Vagal Nuclei

Anatomy

• Dorsal motor nucleus of the vagus (DMV): in the floor of the fourth ventricle, lateral to the hypoglossal nucleus (vagal trigone).
• Nucleus ambiguus (NA): in the ventrolateral medulla, within the reticular formation; motor fibers of nerves IX, X and XI.
• The neighboring nucleus tractus solitarius (NTS): the first stop of vagal afferents.
• The vagus nerve leaves the lateral medulla between the olive and the inferior cerebellar peduncle (the nerve root in the model).

Functions

• NA: fast, breath-linked braking of heart rate (respiratory sinus arrhythmia); muscles of the larynx and pharynx (voice, swallowing).
• DMV: organs below the diaphragm (stomach, intestine); digestion, motility, secretion.
• Vagal afferents (about 80% of the fibers) report the state of the body to the brain via the NTS.
• Inflammatory reflex: the cholinergic anti-inflammatory pathway.
• A note on polyvagal theory: the Porges model, also used in the book, ties the ventral vagal (nucleus ambiguus) system to social engagement and the dorsal vagal (DMV) system to freezing and shutdown. The theory’s core premises (separate cardiac roles for the two nuclei, RSA reflecting overall vagal tone, RSA being unique to mammals) have been seriously criticized in the physiology literature (Grossman, 2023). It is a useful explanatory model in the clinic, but should be taught as a theory, not as anatomical fact. B

Connections and chemistry

• NTS → parabrachial → amygdala, hypothalamus, insula (afferent limb)
• NA → heart (SA node), larynx, pharynx
• DMV → stomach, intestine
• Acetylcholine (efferent), glutamate (afferent)

Development

Developmental course through childhood and adolescence.

• Myelination of vagal fibers increases in the last trimester and after birth.
• Vagal tone (RSA) increases from infancy and has been linked to emotion regulation and social engagement.

Clinical

• Anxiety and trauma: reduced resting heart rate variability (RSA); shown by meta-analysis in anxiety disorders (Chalmers et al., 2014). Its link with long-term cardiovascular risk is also discussed. A
• Anorexia nervosa: bradycardia from vagal dominance.
• Blood-injection-injury phobia and vasovagal syncope (common in adolescents): a biphasic response.
• Vagus nerve stimulation: used in refractory epilepsy (also in children) and in adult treatment-resistant depression.

Treatment

This region from the perspective of medication, psychotherapy and neuromodulation. Letter badges are evidence levels.

• Vagus nerve stimulation (implanted): FDA-approved from age 4 for drug-resistant epilepsy (2017; previously from age 12). Also approved for adult treatment-resistant depression. A
• Paired VNS for stroke rehabilitation: vagus stimulation delivered with movement exercises improved upper-limb function in chronic ischemic stroke (108 patients); FDA approval 2021. It relies on the vagus nerve’s “learning-enhancing” (plasticity) effect. A
• Heart rate variability biofeedback and slow-breathing exercises are low-risk approaches that target vagal regulation in anxiety. C

Assessment

Neuropsychological tasks and measures that probe this region's function.

• Heart rate variability / RSA (an index of vagal tone)
• Orthostatic test, Valsalva maneuver
• Swallowing and phonation assessment

Lesions and damage

Clinical findings expected with damage or dysfunction.

• Hoarseness, dysphagia, uvular deviation (NA); autonomic dysregulation.

In the model

How this structure is defined in the 3D model, and the data source.

No atlas data: the dorsal motor nucleus and nucleus ambiguus were positioned by hand on medullary sections; the vagus root is schematic.

References

Full citations for the card; links go to the paper (DOI) or a PubMed search.

1. Grossman P. Fundamental challenges and likely refutations of the five basic premises of the polyvagal theory. Biol Psychol 2023;180:108589. Search PubMed
2. Chalmers JA et al. Anxiety disorders are associated with reduced heart rate variability: a meta-analysis. Front Psychiatry 2014;5:80. Search PubMed
3. FDA: VNS Therapy 4 yaş and üstü epilepsi, Temmuz 2017; Vivistim eşleştirilmiş VNS inme rehabilitasyonu, Ağustos 2021. Search PubMed