What Happens to YOUR BRAIN When You Hum for 60 Seconds? leonard Susskind explains
https://www.youtube.com/watch?v=oens89rTJFo
TRANSCRIPT
60 seconds. That's [snorts] all. And in 60 seconds, your brain stem, your vagus
nerve, your prefrontal cortex, and your auditory cortex enter into a negotiation
that modern neuroscience is still right now in uh 2026 trying to fully decode. I
want you to sit with that for a moment. Uh not because it sounds impressive. I am not here to impress you but because
the word negotiation is doing real work in that sentence and if you let it slide past you like a metaphor you will miss
the entire point of what I am about to tell you. The brain does not have a
central command. There is no little man behind the console pulling levers. What
the brain has instead is a collection of semi-aututonomous systems that are constantly sending signals to each
other, arguing, competing, synchronizing, falling out of sync, and
then finding their way back. What humming does, and I mean the specific
physical acoustic act of producing a sustained tone through a closed mouth,
is force those systems into a particular kind of coordination. And that coordination has measurable,
reproducible, physiologically significant consequences that reach from your throat all the way to the
electrochemical storms firing across your cortex. That is what I am here to talk about. Not mindfulness, not
wellness, whatever your yoga instructor told you about vibrations in the universe, the actual mechanism, the
plumbing, because the plumbing is where the real story lives. And the real story is stranger and more interesting than
anything the wellness industry has managed to sell you. So strip everything away. Forget what you think you know
about sound in the brain. Go back to the beginning. The brain runs on electricity. Not metaphorically,
literally. Neurons fire by generating electrical potentials across their
membranes. And when enough of them fire together in coordinated patterns across
large populations, those patterns become measurable. This is what an EEG records.
Not individual neurons. There are roughly 86 billion of those. And no
technology we currently possess can track them all simultaneously, but the aggregate electrical activity of large
neuronal populations oscillating together. And what you see when you put an EEG on a human head and record what
is happening is this. The brain is never silent. Even when you are sitting still,
eyes closed, doing nothing, the brain is generating waves. It is oscillating at
multiple frequencies simultaneously, different regions oscillating at different rates. And the relationship
between those oscillations, whether they are in phase or out of phase with each other, whether they are coupled or
decoupled, determines in ways we are only beginning to understand what kind
of mental state you are in. The classic taxonomy goes like this. Delta waves
below four hertz, dominant during deep dreamless sleep. Theta waves 4 to 8
hertz associated with drowsiness, memory consolidation, certain meditative
states. Alpha waves 8 to 13 hertz. The signature of relaxed, wakeful attention.
Eyes closed, mind quiet but not asleep. Beta waves [snorts] 13 to 30 hertz. The signature of active,
engaged, alert cognition. the frequency your brain is running at right now, listening to me, working to track the
argument. And then gamma, 30 hertz and above, associated with highlevel
cognitive binding, the process by which disperate pieces of information are integrated into a unified conscious
experience. These are not rigid categories. The brain does not switch cleanly from one to another like
changing a radio station. What actually happens is more like a symphony where multiple instruments are playing
simultaneously and what you are measuring at any given moment is the composite sound. The question, the
genuinely hard question is what determines which instruments dominate and what can you do from outside the
system to shift that balance? And this is where humming enters the picture in a
way that is not trivial, not soft and not a matter of opinion. When you hum,
you are generating a sound internally, not externally. This distinction matters
enormously and almost nobody talks about it, which tells you something about the state of the popular conversation around
this topic. When you hear an external sound, someone speaks to you, a door slams, music plays, your auditory system
engages in a process called apherrant processing. Signals travel from your ear
through the cclear nerve up through the brain stem through the medial geniculate nucleus of the phalamus and then out to
the primary auditory cortex in the temporal lobe. That is the standard upstream pathway. Information from
outside goes in, gets processed, gets interpreted. When you hum, something different happens. The sound is
generated internally by your vocal cords and it travels two ways. Simultaneously,
