Stress peeks through the skin - Part 2
Stressful events result in many changes within the body - even in the skin. Yesterday we outlined how this comes about and in part II of this article we look at exactly how stress appears on our skin and what we can do to make use of that fact in biofeedback.
When the body reacts to something we perceive as stressful our Autonomic Nervous System (ANS) powers us up for fight or flight. This is intended to be a short term event where we are physiologically prepared to meet the danger. The part of the brain called the amygdala acts in basic terms like a switch - it disconnects us from the ability to think and reflect on events and sends a signal down the vagus nerve and on to many parts of the body. As we noted yesterday, the heart is one such organ and our heart rate varies with the stimulation that results.
The property Heart Rate Variability is shaped by both the Sympathetic (SNS) and Parasympathetic (PNS) pathways of the ANS. A stressful event activates the SNS pathway and the heart rate increases. When the stressful event is over and we are able to relax, the PNS pathway acts to slow down the heart and hopefully we then can find ANS balance.
Biofeedback using HRV has been popular for many years and HRV is dependent on both the SNS and the PNS. Certain frequencies in the HRV correlate with SNS activity and others with PNS activity. However, the HRV signal is not always unambiguous. That's not to say that HRV is not interesting in relation to the stress response, but the jury is definitely out on whether it is an ideal way of looking at stress.
An alternative to HRV biofeedback?
Yesterday we introduced Electrodermal Activity (EDA) and this provides a modern alternative to HRV Biofeedback. Once upon a time referred to as Galvanic Skin Response, modern instrumentation design has eliminated some of the technical challenges of monitoring this property. EDA has been a phenomenon known about since the 1800's and has a long history of use in psychophysiological research. Basically when the SNS is powered up by a stressful event, sweat glands in our skin are innervated too. This causes a variation in the electrical conductance of the skin.
Research has shown a firm link between skin conductance and stress. For example Jacobs (see reference below) reports that
"skin conductance level appears to be a more stable and reliable index of autonomic arousal than blood pressure or heart rate in response to serial mental stress testing"
In the context of stress management the goal of EDA biofeedback is to train the user to gain voluntary control of their skin conductance in order to thereby reduce the arousal of the SNS. The idea is not new but the implementation in the Pip product brings together improved instrumentation that eliminates some of the measurement errors that plauged earlier systems. The Pip also takes advantage of the immersive environment possible with modern phone and tablet Apps.
For the purpose of biofeedback the Pip detects the changes in skin conductance over a training session and uses this data to drive an animation that the user receives as feedback..
The Pip platform puts a very effective stress management system into a discreet inexpensive package whose key advantages are
- wireless, discreet and ergonomic form factor
- Highly intuitive user interface to minimise barrier to entry to non-technically minded users.
- Finger-tip based for maximum responsiveness to emotional sweating.
- Optimised sensor technology for robust and sensitive transducing of EDA.
- Adaptive electronic circuitry for maximum measurement resolution.
- Bespoke signal processing algorithm formulated specifically for the purpose of BART.
- Sophisticated, gaming-based applications for smart-devices to maximise user engagement and training outcomes.
The Pip Cloud platform allows a user to record and analyse their sessions in greater detail. By using one of the free Apps on IOS or Android the users data are uploaded to a secure platform for later review.