16 ms·

The brain isn’t supposed to change this much

196 points by tardismechanic 5y ago

ajju 5y ago
Sounds like defragmentation are first sight. Seems likely that the storage algorithm for human memory could use periodic optimization, especially since we recontextualize memories over time. For example, let’s say we smell a lychee for the first time in a shop, and the brain stores that memory using a given set of neurons. Later, a hawker starts selling lychees in the local train in Mumbai we commute on everyday. Now memories of the smell of lychees and the smells and experiences of Mumbai local trains become strongly linked. At that point, in a simplified model of the brain, I can imagine why the brain may want to move those memories so they are using neurons that are closer together. Defragmentation! I am likely terribly wrong, but would love to learn in what way I am wrong :)
- deleted 5y ago
  [deleted]
- gremlinsinc 5y ago
  I had a similar thought, albeit dumbed down just that neurons represent RAM locations, and memory locations can change but the data can be identical to data that was stored in other locations previously...
- vbsteven 5y ago
  There is I believe also a theory that suggests that the brain actively rewrites and combines/compresses memories to make them more useful. That also fits in well with this defragmentation concept.
- icheishvili 5y ago
  I've had a hypothesis for a while that the brain performs compacting garbage collection while it sleeps at night. While it's probably not that simple, seeing that various sibling posters are hinting at the same notion is interesting.
striking 5y ago
I hate to quote the article so directly, but to make the headline a little less click-baity: > Put it this way: The neurons that represented the smell of an apple in May and those that represented the same smell in June were as different from each other as those that represent the smells of apples and grass at any one time. > This is, of course, just one study, of one brain region, in mice. But other scientists have shown that the same phenomenon, called representational drift, occurs in a variety of brain regions besides the piriform cortex. Its existence is clear; everything else is a mystery.
- shoto_io 5y ago
  How to write an article these days: - Find a newly published paper - Assume it’s true - Build clickbait title - Write 2,000 words, make sure to include references to old Greek philosophers - Publish
  - mananaysiempre 5y ago
    Honestly, “[Anything-s]cientists have discovered a phenomenon that they can’t explain” is like the least clickbaity title ever. It’s basically equivalent to “Scientists have had a good day at work”.
    - fsckboy 5y ago
      actually, it's "Scientists have a bad day at work." Scientists explaining a phenomenon is a good day at work. but you're right, it's not clickbaity, except for the elephant in the room, there are way more things neuroscientists can't explain than there are things they can explain.
      - mananaysiempre 5y ago
        Well, kind of, finding things you can’t explain (but still feel you should be able to) can be difficult, so I’d say that “skimmng papers all day and walking away feeling you haven’t changed the contents of your brain much” is the bad day. But yes, actively reducing humanity’s or even your own personal ignorance is a much better day, of course.
senectus1 5y ago
*Yet
bejelentkezni 5y ago
I find the assumption built into this article's incredulousness odd and I doubt I would ever had made it myself. Why would we ever expect qualia to be based on specific and static combinations of neurons? The fact alone that memories last a finite amount of time should be reason enough to conclude (given our limited number of them) that that's not how neurons work, at least insofar as the qualia of memory and present experience are the same, which seems like a sane null hypothesis to me. I think there is a strong cognitive bias in the present culture of thinking of the brain like a computer or hard drive. It's not, and I would have been more surprised if the scientists here had made the opposite finding that they did: that the constant qualia (in these mice's smells) was linked to constant combinations of activating neurons. That would contradict existing observations on brain damage and imply uncomfortable things about electrically programming the brain to produce known outcomes.
- frzj 5y ago
  Programs are executed in different memory addresses all the time. The hardened linux kernel randomizes itself. It's like a computer alright, just very different from a von-Neuman one and a completely parallelized one. When I started reading the article I expected something mind-blowing, but it always seemed obvious given the sheer number of neurons that they would load balance and feedback, rewire themselves and do all sort of cool, difficult to predict stuff all the time.
  - michaelerule 5y ago
    I think part of the mystery is that computers can copy binary information losslessly, ad infinitum. So they can move information as often as needed with (almost) no error. We don't think neurons are as reliable, and excessive copying is expected to degrade a memory/representation. It seems like this might work for discrete categorical representations, whose activation is essentially binary, but would gradually fail for anything analog/continuous.
    - retrac 5y ago
      If the computational hypothesis for minds and brains is true, and it is only conjecture though a tempting one, I can only see one way out. Analogies are a wicked thing to indulge in here. But bear with me. If an engineer designs a computer that computes on encrypted information, from an observer's naive perspective, the entire contents of memory is rewritten with a random value for each step. Yet there is a mathematical relationship between those seemingly random bits and whatever is encoded. Even just using some error correction and non-deterministic parallel processing and it might look pretty much like noise if you don't have the decoder ring. Something like that is the only explanation I can come up with. Information is stored at a level of abstraction in a structure that is maintained by being continuously re-encoded in the ephemeral computations at a lower level.
boardwaalk 5y ago
Well, I do find it’s easier to do significant refactors by copying bits of code into a new file or project rather than trying to make changes in-place.
rlkf 5y ago
Wouldn't this be similar to how weights for individual terms in a interpolation polynomial can change when adding a new point, while it still (to some approximation at least) captures all the old?
Lammy 5y ago
Is this what happens during sleep? Maybe this is what causes dreams.
- michaelerule 5y ago
  I'm (weakly) leaning in this direction as well. But, there are other proposed functions of dreams that are hard to reconcile with this. Some people think that dreams prevent overfitting and/or sample the negative gradient in a contrastive learning algorithm. Perhaps these are the same thing in end? But I'm not sure how it all fits together.
hhs 5y ago
It’s worth reading the linked paper on the causes/consequences of representational drift: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7385530/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7385530/