it travels through the air and enters your ear from outside following the afrant pathway I just described. But it
also travels through bone conduction through the bones of your skull and reaches the coia via a completely
different route at a slightly different timing and uh at a slightly different uh
frequency profile than the airborne version. Your auditory system is receiving two versions of the same sound
from two different sources simultaneously and it is integrating them in real time. This dual input is
one of the reasons your voice sounds different to you on a recording than it does inside your head. The recording
captures only the airborne version. The version you hear when you speak or hum
includes the bone conducted component which enriches the low frequencies and
gives you the sense of resonance of depth that you hear when you hum but that the microphone only partially
captures. But here is where it gets strange. The internal generation of
sound during humming activates not just your auditory system but your motor system. Because humming requires
muscular control of your larynx, your diaphragm, your soft pallet, the muscles
of your face and throat. The motor cortex is recruited and the motor cortex and the auditory cortex are not isolated
from each other. There is a well doumented birectional pathway between them. It is part of what allows you to
learn to sing to hear a pitch, model it internally, generate a motor command
that attempts to match it, listen to the result, compare it to the target, and adjust. That feedback loop is happening
in real time when you hum. Even when you are not consciously trying to match any external pitch, you are generating a
sound, hearing it, and your motor system is continuously monitoring and
fine-tuning the output. This is an active computationally expensive process
and it is engaging a much larger network of brain regions than simply listening to music or making a non-vocal sound
like tapping your finger. And we have not even gotten to the vagus nerve yet.
The vagus nerve is the 10th cranial nerve and it is one of the most
important structures in your body and it is chronically underappreciated in
popular discussions of neuroscience which tend to fixate on the cortex and
ignore the brain stem and peripheral nervous system where enormous amounts of regulation are actually occurring. The
vagus nerve is the primary conduit of the parasympathetic nervous system, the rest and digest system, as opposed to
the fight orflight sympathetic system. And it runs from the brain stem down through the neck, through the chest,
past the heart and lungs, all the way into the abdomen, innovating the gut,
the liver, the spleen, the kidneys. Approximately 80% of the fibers in the
vagus nerve are apherent. They carry signals from the body up to the brain. not from the brain down to the body.
This is a fact that surprises most people because we tend to think of the nervous system as the brain issuing
commands to the body. The vagus nerve is mostly the body reporting to the brain.
It is a surveillance system as much as a control system. Now the vagus nerve also
innovates the larynx. [snorts] Specifically, the recurrent laryngal nerve, which is a branch of the vagus,
controls the muscles of the larynx that govern your vocal cords. When you hum,
you are activating those muscles rhythmically. And that activation sends signals back up the vagus nerve to the
brain stem, specifically to a region called the nucleus tractus solitarius,
which is a major hub for integrating visceral sensory information and regulating autonomic function. What this
means is that the mechanical act of humming the vibration, the controlled
tension in your leneal muscles, the rhythm of your breath is directly stimulating the vagus nerve in a way
that is physiologically equivalent in some respects to a less aggressive
version of vag nerve stimulation therapy, which is a clinical intervention used to treat epilepsy and
depression by implanting an electrode near the vagus nerve in the neck and delivering controlled electrical pulses.
You are doing a version of that voluntarily for free every time you hum.
And I know what you are thinking right now. You are thinking, "This sounds too convenient, too neat. The kind of thing
that shows up on health blogs next to articles about superfoods and detox cleanses." I understand that instinct.
It is a good instinct. The history of medicine is littered with mechanisms that sounded elegant and turned out to
be nonsense. So let me be very precise about what the evidence actually says and what it does not say because the
distinction matters. What is established and has been established in multiple
peer-reviewed studies with reproducible results is this humming significantly
increases nasal nitric oxide production. This was demonstrated rigorously by John
Lunberg and Eddie Whitesburg at the Carolinska Institute in Sweden, published in the American Journal of
Respiratory and Critical Care Medicine in 2002. And the effect is not small.
