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Intercellular communication in the brain through a dendritic nanotubular network

voxleone

Penrose’s vindication: In a broad philosophical sense. His intuition that quantum effects might play some role in cognition seems less far-fetched now than it did 30 years ago.

But vindication of Orch OR specifically (microtubule-based quantum gravity collapses driving consciousness) not yet.

https://royalsocietypublishing.org/doi/10.1098/rsta.1998.025...

fair_enough

The OP's article does a lot more to disprove such a hypothesis by instead offering a more credible alternative explanation:

Neurons found in the CNS have tubles large enough to allow transport of ions and even relatively large polypeptides similar to, but more permissive than, the well-known gap junctions found between smooth muscle and cardiac muscle cells.

Penrose's hypothesis is crank science about quantum gravity messing with your CNS in a way comparable to "body thetans" in Scientology.

sarchertech

Penrose doesn’t hold the microtuble hypothesis strongly at all.

He’s very very careful to say that it’s just something he’d like to see tested and he has no idea whether it’s true or not.

That very much distinguishes it from Crank science.

btilly

In 1989, Penrose picked up Lucas' 1961 argument that no computer can possibly simulate intelligence. The argument rests on fundamental misunderstandings of logic, that are well-known among logicians. See, for example, https://www.ams.org/journals/bull/1995-32-03/S0273-0979-1995... for an article explaining this, written some 30 years ago.

The fact that Penrose has maintained his misunderstandings for 30 years, demonstrates that, on this topic, he has been a crank for a long time. No matter his other accomplishments.

russdill

That's the problem with Penrose's thinking though. He's absolutely convinced that consciousness cannot boil down to something computable. So he reaches for the quantum shelf, but not just the quantum shelf, the quantum processes we don't yet understand since otherwise it'd just be something computable, but with more steps.

BurningFrog

Penrose may well be completely wrong about this, but I think he's easily done enough important science work to not be called a crank.

Marazan

You can be a genius in one field and a crank in another.

For example: Penrose.

chvid

Why is it crank science? He clearly states that it is hypothetical, speculative and open research.

markhahn

The main reason is because it's arbitrary.

His "speculation" is litereally: I think quantum is mysterious, and brains are mysterious, so there must be quantum in the brain. That's just silly - even if only because his opinions about mysteriousity is of no importance.

oh_my_goodness

I don't see that offering an alternative hypothesis disproves anything.

tsimionescu

By Occam's razor, it could be said that offering an alternative hypothesis that explains all facts equally well but is also simpler does "disprove" more complex hypotheses. For example, it is often said that Einstein's special theory of relativity disproved the idea of an aether - but special relativity is compatible with the existence of an aether with certain properties, it just is a completely unnecessary extra complication.

westurner

But does this help explain Representational drift?

From "Concept cells help your brain abstract information and build memories" https://news.ycombinator.com/item?id=42784396 :

> the regions of the brain that activate for a given cue vary over time

"Representational drift: Emerging theories for continual learning and experimental future directions" (2022) https://www.sciencedirect.com/science/article/pii/S095943882...

>> Future work should characterize drift across brain regions, cell types, and learning.

How do nanotubules in the brain affect representation drift?

There is EMF to cognition given that, for example, "Neuroscience study shows the brain emits light through the skull" (2025) https://news.ycombinator.com/item?id=44697995

Aren't there certainly quantum effects in the EMF wavefield of and around the brain?

soulofmischief

The common understanding is that at the molecular scale that your nervous system operates, quantum effects are averaged out and don't lead to instability of neuronal activity.

Noaidi

Wow, this is such an odd response. There’s plenty of research that link microtubules to consciousness. I don’t understand this pushback other than one being sped in a certain scientific dogma that doesn’t allow new thoughts or questioning to creep in.

Just say that Penrose is a crank is way off chart in my opinion

ben_w

The word "consciousness" means at least 40 distinct things; some of those (e.g. brain being alive and functioning) are obviously connected to microtubles; others (e.g. qualia, which is what most understand Penrose invoked microtubles to explain) are so ill-defined as to be untestable and unfalsifiable.