just_steve_h 5y ago
I have a similar reaction as bejelentkezni – why would we expect a specific sensation to always activate the same set of neurons over time? It would seem to me that we are observing patterns in a dynamic system. Their relations to other patterns seem more relevant than the specific substrate members participating in the pattern. While too simple, I think by analogy of a whirlpool current in a stream: we would not be surprised at all to observe that a given molecule of water participating in the whirlpool pattern at time (t) has only a (p)% chance of being in the pattern at time (t+1).
- slver 5y ago
  > why would we expect a specific sensation to always activate the same set of neurons over time? For at least two reasons. First, the perception of smell is extremely stable in humans. You can immediately recall a smell you smelled like a child and where you were and what you were doing. And related to that, smell is a very strong association factor for memories. Meaning you much more easily remember something if it smells like before, rather than if it just sounds or looks like before. If the neurons of this association drift all the time, question is how come those associations stick through the decades. As a programmer, you know that if you start moving associated data in your database around, it's very easy to break your data structure (dangling foreign keys etc.). A brain isn't digital but connected things must stay connected somehow. I like how to a layman, every finding is so obvious, but to a scientist it's not obvious because it doesn't match the other things they know about the brain.
  - FeepingCreature 5y ago
    I mean if you don't remember a smell, how would you notice? It's not like your brain will throw up an error message. The memory just won't come to mind.
    - deleted 5y ago
      [deleted]
    - michaelerule 5y ago
baybal2 5y ago
> Neuroscientists have discovered a phenomenon that they can’t explain Is this a trend for weird, meaningless headlines?
- Layke1123 5y ago
  This is one of the best responses. What a fucking hugely sensationalized title. They think they can manipulate is thinkers too. They think we are largely still human and will follow the same pathways with more repetition and pressure. I can't wait to watch this site crumble.
- cung 5y ago
  > “Scientists are meant to know what’s going on, but in this particular case, we are deeply confused.” Add to that the subheading. The combination made me back out straight away in protest.
- MaxBarraclough 5y ago
  It's clickbait, nothing more.
gremlinsinc 5y ago
What if neurons are just like storage spots? RAM. I can move information from one memory location to another but the info can be identical.
- Xplune13 5y ago
  That's the question put forward in the article itself, just not framed like yours. The question is if the neurons are just like storage spots then there has to be some mechanism that we don't know yet that does that transfer without losing the information (in the case of RAM, we give the instruction to transfer). That not-yet-known thing is the main mystery here (that is if the neurons are just like storage spots. They can be entirely different as well).
  - michaelerule 5y ago
    I'm working on this at the moment; Reconsolidation should work, but requires that representations/memories be periodically re-activated so that the neurons can re-learn how to encode them. Still very preliminary: https://www.biorxiv.org/content/10.1101/2021.03.08.433413v1.abstract https://www.biorxiv.org/content/10.1101/2021.03.08.433413v1....
harry8 5y ago
As titles go this one is pretty special. It's my understanding that Neuroscientists themselves claim to understand next to nothing about phenomena in the brain. Meanwhile large amounts of what they think they might understand has such large error bars on it won't surprise them to have it all turned over in the future. They claim to have profound second level ignorance, not to even know most of what it is that they don't know yet. That's kind of what makes the field so exciting, what we don't know is almost all of it! Plus it's not some peripheral thing, it's right there at the core of everything we are individually and collectively. Sadly it's had more than its fair share of charlatans and credulous followers. Sure, the Atlantic, nobody expects them to be any good, right? Well we probably shouldn't but sometimes we still do.
- jonnycomputer 5y ago
  I agree with the gist, though I think you maybe over-stating things a bit. Also, neuroscience is pretty wide field.
yellow_lead 5y ago
> Scientists are meant to know what’s going on, but in this particular case, we are deeply confused. This kinda sounds like a high school essay.
- louloulou 5y ago
  And one that doesn't seem to understand that science is the process by which we discover/uncover things we DON'T know.
hyperpallium2 5y ago
Prediction: neurons are more like cfd than ann.
- slver 5y ago
  ANN are already producing phenomena that match our perception. The key difference is ANN is trained, then training stops, and it's used. And the brain has to always learn while in use.
- qrybam 5y ago
  What is CFD?
  - nicwilson 5y ago
    Probably computational fluid dynamics
Fatboyrunning 5y ago
Maybe it's like SHA256. You change a single pixel in an image, for example, and you get a completely different result.
nxpnsv 5y ago
The title reeks of scientific ignorance - science is all about investigate things unexplained...
- vimacs2 5y ago
  Your comment ironically reeks of scientific ignorance itself. Science is as much about confirmation of prior observations and testing of established theories (and in fact more so by sheer volume of studies) as it is investigation of unexplained phenomena.
  - nxpnsv 5y ago
    I spent 2 decades working as a scientist publishing and applying for grant money. If publishing or having a paid position matters to you as a scientist, then you have to do something novel. It doesn't preclude doing what you said - but that certainly isn't enough.
Salgat 5y ago
Reminds me of how if you take out the speech center of the brain immediately, you permanently lose the ability to speak, but if a slow growing tumor takes out the same region, the brain has enough time to slowly shift over to peripheral areas. As an aside, I wonder if the drift seen in neurons represents thought. Perhaps drift has to occur for the brain to continually think and self improve, even with limited inputs. I wonder how different drift rates in regions of the brain relate to things like better long term memory or creativity.
calkuta 5y ago
Ah, more animal experimentation. I wonder if consent was obtained?
cm-t 5y ago
Someone have found a long post title that can't spoil anything from the article content, so HN users have to click to understand what it is about :/
lostmsu 5y ago
TL;DR; over time the same physical objects/processes fire up different neurons when we experience them. Nothing unexplainable to see here.
teekert 5y ago
"Scientists are meant to know what’s going on, but in this particular case, we are deeply confused." What? I'm a scientist, I often don’t know what’s going on! I see it more as my duty to help others understand that that is ok, and often even a good thing because that is when the fun starts. Science is a method, not a “state”. States are for religions, they “know” what’s going on because "it has been written!". Us scientists are always writing.