Humming increases nasal nitric oxide levels by approximately 15fold
compared to silent nasal breathing. 15fold. Nitric oxide is a signaling
molecule with a wide range of physiological functions. It is a vasod diilator. It has antimicrobial
properties in the nasal passages and sinuses. And it plays a role in
neurotransmission in the brain where it functions as a retrograde messenger moving from post synaptic to presinaptic
neurons and modulating synaptic plasticity. The mechanism for the nitric oxide increase during humming is the
oscillating air flow in the nasal cavity which enhances the exchange of air between the nasal passages and the
paranasal sinuses where nitric oxide is produced by the sinus epithelium. Uh
silent nasal breathing creates relatively little oscillation. Humming
creates a lot. The sinuses drain more efficiently. The nitric oxide gets picked up by the airirstream and the
concentration in the nasal cavity spikes. This is not wellness mythology.
This is gas chromatography. This is quantitative mass spectrometry.
These are measurements and they are reproducible. And the 15-fold increase is a real number
attached to a real physical mechanism that you can explain from first principles without invoking anything
mystical. Now what does this mean for the brain specifically here? We have to be more careful because the chain of
inference gets longer and the longer a chain of inference the more places it can break. Nitric oxide crosses the
bloodb brain barrier. It is produced in the brain itself by neurons that express
nitric oxide synthes. It functions as a neurom modulator influencing the release
of dopamine, serotonin, and norepinephrine. It is involved in long-term potentiation which is one of
the primary cellular mechanisms of learning and memory. So the argument that increased nasal nitric oxide during
humming has downstream effects on brain chemistry is not outlandish. There are plausible mechanisms at every link in
the chain, but the specific cognitive and emotional effects of 60 seconds of humming on a healthy human brain have
not been measured with the rigor I would want to see before making strong claims.
The studies on nitric oxide are solid. The extrapolation from nitric oxide to
improved mood or enhanced cognition is currently running ahead of the control trials. I want to be honest about that
gap because the gap is where the interesting science lives. Here is a
moment of personal history. In the early 1970s when I was deep into the work that
would eventually become string theory, I had a conversation with uh a colleague.
I will not name him because he is still alive. And this reflects poorly on both of us about whether the mathematical
structures we were exploring had any physical content or whether they were just beautiful algebra. And I argued
with a confidence I did not entirely feel that physical intuition had to lead
the mathematics that if you could not point to something in the physical world that the formalism was capturing you
were doing mathematics not physics. And uh I was wrong. Not completely wrong,
but wrong in a way that took me years to understand. The mathematics sometimes
knows things before the physics does. The formalism can point you toward
territory that physical intuition has not mapped yet. This is relevant to the humming story because the mechanism, the
nitric oxide, the veagal stimulation, the dual auditory pathway is pointing
toward cognitive and neurological effects that the controlled clinical
trials have not fully caught up to yet. That does not mean the effects are real.
It means the question is worth taking seriously and dismissing it because the wellness industry has adopted the
vocabulary is exactly the wrong move. Bad people carrying a good idea does not
make the idea bad. So let me build a picture more carefully. The autonomic
nervous system, the system that regulates heart rate, blood pressure, digestion, respiratory rate, pupil
dilation, and a 100 other functions you do not consciously control, operates in a state of dynamic balance between its
two branches. The sympathetic branch accelerates, mobilizes, prepares for
action. The parasympathetic branch decelerates, recovers, restores. Most of
the time in a healthy person, these two branches are in dynamic equilibrium with
the balance shifting moment to moment in response to internal and external conditions. One of the best indices of
this balance is heart rate variability, the variation in the time interval between successive heartbeats. A healthy
heart does not beat with metronomic regularity. It speeds up slightly on inhalation and slows down slightly on
exhalation. A phenomenon called respiratory sinus arrhythmia. And the
magnitude of this variation is a measure of veagal tone. The degree to which the
parasympathetic system is actively engaged. Higher heart rate variability,
all else being equal, is associated with better cardiovascular health, better
stress regulation, better emotional regulation, and better cognitive flexibility. It is one of the most
robust physiological markers in the literature. Humming affects heart rate
variability. The effect is mediated by the same mechanism I described earlier, the rhythmic stimulation of the vagus
nerve through lingial muscle activation. combined with the breath control that humming requires. You cannot hum on
inhalation. Humming happens on exhalation. This means that humming naturally extends the exhalation phase
of your breathing cycle. And extended exhalation preferentially activates the
parasympathetic branch of the autonomic nervous system. The exhalation is the rest stroke. The inhalation is the
activation stroke. When you extend the exhalation, as you do when you hum a sustained note, you are tipping the
autonomic balance toward the parasympathetic. Your heart rate slows, your heart rate variability increases,
the veagal tone goes up, and this is measurable with equipment that costs
less than a decent bicycle, which is one of the reasons I find it frustrating that more rigorous study has not been
done. Here is where it gets strange again, and this time we are going deeper. The brain oscillates. I said
this before and I want to return to it because I did not give it its full due. The brain oscillates and one of the most
important oscillations is in the theta range 4 to 8 hertz. Theta oscillations
