GALVANIC SKIN RESPONSE (GSR) BIOFEEDBACK
Galvanic skin response biofeedback is widely and effectively used for biofeedback training in the management of stress and its effect, treatment of anxiety, panic disorders, and specific phobias, as well as for therapy of high blood pressure, tinnitus, sleep disorders, and many other conditions that caused by disbalance of the Autonomic Nervous System.
Skin response, also known as galvanic skin response (GSR), electrodermal response (EDR), or skin conductance (SC) is a measurement method based on bio-electrical properties of the skin: it measures the continuous variations in the electrical characteristics of the skin, i.e., for instance, the conductance, caused by the changes of the human body sweating. Skin conductance depends on the activity of the sweat glands of the skin and reacts to the smallest changes, which we can’t detect as wet hands yet.
The activity of the perspiration glands is determined by the Autonomic Nervous System, which contains two main subunits: the parasympathetic nervous system and the sympathetic nervous system. The perspiration glands of the skin are solely controlled by the sympathetic nervous system, making them a good indicator of inner strain and stress. The sympathetic nervous system reacts to stress stimuli by activating all the “emergency functions” of the body, bringing it to a state of heightened responsiveness: Pulse and blood pressure rise along with the glucose level in the blood and general alertness. With these changes comes the effect of “wet hands” on which relies the electrodermal response measurement.
We all know a time in our lives when we got wet hands. Think of the speech you gave in front of an audience or a job interview. If in those situations you were excited, can you remember the cold, sweaty hands?
A scientific theory for this effect assumes that our ancestors needed wet hands to have a firmer grip on things; for example, in an escape or pursuit through difficult terrain. When the threatening situation is over, the parasympathetic nervous system becomes dominant: Pulse, blood pressure, and glucose level fall again. The body enters a rest state to allow recovery. The hands become dry again.
The increased activity of the perspiration glands through a stimulus (stress) is easily visible through the associated increase in skin conductance. The stimulus can be a mental or emotional strain or taking a sudden, deep breath, or a startling action like someone unexpectedly clapping hands or the loud drop of an item onto the floor.
Thus, skin conductance is not under conscious control. If the sympathetic branch (SNS) of the autonomic nervous system is highly aroused, then sweat gland activity also increases, which in turn increases skin conductance, and vice versa. In this way, skin conductance can be a measure of the human Sympathetic Nervous System responses. Such a system is directly involved in emotional behavioral regulation in humans. Additional studies highlighted the relationship between the GSR signal and some mental states, such as stress, drowsiness, and engagement.
GALVANIC SKIN RESPONSE BIOFEEDBACK TRAINING
Galvanic skin response biofeedback is a universal tool for biofeedback training. It is widely used in the therapy of anxiety, panic disorders, and specific phobias as well as for the management of stress and its effect. Further fields of use are high blood pressure, tinnitus, and sleep disorders. If you suffer from a serious disorder or medical condition, always consult a professional physician or therapist, and do not attempt to treat yourself.
Stress and its vegetative symptoms can be greatly reduced through biofeedback training, where you intentionally work on lowering your skin response.
A GSR sensor allows us to measure sweat gland activity, which is related to emotional arousal. To measure GSR, the electrical properties of the skin are used. Specifically, how skin resistance varies with sweat gland activity, i.e. the greater sweat gland activity, the more perspiration, and thus, less skin resistance. The most common measure of a GSR signal is not resistance, but conductance. Conductance is the opposite of resistance and is measured in Siemens (Conductance = 1/Resistance). The conductance makes the signal interpretation easier, since the greater the sweat gland activity, the higher the skin conductance.
The Skin Response measures the Skin Conductance in Micro Siemens or μSiemens. Skin conductance is measured in μSiemens or symbolized as μS (where μ denotes a millionth and Siemens is the unit of conductance). “Skin resistance” is also a common term, simply indicating the inverse of conductance (1S = 1/Ω).
Through the changes of this small current, we can measure the activity of the perspiration glands of the skin far below the threshold of self-perception. The higher the activity of the sweat glands, the more the skin gets wet and the better the current is conducted. As a result, Skin Conductance rises.
The amount of sweat glands varies across the human body but is the highest in hand and foot regions (200–600 sweat glands per cm2), where the GSR signals are typically collected.
