Control Your Vagus Nerve to Improve Mood, Alertness & Neuroplasticity

Key Concepts

Vagus Nerve (Cranial Nerve 10), Sensory vs. Motor Neurons, Autonomic Nervous System (Sympathetic & Parasympathetic), Heart Rate Variability (HRV), Autoregulation, Dorsolateral Prefrontal Cortex, Nucleus Ambiguous, Sinoatrial Node, Physiological Sigh, Adrenaline (Epinephrine), Nucleus Tractus Solitaris (NTS), Locus Ceruleus, Norepinephrine, Neuroplasticity, Acetylcholine, Nucleus Basalis, Dorsal Raphe Nucleus, Serotonin, Gut Microbiota, Tryptophan, Fermented Foods.

Vagus Nerve: An Extensive Overview

Introduction to the Vagus Nerve

The vagus nerve, or cranial nerve 10, is a vast network connecting the brain and body, acting almost as a separate nervous system within the larger system. It's highly actionable, offering tools to control alertness, calmness, mood, and learning ability. Recent research has illuminated pathways within the vagus nerve and how to stimulate them for specific outcomes.

Vagus Nerve Anatomy and Function

The vagus nerve differs from other cranial nerves by connecting to the head, neck, chest, abdomen, and lower intestines. "Vagus" translates to "wandering," reflecting its extensive reach. The nerve carries sensory and motor information. Sensory information includes light, sound, and chemical signals, while motor information controls muscle and organ contractions. The vagus nerve is unique because it is both a sensory and motor pathway.

Sensory Pathways of the Vagus Nerve

85% of the vagus nerve is sensory, transmitting information from the body to the brain. Vagal neurons have a cell body in the nodose ganglion near the neck and back of the head, with one axon extending to organs and another to the brainstem. This is unlike typical neurons where the axon is the output end. Sensory information includes chemical (e.g., gut acidity, serotonin levels) and mechanical (e.g., gut distension, lung expansion) signals.

Sensory Information: Chemical and Mechanical

The gut contains mechanoreceptors that sense stretch and chemoreceptors that sense acidity and serotonin levels. 90% of the body's serotonin is manufactured in the gut, influencing gut motility and health. Serotonin levels in the gut are conveyed to the brain via the vagus nerve, impacting mood. The lungs also communicate mechanical (expansion/contraction) and chemical (oxygen/carbon dioxide ratio) information to the brain.

Parasympathetic vs. Sympathetic Activity

Cranial nerve 10 is classified as a parasympathetic nerve, part of the autonomic nervous system that controls alertness and calm. The sympathetic nervous system increases alertness, while the parasympathetic nervous system promotes rest and digestion. The vagus nerve is a mixed parasympathetic nerve, meaning that activating certain branches can increase alertness (sympathetic activity) or decrease alertness (parasympathetic activity).

Calming Effects: Rubbing Behind the Ear

Rubbing behind the ear activates a sensory branch of the vagus nerve, carrying mechanical pressure information to the brainstem. This can induce a calming effect, but it's a minor branch and won't drastically shift the autonomic nervous system.

Motor Pathways of the Vagus Nerve

The remaining 15% of the vagus nerve consists of motor pathways originating from brainstem nuclei. These pathways control organs and can be selectively activated to improve health, mental well-being, performance, and recovery from conditions like stroke.

Autoregulation and Heart Rate Variability (HRV)

Autoregulation is the vagus nerve's ability to maintain balance between the sympathetic and parasympathetic nervous systems. This is linked to heart rate variability (HRV), the variation in time between heartbeats. Higher HRV is associated with positive health outcomes.

Deliberate Exhales and HRV

A key neural circuit for autoregulation originates in the left dorsolateral prefrontal cortex, connects to the nucleus ambiguous in the brainstem, and projects to the sinoatrial node of the heart. This pathway decelerates heart rate. The vagus nerve controls the sinoatrial node, coordinating with breathing. Inhaling speeds up heart rate, while exhaling slows it down. Deliberately extending exhales activates this pathway, increasing parasympathetic activity and improving HRV.

Physiological Sigh

The physiological sigh (two inhales through the nose followed by a long exhale through the mouth) is the fastest way to activate the parasympathetic nervous system. It provides both a chemical signal (reduced carbon dioxide) and a mechanical signal (decelerated heart rate) to the brain.

Aging and HRV

HRV tends to decrease with age, potentially due to atrophy of the dorsolateral prefrontal cortex. Activating the dorsolateral prefrontal cortex through transcranial magnetic stimulation or deliberate exhales can increase HRV.

Vagus Nerve and Alertness: Adrenaline and Exercise

Movement of large muscles triggers the release of adrenaline (epinephrine) from the adrenal glands. Adrenaline binds to receptors on the vagus nerve, which then releases glutamate in the nucleus tractus solitarius (NTS). The NTS activates the locus ceruleus, which releases norepinephrine in the brain, increasing alertness. This pathway explains how physical activity can increase alertness and motivation.

Exercise and Brain Plasticity

High-intensity exercise stimulates the vagus nerve, leading to the release of norepinephrine from the locus ceruleus (alertness) and acetylcholine from the nucleus basalis (focus). Acetylcholine release from nucleus basalis is permissive for plasticity. Alertness and focus are prerequisites for adult neuroplasticity.

Serotonin and the Gut-Brain Axis

90% of the body's serotonin is manufactured in the gut, but it doesn't directly travel to the brain. Instead, serotonin in the gut stimulates vagal nerve endings, which relay the signal to the dorsal raphe nucleus in the brain, triggering serotonin release there.

Improving Serotonin Levels

To maintain healthy serotonin levels, ensure adequate production in the gut by:

• Consuming 1-4 servings of low-sugar fermented foods daily (e.g., kimchi, sauerkraut, kefir).
• Ensuring sufficient tryptophan intake through diet (e.g., turkey, dairy).
• Consider occasional probiotic supplementation.

Calming Down: Specific Vagal Pathways

Specific vagal pathways can be activated to induce calmness:

1. Neck Stretch: Gently stretching the neck by pushing the elbows down and away from the ears, turning the head up and to the right, and then up and to the left, can mechanically activate vagal nerve fibers.
2. Humming: Humming with an emphasis on the "H" sound (e.g., "Hhhhhmmmm") vibrates the larynx and activates vagal branches. Focus on moving the vibration from the back of the throat down the neck and into the chest.
3. Exhales: The hum is like all speech an exhale, so this is the third part there's also a collateral activation which is just neuroscience speak for activation of that deceleration pathway when you do this humming at the back of your throat and down into your chest and into your belly you're also getting the same effect that you get with an exhale which is to slow the heart rate way way down

Conclusion

The vagus nerve is a complex and multifaceted system with significant influence over various aspects of health and well-being. Understanding its specific pathways and functions allows for targeted interventions to improve alertness, calmness, mood, learning, and overall autonomic balance.