originate primarily in the hippocampus and the entrinal cortex which together
form the core of the brain's memory system. The hippocampus is where new episodic memories are formed, where
spatial navigation is computed, where the brain does its indexing and organizing of experience. And theta
oscillations in the hippocampus are strongly correlated with memory encoding
with the process of converting short-term experience into long-term memory. When you are in a state of high
hippocample theta activity, you are broadly speaking in a state of high
memory consolidation and high associative learning. Things stick,
connections form. What shifts hippocample theta? Several things,
certain drugs, physical movement, particularly walking, which is why walking improves cognition and why so
many people find they think better when they move. Certain meditative states. And here is the interesting part.
Certain patterns of rhythmic vocalization. The data on this is not as
clean as I would like. The specific effect of humming on hippocample theta has not been isolated in a control trial
in the way that uh say the nitric oxide data has been. But what we know about
the broader relationship between rhythmic vocalization, veagal tone,
autonomic regulation, and hippocample oscillations gives us a mechanistically coherent picture of how
60 seconds of humming could plausibly shift your theta activity in ways that affect memory, attention, and the
subjective sense of calm that people reliably report. Uh, I want to pause on
that last phrase, the subjective sense of calm that people reliably report. In
neuroscience, subjective reports are evidence, not conclusive evidence, not
evidence that should be trusted uncritically, but evidence. If you design an experiment where you have a
100 people hum for 60 seconds and then fill out a validated measure of
subjective arousal and affect and the results are consistent across 100 people
and replicate across laboratories that is telling you something real about the brain even before you have identified
the mechanism. The mechanism question why does this happen is downstream of the phenomenon question does this happen
and the phenomenon question for humming and subjective calm has a fairly
consistent answer across the literature. It happens. What is not established is the causal chain at the mechanistic
level and what is not established is the dose response curve. How much humming at what frequency in what context produces
what magnitude of effect and for how long? These are the questions that good
science would answer and these are the questions that the wellness industry has zero interest in answering because the
answers might complicate the sales pitch. Either the effect requires more than 60 seconds, in which case hum for
60 seconds to transform your brain is an overstatement, or the effect is highly
individual, in which case population level recommendations are misleading,
or the effect is real and robust at 60 seconds, in which case it is a genuinely
useful public health intervention that deserves serious clinical development. We do not know which of these is true
and that is the honest answer. But let me tell you what I think and I want to be clear that this is informed
speculation not established science which is a distinction that matters
enormously and that far too few people making public claims about neuroscience bother to make. I think the effect is
real. I think 60 seconds of sustained humming produces a measurable shift in autonomic tone, a real increase in nasal
nitric oxide and a genuine if transient alteration in the oscilly dynamics of
the brain. I think the subjective reports of calm and clarity following humming are tracking something real in
the neurohysiology. And I think the reason this has not been studied with the rigor it deserves is
partly because it does not fit neatly into a pharmaceutical paradigm. You
cannot patent humming. You cannot run a double blind trial where neither the
subject nor the experimentter knows whether humming occurred. And the people who tend to be interested in this topic
are either in the wellness industry which has no interest in rigor or in clinical medicine which is focused on
pathology rather than optimization. Basic neuroscience labs are interested
in mechanism and the mechanism questions here are genuinely interesting. But the
translation from mechanism to intervention requires a kind of interdisciplinary collaboration that
academic incentive structures make difficult. This is one of the frustrating realities of the current
scientific landscape. The most important questions are not always the ones that get the most rigorous attention. The
most
important questions are the ones that get the most funding and the
funding goes where the returns are largest. And the returns in
neuroscience
are largest in drug development. Not in understanding why 60 seconds of a
behavior that every human being can perform for free produces measurable physiological changes. There is
something deeply wrong with that prioritization. And I am not going to stand here and pretend otherwise. Let me
tell you about something that I think is the most underappreciated aspect of a humming story. And it
connects to something that has occupied my thinking about physics and information for the last three decades
in a way that I did not expect when I first started thinking about it. The brain is a prediction machine. This is
not a metaphor. This is the current dominant framework in theoretical neuroscience predictive coding. And
while it is not proven in every detail, it is the most productive organizing idea in the field right now. and the
evidence for its broad outlines is extensive. The core claim is this. The
brain does not passively receive sensory input and then process it. The brain is
constantly generating predictions about incoming sensory data based on its
internal models of the world. The sensory data that actually arrives is
compared to the prediction and what gets propagated up through the hierarchy of
cortical processing is not the raw sensory input but the prediction error the difference between what the brain
expected and what it got. The brain is updating its internal model continuously
trying to minimize prediction error trying to become a better and better predictor of its own sensory experience.
