Control Your Vagus Nerve to Improve Mood, Alertness & Neuroplasticity
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- 23 Jun 2025
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KEYPOINTS
- 01
The vagus nerve (cranial nerve 10) is mostly a sensory highway, not a 'calm-down switch'
About 85% of vagal neurons are sensory: their cell bodies sit in ganglia near the brainstem (the nodose ganglion), with one branch reaching an organ and another going to the brainstem. They carry chemical and mechanical information from the gut, lungs, heart, spleen and other organs. The remaining ~15% are motor outputs from brainstem nuclei back to the organs.
- 02
Activating the vagus can raise alertness as easily as it lowers it
Huberman calls the idea that vagal activation always calms you a pervasive myth. For an exam the vagus is 'mixed, parasympathetic', but which branch is engaged determines whether you get more sympathetic (alert) or parasympathetic (calm) tone. Neurophysiologists stimulate the vagus to wake up the brain, and it has been used to pull patients out of too-deep planes of anesthesia.
- 03
Rubbing in or behind the ear calms you only slightly
An auricular sensory branch of the vagus runs behind and just inside the ear, and gentle pressure there does feed a parasympathetic pathway. Huberman's caveat: it nudges arousal down a bit and will not rescue you from a panic attack. It is one minor branch, not enough to tilt the autonomic seesaw.
- 04
Exhales slow your heart through a vagal brake on the sinoatrial node
On an inhale the diaphragm drops, the heart gets slightly more room, blood moves more slowly through it, and the sympathetic system speeds the heart up. On an exhale the heart has less space and blood moves faster, which is sensed and relayed to nucleus ambiguus. Vagal motor neurons there release acetylcholine onto the sinoatrial node and slow the heart. That periodic braking is the basis of heart rate variability (HRV).
- 05
The heart-slowing pathway is under conscious control and gets stronger with use
Input runs from the left dorsolateral prefrontal cortex via the cingulate and insula to nucleus ambiguus, so a deliberate long exhale engages it. Because the circuit is plastic, using it strengthens background autoregulation, including during sleep. Transcranial magnetic stimulation over dorsolateral prefrontal cortex slows heart rate and raises HRV even after stimulation stops.
- 06
HRV falls with age partly because this circuit degenerates
Higher HRV correlates with better health, longevity and performance outcomes. It declines with age partly from lower physical activity and partly from atrophy or strokes affecting dorsolateral prefrontal cortex. Huberman frames regular deliberate exhales, plus high-intensity interval training, as ways to keep HRV higher over time.
- 07
Moving large muscles wakes the brain through adrenaline acting on the vagus
Peter Strick's tracing work at the University of Pittsburgh showed that motor, cognitive and emotional brain areas all connect to the adrenals. Moving the legs and trunk releases adrenaline, which cannot cross the blood-brain barrier. Instead it binds receptors on vagal sensory axons, which release glutamate in the nucleus tractus solitarius (NTS). The NTS activates the locus coeruleus, which sprays norepinephrine across the brain.
- 08
Adult neuroplasticity needs alertness plus focus, and the vagus feeds both
After roughly age 25, passive exposure no longer rewires the brain much; you need alertness, focus and incremental effort, and the rewiring itself happens during deep and REM sleep. Acetylcholine from nucleus basalis acts as a gate for plasticity (Mike Merzenich's experiments showed rapid remapping when it is stimulated). The NTS also drives nucleus basalis, which helps explain why vagus nerve stimulation speeds motor recovery after stroke.
- 09
Gut serotonin stays in the gut but tells the brain to make more
About 90% of the body's serotonin is made in the gut by enterochromaffin cells from dietary tryptophan, but it does not travel to the brain. It binds vagal sensory endings in the stomach and intestines. The signal passes through the nodose ganglion and NTS to the dorsal raphe nucleus, the source of most brain serotonin. Huberman stresses that serotonin should be neither too high nor too low.
- 10
Only some popular vagus 'hacks' actually activate calming fibers
Huberman ran five common practices past a neurologist-psychiatrist and a neurosurgeon. They said three are supported by recordings from those pathways: a neck stretch, correct humming, and extended exhales. He still ranks the physiological sigh as the fastest way to calm down.
EXAMPLES
- 01
Physiological sigh: chemical plus mechanical signal
Two inhales through the nose (the second a short, sharp top-up) followed by a long exhale through the mouth to empty lungs. Offloading carbon dioxide sends a chemical calming signal and the exhale slows the heart. A plain long exhale gives mostly the mechanical signal.
- 02
Neck peri-arterial stretch
Sitting with palms down and elbows at the table edge, press the elbows down and away from the ears, then turn the head up and to the right, then up and to the left. This mechanically engages vagal fibers along the side of the neck, with most of the parasympathetic effect on the right side. He judges it slower and weaker than the sigh.
- 03
Humming 'H', not 'M'
A speech neurophysiology expert told him to extend the throaty H part of the hum. That keeps the vibration in the back of the throat (similar to gargling) and lets you move it down into the chest and belly, where vagal branches to the larynx are engaged. Since a hum is also a long exhale, it slows the heart too. He finds it easier lying down, and notes that singers use the same trick for low notes.
- 04
Stanford fermented-food data
He cites Justin Sonnenburg and Christopher Gardner's work: 1–4 servings a day of low-sugar fermented foods (refrigerated sauerkraut, kimchi, kefir, low-sugar yogurt, kombucha) improve microbiome diversity. That supports gut serotonin production, but only when dietary tryptophan is sufficient, for example from dairy or white turkey meat. He warns that kombucha contains some alcohol.
- 05
Nostril cycling from Noam Sobel
Huberman notes that olfaction researcher Noam Sobel confirmed that dominance switching between the left and right nostrils, roughly every 90 minutes, tracks the autonomic seesaw. He uses it to show that some yogic claims are mechanistically on target.
OTHER RELEVANT
- 01
Sprinkle 10–20 extended exhales through your day
Whenever you remember, lengthen or intensify an exhale to tap the heart brake, then carry on. More repetitions likely strengthen the pathway more, but no one knows the exact dose. The effect fades if you stop entirely.
- 02
When you feel lethargic, move big muscles hard instead of jogging gently
After a warm-up, do jumping, sprints or heavy sets (six reps or fewer, near failure) with the legs and trunk to release enough adrenaline to drive the vagus–locus coeruleus pathway. Long, rhythmic, low-intensity work may stay below that threshold.
- 03
Schedule learning for 1–3 hours after non-exhausting exercise
That window combines norepinephrine-driven alertness with acetylcholine-driven focus. Avoid training to exhaustion, which tips you into a parasympathetic slump. Protect sleep that night, because that is when the rewiring happens.
- 04
Be cautious with chemical shortcuts to focus
Alpha-GPC, huperzine, caffeine and low-dose nicotine can raise acetylcholine or norepinephrine. Huberman stresses that nicotine is highly habit-forming, raises blood pressure and constricts blood vessels, and is not something he recommends for young people. He calls smoking, dipping and vaping terrible for health.
- 05
Do not expect SSRIs or gut fixes to be simple mood switches
SSRIs help some people (including with clinical OCD) and give others troublesome side effects, so psychiatrists adjust them by trial; Wellbutrin is a non-SSRI alternative. Raising serotonin may help partly by enabling plasticity, which lets depressed patients learn new, more hopeful contingencies.