The nervous system is the foundation for all of our experiences in life. For this reason, to optimize all aspects of our life, it is important to understand how it performs its tasks and how we can use this information to modulate our nervous system to be in alignment with our goals and objectives.
Through its various components, the nervous system is responsible for how our senses take in information from our surroundings and within ourselves. The nervous system is then responsible for how we interpret and make sense of that information. Our nervous system then determines our thoughts and decisions in response to the information we take in and, ultimately, brings about a reaction. In particular, the autonomic nervous system is critically responsible for these processes. The autonomic nervous system functions in our subconscious and, therefore, is not readily available to our attention and happens at such a rapid speed that it has acted before we become aware of the result. While we may not be aware as it functions, it is a critical foundation for all that we experience!
The autonomic nervous system is comprised of two parts: the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is synonymous with the “fight and flight” response that occurs when we interpret a threat in our internal or external environment. Traditionally the parasympathetic nervous system has been thought to be a single system and function in the “rest and digest” mode. This has found, however, not to be the case.
Stephen Porges, PhD first presented his groundbreaking work on the polyvagal theory in 1994. This theory describes a more complex function of our autonomic nervous system and the vagus nerve, in particular. According to the theory, the vagus nerve has two branches: ventral and dorsal branches. Each branch has a particular functionality. The ventral vagal branch is responsible for a more grounded state in which we are expansive, have capacity to respond to internal and external events, and are able to perform at our best. This branch is also necessary for recovery. The dorsal vagal branch is responsible for the “rest and digest” function when there are no cues of threat, however if there is a sense of threat or danger that persists beyond the sympathetic nervous system response, this branch will lead to a “shutdown” mode in which our body attempts to conserve all available resources to manage the threat.
Each of the three branches of the autonomic nervous system are associated with specific physiological states and have their respective adaptive function. What becomes important is maintaining the appropriate physiological state for the specific situation.
There are additional considerations within the polyvagal theory which are important to understand. The first is the concept of neuroception. This process refers to the rapid and subconsciously acquisition of information about stimuli, both internal and external, and determine whether the specific stimulus represents a cue of safety or a cue of threat. If a cue of safety is determined, there is a predominant ventral vagal response. If there is a cue of threat then there will be either a sympathetic or a dorsal vagal response, depending on the degree of threat and risk.
In addition to neuroception, there is the concept of physiological state as an “intervening variable”. Dr. Porges describes this as the ability of our current physiological state to influence neuroception, such that the same stimulus could be interpreted as a cue of safety or a cue of threat on the basis of the physiological state we are in at the time of the stimulus. As an example, consider becoming stuck in traffic and how we may, at one time, become frustrated or upset and at another time remain relaxed and unaffected.
An additional consideration is the social engagement system. This is the result of connections between our vagus nerve and the muscles of our face and larynx. When we are in a ventral vagal state, this system results in facial expressions and changes in the tone and frequency of our voice which is calming to ourselves and those around us. Conversely, when we are in a sympathetic or dorsal vagal state, this system leads to facial expressions and restriction in tone of voice which depict a cue of threat. This system allows us to not only regulate our own physiological state, but also those around us, a process referred to as co-regulation.
The understanding of this theory is crucial because it is the foundation for how we interpret events in our experience and respond to those events. Whether or not we choose to be aware of how this occurs and use the information to influence our nervous system, these systems are always occurring beneath our subconscious. It allows us to understand how to better regulate our own states as well as those around us. In short, it allows us to influence our ability to be at our best and to help others be at their best in any, and all, aspects of life. By training our ability to modulate our physiological states towards a more ventral vagal oriented state, we develop, what Dr. Porges refers to as, vagal efficiency. The theory suggests that there is a constant sympathetic tone and it is our ability to engage the vagus nerve, that determines the extent of sympathetic or vagal tone that predominates, a process referred to as vagal brake.
The extent to which we are able to train our vagal efficiency can be reflected through our subjective experience. More precisely, however, it can be measured through metrics of heart rate variability, a measure of the difference between our heart beats over time, and respiratory sinus arrhythmia, a measure of the variation in our heart rate during respiration. Heart rate variability is currently widely measurable by various wearable devices.
Through the understanding of polyvagal theory, it is possible to better understand how our nervous system interprets stimuli and our resulting experience, train our ability to understand our current physiological state and help modulate those states towards the preferred state for the situation and to help others do the same, including our children, loved ones, and all those around us. For these reasons, polyvagal theory not only provides a foundational understanding, but an operational framework for how we can influence our experience and our performance. The choice to train our ability to influence our autonomic nervous system is at the core of The Practices of the Healthcare Athlete as it allows us to maximize our health, wellbeing, and promote sustainable high performance.
Future posts related to Polyvagal Theory will focus on the application to human performance.
Dana, D. Polyvagal Exercises for Safety and Connection: 50 Client-centered Practices. New York: W.W. Norton & Company; 2020.
Dana, D. Anchored: How to Befriend Your Nervous System Using Polyvagal Theory. Boulder, Colorado: Sounds True, 2021.
Porges, SW. Polyvagal Safety: Attachment, Communication, Self-Regulation. New York: W.W. Norton & Company; 2021.
Porges, SW. The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication, Self-Regulation. New York: W.W. Norton & Company; 2011.