Polyvagal theory
Polyvagal theory (PVT) is a collection of proposed evolutionary, neuroscientific, and psychological constructs pertaining to the role of the vagus nerve in emotion regulation, social connection and fear response. The theory was introduced in 1994 by Stephen Porges.[1] There is consensus among experts that the assumptions of the polyvagal theory are untenable.[2] PVT is popular among some clinical practitioners and patients,[3] but it is not endorsed by current social neuroscience.[4][5][6][7][8][9]
Polyvagal theory takes its name from the vagus nerve, a cranial nerve that forms the primary component of the parasympathetic nervous system.[10][11][12] The traditional view of the autonomic nervous system presents a two-part system: the sympathetic nervous system, which is more activating ("fight or flight"), and the parasympathetic nervous system, which supports health, growth, and restoration ("rest and digest").[13] Polyvagal theory views the parasympathetic nervous system as being split into two distinct branches: a "ventral vagal system" which supports social engagement, and a "dorsal vagal system" which supports immobilisation behaviours, both "rest and digest" and defensive immobilisation or "shutdown".[14] This "social engagement system" is a hybrid state of activation and calming that plays a role in our ability to socially engage.[14]
Vagus Nerve and Polyvagal Theory
The vagus nerve, also known as the tenth cranial nerve, is a fundamental component of the autonomic nervous system. It facilitates the transmission of parasympathetic signals to and from internal organs, including the heart, lungs, and digestive system.[15]
Overview
The Polyvagal Theory was proposed in 1994 by Stephen Porges during his tenure as director of the Brain-Body Center at the University of Illinois at Chicago.[16] The theory explores the structure and function of the vagus nerve, emphasizing its two efferent branches originating in the medulla oblongata.[17]
According to Porges, each branch of the vagus nerve is associated with distinct adaptive behavioral strategies:
- The ventral vagal complex (VVC) is proposed to support social engagement and states of calm.
- The dorsal vagal complex (DVC) is associated with immobilization behaviors, such as freezing or shutdown.[18]
Core Principles
Three central principles are foundational to the theory:
- Hierarchy: The autonomic nervous system is proposed to function in a hierarchical manner, responding to stimuli in an order that prioritizes social engagement, fight-or-flight responses, and immobilization.
- Neuroception: Unlike conscious perception, neuroception refers to subconscious detection of safety or danger, which influences physiological responses.[19]
- Co-regulation: The theory emphasizes the need to feel safe within relationships to enable self-regulation and social interaction, which can be challenging for individuals with trauma.[20]
Porges' work has significantly influenced trauma therapy and has been referenced by practitioners such as Bessel van der Kolk, Peter A. Levine, and others in fields like somatic therapy and childhood trauma intervention.[21]
Mainstream Scientific Perspectives
While Polyvagal Theory has been influential in therapeutic and trauma-informed practices, it has faced critiques within the scientific community:
- Lack of Empirical Evidence: Critics argue that the proposed division of the vagal branches into "ventral" and "dorsal" functions lacks robust empirical validation. The evolutionary assumptions underlying the theory are considered speculative by some researchers.[22]
- Oversimplification: Some researchers believe the theory oversimplifies the complexities of the autonomic nervous system and emotional responses. It may not fully capture individual differences or the intricate interplay between neural and physiological mechanisms.[23]
- Limited Acceptance in Neuroscience: While popular in therapeutic settings, the theory has not achieved widespread acceptance within the mainstream neuroscientific community. Experts suggest additional rigorous studies are necessary to substantiate its claims.[24]
The Polyvagal Theory provides a novel framework for understanding the relationship between the autonomic nervous system and behavior, particularly in trauma-informed practices. However, its scientific foundations remain a subject of ongoing research and debate, highlighting the need for further empirical validation.
