GSR-POLYGRAPH LAB

Physiology lab

GSR-Galvanic SkinResponse• Electricity flows through an electrical circuit because of difference

in the electrical pressure between the beginning and the end of a circuit.

• Electrical pressure (electromotive force-E) is measured in volts (V).• The flow of electricity is called current (I=amperes)• As electricity flows through the circuit, resistance (R) is measured

in ohms (Ω)

Ohm’s law: I (Amps)= E(Volts)/ R (Ohms)

In this lab• We’re going to apply principles of Ohm’s Law and record changesin the

electrical resistance of the skin.• GSR (Galvanic skin resistance) – When a feeble electric current is steadily

applied between two electrodes placed about an inch apart, the recorded electrical resistance between them, referred to as GSR (depends on subject’s emotional state)

• Galvanic skin potential (GSP) – Similarly if the electrodes are connected to a suitable voltage amplifier, but without any externally applied current, the voltage measured between them, referred to as galvanic skin potential (GSP)

Galvanic skin response

Galvanic skin response

• It is effected by autonomic tone (largely sympathetic) occuring in the skin and subcutaneous tissue in response to a change in the state of the subject.

• Changes in peripheral autonomic tone alter sweating and cutaneous blood flow, which in turn change GSR and GSP.

A polygraph

• The detection and recording og the galvanic skin responce is often combined with the detection and recording of other autonomic-dependant psycophysiological variables such as heart rate, respiratory rate nad blood pressure.

• The device that detects and records these variables is called polygraph.

The experiment

• We’re gonna measure:• Respiratory responses• Heart rate and • GSRsimultaneously.

Calibration

• Seat teh subject facint the director and away from the screen.

• Click calibrate• Three sec.after a beep will sound and subject

should inhale and exhale deeply for one cycle then return to normal breathing.

• End calibr.

There are 3 segments

• 1. seg: Subject faces the director – recorder faces screen and listens the directors instr. To subject.

• Click record• Wait 5 secs• Recorder needs to insert an event marker at

the precise moment that the subject answers each question (F9)

Questions

• Quietly say his-her name ( )• Quietly count backward from 10 ( count from

10)• Count backward from 30 by substracting

increasing odd numbers-exmp. 30,29,26,21 ( count from 30)• Director touches subject on the side of the

face face touched• Click suspend

Name

Seg2

• Click resume• Director holds paper 1

about two feet from subject’s face

• Display the colors and insert event markers in the following order:

white

black

brown

purple

yellow

orange

bluegreen

red

Seg3

• Click resume• Director asks subject the ten questions.• Subject responds yes or no• Recorder inserts event markers when the

question asked and when the answer starts

Analysis

• Set up your display window for optimal viewing of the first 5 secs of the recording.

• Set up the measurement boxes as follows

Respiration rate

GSR

• Scroll to view a 10 secs interval beginning at the first event marker

BPM