The GSR signal is very easy to record: in general just two electrodes put at the upper or middle phalanges of the index and middle finger of the same hand are necessary. The variation of a low-voltage applied current between the two electrodes is used as a measure of the electrodermal activity (EDA). Skin Response is a precise device. It can measure the smallest changes which would be impossible to recognize yourself. Recently, new commercial healthcare devices more and more wearable and fancy (bracelets, watches) have been developed.
The goal of Galvanic skin response biofeedback training is twofold:
- a reduction of the permanent, basic level of stress and
- a reduction of the immediate stress response to a particular stimulus.
Galvanic skin response biofeedback
STAGES OF GALVANIC SKIN RESPONSE BIOFEEDBACK TRAINING
Biofeedback training consists of four training stages.
For the first training, it is necessary to schedule about 60 to 90 minutes of free time which could be conducted undisturbed and flexible training.
The second stage consists of multiple sessions directed to exercise conscious relaxation with the feedback signal. At the start, the values are measured and watched for a while. Then through active, conscious intervention client try to bring them down. There are many ways to do this, such as breathing in a controlled and calm pattern or using techniques of muscle relaxation, or autosuggestion. The exact way is up to a person, his knowledge of relaxation, and his will to experiment. A part of the training focuses on the general reduction of the tonic skin conductance level, while a second part focuses on the reduction of the fluctuations. In the second training phase, the aim is to lower the general level of skin conductance and reduce the increase as a result of a stimulus as quickly as possible. They train to reduce their general tension and be able to switch off flexibly after stressful situations.
During the third stage actively used stress stimuli (stressors) to improve the ability to deal with them. Skin conductance biofeedback is particularly suitable for the use of targeted provocation methods because it shows a timely and sensitive response to a stimulus, and because this response is also proportional to the strength and significance of the stimulus. The training starts with a rest period of a few minutes. Then a selective stressor should be applied. Almost every person knows certain things or situations that distress them. For example, if you have trouble speaking out loud before a larger group of people, try to imagine the situation and hold a speech before them. Under the influence of such a stressor, you are likely to see a surge in skin response. Try to relax to bring it down again and reduce the spontaneous fluctuations. Alternating three or four rounds of the phases of relaxation and stress stimuli during the session training should finish the session with a relaxation phase.
It is necessary to perform multiple sessions over a longer period of time until you have the impression that your stress response is significantly reduced, or you recover quicker after a stressful situation.
During the fourth stage, it is necessary to achieve improved relaxation with lower skin response levels and fewer fluctuations, even without feedback.
Record a ten-minute baseline WITHOUT watching the measurement while relaxing as best as you can. Afterward, compare it to the baseline measurement from the first stage. Your overall level of skin conductance should have dropped, and/or the spontaneous fluctuations should have reduced. Your daily condition can affect the measurement a lot, so repeat the record of the baseline later again if you feel you had an unusual day.
When you encounter stressful situations in everyday life, recall the training situation, and use your new skills to stay relaxed. Skill comes with practice!
It must also be differentiated between different types of stress. There is “bad/negative stress,” (“threatening” or “saddening”) distress, and there is “good/positive stress,” (“happy” or “joyful”) eustress. You need to ask yourself if you are stressed because you feel overwhelmed and are angry about something or because you are upset. Or are you “stressed” because you are full of drive and are excited? The GSR signal is therefore not representative of the type of emotion, but the intensity of it. In both cases, the eSense Skin Response shows elevated values. However, in the first case, this is to be judged negatively. In the second case, you can simply enjoy and use the active or euphoric state.
HOW DOES A GSR SENSOR WORK?
Most modern GSR electrodes have an Ag/AgCl (silver-chloride) contact point with the skin. Ag/AgCl electrodes are used as they are cheap, robust, safe for human contact, and of course, are able to accurately transmit the signal from the ionic activity. Some electrodes also come prepackaged with an ionic gel that can increase the signal fidelity or ionic gel can be applied to achieve the same effect. Either way, the signal is sent through the electrode, to the wire (usually lead) that passes the information to the GSR device. From here the data is either stored within the device to be later uploaded is transmitted wirelessly to a computer system, or the signal is sent through a further wired connection to a computer. Different GSR sensors allow different means of transmission, and the choice of each will depend on the kind of research you’re carrying out.
Skin conductance is captured using skin electrodes which are easy to apply. Data is acquired with sampling rates between 1 – 10 Hz and is measured in units of micro-Siemens (μS).
HOME USE GALVANIC SKIN RESPONSE DEVICE FOR BIOFEEDBACK