Mainstream Views and Criticism
The Polyvagal Theory (PVT), introduced by Stephen Porges in 1994, has been widely discussed in therapeutic settings and has influenced approaches to understanding trauma, emotional regulation, and social connection. However, it has also faced scrutiny from the mainstream scientific community. A balanced view includes both its potential contributions and limitations:
- Support for the Theory: Proponents of PVT highlight its innovative framework for explaining the role of the vagus nerve in emotional regulation and social behavior. The theory has been widely adopted in trauma therapy, where practitioners use its concepts to help patients understand their physiological responses to stress and trauma. Therapists such as Bessel van der Kolk, Peter A. Levine, and others have incorporated elements of PVT into practices like somatic experiencing and trauma-informed care.[18]
- Lack of Empirical Evidence: Critics argue that PVT relies on assumptions about evolutionary biology that remain speculative. For example, the division of the vagal nerve into "restful" (ventral) and "active" (dorsal) roles has been questioned due to limited direct evidence. Systematic reviews have called for further empirical studies to validate concepts such as neuroception and its purported role in human behavior.[22][24]
- Oversimplification of Complex Systems: Some researchers contend that PVT oversimplifies the complexity of the autonomic nervous system and emotional responses. The broad generalizations about the ventral and dorsal branches may not fully account for individual differences or the intricate interplay between neural and physiological mechanisms.[23]
- Limited Acceptance in Neuroscience: While PVT has gained popularity among clinicians and therapists, it has not been widely endorsed within the mainstream neuroscientific community. Some experts have suggested that the theory’s foundational assumptions lack sufficient experimental support and advocate for more rigorous validation of its claims.[23]
- Alternative Models: Other frameworks, such as the Social Engagement System Theory and the Biopsychosocial Model, offer alternative explanations for the relationship between the nervous system and behavior. These models emphasize the interplay of biological, psychological, and social factors, providing a more integrative view of emotional regulation.[25]
Scientific Criticism
While the Polyvagal Theory has garnered attention in trauma studies and therapeutic practices, some researchers and clinicians have expressed skepticism regarding its empirical foundations.
Critics argue that the theory relies on assumptions about evolutionary biology that remain speculative. Specifically, the division of the vagal branches into "restful" (ventral) and "active" (dorsal) roles has been questioned due to limited direct evidence.[22]
A systematic review of the evidence supporting Polyvagal Theory called for additional studies to validate the claims, particularly regarding the concept of neuroception and its role in human behavior.[24]
Alternative Theories Other models, such as the Social Engagement System Theory and the Biopsychosocial Model of Trauma, offer competing explanations for the relationship between the nervous system and human behavior. These frameworks emphasize the interplay of biological, psychological, and social factors without strictly segmenting autonomic functions.[10]
Alternative Theories
Other models, such as the Social Engagement System Theory and the Biopsychosocial Model of Trauma, offer competing explanations for the relationship between the nervous system and human behavior. These frameworks emphasize the interplay of biological, psychological, and social factors without strictly segmenting autonomic functions.[25]
Conclusion
While the Polyvagal Theory has made notable contributions to understanding trauma and emotional regulation, its scientific validity remains a topic of debate. Further research is needed to substantiate its claims and integrate its concepts into a broader understanding of the autonomic nervous system.
See Also
References
- ^ Porges, Stephen W. (1995). "Orienting in a defensive world: Mammalian modifications of our evolutionary heritage. A Polyvagal Theory". Psychophysiology. 32 (4): 301–318. doi:10.1111/j.1469-8986.1995.tb01213.x. PMID 7652107.
- ^ Cite error: The named reference
Grossman23
was invoked but never defined (see the help page). - ^ "Polyvagal theory in practice". Counseling Today. 2016-06-27. Retrieved 2020-10-31.
- ^ Todorov, Alexander; Fiske, Susan; Prentice, Deborah (2011). Social Neuroscience: Toward Understanding the Underpinnings of the Social Mind. Oxford University Press. ISBN 978-0-19-972406-2.[page needed]
- ^ Ward, Jamie (2016). The Student's Guide to Social Neuroscience. Psychology Press. ISBN 978-1-317-43918-9.[page needed]
- ^ Schutt, Russell K.; Seidman, Larry J.; Keshavan, Matcheri S. (2015). Social Neuroscience: Brain, Mind, and Society. Harvard University Press. ISBN 978-0-674-72897-4.[page needed] Litfin, Karen T.; Berntson, Gary G. (2006). Social Neuroscience: People Thinking about Thinking People. MIT Press. ISBN 978-0-262-03335-0.[page needed]
- ^ Baron-Cohen, Simon; Tager-Flusberg, Helen; Lombardo, Michael (2013). Understanding Other Minds: Perspectives from Developmental Social Neuroscience. Oxford: Oxford University Press. ISBN 978-0-19-969297-2.[page needed]
- ^ Cacioppo, Stephanie; Cacioppo, John T. (2020). Introduction to Social Neuroscience. Princeton University Press. ISBN 978-0-691-16727-5.[page needed]
- ^ Decety, Jean; Cacioppo, John T. (2011). The Oxford Handbook of Social Neuroscience. Oxford University Press. ISBN 978-0-19-534216-1.[page needed]
- ^ Anthony, Andrew. "Stephen Porges: 'Survivors are blamed because they don't fight'". The Guardian. Retrieved 2021-09-17.