- heyoo 5y ago
  Also, how can it be surprising that a brain-related phenomenon is not well understood? I mean, I can think of a few brain-related questions with no good answers: - What is consciousness and how does a brain become conscious? - How and why is one specific consciousness attached to one specific brain (& body)? Why am I controlling my body and not yours?
  - tsimionescu 5y ago
    I agree with your sentiment in general. However, I will note that the second question only makes sense for non-biological, dualistic notions of consciousness. If consciousness is taken to be a function or phenomenon happening in my brain&body, then there is no question to ask. It would be like asking 'why am I digesting my food and not yours'.
    - konschubert 5y ago
      > why am I digesting my food and not yours haha :D To take it a bit further, I am not sure if the first question makes a lot of sense either.
      - tsimionescu 5y ago
        I think the first question does make sense. By the same analogy, asking what is digestion precisely and how the stomach digests food is perfectly sensible. I would also note that the second question can make sense, but only if you believe consciousness is not strictly tied to the brain and body.
2bor-2n 5y ago
can someone comment tldr?
uCantCauseUCant 5y ago
Imagine the learning of new skills, as a travelling circus, traversing a road through a land covered in towns. Now those towns, depending on usefulness, will put up resistance to the circus reshaping them and the area they depend upon. And the circus must travel on, for it leaves towns in its wake. So what one watches as the learning happens in pre-disposed sensory input classification areas, i imagine, is the newly created towns moving away from the circus so to speak. Im sorry for the lack of expression and cohesion.
cblconfederate 5y ago
> If representational drift can happen in the piriform cortex, it may be common throughout the brain. Instead of looking at individual neuron response properties, look for population codes. This would be actually an interesting experiment with an artificial network, to observe how the population activation drifts over time (but remains identifiable) as the network is fed with more and more data
nanna 5y ago
> They needed to develop surgical techniques for implanting electrodes into a mouse’s brain and, crucially, keeping them in place for many weeks. Poor poor mice. Vivisection is done for the 'greater good', but not for the greater good of the millions (billions?) of critters who have suffered it. Yes I know that modern physiology is premised on it as method, the knowledge of organisms as they live not as they are dead, but what a toll.
- ljf 5y ago
  Reminds me of the joke I heard the other day: Q: Which is heavier, 100kg of lead or 100kg of feathers? A: The feathers, as you have to carry around what you did to those poor birds...
jek0 5y ago
There are theories [1] that part of the brain's function might work at the quantum level. If true, we probably won't be able to really understand what happens by measuring it this way... [1] https://en.wikipedia.org/wiki/Quantum_mind https://en.wikipedia.org/wiki/Quantum_mind
- beaconstudios 5y ago
  there is also the almost-definitely-true idea that the mind is an emergent property of the body. We can't understand emergent phenomena using reductive approaches, in the same way that we can't understand quantum phenomena using classical approaches.
- astrange 5y ago
  Classical computers also do things "at the quantum level"; CPU gates rely on quantum effects, probably the HDD does too, etc. But it doesn't prevent understanding because that computer part implements a simpler interface. The brain probably isn't a quantum computer, or else we'd be able to factor integers quickly in our heads.
  - jek0 5y ago
    Not necessarily. According to philosopher Paavo Pylkkänen, Bohm's suggestion of the quantum mind "leads naturally to the assumption that the physical correlate of the logical thinking process is at the classically describable level of the brain, while the basic thinking process is at the quantum-theoretically describable level". [1] Factoring integers is a logic operation (thus not performed at the quantum level). But an operation like identifying an object or a smell (as it is what the article here is about) could be performed at a more deep level using quantum mechanics. [1] http://philpapers.org/archive/PYLCQA.1.pdf http://philpapers.org/archive/PYLCQA.1.pdf
    - astrange 5y ago
      Hmm… it seems like that's only true if it doesn't actually mean anything impressive. Your neurons or nose obviously can rely on quantum effects in the same way a modern semiconductor transistor process does. But that doesn't imply anything huge like "consciousness can't be emulated on a classical computer."
xchip 5y ago
Thanks for the click bait headline :(
m12k 5y ago
It seems to me that this phenomenon of "representational drift" fits well with the results that show that every time a memory is remembered, it is essentially deleted, and re-recorded. Given what we know about how memory and experience make use of large swaths of the same neural pathways, it would make sense that this is the case with re-experiencing sensations too, not just re-remembering them. And if that is the case, then it would make sense that it's possible for these representations to be re-recorded in a different place or in a different way. For example mixed together with other neural wiring that is correlated but wasn't there when the original representation was made (basically de-duplicating the file system). It would also suggest that either pathways are mutating, or different neural pathways are "competing" for the right to be the ones to process a given input (and if it's the latter, then it also implies that there must be some kind of fitness function "how well did this pathway process this input" that allows a new pathway to win out over a previous one).
layoutIfNeeded 5y ago
This is one of the reasons why NeuraLink wouldn't work.
deleted 5y ago
[deleted]
antattack 5y ago
Could it be that learned/familiar experience is processed with different part of brain?
Kim_Bruning 5y ago
When anything like this gets published, I always wonder "what would it look like on a 6502?" https://storage.googleapis.com/plos-corpus-prod/10.1371/journal.pcbi.1005268/1/pcbi.1005268.pdf?X-Goog-Algorithm=GOOG4-RSA-SHA256&X-Goog-Credential=wombat-sa%40plos-prod.iam.gserviceaccount.com%2F20210610%2Fauto%2Fstorage%2Fgoog4_request&X-Goog-Date=20210610T111033Z&X-Goog-Expires=86400&X-Goog-SignedHeaders=host&X-Goog-Signature=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 https://storage.googleapis.com/plos-corpus-prod/10.1371/jour...
- rantwasp 5y ago
  > We can thus conclude they are uniquely necessary for the game perhaps there is a Donkey Kong transistor or a Space Invaders transistor. This is hilarious. Thanks for sharing this. It brightened my day.
- tardismechanic 5y ago
  Getting "ExpiredTokenThe provided token has expired.Request signature expired at: 2021-06-11T11:10:33+00:00"
  - Kim_Bruning 5y ago