That Penrose also seems to have a fundamental error in his understanding of the implications of Gödel's incompleteness theorems, doesn't help.

ljlolel

Also microtubules with quantum…

exe34

Penrose's theory is this: consciousness is really weird. quantum is really weird. there's got to be a connection.

Just because he is brilliant in one field doesn't mean he's remotely competent in every field.

null

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IdSayThatllDoIt

This seems like a straw man argument.

That the brain uses electrical/chemical signals is crank science about subatomic particles messing with your aura in a way comparable to "body thetans" in Scientology.

If that were not so, electrical/chemical engineers could upgrade our brains with their knowledge of electricity/chemistry.

Scientific progress is thinking about stuff. And my Occam's razor is leaning toward "if just arithmetic could yield consciousness we would have figured it out by now".

sarchertech

If you’ve listened to anything he’s said in the last few years he doesn’t hold very tightly to the microtublule explanation.

Paraphrasing what he said in a video from a year ago or so: it’s an interesting theory that he’d like to see tested, but he has no idea whether it’s correct or not.

robwwilliams

No, nothing to do withPenrose’s idea. No quantum effects just the traditional use of microtubules for transport of cargo — in this case between adjacent dendrites.

sim04ful

I don't see why this idea is controversial at all; of course intelligence would evolve to leverage every possible physical mechanism and property inherent in matter, from classical structures like dendritic nanotubular networks facilitating intercellular communication, to potentially quantum effects that support intricate computation and the emergence of thought, since that's the nature of evolution: massively exploring the possibility space.

tshaddox

It's controversial because of how specific the hypothesis is, now novel the physical mechanism would be if it existed, and how little evidence there is that it exists. I don't think it's controversial because people that evolution couldn't possibly explore that possibility space. The fact that evolution explores a very large possibility space doesn't mean that anything you can conceive of must exist. I mean humans aren't even capable of biological flight, and we know that has evolved multiple times!

sarchertech

Penrose has 2 different theories really. 1 is that there are quantum effects involved in consciousness.

2 is that microtubles are directly involved. He feels fairly strongly about 1. He doesn’t feel strongly about 2. He is very open to it being incorrect and just thinks it’s an interesting theory to explore.

IsTom

There is a question if there is actual physical possibility to do useful quantum computation with tools available to biological systems. Cells are very noisy environments and nonclasical states are very fragile.

tsimionescu

Wheels and motors and jet engines and electrical transmission lines are also physically possible, but they are completely missing from the animal world (I believe there is one known unicellular organism that has a locomotion method that is similar to a motor or at least a propeller, but that is still completely unique).

joquarky

ATP synthase is pretty much a micro-mechanical turbine.

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

supportengineer

This type of animal has evolved a gear mechanism.

https://en.wikipedia.org/wiki/Issus_(planthopper)

markhahn

sure. but there are very tangible bounds on the sorts of physical interactions that can cause any effect.

for instance, lots of people love the idea of "brain waves". in general, neurons are event-driven, not given to "waving". indeed, the mystique of brainwaves is counter-physical, in that when there is synchronized activity, it produces EM signals that are fairly hard to pick up (EEG, MEG have gains O(1e6)). a neuron simply lacks a physical mechanism to be affected by such a wave.

not unlike Tegmark pointing out that the brain is dense and warm and that means short/fast decoherence.

Tadpole9181

Because there's no evidence and the fundamental claim isn't boring "how it works", but the idea that this "quantum magic" is what binds a soul/consciousness to your body and gives rise to "free will" that deterministic physics very clearly does not allow for.

sim04ful

Oh i see now

akomtu

The same deterministic physics that says that the spot where an electron ends up in the double slit experiment is not only nondeterministic, but doesn't exist in principle until it's measured.

make3

the "conscious emerges from quantum superposition" idea is controversial because it's thinly veiled mysticism

cnity

Materialists always seem to forget that they're kicking the can down the road.

sarchertech

Penrose is very much a materialist. He thinks that humans could someday create machines that can tap into whatever quantum effects the brain uses.

sim04ful

There's no non-physical "ghost in the machine," and I don't even see the value in probing consciousness down to its most fundamental essence.

