Neurons outside the brain | Hacker News Reader

Neurons outside the brain

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153 pointsyichab0d82 comments

> What does it mean that that I feel my anxiety in my gut? And that I clearly feel when I’m speaking from my head or my heart (or both)? [...] What does it mean that that I feel my anxiety in my gut? And that I clearly feel when I’m speaking from my head or my heart (or both)?

An unjustified logical jump here seems to be that where you feel your thoughts and feelings are coming from is where the responsible neurons are. The assignment of the feeling of origin may be a separate mechanism.

The article reads like a naïve person coming to terms with the idea of consciousness… like “whoa maaan, my fingers… they’re finging!”

“Extra-cerebral” neurons are optimized for different functions than neurons proper in the brain.

It’s unlikely that the gut has thoughts and feelings, given neuronal tissue is distributed throughout viscera (versus concentrated in one spot like the brain). They are distributed so that smooth muscle tissue can contract appropriately and push food and wastes down the line.

The author compares the number of GI neurons to the number of neurons in a dog’s brain, but gleans over the number of neurons in a dog’s GI tract which is probably similar or proportionally less because the tract is physically smaller.

The neurons the author highlights in the heart are concentrated at the base, because the shape of the heart is optimized for coordinated contraction via electrical impulse propagation.

I think people are just confusing cause and effect here.

Anxiety triggers release of hormones like adrenaline and cortisol, which trigger a host of physical symptoms ranging from cold hands (reduced blood flow in extremities) to upset stomach, nausea, increased heart rate, etc.

Brain can anticipate these changes and associate anxiety with the effects of these hormones. There might be all sorts of interesting interactions, but saying that gut is responsible for processing of these feelings is definitely a stretch.

Another physical reaction which is associated with an emotion is blushing. But somehow nobody is talking about face skin taking control...

Yes actually in my experience the physical feelings concomitant with anxiety often make the mental feelings of worry and dread much worse. If anything the author sounds like they are conflating having bad feelings for “processing”.

I also found it sloppy. The reference for heart transplant patients getting memories from the donor actually says that there are self reported personality changes in 89% of heart transplant patients, which was statistically the same as other organs. So it doesn’t say what the author wants it to say.

> I find it more plausible that the feeling of speaking from the gut is akin to allowing that center of intelligence coordinate the rest of our body.

The author thinks that mentally poking the bodymap created by the brain can cause changes in the actual processing. I wouldn't believe this without proofs other than introspection(1). Technically, the vagus nerve can carry enough information to produce speech (the gut should be articulate, of course), but it certainly nowhere near the corpus callosum or the spinal cord. I doubt that it can allow to "coordinate the rest of our body".

(1) As far as know conscious manipulation of the heart rate is achieved by changing respiratory patterns, not thru direct control of the signals that the brain sends there.

The first time I heard of how many neurons the gut has, I went: "well obviously, there's a lot of receptors and muscles to support peristaltic movement; plus probably some start to end connection for proper synchronization and total volume management - it just has to be processed somehow and locally (in the gut, as opposed to the far brain) seems like an obviously good choice". Never tried to verify that with state of the art though

> In several cases, memories of the old heart’s host seem to become accessible to the recipient ^2.

That does not seem at all to be what citation 2 is saying.

There's a case cited in that paper which does suggest something similar:

> A report in the lay literature describes the case of Claire Sylvia who reported changes in her personality, preferences, and behaviors following a heart and lung transplant at Yale-New Haven hospital in 1988. Following surgery, Sylvia developed a new taste for green peppers and chicken nuggets, foods she previously disliked. As soon as she was released from the hospital, she promptly headed to a Kentucky Fried Chicken to order chicken nuggets. She later met her donor’s family and inquired about his affinity for green peppers. Their response was, “Are you kidding? He loved them… But what he really loved was chicken nuggets” (p. 184, [9]). Sylvia later discovered that at the time of her donor’s death in a motorcycle accident, a container of chicken nuggets was found under his jacket [9].

I haven't read the whole thing, maybe there's something more relevant as well. That report isn't really about accessing the previous persons "memories" but at least claims she adopted a part of their personality. I'd be skeptical about its accuracy without more such reports, however.

