The Effects of Sensory Flow on The Autonomic Nervous System

Abstract

Treating patients who have chronic pain is often challenging for health care professionals. Typically, patients with chronic pain present with a variety of comorbidities, including, but not limited to decreased range of motion, muscle spasm, and recurring muscle tenderness [1]. Many of these protective patterns have also been observed as components of the fight, flight or freeze response. An overactive fight, flight or freeze response, a product of the Autonomic Nervous System (ANS), has been shown to be a major contributor to chronic pain response patterns and persistent pain [1-3]. One fight, flight or freeze theory that is starting to gain momentum is explained well in Bessel van der Kolk's book, The Body Keeps the Score: Brain, Mind and Body in the Healing of Trauma [4]. Van der Kolk explains that if the person having a stressful experience successfully completes the fight or flight cycle, the body recognizing that the threat has passed, will allow the stress of the trauma to dissipate. If the brain chooses fight or flight, but the body is unsuccessful, it enters a freeze cycle. During the freeze cycle the body becomes immobile. Often, predators become less interested in prey that is not moving, which allows the prey to escape. Successful evasion of a threat prepares the body to discharge trauma. If a body never experiences a discharge, the cycle is incomplete, and the stress is stored in the brain as procedural memory [4]. The stored input tells the brain how to react every time a similar sensory input or memory a rises [4,5]. An important thing to note is every detail about the event is stored [2,5]. Stimuli like scents, lighting, noises, sensations and objects become part of the sensitizing factors. These stored stimuli are called kindling [5]. While kindling often strengthens the original traumatic memory, it can also branch out into new pathways. When kindling recurs in everyday life, the amygdala prepares the body by activating the Sympathetic Nervous System (SNS) for fight or flight [3,4,6]. When the fight, flight, or freeze cycle completes properly, the threat to the body is extinguished, sensory information is stored, and the body returns to its normal set point. When it does not complete the cycle properly, the amygdala continues to seek resolution. The incomplete cycle results in chronic up-regulation of the ANS [3,5,7-10].