    https://www.biorxiv.org/content/10.1101/055624v2.full.pdf https://www.biorxiv.org/content/10.1101/055624v2.full.pdf This should be a more permanent link I hope.
nobrains 5y ago
Its just moving from short term memory to long term memory.
pvaldes 5y ago
"Stupid article tries again to make fun of smart people" THAT would be a great title. They are trying to sell this idea all the time.
- slver 5y ago
  They're not trying to make fun of smart people, they're trying to basically to Shyamalan the research, so every next paragraph wows you with its unexpected plot twists.
slver 5y ago
Imagine if we discover most of the brain's functionality isn't in the brain or any other identifiable part of the body. Rather the brain just connects to something else, that's outside the known timespace.
9wzYQbTYsAIc 5y ago
The real question here is: what insights do computing professionals, whom work with neural networks or parallel distributed processing as their day job, bring to the table? The sort of reasoning that neuroscientists are struggling with is that very same kind of reasoning that computer scientists and practitioners use when thinking about ANN/PDP and deep learning.
benlumen 5y ago
Isn't Neuralink (and other brain interfaces, I assume) also based on the idea that you can pinpoint which neurons are responsible for each function in the brain? If I've read the article correctly, it seems to suggest that they're a moving target. How can permanent implants interface with a moving target? Might the entire Neuralink concept be based on a flawed assumption?
- FatalLogic 5y ago
  Perhaps the brain will naturally adjust to Neuralink, and similar technology, via a feedback loop that would tend to keep the Neuralink-monitored neurons more static?
jonnycomputer 5y ago
I find the whole spin of this article a little odd. Isn't it enough to talk about how interesting representational drift is without spinning fairy tales about science?
- billytetrud 5y ago
  I would really like to find a way to incentivize journalists to stop doing that kind of thing. Artistically misleading people shouldn't be seen as acceptable in factual journalism. This should have been rejected and rewritten.
andred14 5y ago
In summary: "Lifeforms are dynamic and sometimes behave unpredictably" Wow great work! BTW is it just me that finds the implantation of things into the brains of test animals to be cruel? Do we really not have better things to do?
philprx 5y ago
Wear management and prevention? just like in SSD ;-)
croehrig 5y ago
TLDR: Representation of the world doesn't seem to be locked to specific neurons or groups of neurons; over time, they drift around to completely different groups of neurons. Someone here likened it to how programs can move around in computer memory. If neurons are the "silicon of the brain" or the "PHY" layer, the biggest problem in neuroscience IMHO is that we have virtually no understanding of what is the next layer up, (i.e. the "logical layer"). What is the equivalent of program counters, CPU instructions, etc. in the brain? The brain is a nonlinear recurrent dynamical system and we are really in the dark as to how to break the dynamics down into understandable subcomponents. To get an idea of the complexity, this paper by Randall Beer analyzes the possible behaviours of 1 and 2 neuron circuits: Beer, R. D. (1995). On the Dynamics of Small Continuous-Time Recurrent Neural Networks. Adaptive Behavior, 3(4), 469–509. doi:10.1177/105971239500300405 Obviously this kind of analysis doesn't scale to 10^10 neurons.
boringg 5y ago
What I like about this, and what I like about existence in general is: While we continue to learn new things sometimes rapidly sometimes slowly, there is so much we truly don't know and it's both frightening and exciting. Constantly updating our priors. What I don't like: so many humans think they know everything or at least position themselves that way. FYI this isn't an attack on experts.
- i5heu 5y ago
  In my experience people that call themselves “expert” think they know everything. So no hot take there.
darkerside 5y ago
What is so confusing about this? The first time I read a book, it impacts me in a certain way. Every successive time, it hits me differently. I take different life experiences to it, and I understand it more deeply because I've read it before. Why would a smell be any different? Each time I smell an apple, or taste wine, or examine a painting, I am a different person, and I also discover more nuance about the subject.
- Voloskaya 5y ago
  That your brain continually learns and evolves is not surprising at all. What is surprising is that the location of the subset of neurons that reacts to a specific thing (say the smell of wine) changes over time. So neurons that were used to identify the smell of wine at time T, might be doing something completly unrelated 6 months later, and the task of identifying wine smell is now handled by another subset of neurons in the brain. It is surprising and on the surface seems ineficient since your brain has to continually transfer knowledge from one region to another rather that just ajusting the existing region to new learnings.
  - rantwasp 5y ago
    we are making a big assumption here: that neurons have tasks and are responsible for X. What if a neuron (actually a cortical column) could learn thousands of X and fire only when specific environmental conditions are met? What if you constantly wire and rewire the connections between neurons? What if multiple areas can do some thing and they arrive at a conclusion through consensus? what if your brain can predict a lot of things and just discards sensory input when it matches the expected prediction?
makz 5y ago
Doesn’t the brain rearrange itself during sleep?
airhead969 5y ago
My bet is reinforcement decay and strengthening exists to promote novelty rewards. Smell 1000 roses, it's a big "meh" but the identification of them becomes easier and better with strengthened pathways. This would be adaptive for the organism to: 1. seek new, potentially-massive rewards, stimulation rather than do the same thing over and over again without ever trying anything new 2. improve processing of stimuli that are more frequent
derefr 5y ago
It’s good to study the piriform cortex to understand memory formation / neuroplasticity, as (IIRC) it’s one of the most primitive “plastic” parts of the brain. In some species (e.g. fruit flies) the piriform cortex is the only part of the brain that changes at all after birth; i.e. it’s the only place where learning could possibly be going on. So, even if the it’s not intimately linked with human memory, the piriform cortex may be the origin of the cellular template that later diverged into whichever other brain tissues are responsible for other types of memory.
adenozine 5y ago
That little line is so toxic and terrible. If my boss came round and said, "This is adenozine, he's supposed to know what's going on," I'd be pissed. That's just dumping blame.
wizeman 5y ago
How do they know that it's not the neurons who are themselves slowly drifting position over those timescales?
RocketSyntax 5y ago
yes, it is. it adapts. firings get less strong as we get used to stimulus, and neurons that fire together wire together. so different connections form on more important info.