A safer assumption would be that our body influences our behavior and tastes, and in turn they are directly affected by changes in our body, like an organ transplant.

A more interesting question regarding the case above would be "what's in our hearth and lungs that affects our perception of capsaicin?".

It's still way, way too different from

> In several cases, memories of the old heart’s host seem to become accessible to the recipient

Came here to say the same thing — 2's abstract claims the exact opposite. Really damning.

That's where I have stopped reading.

So if this were true you'd expect people with spine injuries to forget large parts of their lives? Or what is the mechanism to be able to transfer these memories from organs to the brain?

The assumption that neuron activity == consciousness is incorrect.

A lot of neurons in our brain are doing visual processing. How much of it is conscious?

Writing this comment, I have very little insight into how I am able to create this sentence and then read it. Makes me wonder what's the point of being conscious anyway.

Well, I can provide a thought experiment I did back in high school... imagine a universe identical to ours, except that nobody was conscious. There would be "no one there" to experience it, by definition. So would such a universe exist?

I guess yes? Why would it cease to exist if no one experienced it? It wouldn't change its physical properties.

That question isn’t as deep as you think it is.

If we accept the existence of that which cannot by definition be observed in any way... then is that not an infinitely large category?

These kind of trick questions are variations of the tree falling when no one heard it. They aren't asking "did it generate soundwaves?", they're asking "if sound included perception, did it make a sound?". It's weird to ask questions like these outside quantum mechanics, where observation actually affects the result.

https://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest_an...

Imagination will give you something to think about, but it alone will not tell you which thoughts are correct.

Blindsight, by Peter Watts, is a good, sci-fi fiction meditation on the pitfalls / dubious value of consciousness / self awareness.. if you haven’t read it, I would recommend it - it’s a dense, perhaps ‘dry’ read for some - but very rewarding nonetheless IMO.

[1] https://www.reddit.com/r/printSF/comments/y19ck8/i_finally_r...

[2] https://www.reddit.com/r/printSF/comments/1fze6sx/blindsight...

Seconding this. I recommend Blindsight whenever the subject of consciousness—specifically lack thereof—comes up. It basically asks the question "What would it mean for there to be an intelligent species that was not conscious?"

Even more relevant now with LLMs (not that they're an "intelligent species." But a lot of people seem to think they are)

The extended mind theory takes the “neuronal activity is not the mind” (which seems trivially true to me) slightly further: not only it is not happening merely in the brain, it might not even be technically limited to our bodies and extends into the surrounding physical world.

So far whenever I read summaries about it I can’t say EMT exactly “clicks” with me, though I would at least lean towards our consciousness necessarily involving/extending to people in our lives whom we are in contact with.

[0] https://en.wikipedia.org/wiki/Extended_mind_thesis

Trivially true? Why?

https://en.wikipedia.org/wiki/Hard_problem_of_consciousness#...

https://www.researchgate.net/publication/365412617_Polyatomi...

Btw, from the threads's article, the personality change over transplant it's literally an episode from The Simpsons, but you, know, creators are actually PhD people, as it shows off under Futurama.

How do we know if the visual cortex isn't conscious? There are conscious parts of our brain that we aren't aware of, just as we are alive, but we can't be aware of how all our cells are also alive.

I think quantifying consciousness is a problem we are absurdly far from solving yet. Most we are able to do is philosophize about it.

You're doing that "we just don't understand the brain" thing that everyone apparently loves doing, I guess because it makes them sound smart? Asking questions like "How do we know if the visual cortex isn't conscious" is not the same as actually knowing anything about cognitive neuroscience.

> Asking questions like "How do we know if the visual cortex isn't conscious" is not the same as actually knowing anything about cognitive neuroscience.

Can you explain me how neuroscience proves the visual cortex can't be conscious? Why is it so wrong of me to ask that question?

You can invent an arbitrary number of meaningless questions, but it's not the same as actually knowing anything about the subject you're inventing questions about. Nobody has any obligation to prove or disprove any of your questions. You have the obligation to prove your claim (if you were to actually make one).

