What is VNS?
The vagus nerve is the largest nerve in the autonomic nervous system; it travels through much of the body connecting the brain to major organ systems. As the primary communication route with the body, the vagus nerve and its branches are the key components of the parasympathetic branch of the autonomic nervous system. The parasympathetic branch reaches important components of the brain, stimulating synaptic activity while dampening the sympathetic stress response. Because the sympathetic and parasympathetic nervous systems are perceived as being in paired antagonism – when one goes up, the other goes down - the vagus nerve is critical to our therapy due to its effect on the autonomic nervous system.
Transcutaneous (through the skin) vagal nerve stimulation (tVNS) affects the systems involved in emotional regulation, including the amygdala. tVNS also activates the locus coeruleus (the principal site for brain synthesis of norepinephrine) which affects the limbic system. The limbic system is a complex system of nerves and networks in the brain concerned with instinct and mood, controlling the basic emotions (fear, pleasure, anger) and drives (hunger, sex, dominance, care of offspring.) A variety of studies support the hypothesis that VNS diminishes emotional reactivity and increases socially adaptive emotional regulation in the limbic system. These are the same regions and networks that are abnormally active in response to emotional stimuli in PTSD patients.
How It Works:
Sympathetic arousal is the body’s response to stress. Moments of stress or danger cause the amygdala to send a signal to the hypothalamus. After the amygdala sends a distress signal, the hypothalamus activates the sympathetic nervous system which in turn leads to the fight or flight phenomenon.
During a stress response that has triggered the sympathetic nervous system, the parasympathetic nervous system can help in two ways. First, it modulates the sympathetic response. Second, once the stressful situation is over, the parasympathetic nervous system puts the body back into a therapeutic recuperative state.
The vagus nerve directly affects how the parasympathetic nervous system operates in the body, so vagal nerve stimulation can trigger the parasympathetic response for someone who, because of trauma, has a diminished ability to do so.
Given this ability of the vagus nerve to enhance learning, scientists have been investigating the ability of pairing VNS to improve the results of certain therapies, with good results. These therapies include treatment of tinnitus, physical rehabilitation, and Cognitive Behavioral Therapy (CBT), more specifically CBT for PTSD.