The Electrodermal System Flashcards
History
Study of electrodermal activity
Dates back to the 1800
History (3)
Laboratory of Jean Charcot
Studied patients with hysteria
Measured skin resistance in patients
Modern era of electrodermal activity (2)
Dates to the 1970s
Lykken & Venables standardized recording
Electrodermal activity
Linked to
Linked to emotion, attention, and arousal from the start
Carl Jung (1875-1961)
Measured EDA to objectively measure emotional aspects of “hidden complexes” during word-association experiments
Two types of sweat glands
Eccrine and Apocrine
Eccrine (3)
Forms basis of skin conductance
Located all over body
Dense concentration on surface of feet & hands (3000/inch2)
Apocrine (3)
Associated with hair follicles in armpits & pubic region
Function is a matter of debate
Not important for this course
What we care about in this class
Eccrine
Functions of Eccrine sweat glands (2)
Thermoregulation
Grasping
Thermoregulation
Cooling of the body
Grasping
sweat works as an adhesive (creates fiction)
objects (ex: paper sticks to sweaty hands)
Sweat glands on hands (palmar) and feet (plantar) surfaces
More responsive to psychologically significant stimuli than to thermal stimuli
Electrodermal activity & the Eccrine gland
Electrodermal activity
Measure of filling of sweat glands NOT the sweat on the surface of the skin
As sweat fills the duct (2)
What is measured?
Conduction increases and Resistance decreases
This is what is measured
Electrodermal activity
Activated by
Sympathetic nervous system (SNS)
Cholinergic innervation
With higher SNS activity, (2)
Sweat rises in the ducts & greater number of ducts fill
Which leads to changes (increases) in EDA
Electrodermal activity
Several CNS pathways (3)
First and Highest Level of Control
Second Level of Control
Third Level of Control
Electrodermal activity
First and Highest Level of Control (3)
Originates in Premotor cortex
Descends through pyramidal tract (motor control)
More general frontal cortex
Electrodermal activity
Second level of control
Hypothalamus and limbic system
Electrodermal activity
Third level of control
Reticular formation
Electrodermal activity
Brain lesions affect EDA
Ventromedial, Anterior cingulate, Orbital frontal lesion studies suggest that this region is important for EDA
Electrodermal activity
Brain lesions affect EDA diagram
The corticolimbic system
Anterior cingulate cortex: Affect selective attention and social interactions
Dorsolateral prefrontal cortex: Motivation/Executive function
Amygdala: Emotional stress and learning
Hippocampus: Learning and Memory
Advantages and Disadvantages of SCR in research
Disadvantage:
EDA does not occur in isolation
It is part of complex responses mediated by the ANS
Slow moving responses: 1-3 secs
Therefore, not good for tracking rapid mental processes
Advantages and Disadvantages of SCR in research
Disadvantage: (what I wrote)
Slow moving response; Not good for tracking rapid mental processes
Can’t tie one to another
Advantages and Disadvantages of SCR in research
Advantage: (2)
Sensitive to arousal, attention, novelty and significance
Response is quite discriminable: After single presentation of a stimulus, you can see if a response occurred.
Advantages and Disadvantages of SCR in research
Advantage: (what I wrote)
Sensitive to arousal, attention, novelty, and significance; Response is quite discriminable
Good thing: Can see a response after one trial
Skin conductance response
Two types
Nonspecific (NS) SCR (tonic levels)
ER-SCR: Event-Related SCR (Phasic levels)
Skin conductance response
Nonspecific (NS) SCR (tonic levels) (3)
Tonic skin conductance level varies widely between 5s (range: 2-20 us)
Occurs at a rate of 1-3/minute while 5s at rest
May be elicited by deep breaths and body movements
Skin conductance response
ER-SCR: Event-Related SCR (Phasic levels)
Response to specific stimulus; Average range is 0.1-1.0 uSiemens
Onset latency: usually occurs 1-3 seconds after stimulus onset
Terms and Units of measurement
Generic terms (2)
EDA=
GSR=
EDA= electrodermal activity
GSR= Galvanic skin response
Skin resistance is
Measured in ohms
Skin resistance
SRL=
SRR=
SRL= Skin resistance level (tonic); 10,000-500,000
SRR= Skin resistance response (Phasic); 100-10,000
Skin conductance is measured in
Measured in Siemens
Skin conductance
SCL=
SCR=
SCL= Skin conductance level (tonic); 2-20 u(micro)siemens
SCR= Skin conductance response (Phasic); 0.1-1.0 u(micro)siemens
Measure and definition
Skin conductance level (SCL)
Tonic level of electrical conductivity of skin (2-20 uS)
Measure and definition
Change in SCL
Gradual changes in SCL measured at two or more points in time
(1-3 uS)
Measure and definition
Frequency of NS-SCRs
Number of SCRs in absence of identifiable eliciting stimulus
(1-3 per min)
Measure and definition
SCR amplitude
Phasic increase in conductance shortly following stimulus onset (0.1-1.0 uS)
Measure and definition
SCR latency
Temporal interval between stimulus onset and SCR initiation (1-3 s)
SCR rise time
Temporal interval between SCR initiation and SCR peak (1-3s)
SCR half recovery time
Temporal interval between SCR peak and point of 50% recovery of SCR amplitude (2-10 s)
SCR habituation (trials to habituation)
Number of stimulus presentations before two or three trials with no response
(2-8 stimulus presentations)
SCR habituation (slope)
Rate of change of ER-SCR amplitude (0.01-0.5 uS per trial)
Skin conductance response
Conductance and resistance
Conductance measured in mhos or Siemens (1 S=1 mho)
Resistance measured in ohms
Skin conductance response
Origin of EDA
Level of sweat in the duct:
The higher the level, the lower the resistance & therefore higher conductance
Addition of sweat on skin surface
Enhances SCL
Skin conductance measurement (5)
- Level of conductance (SCL) in a time window
- Number of conductance changes (SCR) in that window
- Latency of response
- SCR recovery halftime
-SCR rise time
Skin conductance measurement
Latency of response
Time between stim and SCR onset
Skin conductance measurement
SCR recovery halftime
Time between peak and 50% recovery to pre-stim baseline
Skin conductance measurement
SCR rise time
Time between onset of SCR and peak of SCR
Skin conductance measurement
Diagram
Graphical representation of principal EDA components
Stimulus
Graph: Latency, Rise Time, Amplitude, Half recovery time
Rise time (what I wrote)
Time to get to highest peak
Half recovery time (what I wrote)
Is the highest peak
Skin conductance response
Measurement
Note: This is termed
Very small current is applied across the skin
Exosomatic: it relies on external current source
(Endosomatic does not require external source, one active and one reference electrode (for skin potentials))
Skin conductance response
Electrode placement
Bipolar placement (on inside middle of pointer and middle finger)
Skin conductance response and placement
SCR & Mental activity
Weak link between working memory and SCR
SCR suggests registration of material (better learners, greater SCR)
Skin conductance response and placement
SCR Habituation
Learning increases SCR, Overlearning (Habituation) decreases SCR
EDA & Behavior
Emotions and SCR (3)
Emotional stimuli in general elicit increases in SCR
Greater SCR to fear compared to anger
Also SCL is high during expression of negative emotions
EDA & Behavior
SCR in Psychopathic inmates (2)
- Compared to nonpsychopathic inmates and college students: psychopaths had lower SCR at rest and while performing a task involving electric shock
- Lower levels of tonic EDA have been reported in adolescents who later exhibit antisocial behavior