ajju 5y ago

Sounds like defragmentation are first sight. Seems likely that the storage algorithm for human memory could use periodic optimization, especially since we recontextualize memories over time. For example, let’s say we smell a lychee for the first time in a shop, and the brain stores that memory using a given set of neurons. Later, a hawker starts selling lychees in the local train in Mumbai we commute on everyday. Now memories of the smell of lychees and the smells and experiences of Mumbai local trains become strongly linked. At that point, in a simplified model of the brain, I can imagine why the brain may want to move those memories so they are using neurons that are closer together. Defragmentation! I am likely terribly wrong, but would love to learn in what way I am wrong :)

deleted 5y ago
[deleted]
gremlinsinc 5y ago
I had a similar thought, albeit dumbed down just that neurons represent RAM locations, and memory locations can change but the data can be identical to data that was stored in other locations previously...
vbsteven 5y ago
There is I believe also a theory that suggests that the brain actively rewrites and combines/compresses memories to make them more useful. That also fits in well with this defragmentation concept.
icheishvili 5y ago
I've had a hypothesis for a while that the brain performs compacting garbage collection while it sleeps at night. While it's probably not that simple, seeing that various sibling posters are hinting at the same notion is interesting.

striking 5y ago

I hate to quote the article so directly, but to make the headline a little less click-baity: > Put it this way: The neurons that represented the smell of an apple in May and those that represented the same smell in June were as different from each other as those that represent the smells of apples and grass at any one time. > This is, of course, just one study, of one brain region, in mice. But other scientists have shown that the same phenomenon, called representational drift, occurs in a variety of brain regions besides the piriform cortex. Its existence is clear; everything else is a mystery.

