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[@hubermanlab] Control Your Vagus Nerve to Improve Mood, Alertness & Neuroplasticity

· 10 min read
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@hubermanlab - "Control Your Vagus Nerve to Improve Mood, Alertness & Neuroplasticity"

Link: https://youtu.be/CLbVW3Pj46A

Short Summary​

Action Item: Incorporate deliberate, extended exhales throughout the day (10-20 times) to improve HRV and overall well-being.

Executive Summary: This podcast episode delves into the multifaceted roles of the vagus nerve, highlighting its influence on alertness, mood, learning, and calming. It emphasizes actionable tools, such as deliberate extended exhales, to leverage the vagus nerve for improved mental and physical health. The vagus nerve is a superhighway of sensory and motor connections involved in slowing the heart rate, autoregulation, increasing HRV as well as increasing the levels of alertnes and brain serotonin levels.

Key Quotes​

Okay, here are 5 quotes that I found particularly insightful or interesting from the provided transcript:

  1. "The vagus nerve or what neuron anatomists call cranial nerve 10 is an extremely interesting nerve because when we hear the word nerve we often think of a small you know connection between one thing and another the wires of the nerve which of course we call axons if you didn't know that now you know they're called axons but actually the cranial nerve is an extensive pathway it's a whole set of connections that link the brain and body in fact in many respects it looks kind of like its own nervous system within the traditional nervous system of the brain and the spinal cord, the connections between spinal cord and muscle." This quote highlights the vast and complex nature of the vagus nerve, dispelling the common misconception of it being a simple connection.
  2. "Different neurons or different nerve cells within the vagus nerve for instance are receiving or giving different types of information for different purposes. For instance, there is sensory information carried by neurons, nerve cells in your nervous system... Other neurons control motor functions literally the movement of your limbs by controlling contraction of your muscles or the movement of your lips or the closing or opening of your airways for instance." This quote succinctly explains the dual nature of the vagus nerve as both a sensory and motor pathway, which is crucial for understanding its diverse functions.
  3. "When you inhale air, of course, your lungs expand. You have a muscle that sits below your lungs called the diaphragm. As you inhale air, of course, that diaphragm moves down. Now, as your diaphragm moves down and your lungs expand, your heart literally has a bit more space in the thoracic cavity to expand... Put differently, inhaling speeds your heart rate up. Now, the converse is also true. When you exhale, your lungs deflate, your diaphragm moves up, and as a consequence, there's slightly less space for the heart. So, the heart shrinks a little bit. Not a ton, but it shrinks a little bit...Put differently, exhales slow your heart rate down and they do so by way of veagal control over the syinoatrial node." This quote provides a clear and detailed explanation of the physiological mechanisms linking breathing to heart rate via the vagus nerve, underpinning the rationale for breathing exercises.
  4. "Turns out that when the adrenals release adrenaline, it binds to receptors on the vagus nerve itself, those sensory axons that extend into the body. There are receptors on those wires, right? Not all the receptors are at one end or the other. They're also on those axons. The adrenaline binds to the receptors on those axons. And the vagus nerve in turn releases glutamate, an excitatory neurotransmitter in a structure in the brain called the nucleus tractus solitaris." This quote reveals the surprising connection between the adrenal glands, the vagus nerve, and brain activation, explaining how physical activity can boost alertness and motivation, and highlighting that adrenaline cannot cross the blood-brain barrier.
  5. "In your gut you have cells including neurons but you also have a lot of other cells mostly other cells frankly. And there's a particular category of cells called the intereroch chromophin cells. You don't need to know that name, but if you want, they're the interocchromophin cells. And they manufacture serotonin...That serotonin binds to the ends of neurons, the axons of neurons in the vagus nerve that intervate your gut...and stimulates a particular category of them that then relays the signal up and through noo's ganglen...into the brain to the nucleus tractus solitaris...then...sends a powerful signal to what's called the dorsal rafé nucleus." This quote describes the mechanisms by which the levels of serotonin in the gut are communicated to the brain and how gut health and diet influence serotonin production, which then impacts mood.

Detailed Summary​

Here's a detailed summary of the YouTube video transcript, focusing on the key topics, arguments, and information presented, and excluding sponsor announcements:

  • Introduction to the Vagus Nerve:

    • The vagus nerve (cranial nerve 10) is an extensive pathway linking the brain and body.
    • It's more than just a connection; it's almost a separate nervous system.
    • Highly actionable: knowledge about it can change beliefs and educate on the latest findings.
    • Provides tools for alertness, calmness, mood alteration, and improved learning (without pharmacology).

  • Vagus Nerve Basics:

    • Connects to head, neck, chest, abdomen, and lower intestines.
    • "Vagus" means "wandering" (vagabond), reflecting its extensive connections.
    • Wiring is precise, not random.
    • Carries sensory, motor, and modulatory information.

  • Sensory vs. Motor Functions:

    • Sensory Information: Conveys light, sound, chemical (gut acidity), and mechanical (stretch) information to the brain.
    • Motor Information: Controls muscle contraction and organ function (gut, pancreas, liver, spleen).
    • Vagus nerve contains both sensory and motor neurons.
    • Important to distinguish between activating sensory vs. motor pathways for specific effects (calming vs. energizing).

