Vagal Nerve Stimulation Through the Lens of the Polyvagal Theory: Recruiting Neurophysiological Mechanisms to Dampen Threat Reactions and Promote Homeostatic Functions

Vagal nerve stimulation, when viewed through the lens of the Polyvagal Theory, emphasizes three points. First, it emphasizes the link between the functions of the ventral vagal complex and symptoms reduced by vagal nerve stimulation, which functionally enhance mental and physical health. Second, it shifts the emphasis of vagal nerve stimulation from the entire nerve to select afferent pathways that communicate with brainstem areas that regulate both somatomotor and visceromotor efferent pathways originating in the ventral vagal complex. Third, by documenting the positive impact of vagal nerve stimulation, it acknowledges that trauma and chronic stress can “retune” autonomic function and disrupt the adaptive function of the ventral vagal complex in mitigating threat reactions and optimizing homeostatic functions of health, growth, and restoration. It is anticipated that methods and clinical targets of vagal nerve stimulation will evolve as we become more informed about the specific anatomical pathways traveling through the vagus. As this knowledge becomes integrated into technologies and procedures, there may be a category of vagal neuromodulators that function as neural exercises that would result in a more resilient autonomic nervous system and would not require chronic use.