apocrine sweat glands (armpits, eyelids, …)

2. Grasping behavior (palms of hands and feet), also for thermoregulation in almost the whole body

Question 8

Where to place electrodes on the body?

Answer 8

Often on the hands, wrist, or feet.

Question 9

Why are electrodes placed on the non-dominant hands of people? (three reasons)

Answer 9

1. Avoid cuts etc.
2. Leaves the dominant hand free for tasks
3. Less movement interference

Question 10

What do the ipsi and contralateral sides mean for measuring emotions?

Answer 10

Since emotions are represented in the hypothalamus and the limbic system, which is ipsilateral, the measurements should be done on the ipsilateral side of where the brain is activated.

Since things other than emotions are connected to the basal ganglia and the cortex, these measurements should be performed on the contralateral side of the activation site

Question 11

What can we features can we extract from skin conductance response and skin conductance level graphs? (mention 5/8).

And which ones give the highest correlation?

Answer 11

1. SCL
2. Change in SCL
3. Frequency of NS-SCRs (non-specific skin conductance response)
4. SCR amplitude
5. SCR latency
6. SCR rise time
7. SCR half recovery time
8. SCR habituation

• Rise time and half recovery time are very highly correlated

Question 12

What does SCR amplitude mean? And what is SCR magnitude?

Answer 12

SCR amplitude = the mean of all SCR amplitudes present

SCR magnitude = mean of all SCR amplitudes expected after each stimulation

Question 13

How to obtain a more normal distribution for SCR?

Answer 13

By either taking the logarithm of SCR + 1

Or by taking the square root of SCR

Question 14

What is SCR habituation?

And how can this be quantified?

Answer 14

SCRs get less and less after being presented with the same stimuli over time.

Measure trials-to-habituation (until 3 times no SCR)
Trials interaction or main effect ANOVA
Regression of SCR against trial number, giving a slope

Question 15

How to compare for SCR effects between individuals?

How to correct for intra-individual differences?

Answer 15

1. Correcting for SCL range: SCLcor = (SCL - SCLmin) / (SCLmax - SCLmin)
2. Z-transformation: SCLcor = (SCL - SCLmean) / std.dev.(SCL)
3. Measuring an additional baseline: SCLcor = SCLstimulus - SCLbaseline

Question 16

Name the advantages of EDA

Answer 16

• Only connected to the sympathetic nervous system
• Can be easily seen
• Quick in responding (compared to HR)
• General arousal indicator

Question 17

Name the disadvantages of EDA

Answer 17

• Slow in responding (compared to EEG)

- Reacts to different types of stimuli (is ‘just’ arousal)