Bjartr

I agree. I'm pretty sure both photosynthesis (superposition) and our sense of smell (quantum tunneling) involve quantum effects, so it's not that wild to think that quantum effects are at play in the mechanistic operation of the brain and therefore contribute to the phenomenon of consciousness.

markhahn

everything is quantum. it's just convenient to deal with the emergent behavior instead (like "chemistry").

yes, photosynthesis is quantum. so is vision, smell, etc. heck, metabolism is quantum!

but these are fast and local, because most of the world is decoherence-friendly. the quantum effects of a photon in your rod cell is not going to cause any quantum weirdness in a smell receptor in your nose.

ZYbCRq22HbJ2y7

that seems kind of pointless to speculate about? unless you were into reading this sort of thing a long time ago and it is interesting to you? aren't there more convincing modern models of consciousness that don't rely on spookiness?

amelius

But chemistry is basically impossible without quantum effects ...

CGMthrowaway

Would do a lot to explain many's understanding of the brain as a non-deterministic machine (or, their reasonable resistance to the idea that it is a deterministic one)

bbor

How does this vindicate Penrose in any slight sense?? This is using "nanotubular" in the sense of "ultrathin membrane bridges" that serve as "long-range intercellular transport" for macro objects in the um range, NOT "polymers of tubulin" that "provide platforms for intracellular transport" with an inner diameter in the low nm range. (quotes from https://en.wikipedia.org/wiki/Microtubule)

More importantly, these are transporting things that can plausibly impact other neurons, instead of possibly interacting with things that are far too small to ever impact a neuron in any way we've ever seen before (AKA without magic).

IMHO, this vindicates Penrose and Hamerhoff in no way whatsoever; nonetheless, I'm sure there will be a flood of YouTube videos subtly conflating the two senses of the term "nanotube" in order to promote the idea of a universal noosphere that ties us all together through the magic of quantum entanglement and positive vibes. Fun...

(More on topic: anyone with access to Science know why these are called "nanotubes" if they transport things in the micrometer range? Microtubules are named for their length, but it doesn't really make sense in reverse to have a tube 1000 times as wide as it is long... Maybe they're elastic? Or does "nano" just mean "really small" here?)

Noaidi

to understand that nano tubules interact with microtubules is part of the answer to your question.

https://www.sciencedirect.com/science/article/pii/S221137971...

And you’re talking about transporting “things” and microtubules are not about transporting things in Penrose theory, but rather serving as quantum machines that are linked across the brain.

lorenzohess

Editor's summary:

> Synaptic connections mediate classical intercellular communication in the brain. However, recent data have demonstrated the existence of noncanonical routes of interneuronal communication mediating the transport of materials including calcium, mitochondria, and pathogenic proteins such as amyloid beta (Aβ). Using super-resolution and electron microscopy, Chang et al. identified and characterized structures called nanotubular bridges that connect dendrites in the brain (see the Perspective by Budinger and Heneka). These bridges mediate the transport of calcium ions, small molecules, and Aβ peptides, and may contribute to the spreading and accumulation of pathological Aβ in Alzheimer’s disease. —Mattia Maroso

siavosh

does super-resolution refer to the image processing technique of interpolating/hallucinating higher resolutions? if so, is this a common/respected part of evidence gathering?

cwillu

Super resolution refers to imaging below the refraction limit, more or less by having the receiving sensor within a wavelength or two of the material being imaged, allowing you to use the nearfield (which doesn't have a diffraction limit, but which also doesn't propagate beyond a couple wavelengths) instead of the farfield (which does, and does).

It's unrelated to the nvidia marketing term for ai filtering of images.

cma

Nvidia's DLSS Super Resolution doesn't do anything with bypassing the diffraction limit, but does go beyond the single image nyquist limit by undersampling the input render, jittering the projection matrix each frame, and reconstructing higher resolution with frame history. It's reconstructing real extra detail. Some parts of it like handling disocclusion areas between frames etc. are fully hallucinated though.

With camera movement and things like gaps between camera sensor elements acting as the undersampling, their video super resolution may be learning similar ways of legitimately reconstructing at a higher res from temporal data, though it also hallucinates some in and is dealing with already compressed video where a lot of that might be lost.