- ^ Brookes, David (2019-11-28). "The Wisdom Your Body Knows". The New York Times. ISSN 0362-4331. Retrieved 2021-09-17.
- ^ Quinn, Robert E.; Fessell, David P.; Porges, Stephen W. (2021-01-15). "How to Keep Your Cool in High-Stress Situations". Harvard Business Review. ISSN 0017-8012. Retrieved 2021-09-19.
- ^ Davidson, R. J.; Scherer, K. R.; Goldsmith, H. H., eds. (2003). "The autonomic nervous system and its coordination by the brain". Handbook of affective sciences. London: Oxford University Press. pp. 135–186. ISBN 978-0195377002.
- ^ a b Porges, Stephen W. (April 2009). "The polyvagal theory: New insights into adaptive reactions of the autonomic nervous system". Cleveland Clinic Journal of Medicine. 76 (Supplement 2): S86 – S90. doi:10.3949/ccjm.76.s2.17. ISSN 1939-2869. PMC 3108032. PMID 19376991.
- ^ Lehrer, P. M., et al. (1996). "Heart rate variability biofeedback increases vagal tone." Psychosomatic Medicine.
- ^ Porges, S. W. (1995). "Orienting in a defensive world: Mammalian modifications of our evolutionary heritage." Psychophysiology.
- ^ Friedman, B. H. (2007). "An autonomic flexibility–neurovisceral integration model of anxiety and cardiac vagal tone." Biological Psychology.
- ^ a b Porges, S. W. (2011). The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication, and Self-Regulation. W.W. Norton & Company.
- ^ Porges, S. W. (2004). "Neuroception: A subconscious system for detecting threats and safety." Zero to Three Journal.
- ^ Ogden, P., & Fisher, J. (2006). Sensorimotor Psychotherapy: Interventions for Trauma and Attachment. Guilford Press.
- ^ van der Kolk, B. A. (2015). The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma. Penguin Books.
- ^ a b c Grossman, P., & Taylor, E. W. (2020). "Toward understanding respiratory sinus arrhythmia: relations to cardiac vagal tone, evolution, and biobehavioral functions." Biological Psychology.
- ^ a b c Polyvagal Theory: Useful Narrative, But Still Just a Theory. Psychology Today (2022).
- ^ a b c Gerritsen, R. J., & Band, G. P. (2018). "Breathing slows down decision-making: The impact of respiratory sinus arrhythmia on reaction times in humans." Frontiers in Psychology.
- ^ a b Engel, G. L. (1977). "The need for a new medical model: A challenge for biomedicine." Science.
Reception
In a 2023 review of the literature, Paul Grossman lists five premises of polyvagal theory and states that "there is broad consensus among experts [...] that each basic physiological assumption of the polyvagal theory is untenable. Much of the existing evidence, upon which these consensuses are grounded, strongly indicates that the underlying polyvagal hypotheses have been falsified."[1]
Although proponents like Bessel van der Kolk praise the theory's explanatory power,[2] Grossman considers the theory an unnecessary and unsubstantiated conflict imposed on the public dialogue.[3]
Neuroscientific claims
Neuhuber and Berthoud (2022) state that polyvagal theory's "basic phylogenetic and functional-anatomical tenets do not withstand closer scrutiny".[4] They argue that polyvagal theory incorrectly portrays the role of the different vagal nuclei in mediating the freeze response. According to their analysis, the evidence "does not support a role of the 'dorsal vagal complex' in freezing as proposed by the PVT" and the dorsal vagal complex "should not be linked to passive defensive behavior". Regarding the proposed "ventral vagal complex", they state that "the PVT, by construeing a 'new ventral vagal complex' encompassing the entire branchiomotor column ascribed to the vagus much more than it actually can serve." They see it as "misleading to propose that brainstem branchiomotor ('source') nuclei 'communicate directly with the visceromotor portion of the nucleus ambiguus'", and conclude that the relevant networks "should not be termed 'ventral vagal complex'. This terminology may insinuate that the vagus is a "prime mover". This not the case [...]".