If I walk into a city council meeting and start yelling "Why haven't you greened the fish sun???" all I'm doing is wasting everyone's time, and yet I can then say "Hey, I'm just asking questions! They won't answer my questions!" as though I'm some kind of victim and the city council is some kind of mysterious evil cabal.

Similarly, the phrase "Do your research" is designed to signal that I'm the smart one, the one in the know, the one who knows what's REALLY going on, even though I know nothing about x, y or z.

We don’t have a definition of consciousness that allows us to tell whether a single electron is conscious or not, so literally anything can be „conscious“.

Check into panpsychism.

By the same logic, you could ask "what part of a computer 'is' the computer? The CPU? The hard drive? The RAM? The TPM? The power supply? The sum of all peripherals? Etc"

You could ask all kinds of philosophical questions about this, but at the end of the day, there are parts that are easily replaceable and parts that are harder if you want to preserve the identity of a particular machine.

E.g. while RAM, CPU, GPU, power supply etc are all essential for running a PC, you can also swap them out without many problems. In contrast, the data on the hard drives or the TPM might be hard or impossible to restore.

In the same way, I'd still see the brain as the center of the self, because so much cognitive information is stored there.

A modern computer looks more like a worm that believes it is self-aware.

There are so many SoC subsystems in a computer that the CPU only thinks it knows what's going on and can be catastrophically wrong about it in some cases. Brian Cantrill has a pretty good rant about it in one of the recent Oxide videos.

A human is basically just a worm that evolved a lot of extra stuff to feed itself better.

As a fun fact, humans and worms have a common hypothetical ancestor we call “urbilateria”, likely living over 550-600 million years ago, before the Cambrian explosion.

This ancestor gave rise to a branch called protosomes (worms, insects, mollusks) and another branch called deutorosomes (which includes humans and other vertebrates).

Worms and humans share: bilateral body organization, a digestive tract, basic nerve structures, many shared genes that control body development.

How dare you sir. I am a high-functioning fungus.

Identity isn't a scientific question, science can't tell you who you are. Collectivist ideologies throughout history have encouraged people to think of themselves as - or rather maybe, be subsumed in an identity outside their body. And it might be wrong in a moral sense, but in a scientific sense it's neither right or wrong. Of course there's complex interaction and information exchange going on inside a state or a "race", and it's not clear why that shouldn't make collective "intelligent" in the same way we argue an individual human is intelligent. Philosophies which derive identity/value from intelligence (I don't agree with those philosophies) have very little to answer to collectivist ideologies which reject humanism.

What really called my attention is the personality change after transplants. I am not super sure about how good the science is.

Also. We are very neuro-centric, but the system also had all type of hormones and other chemical messages affecting it.

There's a short science book called Hidden Guests, it talks about why women have the potential to end up with microchimeric "incursions" from sexual partners and their own fetuses, fetuses can have microchimerism with each other (not just twins but prior fetuses from same mother) and fetal cells crossing into the mother and towards the end talks about the resemblance between this and transplants( someone else's cells thriving in one's body). So if organ transplants can potentially have that effect, it's already happening to sexually active women, with the caveat that for the fetal cells it wouldn't have much formed personality, yet.

I found a good review of it:

https://undark.org/2025/11/28/book-review-hidden-guests/

That reminds of a piece which frames pregnancy as a biochemical cold-war between the body of the mother and the child, which can turn "hot" to the detriment of both. In this framing, the chimerism isn't just from cells getting lost, it's the legacy of structured infiltration and sabotage.

______________

> In primates and mice, it’s a different story. Cells from the invading placenta digest their way through the endometrial surface, puncturing the mother’s arteries, swarming inside and remodelling them to suit the foetus. Outside of pregnancy, these arteries are tiny, twisty things spiralling through depths of the uterine wall. The invading placental cells paralyse the vessels so they cannot contract, then pump them full of growth hormones, widening them tenfold to capture more maternal blood.

> These foetal cells are so invasive that colonies of them often persist in the mother for the rest of her life, having migrated to her liver, brain and other organs. There’s something they rarely tell you about motherhood: it turns women into genetic chimeras.

https://aeon.co/essays/why-pregnancy-is-a-biological-war-bet...