This framework changes how you think about every aspect of perception and cognition. And it changes how you think
about humming in a very specific way. When you hum, you are generating a sound
that is to some degree under your voluntary control. You have a motor intention. You generate a sound and you
hear the sound. The auditory system receives the input and compares it to the prediction. But because the sound is
self-generated, the brain has prior knowledge of what the sound should be. It generated the motor command. It knows
what the larynx was supposed to do. This means the prediction error for self-generated sounds is systematically
lower than the prediction error for externally generated sounds. You are less surprised by sounds you make
yourself, which is why you cannot tickle yourself. The prediction cancels the sensation. The low prediction error of
humming has a specific consequence. Because the auditory cortex is not busy
computing large prediction errors, it is freed up. Its computational resources
are not consumed by the process of updating the internal model. And this is where the connection to the oscilly
story gets interesting. When the auditory cortex is in a low prediction
error state, it tends to shift towards slower, more synchronized oscillations
toward alpha, toward the uh lower end of the beta range. The cortex relaxes its
vigilance because it is not encountering surprises. And when the auditory cortex shifts toward alpha, that shift tends to
propagate through corticoortical connections into adjacent and connected
regions. The default mode network which is active during rest and
self-referential thought becomes relatively more engaged. The task
positive network which is active during focused external attention becomes
relatively less engaged. The subjective correlate of this shift is exactly what
people describe when they describe the feeling of humming. A slight softening of the boundary between inside and
outside. A gentle inward turn of attention. a reduction in the felt
urgency of the external world. This is not mysticism. This is the predictive coding framework applied to a specific
behavior and it generates specific testable predictions about what an EEG
should show during and immediately after 60 seconds of humming. And those predictions have not been tested with
the specificity the theory demands which is a gap in the literature that I find
genuinely frustrating. The theory is there, the tools are there, the
experiment is not that hard to design. Somebody should do this work. Let me tell you what happens in the first 10
seconds of humming because the temporal dynamics matter and are usually glossed over in discussions that treat humming
as a monolithic event. In the first two to three seconds, you are in setup. The
larynx is finding its configuration. The breath is being regulated. The motor
command is being refined based on initial auditory feedback. The brain is still running at the whatever state it
was in before you started beta dominant uh prediction error generating attention
directed outward. Nothing dramatic has happened yet. Between 5 and 15 seconds,
the veagal stimulation is beginning to have measurable autonomic effects. Heart rate is starting to slow. The interbeat
interval is increasing. Respiratory sinus arhythmia is increasing. The parasympathetic system is beginning to
gain ground over the sympathetic. This is not dramatic. It is a subtle shift,
not a sudden change, but it is real. and is happening at the level of the autonomic nervous system before it is
happening at the level of conscious experience. Between 15 and 30 seconds,
if you are measuring nasal nitric oxide, you are seeing the concentration beginning to rise. The oscillating air
flow is driving sinus ventilation. The nitric oxide is being picked up by the airream and the concentration in the
nasal cavity is climbing. The nitric oxide is entering the bloodstream through the nasal mucosa and the lungs
and beginning to exert its vasoddilatory effects on the small blood vessels of the nasal mucosa, the lungs, and the
systemic circulation. Between 30 and 60 seconds, the oscilly dynamics of the
brain are shifting. If you have a good enough EEG and you know where to look, you will see
an increase in alpha power in the auditory and parietal regions. You will
see a decrease in high beta power. The default mode network is becoming more
active relative to its baseline state. The prediction error landscape of the auditory cortex is quieter than it was a
minute ago. And the person doing the humming is, if you ask them, feeling
calmer, slightly more focused, slightly more present than they were before they
started. 60 seconds. That is the temporal architecture of the effect. It
is not instantaneous. It is not magic. It is a cascade of physiological events.