  • Sensory Pathways in Detail:

    • Unique neurons: cell body in nodose ganglia near the neck and back of head.
    • Axon extends to a specific organ in the body and another axon extends to the brain stem.
    • 85% of the vagus nerve is sensory.
    • Sensory information includes mechanical (stretch) and chemical (serotonin, acidity) cues.
    • Information goes from organs up to the brain stem (different from typical neuron diagrams).
    • The brain changes alertness, primes learning, and turns on a fever in response to sensory information.

  • Autonomic Nervous System & Vagus Nerve:

    • Cranial nerve 10 (vagus) classified as a parasympathetic nerve.
    • Autonomic nervous system has two branches: sympathetic (alertness) and parasympathetic (calm).
    • Vagus nerve is classified as parasympathetic but also can be alerting depending on which branch you activate.
    • The autonomic nervous system is a seesaw between alertness and calm.

  • Calming the Vagus Nerve:

    • One way to calm down is through the branch of the vagus nerve that carries sensory information coming from the head, behind and in the ear.
    • Rubbing behind or in the ear might help a bit, but it is not going to tilt the autonomic nervous system in the parasympathetic side.

  • Motor Pathways & Autoregulation (HRV):

    • Other 15% of the vagus nerve has motor outputs.
    • Autoregulation prevents sympathetic nervous system from becoming too dominant (heart rate, breathing).
    • Important for stroke recovery.
    • Neural circuit originates in the dorsolateral prefrontal cortex.
    • Dorsolateral prefrontal cortex connects to other brain areas such as nucleus ambiguous.
    • Nucleus ambiguous projects to the sinoatrial node of the heart (decelerating heart rate).
    • This deceleration is the basis of heart rate variability (HRV).
    • Higher HRV is correlated with positive health outcomes.
    • The vagus nerve controls the sinoatrial node and the heart rate is coordinated with breathing.
    • As your diaphragm moves down and your lungs expand, your heart literally has a bit more space in the thoracic cavity to expand and the blood moves a bit more slowly per unit volume.
    • Inhaling speeds your heart rate up.
    • When you exhale, the lungs deflate and there is slightly less space for the heart.
    • The faster movement is sensed by neurons which activate the nucleus ambiguous which signals the sinoatrial node to slow heart rate down.
    • Exhales slow your heart rate down.
    • A deliberate exhale pumps the break on your heart rate through the vagus nerve.
    • Deliberate exhales improve HRV in sleep and in wakeful states.

  • Alertness and the Vagus Nerve:

    • Vagus nerve can increase levels of sympathetic nervous system activity and become alerting.
    • Movement of large muscles causes adrenal glands to release adrenaline.
    • Adrenaline activates organs of the body and binds to receptors on the vagus nerve.
    • Vagus releases glutamate in the nucleus tractus solitarius (NTS).
    • NTS activates the locus ceruleus which releases norepinephrine and increases alertness in the brain.
    • Vagus nerve is central to using physical activity to make the brain more alert.
    • Stimulating the vagus nerve through exercise can increase levels of motivation, alertness, and focus to overcome lethargy and brain fog.
    • High-intensity exercise is important.

  • Neuroplasticity and the Vagus Nerve:

    • Alertness and focus are required for adult neuroplasticity.
    • Acetylcholine released from the nucleus basalis is permissive for plasticity.
    • Electrical stimulation of the vagus nerve increases alertness in the brain and stimulates the release of acetylcholine from nucleus basalis.
    • The enhanced opportunity for neuroplasticity happens by way of locus coeruleus release of norepinephrine and acetylcholine release of nucleus basalis.
    • Organize bouts of learning after some sort of exercise.

  • Serotonin and the Vagus Nerve:

    • Serotonin is a neuromodulator important for mood and gut health.
    • 90% of serotonin is made in the gut but stays in the gut.
    • Levels of serotonin are communicated by the vagus nerve.
    • Cells called intero chromophin cells manufacture serotonin.
    • Neurons in the vagus nerve intervate the gut.
    • Serotonin binds to the ends of axons in the gut and stimulates to relay a signal up and through the nodose ganglen up to the NTS.
    • NTS communicates with the dorsal raphe nucleus (responsible for serotonin release in the brain).
    • Improve gut microbiome to produce short-chain fatty acids for conversion of tryptophan to serotonin.
    • Increase the intake of 1-4 servings of low sugar fermented foods to improve the gut microbiota.
    • Make sure you are eating foods with enough tryptophan.
    • Supplement the diet with a probiotic on occasion.

  • Calming Down via the Vagus Nerve (Specific Techniques):

    • Physiological sigh is still the best for calming down fast.
    • Mechanical Activation of the Vagus Nerve:
    • Stretch the neck by pushing the elbows down, turning head to the right and left to stretch muscles in the neck, which stimulates the vagus nerve.
    • Humming can activate the vagus nerve in the larynx through vibrations.
    • Extend the H portion.
    • Vibration at the back of the throat is key, moving into the chest and belly.

In summary, the video provides a comprehensive overview of the vagus nerve, emphasizing its complex functions beyond just calming the body. It offers actionable tools to influence mood, alertness, learning, and overall health by understanding and leveraging the specific pathways within this remarkable nerve.