I'm not sure if their video super resolution actually does this kind of temporal stuff though or it is just a repeated image upscale, but some of the AI video upscalers do and get much better upscaling on longer windows of frames than when run frame by frame without context.

cma

Usually methods that get past the diffraction limit but not through hallucination https://en.wikipedia.org/wiki/Super-resolution_microscopy

But they say they used ML analysis too in the abstract

> Using super-resolution microscopy,25 we characterized their unique molecular composition and dynamics in dissociated neurons,26 enabling Ca 2+ propagation over distances. Utilizing imaging and machine-learning-based27 analysis, we confirmed the in situ presence of DNTs connecting dendrites to other dendrites28 whose anatomical features are distinguished from synaptic dendritic spines

atarian

it’s amazing to me how we’re still discovering new pieces of the human body every year. you would have thought by now we’d have discovered everything

Sniffnoy

An interesting post I read recently about why we haven't: https://svpow.com/2024/09/07/were-not-going-to-run-out-of-ne...

Of course, that's specifically about human anatomy. In this case we're talking about a feature that I'd bet is present in other animals too, so the factors discussed here don't all apply. In this case though there seems to be a straightforward answer -- the structures involved are very small! The post I linked is largely talking about larger structures we failed to find...

b800h

Science teachers in schools and TV documentaries play a large part in driving this perception.

fsloth

Yup. You teach only 1/4th of the Rumsfeld matrix (known knowns). And TV shows are there for a good story, not philosophy of knowledge.

mcdonje

Don't call it that. He didn't make it up. Descriptive names are better than memorial names anyway. Call it the known-unknown matrix, or known-unknown risk classification system.

SeanAnderson

Wait, what's the fourth? Unknown knowns? How's that work?

thinkingtoilet

Find me one science teacher who says that we literally know everything about the human body there is to know. Just one.

The amount of anti-education/anti-school rhetoric on HN these days is worrying.

stronglikedan

> by now we’d have discovered everything

Until we both discover everything down to the Planck length, and then prove somehow that the Planck length is truly the smallest "unit", then we have not discovered everything. And we have probably hardly discovered anything, relatively.

VagabundoP

The one thing we're discovering is how little we've discovered.

vmilner

I always think about this when alien technology gets reverse-engineered in a remarkably short time in SF novels.

bbor

To paraphrase the great Noam Chomsky: cognitive science is in a pre-Gallilean stage.

Many thousands of incredible scientists have done amazing work over the past ~century, but cutting-edge neuroscience still doesn't have the conceptual tools to go much farther than "when you look at apples this part of your cortex is more active, so we'll call this the Apple Zone".

Sadly/happily, I personally think there's good reason to think that this will change in our lifetime, which mean's we can all find out if trading the medicalization of mental health treatment (i.e. progressing beyond symptom-based guess-and-check) for governmental access to actual lie detecting helmets (i.e. dystopia) is worth it...

rrrrrrrrrrrryan

There's a new theory that we might actually gain a greater understanding of the human mind by studying the AI systems we create, because we can basically get a perfect X-ray of their neural nets at any particular state.

When we look at the "apple zone" part of an AI model that lights up, we see it in way higher resolution than our best scans of the human brain, and this might tell us something about how apples are perceived by both systems, or how language is represented neurally, or any number of other things.

ACCount37

And we can barely figure out how the modern LLMs work.

That doesn't bode well for minds being human-interpretable, not at all.

I used to think that the biggest bottleneck to understanding the workings of the human brain was that it defies instrumentation. Which could be solved by better imaging techniques, high throughput direct neural interfaces, etc. But looking at the state of AI now?

If we had full read/write access to the state of every single neuron in the brain, what would we be able to learn? Maybe not that much.

tsimionescu

I think this is more or less exactly what Chomsky hoped (hopes?) AI research would eventually become, rather than the purely pragmatic pursuit of tool making it has typically been.

fragmede

Given that we're basically in the stone age still as far as the brain is concerned, we've got a long long way before that could be remotely true.

copperx

But we said the same about GenAI.

null

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therein

>you would have thought by now we’d have discovered everything

I genuinely wouldn't.

ape4

Time to re-designed our artificial neural networks

thenobsta

One of the neat and mindnumbing things about the brain is the number of information passing pathways. There are so many and as this discovery evidences, we're still finding new ones.

