[Polyvagal Theory and Its Clinical Potential: An Overview].

The polyvagal theory, proposed by Stephen Porges, describes the adaptive responses of the mammalian autonomic nervous system. According to this novel theory, the vagus nerve functions through two independent pathways, referred to as the ventral and the dorsal vagal pathways. The ventral vagus is a myelinated nerve that has newly emerged in mammals and in coordination with cranial nerves regulates the muscles of the face and head to form the ventral vagal complex, which enables social engagement via exchange of safety cues and downregulating sympathetic defense reaction. In a safe environment, mammals normally adapt using the social engagement system; however, depending on the degree of risk exposure in the environment, activation of the sympathetic nervous system triggers the fight-or-flight response, and the dorsal vagal system initiates the immobilization shutdown response. The involuntary neural process through which the nervous system evaluates risk is referred to as neuroception. The polyvagal theory explains the pathophysiology of trauma and various physical symptoms associated with ventral vagal complex dysfunction. Moreover, this may potentially be useful as a fundamental theory in psychotherapy, in which the quality of social interaction is critical.