POLYGRAPH BIOFEEDBACK

POLYGRAPH BIOFEEDBACK

GALVANIC SKIN RESPONSE (GSR) THE POLYGRAPH Polygraph many measures (many poly, graphein to write) - recording at the same time the changes of several biological parameters (usually GSR, blood pressure, heart rate, respiratory frequency) in order to find abnormal changes during different situations (ex. emotional state of the person) GSR - the variation of the electrical resistance of the skin due to the degree of activation of the autonomic nervous system (ANS stimulation increases the secretion of sweat, rich in ions). It represents one of the electrodermal answers EDA. Polygraph lie detector can interpret how people respond (physiologically) to certain questions. It is based on the assumption that telling a lie is an emotional stress.

GALVANIC SKIN RESPONSE ( GSR) When measuring skin conductance, there is the skin conductance level (SCL) and skin conductance response (SCR). SCL is the slow varying skin conductance value, changing over the course of minutes.. SCR is the fast varying skin conductance value, changing over the course of seconds.. The SCR that rides on top of the SCL reflects a person's mental response to various stimuli. i. Normal value: - Latency <3 sec - Amplitude: μs - Rise time : 1-31 3 sec - Half recovery time: 2-102 sec

THE POLYGRAPH IN BIOPAC SYSTEM 1.Objectives: evaluation of the changes in ANS activation during different emotional states. 2. Materials: - BIOPAC cables : SS5LA, SS4L, SS3L ( GSR transducer, respiration transducer, pulse transducer) - electrode gel - BIOPAC acquisition unit 3. Preparation for recording: - attach the respiratory transducer around the chest - attach the GSR transducer and pulse transducer to the fingertips. - the subject should breath slowly, be relaxed and should not look k at the screen. The questions should be answered with minimal movements (every external e stimulus can change the emotional state of the subject so unnecessary noises and movements through the room should be avoided). The answer will be YES/NO. - perform the calibration for the recording.

THE POLYGRAPH Recording: three different situations 1. SCL, habituation - we will record traces without questions then we will record habituation to the same repetitive question (Your name is XY?) 2. Neutral questions we will measure SCL and SCR during neutral questions 3. Mixed questions we will measure SCL and SCR during ten neutral and emotional questions (first should be neutral but the next questions may be neutral or with emotional content in this situation the amplitude will increase and the rise time will decrease)

Biofeedback Biofeedback the process of relaying physiological information (usually in a graphical or audible format) back to people as they perform various behaviors. It developed as a training method for the control of the body functions. The devices used constantly monitor the function of the body (blood pressure, heart rate, activation of ANS- GSR) and provide real-time information about their changes. - 2 types physiological biofeedback - psychological biofeedback (physiological biofeedback relies on physical changes such as posture shifts and closing eyes to induce relaxation; psychological biofeedback depends on cognitive tasks to alter one s physiological state)

Biofeedback

Biofeedback 1.Objectives: to asses the capacity of the voluntary control over the sympathetic tic activation 2. Materials: - BIOPAC cables : SS2L, SS3L ( ECG cables : white, black, red; GSR transducer ) - electrode gel - BIOPAC acquisition unit 3. Preparation for recording: - place the ECG cables on right foot-black, left foot-red and right forearm -white (we use ECG electrodes to calculate the heart rate). - attach the GSR transducer to the fingertips. - perform the calibration for the recording (during the setup breath normally until you hear a beep and take four deep, rapid breaths; after that relax and breath normally for the remainder of the 30 seconds).

Biofeedback During the recording, the GSR and heart rate will be plotted in X-Y Y mode (one signal is plotted on the horizontal axis GSR; the other signal is plotted in vertical axis - HR). The combination between HR and GSR will be presented on the screen as a dot (the position of the dot will reflect the level of arousal and the level of HR). As the heart rate will increase the dot will move closer to the top of the screen. If the GSR will increase the dot will move towards the t right edge of the screen. We will use specific tasks to modify the position of the dot - Relax your posture! - Clench your fists! - Breath in and out very slowly! - Imagine yourself relaxing seaside, feel the warmth of the sun! - Think about someone you dislike!