Not sure our ANNs will ever be able to model them all.

russdill

Communication here seems to refer more to the passing of proteins and ions than information. Critically the amyloid proteins studied in Alzheimer's.

tsimionescu

Our ANNs have abandoned any similarity with brain neural networks basically right after they appeared. As we've learned more about neuro-biology, the gap has simply grown larger.

GeorgeTirebiter

I've been impressed with CfCs --- and the stuff Liquid https://www.liquid.ai/research/liquid-neural-networks-resear... is trying to do: model neurons as differential equations, and use CfC methods to alleviate runtime ODE solving, using approximations (or tight integral bounds), so there’s often a tradeoff between approximation error and speed. https://chatgpt.com/share/68f2ada8-06ac-8002-9191-269b0cbba4...

The Big question is: WHERE is the Complexity? If Complexity is Fixed in a System, it must be Somewhere. (you can see this at play any time you look at a large software system.) Do you have simple 'blocks' and many of them? OR, do you have more complicated blocks (requiring more computons), but fewer of them? I think this is an exciting research area right now.

tsimionescu

Biological neurons are not easily modeled as any neat mathematical system. They seem to perform significant computational tasks even when alone - as do many other cells in the body, btw. Neuron linking is also more complex than the simplistic weighted connection model. Also, in biological neural networks, you have multiple kinds of neurotransmitters, not just a single signal, and beyond the quantity of neurotransmitters and their electrical properties being transmitted, the frequency of neuron firing is also known to be a significant factor that affects computation; and beyond neurotransmitters, hormones secreted in the brain and other places have some clear effects on cognition. And these are just pieces we know - there are certainly all sorts of other effects that we don't know, some chemical, some structural, some even physical perhaps (consider how all of the moving charges in one part of the brain might interact with other parts through electromagnetic fields).

We have no idea how much of this complexity is fundamental and how much is incidental, of course. But it is certain that every part of the brain is way more complex than the ultra-simplistic ANNs, and replacing the sigmoid function with some ODE will not move that needle significantly.

GeorgeTirebiter

how? Also, is this any different than 'merely' providing more bits of I/O to neurons via this different 'channel'?

searine

This research was primarily done at John's Hopkins in Baltimore and funded by NIH's National Institute of Neurological Disorders and Stroke.

bbor

Good reminder... Presumably, the lab phases were completed before 2025. In February of this year, a neuroscientist at John Hopkins said of the political spending cuts “This is simply the end.” https://www.nbcnews.com/science/science-news/trumps-nih-budg...

:(

bakies

I dont think there is nearly enough attention on how much of our great science in the US has come to a complete halt.

kridsdale3

There has been a lot of attention. But not enough, yes.

Sadly, thanks to Democracy, we have a plurality of voters who do not value research, or understand how it will one day be themselves who are patients.

GeorgeTirebiter

China will pick up the slack.......

SlightlyLeftPad

Bananuler, interactivodular…

fpsvogel

ring, ring, ring, ring, ring, ring, ring …

kridsdale3

I've got my hunches

stepquiet

Totally tubular, man!

cyanydeez

The same thing is hypothesized for most tissue in the body and a source of how cancer seems to spread without direct connectivity. It's been classified so often as just background curioso that it never was investigated further.

Hopefully finer grained imaging will elludicdate this stuff.

null

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m3kw9

And then you have AI “specialist “ like Hinton doing thought experiments saying if we replaced a neuron with ones we made we would still be conscious exactly the same way

api

I still think there's a good chance that evolution has figured out some way to leverage quantum computation, probably in a very different way from the way we're trying to do it with ultra-cold low noise quantum digital circuits. If this is the case it's going to be some kind of high temperature noisy analog stochastic way of harnessing QC. The phrase "stochastic analog quantum computer" comes to mind.

It's how little energy the brain uses, especially for learning. The brain seems to be hundreds of thousands to millions of times more energy efficient than any kind of current AI on a classical computer, not to mention still beating it in terms of performance and versatility. Transistors do not use millions of times more energy than synapses, and processor feature sizes are not millions of times larger. Something else is going on.