Taylor, Wang & Leite (2022) similarly regard it as "invalid to refer to this as a 'vagal system' or to postulate the existence of a 'smart vagus'."[5]
Evolutionary claims
Grossman and Taylor (2007) argue that there is no evidence that the dorsal motor nucleus (DMN) is an evolutionarily more primitive center of the brainstem parasympathetic system than the nucleus ambiguus (NA), and review evidence to the contrary.[3]
A more recent paper by Monteiro et al. (2018) finding myelinated vagus nerve fibers of lungfish leading from the nucleus ambiguus to the heart also indicates that polyvagal theory’s hypothesis that the nucleus ambiguus is unique to mammals is incorrect.[6] They state that "the mechanisms [Porges] identifies as solely mammalian are undeniably present in the lungfish that sits at the evolutionary base of the air-breathing vertebrates."
Grossman (2023) concurs, stating that "the polyvagal notion that the ventral vagal area is unique to mammals is opposed by years of evidence" and that the "findings, as a whole, firmly and consistently contradict the polyvagal hypotheses that propose the [dorsal vagal motor nucleus] as the “source nucleus” of unmyelinated pathways and the [nucleus ambiguus] as the “source nucleus” of myelinated pathways in mammals".[1]
Results reviewed by Taylor, Leite and Skovgaard (2010) also "refute the proposition that centrally controlled cardiorespiratory coupling is restricted to mammals, as propounded by the polyvagal theory of Porges".[7] In Taylor, Wang & Leite's 2022 review, the evidence for the presence of cardio-respiratory interactions similar to respiratory sinus arrhythmia (RSA) and their potential purpose in blood oxygenation in many vertebrate species (both air- and water-breathing) leads them to conclude that RSA may be a relic of older cardio-respiratory systems, contrary to polyvagal assumptions.[5]
The dichotomy between asocial reptiles and social mammals subscribed to by polyvagal theory has been contested. Doody, Burghardt & Dinets [8] consider several ways of assessing and classifying animal sociality and state that "Porges’ dichotomy is incorrect. While many mammals (particularly humans) may show more complex social behavior than reptiles, there is considerable overlap in social tendencies between the two groups. The labels ‘social’ and ‘asocial’ are too crude to have utility in a comparative framework of social behavior and should not be used to describe taxa". Listing examples of social behavior in reptiles and other non-mammal vertebrates, they observe that "PT appears to rest upon 20th century folk interpretation of vertebrate evolutionary biology rather than on current scientific understanding of it."
Claims regarding cardiac functioning
Polyvagal theory proposes a relationship between RSA responses and forms of psychopathology, but a meta-analysis finds the empirical evidence to be inconclusive.[9]
According to Grossman and Taylor,[3] the existing research indicates that respiratory sinus arrhythmia is not a reliable marker of vagal tone, since it is subject to both respiratory variables and sympathetic (beta-adrenergic) influences in addition to vagal influences. In addition, they argue that the results of Porges' 2003 study on two species of lizard was flawed due to incorrect measurements of heart rate variability.
Reviewing more recent evidence, Paul Grossman again finds RSA not "a direct measure of cardiac vagal tone" due to confounding factors. In addition, he concludes that contrary to polyvagal claims "there is no credible evidence that the [dorsal vagal motor nucleus] plays any role in massive bradycardia", and that it "appears to have almost no effect upon vagal heart rate responses".[1]
Scientific standards
In a 2021 publication, Porges stated that "the theory was not proposed to be either proven or falsified".[10] Falsifiability is a central tenet of the scientific method.
See also
References
- ^ a b c Grossman, Paul (2023). "Fundamental challenges and likely refutations of the five basic premises of the polyvagal theory". Biological Psychology. 180. doi:10.1016/j.biopsycho.2023.108589. PMID 37230290.