shoto_io 5y ago
How to write an article these days: - Find a newly published paper - Assume it’s true - Build clickbait title - Write 2,000 words, make sure to include references to old Greek philosophers - Publish
- mananaysiempre 5y ago
  Honestly, “[Anything-s]cientists have discovered a phenomenon that they can’t explain” is like the least clickbaity title ever. It’s basically equivalent to “Scientists have had a good day at work”.
  - fsckboy 5y ago
    actually, it's "Scientists have a bad day at work." Scientists explaining a phenomenon is a good day at work. but you're right, it's not clickbaity, except for the elephant in the room, there are way more things neuroscientists can't explain than there are things they can explain.
    - mananaysiempre 5y ago
      Well, kind of, finding things you can’t explain (but still feel you should be able to) can be difficult, so I’d say that “skimmng papers all day and walking away feeling you haven’t changed the contents of your brain much” is the bad day. But yes, actively reducing humanity’s or even your own personal ignorance is a much better day, of course.

senectus1 5y ago

*Yet

bejelentkezni 5y ago

I find the assumption built into this article's incredulousness odd and I doubt I would ever had made it myself. Why would we ever expect qualia to be based on specific and static combinations of neurons? The fact alone that memories last a finite amount of time should be reason enough to conclude (given our limited number of them) that that's not how neurons work, at least insofar as the qualia of memory and present experience are the same, which seems like a sane null hypothesis to me. I think there is a strong cognitive bias in the present culture of thinking of the brain like a computer or hard drive. It's not, and I would have been more surprised if the scientists here had made the opposite finding that they did: that the constant qualia (in these mice's smells) was linked to constant combinations of activating neurons. That would contradict existing observations on brain damage and imply uncomfortable things about electrically programming the brain to produce known outcomes.

frzj 5y ago
Programs are executed in different memory addresses all the time. The hardened linux kernel randomizes itself. It's like a computer alright, just very different from a von-Neuman one and a completely parallelized one. When I started reading the article I expected something mind-blowing, but it always seemed obvious given the sheer number of neurons that they would load balance and feedback, rewire themselves and do all sort of cool, difficult to predict stuff all the time.
- michaelerule 5y ago
  I think part of the mystery is that computers can copy binary information losslessly, ad infinitum. So they can move information as often as needed with (almost) no error. We don't think neurons are as reliable, and excessive copying is expected to degrade a memory/representation. It seems like this might work for discrete categorical representations, whose activation is essentially binary, but would gradually fail for anything analog/continuous.
  - retrac 5y ago
    If the computational hypothesis for minds and brains is true, and it is only conjecture though a tempting one, I can only see one way out. Analogies are a wicked thing to indulge in here. But bear with me. If an engineer designs a computer that computes on encrypted information, from an observer's naive perspective, the entire contents of memory is rewritten with a random value for each step. Yet there is a mathematical relationship between those seemingly random bits and whatever is encoded. Even just using some error correction and non-deterministic parallel processing and it might look pretty much like noise if you don't have the decoder ring. Something like that is the only explanation I can come up with. Information is stored at a level of abstraction in a structure that is maintained by being continuously re-encoded in the ephemeral computations at a lower level.

boardwaalk 5y ago

Well, I do find it’s easier to do significant refactors by copying bits of code into a new file or project rather than trying to make changes in-place.

rlkf 5y ago

Wouldn't this be similar to how weights for individual terms in a interpolation polynomial can change when adding a new point, while it still (to some approximation at least) captures all the old?

Lammy 5y ago

Is this what happens during sleep? Maybe this is what causes dreams.

michaelerule 5y ago
I'm (weakly) leaning in this direction as well. But, there are other proposed functions of dreams that are hard to reconcile with this. Some people think that dreams prevent overfitting and/or sample the negative gradient in a contrastive learning algorithm. Perhaps these are the same thing in end? But I'm not sure how it all fits together.

hhs 5y ago

It’s worth reading the linked paper on the causes/consequences of representational drift: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7385530/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7385530/

just_steve_h 5y ago

I have a similar reaction as bejelentkezni – why would we expect a specific sensation to always activate the same set of neurons over time? It would seem to me that we are observing patterns in a dynamic system. Their relations to other patterns seem more relevant than the specific substrate members participating in the pattern. While too simple, I think by analogy of a whirlpool current in a stream: we would not be surprised at all to observe that a given molecule of water participating in the whirlpool pattern at time (t) has only a (p)% chance of being in the pattern at time (t+1).

slver 5y ago
> why would we expect a specific sensation to always activate the same set of neurons over time? For at least two reasons. First, the perception of smell is extremely stable in humans. You can immediately recall a smell you smelled like a child and where you were and what you were doing. And related to that, smell is a very strong association factor for memories. Meaning you much more easily remember something if it smells like before, rather than if it just sounds or looks like before. If the neurons of this association drift all the time, question is how come those associations stick through the decades. As a programmer, you know that if you start moving associated data in your database around, it's very easy to break your data structure (dangling foreign keys etc.). A brain isn't digital but connected things must stay connected somehow. I like how to a layman, every finding is so obvious, but to a scientist it's not obvious because it doesn't match the other things they know about the brain.
- FeepingCreature 5y ago
  I mean if you don't remember a smell, how would you notice? It's not like your brain will throw up an error message. The memory just won't come to mind.
  - deleted 5y ago
    [deleted]
  - michaelerule 5y ago

baybal2 5y ago

> Neuroscientists have discovered a phenomenon that they can’t explain Is this a trend for weird, meaningless headlines?