Either the brain is leveraging QC or our AI training algorithms are just really really horrible compared to whatever is happening in biology. Maybe biology found learning methods that work thousands of times better than differential backpropagation.

aljgz

I like the possibility of QC in brain. However, explaining why brain is much more efficient that computers does not need QC. Computers and Brain evolved in two completely different ways. For the brain, simple cognitive functions emerge first, supporting more complex life behaviours, starting with very simple multi celular life forms. Logical reasoning emerges much later, and is pretty expensive. Then we made computers to do logical computation and they are incredibly efficient at it: a modern low power processor is much more efficient than human brain in this kind of workload, by orders of magnitude.

Now we are trying to implement what the mind is naturally good at with systems designed to do logic well. This is the main reason it's so inefficient. Emulation is costly. It is costly when brain does logic, and is costly when computers do AI.

In theory, we should be able to build computing devices designed for AI workloads, and they can be as efficient as brain or even much better.

jbotz

> The [human] brain seems to be hundreds of thousands to millions of times more energy efficient than any kind of current AI

I don't know about that... I've consumed quite a few calories in my lifetime directly, plus there is all the energy needed for me to live in a modern civilization and make the source material available to me for learning (schools, libraries, internet) and I still only have a minuscule fraction of the information in my head that a modern LLM does after a few months of training.

Translated into KWh, I've used very roughly 50,000 KWh just in terms of food calories... but a modern human uses between 20x and 200x as much energy in supporting infrastructure than the food calories they consume, so we're at about 1 to 10 GWh, which according to GPT5 is in the ballpark for what it took to train GPT3 or GPT4... GPT5 itself needing about 25x to 30x as much energy to train... certainly not 100s of thousands to millions of times as much. And again, these LLMs have a lot more information encoded into them available for nearly instant response than even the smartest human does, so we're not really comparing apples with apples here.

In short, while I wouldn't rule out that the brain uses quantum effects somehow, I don't think there's any spectacular energy-efficiency there to bolster that argument.

throwaway0123_5

> plus there is all the energy needed for me to live in a modern civilization and make the source material available to me for learning (schools, libraries, internet)

To be fair, this is true of LLMs too, and arguably more true for them than it is for humans. LLMs would've been pretty much impossible to achieve w/o massive amounts of digitized human-written text (though now ofc they could be bootstrapped with synthetic data).

> but a modern human uses between 20x and 200x as much energy in supporting infrastructure than the food calories they consume, so we're at about 1 to 10 GWh, which according to GPT5 is in the ballpark for what it took to train GPT3 or GPT4

But if we're including all the energy for supporting infrastructure for humans, shouldn't we also include it for GPT? Mining metals, constructing the chips, etc.? Also, the "modern" is carrying a lot of the weight here. Pre-modern humans were still pretty smart and presumably nearly as efficient in their learning, despite using much less energy.

adastra22

That seems incredibly unlikely given the impossibility of maintaining coherent quantum state in a noisy thermal environment like the brain.

smj-edison

On a semi-related note, it is interesting to see some of the fledgling evidence for quantum processes existing in metabolism[1].

[1] https://en.wikipedia.org/wiki/Quantum_biology (on a phone so can't link the exact section, but it's the section on mitochondria under energy transfer).

Noaidi

Penrose and other talk about this and how it’s possible in the noisy wet messy environment of the human brain.

https://www.pbs.org/video/was-penrose-right-new-evidence-for...

Just cause we don’t understand it yet does not mean it’s not possible.

adastra22

FYI Penrose is a cautionary tale in the physicist community. He is/was once a competent academic, but his quantum consciousness ideas are viewed similarly to tinfoil hat conspiracy theories. It is technobabble word salad; quantum woo driven more by a personal objection to the implications of Newtonian determinism to the philosophy of the mind, not reason.

We understand quantum interactions more than sufficiently enough to know that the thread of hope he clings to, the soul of the gaps via quantum woo, is not in any way plausible. It is comparable to a perpetual motion machine.

Invictus0

LLMs process everything from scratch. The brain is doing virtually everything from memory.

BirAdam

Well, it's more like temporal compression.

The brain too learns from scratch. From birth through death, it's acquiring information, integrating that information, and using it. LLMs do this in a shorter time period.