each one triggering the next, unfolding over time in a way that is completely
comprehensible from the underlying biology. Now, here is the part that I find most
genuinely unsettling. And I mean that in the best sense. Unsettling in the way that a good physics problem is
unsettling. Where the more carefully you look at it, the more it seems to be pointing at something you do not yet
fully understand. The brain is generating its own internal resonances
all the time. The theta oscillations in the hippocampus, the alpha rhythms in
the visual and parietal cortex, the gamma oscillations in the cortex during
high level cognitive binding. The brain is an oscillating system and oscillating
systems have natural frequencies and natural frequencies can be driven by external forcing. This is basic physics.
If you apply a periodic force to an oscillating system at or near its natural frequency, you get resonance.
The amplitude of the oscillation increases. The system responds strongly. This is why soldiers historically broke
step when crossing a bridge because marching in cadence can drive the bridge at its natural frequency with
catastrophic results. This is why opera singers can under the right conditions
shatter glass because the sustained tone drives a glass at its resonant frequency until the amplitude exceeds the glass's
structural limits. [snorts] The brain has natural frequencies. Humming produces a sustained tone experienced
both through air conduction and through bone conduction. The bone conducted component reaches the cookia, the brain
stem and the skull itself at frequencies and with a spatial distribution that is
quite different from any external sound source. And the question, the genuinely
open question, the one that I do not think anyone has answered with sufficient rigor is whether the specific
frequencies produced during humming can drive cortical oscillations through resonance effects that go beyond the
autonomic and predictive coding mechanisms I have already described. I
want to be careful here because this is where responsible speculation ends and irresponsible speculation begins
[snorts] and the line is easy to cross. The resonance frequencies of the human skull are in the range of 100 to 1,000
hertz. The brain's primary uh oscilly frequencies are in the range of 1 to 100
hertz. These are different ranges and the coupling between them is not straightforward. What I am pointing at
is not a simple resonance between the humming frequency and the brain's electrical oscillations. The physics
does not support that in any simple way. And anyone who tells you that humming at
a specific frequency directly drives your brain waves at that frequency does not understand how neural oscillations
work. What I am pointing at is something subtler that the bone conducted
component of humming may be influencing the vestibular system and the propriceptive system in ways that have
downstream effects on brain stem arousal systems on the reticular activating system specifically and that these
effects may contribute to the autonomic and oscilly changes that we observe.
This is a real possibility. It is not proven. It is a direction of inquiry
that I think is worth pursuing and I am genuinely uncertain about the outcome
which is the most honest thing I can tell you about it. There are physicists who find it uncomfortable to say I do
not know. I am not one of them. Saying I do not know is the beginning of science
not the failure of it. I fought Stephven Hawking for a decade over whether information is destroyed in black holes.