You mean, having a medical procedure that involves a major organ disease, a long waitlist with your life on the line, start by knocking you out, cutting you open, replacing one of your organs, follows with a recovery period, and then a lifelong regime of immunosuppressant drugs to prevent rejection might affect your personality somewhat?

Have fun controlling for confounders with this shit.

From an evolutionary perspective, it makes sense that the body would explore all possible ways to increase intelligence, with neurons located anywhere in the body and with chemical in addition to electric signals. It's not like a car or something that was designed with specific functions for specific components.

>but it is also possible to live in more harmonious relation between the head, heart, and gut — all the intelligence centers.

Aren't those the supposed locations of the "chakras"?

Gurdjieff was literally, physically correct: we are three-brained beings.

I'm in the middle of reading "All and Everything" and had the exact same thought!

Link?

Sort of, but it generally goes more like: base/perineum, genitals, navel, heart, throat, forehead, and then one at the top of the head or just above. The Sefer Yetzirah, however, references specifically "Head, Belly, and Chest" as the three loci of the human body. (§ 3.4-5)

There's a healthy debate about whether the dantien is below the navel being mistranslated as near the pubic bone versus three inches toward your spine, either in your viscera or in the lowest layers of muscle in your abdominal wall.

If it is real and people experience it, how is it a mystery where it is located?

We don’t know if we are experiencing the same thing.

Ultimately, muscle guarding can be bad for your health. I can only agree that I’ve experienced muscle unlocking, and the visualizations associated with that concept definitely facilitated that. I can’t say much beyond that. But I’m sure I could find you people who would happily jump to conclusions.

I don't know about chakras, but 'Chi' followed imaginary conduits through the connective tissue that... turned out actually there are conduits through connective tissue for lymph to move. They're just really really tricky to image so we didn't know about them until about ten years ago.

I took a Yoga class years ago (my tight wrists made it very unpleasant) and on the last day of class the instructor pulled out some obscure stuff and had us do some energy work, which I was sure was going to be complete bollocks. And about five minutes before the end of the class I experienced feelings that were identical to Flow state (that slightly buzzy feeling when you're in the grove and just crushing a task.) I recall thinking, "Oh this is potentially addictive. I'm glad this is the last class."

I'm betting that 10-20% of the mysticism stuff eventually turns out to be true and the rest is speculation built on top of correlation with those objectively true bits. Science eventually gets around to studying coincidences. Medicine tends to be more arrogant and dismissive of anything they can't measure, for far longer than is strictly healthy.

> Medicine tends to be more arrogant and dismissive of anything they can't measure, for far longer than is strictly healthy.

There's good reason for that. A huge part of such stuff eventually turns out to be dangerous horseshit.

I know an awful lot of people that have been diagnosed with diseases that they were told as recently as ten years ago, do not exist. If it was one disease, I’d be more sympathetic, but it’s more than half a dozen.

The difference between god and a doctor is God doesn’t think he’s a doctor.

I knew a person who died because they believed in dangerous horseshit.

In the same town, another person died from a different type of dangerous horseshit - specifically the kambo ritual.

In terms of methods dangerous horseshit outnumbers actual medical practice 10:1 at least. How do you know which one works?

The latter at the very least is tested for safety and efficacy.

Category error.

You understand there’s a difference between thinking windex will cure viruses and thinking you have a chronic illness, right?

From top to bottom:

crown of head

center of forehead ("third eye)

throat

heart

solar plexus

belly

bottom of ass/below feet, depending on if your magical tradition prefers to work seated or standing

Gut feelings about bad things are older than dirt. Your brain already noticed something odd and dangerous about the environment, yet your eyes/ears didn't. Maybe some predator related smells, or the hormones from a potential aggresor. Or nearby people having fears...

Any discussion of embodied intelligence or the realization of how much of our nervous system is outside of our brain makes thinking about genital mutilation (such as non consensual infant circumcision) even more horrifying. How many nerves are lost when intersex children or infant boys are mutilated?

Valid points, but will be hopelessly flagged and deleted before long.

More related stuff.

https://www.researchgate.net/publication/365412617_Polyatomi...