Layke1123 5y ago
This is one of the best responses. What a fucking hugely sensationalized title. They think they can manipulate is thinkers too. They think we are largely still human and will follow the same pathways with more repetition and pressure. I can't wait to watch this site crumble.
cung 5y ago
> “Scientists are meant to know what’s going on, but in this particular case, we are deeply confused.” Add to that the subheading. The combination made me back out straight away in protest.
MaxBarraclough 5y ago
It's clickbait, nothing more.

gremlinsinc 5y ago

What if neurons are just like storage spots? RAM. I can move information from one memory location to another but the info can be identical.

Xplune13 5y ago
That's the question put forward in the article itself, just not framed like yours. The question is if the neurons are just like storage spots then there has to be some mechanism that we don't know yet that does that transfer without losing the information (in the case of RAM, we give the instruction to transfer). That not-yet-known thing is the main mystery here (that is if the neurons are just like storage spots. They can be entirely different as well).
- michaelerule 5y ago
  I'm working on this at the moment; Reconsolidation should work, but requires that representations/memories be periodically re-activated so that the neurons can re-learn how to encode them. Still very preliminary: https://www.biorxiv.org/content/10.1101/2021.03.08.433413v1.abstract https://www.biorxiv.org/content/10.1101/2021.03.08.433413v1....

harry8 5y ago

As titles go this one is pretty special. It's my understanding that Neuroscientists themselves claim to understand next to nothing about phenomena in the brain. Meanwhile large amounts of what they think they might understand has such large error bars on it won't surprise them to have it all turned over in the future. They claim to have profound second level ignorance, not to even know most of what it is that they don't know yet. That's kind of what makes the field so exciting, what we don't know is almost all of it! Plus it's not some peripheral thing, it's right there at the core of everything we are individually and collectively. Sadly it's had more than its fair share of charlatans and credulous followers. Sure, the Atlantic, nobody expects them to be any good, right? Well we probably shouldn't but sometimes we still do.

jonnycomputer 5y ago
I agree with the gist, though I think you maybe over-stating things a bit. Also, neuroscience is pretty wide field.

yellow_lead 5y ago

> Scientists are meant to know what’s going on, but in this particular case, we are deeply confused. This kinda sounds like a high school essay.

louloulou 5y ago
And one that doesn't seem to understand that science is the process by which we discover/uncover things we DON'T know.

hyperpallium2 5y ago

Prediction: neurons are more like cfd than ann.

slver 5y ago
ANN are already producing phenomena that match our perception. The key difference is ANN is trained, then training stops, and it's used. And the brain has to always learn while in use.
qrybam 5y ago
What is CFD?
- nicwilson 5y ago
  Probably computational fluid dynamics

Fatboyrunning 5y ago

Maybe it's like SHA256. You change a single pixel in an image, for example, and you get a completely different result.

nxpnsv 5y ago

The title reeks of scientific ignorance - science is all about investigate things unexplained...

vimacs2 5y ago
Your comment ironically reeks of scientific ignorance itself. Science is as much about confirmation of prior observations and testing of established theories (and in fact more so by sheer volume of studies) as it is investigation of unexplained phenomena.
- nxpnsv 5y ago
  I spent 2 decades working as a scientist publishing and applying for grant money. If publishing or having a paid position matters to you as a scientist, then you have to do something novel. It doesn't preclude doing what you said - but that certainly isn't enough.

Salgat 5y ago

Reminds me of how if you take out the speech center of the brain immediately, you permanently lose the ability to speak, but if a slow growing tumor takes out the same region, the brain has enough time to slowly shift over to peripheral areas. As an aside, I wonder if the drift seen in neurons represents thought. Perhaps drift has to occur for the brain to continually think and self improve, even with limited inputs. I wonder how different drift rates in regions of the brain relate to things like better long term memory or creativity.

calkuta 5y ago

Ah, more animal experimentation. I wonder if consent was obtained?

cm-t 5y ago

Someone have found a long post title that can't spoil anything from the article content, so HN users have to click to understand what it is about :/

lostmsu 5y ago

TL;DR; over time the same physical objects/processes fire up different neurons when we experience them. Nothing unexplainable to see here.

teekert 5y ago

"Scientists are meant to know what’s going on, but in this particular case, we are deeply confused." What? I'm a scientist, I often don’t know what’s going on! I see it more as my duty to help others understand that that is ok, and often even a good thing because that is when the fun starts. Science is a method, not a “state”. States are for religions, they “know” what’s going on because "it has been written!". Us scientists are always writing.

heyoo 5y ago
Also, how can it be surprising that a brain-related phenomenon is not well understood? I mean, I can think of a few brain-related questions with no good answers: - What is consciousness and how does a brain become conscious? - How and why is one specific consciousness attached to one specific brain (& body)? Why am I controlling my body and not yours?
- tsimionescu 5y ago
  I agree with your sentiment in general. However, I will note that the second question only makes sense for non-biological, dualistic notions of consciousness. If consciousness is taken to be a function or phenomenon happening in my brain&body, then there is no question to ask. It would be like asking 'why am I digesting my food and not yours'.
  - konschubert 5y ago
    > why am I digesting my food and not yours haha :D To take it a bit further, I am not sure if the first question makes a lot of sense either.
    - tsimionescu 5y ago
      I think the first question does make sense. By the same analogy, asking what is digestion precisely and how the stomach digests food is perfectly sensible. I would also note that the second question can make sense, but only if you believe consciousness is not strictly tied to the brain and body.