I was right and uh he was eventually convinced. He conceded the bet publicly in 2004. Though I will tell you
privately that the concession was somewhat grudging because Steven was not
a man who enjoyed being wrong and neither am I. But I enjoy being wrong
less than I enjoy being corrected, which is why I argue until the argument is settled. The point is there are things I
knew and there are things I guessed and there are things I got wrong. And I have learned to keep those categories honest
in my own mind even when it is uncomfortable to do so. What I know about humming in the brain, the nitric
oxide effect is real. The veagal stimulation is real. The autonomic shift toward parasympathetic dominance is
real. The oscilly changes in the auditory cortex are real. The subjective
reports are consistent and real in the sense that they are reproducible. What I do not know the precise quantitative
relationship between 60 seconds of humming and the magnitude of each of
these effects in any given individual. The duration of the effects and how they
depend on context and baseline state. Whether the effects are additive with other interventions or whether there are
ceiling and floor effects. the specific contribution of the bone conducted component versus the airborne component
versus the veagal stimulation versus the breathing pattern change. The extent to which the effects depend on the
frequency of the hum where the humming at 200 hertz produces the same effects as humming at 100 hertz. These are all
open questions and the fact that they are open is not a reason to dismiss the phenomenon. It is a reason to study it.
And here is the thing that I keep coming back to. The thing that I think connects this specific, concrete, modest story
about 60 seconds of humming to the larger questions that have occupied my
career. The brain is an information processing system. It is the most complex information processing system we
know of. And the question of how information is represented, stored,
transmitted, and transformed in the brain is formally identical in some deep, not yet fully understood way to
questions that physics has been grappling with for a century about how information behaves in physical systems
at the fundamental level. The holographic principle which emerged from the black hole information paradox tells
us that the information content of a volume of space is proportional not to
the volume but to the surface area that bounds it. This is a statement about the fundamental structure of information in
physical reality. And the predictive coding framework, the idea that the brain is fundamentally in the business
of compressing and predicting and updating internal models is a statement about the information architecture of
the most complex physical system we know. These are not unrelated ideas. They are both pointing at the same
question from different directions. What is information? How does it behave in
physical systems? And what are the fundamental constraints on information processing in a universe governed by the
laws of physics? The brain is a physical system. Its information processing
happens in a physical substrate subject to physical laws. The way it oscillates,
the way it synchronizes, the way it responds to self-generated acoustic input. All of this is physics at the
level where biology and physics meet. And that meeting point is in my view
where the most interesting science of the next 50 years is going to happen. 60
seconds of humming. It seems like a small thing, a trivial thing, the kind
of thing that belongs in a self-help book, not a physics lecture. But if you follow the mechanism all the way down
through the vagus nerve to the brain stem through the nitric oxide to the nasal epithelium and the blood vessels
and the neurotransmitter systems through the predictive coding framework to the
oscilly dynamics of the cortex. What you find is that it is not small at all. It
is a window into the self-organizing dynamics of a system that we do not yet fully understand. A system that is
simultaneously generating predictions about the world, regulating its own internal state, processing information
at multiple hierarchical levels, and doing all of this with an energy budget of roughly 20 watts less than the light
bulb above my head, while maintaining a subjective inner life that we do not know how to explain and perhaps do not
know how to even properly describe in physical terms. The hard problem of
consciousness is waiting at the end of every road that leads into the brain. Every mechanism I have described
tonight, every oscillation and every nerve and every molecule of nitric oxide
is a third person description of a system that has a first person inside.
The question of why there is a first person inside at all. Why the lights are on. Why there is something it is like to
be you sitting in this room listening to me is a question that neuroscience has not solved. That physics has not solved
that philosophy has not solved and that I personally believe is the deepest question in all of science. Not because
it is the hardest calculation but because it is the question where our current conceptual frameworks most
visibly fail. where we reach the edge of what our existing ideas can handle and stand there looking into the dark. You
hummed this morning, maybe in the shower, without thinking about it,
without knowing that your vagus nerve was being stimulated and your nasal nitric oxide was spiking and your
auditory cortex was shifting its oscilly dynamics and your autonomic nervous system was tipping slightly toward rest.
You did all of that without knowing it was happening. And that gap between what the brain is doing and what you know the
brain is doing is the most important unsolved problem in science. And you ask
me what happens to your brain when you hum for 60 seconds. That is what happens. All of it. And the
honest answer to the most important part of the question is we do not fully know
yet. And that should not make you comfortable. It should make you the right kind of uncomfortable. The kind
that wants to know more, that recognizes the enormity of what is still not understood, that refuses to accept a
cartoon version of the answer just because it is easier to swallow than the real thing. The real thing is always
harder and it is always worth
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