Anyone here into Systemic Constellations and have a theory of how they work?

See Michael Levin.

I shocked a lot of flatworms for that guy 20 years ago. Really cool stuff.

Interesting article, Douglas Hofstadter's book https://en.wikipedia.org/wiki/I_Am_a_Strange_Loop takes it a step further and says that parts of our consciousness/soul lives outside of ourselves and in the minds and brains of others. Since one can generally guess how person you know would respond in a given situation, such as how a spouse might be able to know exactly what their spouse would say/do, and in that sense our "souls" are distributed. It's a bit more nuanced than that, but I think that gets the point across of how parts of ourselves live in others.

I think that is Hofstadter grieving his wife, and reflecting on how we embed models or predictions of others in our own neural networks, more than anything else.

We build models of the world in order to predict it.

But I guess you could say other people are objectively shaping the neurons in our brains. But so is that fiddly printer tray or whatever, to a small extent.

Hey that printer tray is a bit of someone's soul too. Many people's work and decisions, even a bit of the nature of our whole society is recorded in those flimsy things. It may or may not be comforting that most of what we contribute to the world will ultimately be considered mundane, even and perhaps especially if it's successful.

Makes sense. The boundary we draw around a group of neurons that we call "self" is just arbitrary.

Then, logically, we can cut away 90% of your neurons and you will still be there, right?

Depends on what "being there" actually means. Is a sleeping person "there"? Is a comatose person "there"? Until we define this kind of questions, we won't get anywhere

This is harnessed in Greg Egan's short story "Learning To Be Me": https://gwern.net/doc/fiction/science-fiction/1995-egan.pdf

An alternate theory is that we develop models of other people’s behavior to predict their actions, and then we apply a form of those models to ourselves, which becomes what we think of as self-awareness. But the models are just models, they aren’t the mind, which is why our conscious self often has trouble controlling, or even predicting our own behaviour.

> our conscious self often has trouble controlling, or even predicting our own behaviour.

That doesn’t ring true for me - I hardly ever find myself behaving unpredictably or out-of-control - I remember sometimes feeling that way as a child, but now? As an adult? It almost never happens.

Do you really feel that you are ‘often’ out of control or behaving unpredictably?

> I hardly ever find myself behaving unpredictably or out-of-control - I remember sometimes feeling that way as a child, but now? As an adult? It almost never happens.

Good for you. I almost parted with a very good friend just because I had a very bad day and a big headache yesterday. Fortunately she is understanding enough. Due to lack of mental clarity I've said things that are simply untrue but I felt that the words I'm writing were correct at the time. I felt it was wrong reaction pretty soon after sending and rereading.

But I'm not "often" out of control. It just happens once or twice a year.

"[i]f you look closely at our nervous system, you’ll see that there are neuronal clusters distributed throughout the body. Human computation is better understood as distributed than centralized."

It's kind of like having a computer at the home, but tens of thousands of computers at a data center. Things like reflexes can happen quickly because you don't have to go all the way to the brain, but your arm isn't going to be adding 2+2 by itself.

on the reflexes - does the term "muscle memory" has any truth in it too?

It's almost entirely in your brain. Less "your muscles remember how to do things" and more "your brain remembers how to do things using your muscles".

The muscles and the nerves within your limbs adapt some - they respond to being used - but they don't have the representation capacity to store action patterns in them.

The spine itself is another matter - it's much more complex and adaptive, it has some capacity, it can learn things. It mostly carries a set of reflexes you get at birth, and some commonly used learned action patterns. Less "how to play the piano" and more "a set of finger motions useful for playing piano". The most studied thing is probably the spinal involvement in gait generation and stabilization of bipedal locomotion.

Now, things would be different if you were an octopus. But humans are pretty centralized, as far as nervous system goes.

With 9front you can import devices from other computers. Your body can do the same... with automatic reflexes and even stuff with automatic driving.

A very powerful meditation practice is called self-inquiry. One version of it is after you calm your mind down (say with breath meditation) you look for where u think u r. Wherever that is, ask yourself if that’s where u r, what is looking at it? Keep going, don’t intellectualize it, and keep looking.

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