Polyvagal Theory and the Window of Tolerance

The autonomic nervous system (ANS) plays a key role in the trauma response and the processing of trauma.

The ANS is a branch of the peripheral nervous system that governs many involuntary regulatory aspects of our physical functioning (such as heart rate and sexual arousal). The ANS is divided into two main sub-systems.

The Parasympathetic Nervous System

The parasympathetic nervous system is often referred to as our “rest and digest” system and governs the relaxation response, digestion, cellular repair, and regeneration (healing). It can, however, also become activated under threat, generating physiological states of “freeze” or “collapse”.

The Sympathetic Nervous System

The sympathetic nervous system is often called the “fight or flight” system and is concerned primarily with defensive mobilization responses to perceived threats. Yet the sympathetic nervous system also operates within perceived safety when we feel excited or mobilized in a non-threatening way, such as with exercise or in social contexts.

Video: Trauma and the Nervous System

6:10

Building one’s capacity for ANS regulation largely involves bringing into conscious awareness practices that support stress tolerance and resilience within the nervous system so that such practices may be used proactively to maintain good physical and mental health. This video provides an introduction to self-regulation in the context of the ANS. We will watch the first part of the video here and finish the video in context on the following page.

Polyvagal Theory

Polyvagal theory, developed by Stephen Porges, sees a hierarchy of defences operating within our ANS, mediated in particular by the two branches of the vagus nerve (ventral and dorsal) (Porges, 2011; Schore, 2012; Stanley, 2016). Key to this theory is the distinction between social engagement and defence.

Social Engagement

Social engagement relies on attunement, empathy, and cooperation and is mediated by the ventral vagal nerve.

Defence

Defence may be active or varying degrees of passive with the SNS governing active defence and the dorsal vagus branch initiating a totally passive defence of shutting down (“freeze” and “collapse”).

Poly-vagally-informed psychotherapeutic interventions for the treatment of trauma are first focused on supporting a client’s emerging capacity to modulate ANS arousal using their inner resources in the context of building ventral-vagal social engagement within the therapeutic relationship.

Video: Window of Tolerance and Emotional Regulation

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In this video, we’ll learn more about the window of tolerance. Within the window of tolerance (or in a ventral-vagal mediated state of social engagement), integrative capacity is present; outside the window of tolerance, integrative capacity is greatly diminished. When integrative capacity is diminished, rational thought and the ability to take in new information, the ability to empathize, and to exercise impulse control is compromised because your higher cortical brain centers take the back seat to mid-brain survival-oriented regions of the brain.

Psychedelic-assisted therapy both aims to increase a client’s integrative capacity and relies on a minimum threshold of reliable integrative capacity being present at the outset of treatment to safely engage in the process.

Video: "Flipping Your Lid:" A Scientific Explanation

7:27

In this video, Dan Siegel discusses flipping your lid from a scientific perspective and talks about the role that our autonomic nervous system plays in this reaction and regulating one’s emotions.

References

Porges, S.W. (2011). The Polyvagal theory: Neurophysiological Foundations of Emotions, Attachment, Communication, and Self-Regulation. Norton.

Schore, A. N. (2012). The Science of the Art of Psychotherapy. Norton.

Stanley, S. (2016). Relational and Body-Centered Practices for Healing Trauma: Lifting the Burdens of the Past. Routeledge.