- ^ Van Der Kolk, Bessel (2014). The body keeps the score: brain, mind, and body in the healing of trauma. New York: Viking Penguin. p. 80. ISBN 9780670785933. Retrieved 3 February 2018.
- ^ a b c Grossman, Paul; Taylor, Edwin W. (2007-02-01). "Toward understanding respiratory sinus arrhythmia: Relations to cardiac vagal tone, evolution and biobehavioral functions". Biological Psychology. 74 (2): 263–285. doi:10.1016/j.biopsycho.2005.11.014. ISSN 0301-0511. PMID 17081672. S2CID 16818862.
- ^ Neuhuber, Winfried; Berthoud, Hans-Rudolf (2022-10-01). "Functional anatomy of the vagus system: How does the polyvagal theory comply?". Biological Psychology. 174: 108425. doi:10.1016/j.biopsycho.2022.108425. PMID 36100134. S2CID 252188181.
- ^ a b Taylor, Edwin; Wang, Tobias; Leite, Cleo (2022-06-28). "An overview of the phylogeny of cardiorespiratory control in vertebrates with some reflections on the 'Polyvagal Theory'". Biological Psychology. 172: 108382. doi:10.1016/j.biopsycho.2022.108382. PMID 35777519. S2CID 250095867.
- ^ Monteiro, Diana (2018). "Cardiorespiratory interactions previously identified as mammalian are present in the primitive lungfish". Science Advances. 4 (2): eaaq0800. Bibcode:2018SciA....4..800M. doi:10.1126/sciadv.aaq0800. PMC 5833999. PMID 29507882.
- ^ Taylor; Leite; Skovgaard (2010). "Autonomic control of cardiorespiratory interactions in fish, amphibians and reptiles". Brazilian Journal of Medical and Biological Research. 43 (7): 600–610. doi:10.1590/S0100-879X2010007500044. hdl:11449/21090. PMID 20464342.
- ^ Doody; Burghardt; Dinets (2023). "The Evolution of Sociality and the Polyvagal Theory". Biological Psychology. 180. arXiv:2304.09238. doi:10.1016/j.biopsycho.2023.108569. PMID 37094735. S2CID 258212987.
- ^ Beauchaine, Theodore P.; Bell, Ziv; Knapton, Erin; McDonough-Caplan, Heather; Shader, Tiffany; Zisner, Aimee (2019). "Respiratory sinus arrhythmia reactivity across empirically based structural dimensions of psychopathology: A meta-analysis". Psychophysiology. 56 (5): e13329. doi:10.1111/psyp.13329. ISSN 1469-8986. PMC 6453712. PMID 30672603.
- ^ Stephen W. Porges (2021-08-01), "Polyvagal Theory: A biobehavioral journey to sociality", Comprehensive Psychoneuroendocrinology, vol. 7, p. 100069, doi:10.1016/j.cpnec.2021.100069, ISSN 2666-4976, PMC 9216697, PMID 35757052
Further reading
- Ulrich F. Lanius, Sandra L. Paulsen, Frank M. Corrigan: Neurobiology and Treatment of Traumatic Dissociation: Towards an Embodied Self. Springer Publishing Co., 2014
- Porges, S. W. (2006). "The Polyvagal Perspective". Biological Psychology. 74 (2): 116–143. doi:10.1016/j.biopsycho.2006.06.009. PMC 1868418. PMID 17049418. (Review).
- Holly Bridges: Reframe Your Thinking Around Autism: How the Polyvagal Theory and Brain Plasticity Help Us Make Sense of Autism ISBN 978-1849056724 Jessica Kingsley Publishers. 2015
- Robert Bright: The Polyvagal Theory: The Simplified Guide to Understanding the Autonomic Nervous System and the Healing Power of the Vagus Nerve – Learn to Manage Emotional Stress and PTSD Through Neurobiology. White Publishing, Ltd., 2020, ISBN 978-1801119689
External links
- The Polyvagal Theory – www.wam.umd.edu
- After 20 years of "polyvagal" hypotheses, is there any direct evidence for the first 3 premises that form the foundation of the polyvagal conjectures? Paul Grossman, University Hospital of Basle, Switzerland, on ResearchGate, with references and some discussion starting January 2016
- Dunning, Brian (25 January 2022). "Skeptoid #816: The Dark Side of Polyvagal Theory". Skeptoid.