2bor-2n 5y ago

can someone comment tldr?

uCantCauseUCant 5y ago

Imagine the learning of new skills, as a travelling circus, traversing a road through a land covered in towns. Now those towns, depending on usefulness, will put up resistance to the circus reshaping them and the area they depend upon. And the circus must travel on, for it leaves towns in its wake. So what one watches as the learning happens in pre-disposed sensory input classification areas, i imagine, is the newly created towns moving away from the circus so to speak. Im sorry for the lack of expression and cohesion.

cblconfederate 5y ago

> If representational drift can happen in the piriform cortex, it may be common throughout the brain. Instead of looking at individual neuron response properties, look for population codes. This would be actually an interesting experiment with an artificial network, to observe how the population activation drifts over time (but remains identifiable) as the network is fed with more and more data

nanna 5y ago

> They needed to develop surgical techniques for implanting electrodes into a mouse’s brain and, crucially, keeping them in place for many weeks. Poor poor mice. Vivisection is done for the 'greater good', but not for the greater good of the millions (billions?) of critters who have suffered it. Yes I know that modern physiology is premised on it as method, the knowledge of organisms as they live not as they are dead, but what a toll.

ljf 5y ago
Reminds me of the joke I heard the other day: Q: Which is heavier, 100kg of lead or 100kg of feathers? A: The feathers, as you have to carry around what you did to those poor birds...

jek0 5y ago

There are theories [1] that part of the brain's function might work at the quantum level. If true, we probably won't be able to really understand what happens by measuring it this way... [1] https://en.wikipedia.org/wiki/Quantum_mind https://en.wikipedia.org/wiki/Quantum_mind

beaconstudios 5y ago
there is also the almost-definitely-true idea that the mind is an emergent property of the body. We can't understand emergent phenomena using reductive approaches, in the same way that we can't understand quantum phenomena using classical approaches.
astrange 5y ago
Classical computers also do things "at the quantum level"; CPU gates rely on quantum effects, probably the HDD does too, etc. But it doesn't prevent understanding because that computer part implements a simpler interface. The brain probably isn't a quantum computer, or else we'd be able to factor integers quickly in our heads.
- jek0 5y ago
  Not necessarily. According to philosopher Paavo Pylkkänen, Bohm's suggestion of the quantum mind "leads naturally to the assumption that the physical correlate of the logical thinking process is at the classically describable level of the brain, while the basic thinking process is at the quantum-theoretically describable level". [1] Factoring integers is a logic operation (thus not performed at the quantum level). But an operation like identifying an object or a smell (as it is what the article here is about) could be performed at a more deep level using quantum mechanics. [1] http://philpapers.org/archive/PYLCQA.1.pdf http://philpapers.org/archive/PYLCQA.1.pdf
  - astrange 5y ago
    Hmm… it seems like that's only true if it doesn't actually mean anything impressive. Your neurons or nose obviously can rely on quantum effects in the same way a modern semiconductor transistor process does. But that doesn't imply anything huge like "consciousness can't be emulated on a classical computer."

xchip 5y ago

Thanks for the click bait headline :(

m12k 5y ago

It seems to me that this phenomenon of "representational drift" fits well with the results that show that every time a memory is remembered, it is essentially deleted, and re-recorded. Given what we know about how memory and experience make use of large swaths of the same neural pathways, it would make sense that this is the case with re-experiencing sensations too, not just re-remembering them. And if that is the case, then it would make sense that it's possible for these representations to be re-recorded in a different place or in a different way. For example mixed together with other neural wiring that is correlated but wasn't there when the original representation was made (basically de-duplicating the file system). It would also suggest that either pathways are mutating, or different neural pathways are "competing" for the right to be the ones to process a given input (and if it's the latter, then it also implies that there must be some kind of fitness function "how well did this pathway process this input" that allows a new pathway to win out over a previous one).

layoutIfNeeded 5y ago

This is one of the reasons why NeuraLink wouldn't work.

deleted 5y ago

[deleted]

antattack 5y ago

Could it be that learned/familiar experience is processed with different part of brain?

Kim_Bruning 5y ago

When anything like this gets published, I always wonder "what would it look like on a 6502?" https://storage.googleapis.com/plos-corpus-prod/10.1371/journal.pcbi.1005268/1/pcbi.1005268.pdf?X-Goog-Algorithm=GOOG4-RSA-SHA256&X-Goog-Credential=wombat-sa%40plos-prod.iam.gserviceaccount.com%2F20210610%2Fauto%2Fstorage%2Fgoog4_request&X-Goog-Date=20210610T111033Z&X-Goog-Expires=86400&X-Goog-SignedHeaders=host&X-Goog-Signature=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 https://storage.googleapis.com/plos-corpus-prod/10.1371/jour...

rantwasp 5y ago
> We can thus conclude they are uniquely necessary for the game perhaps there is a Donkey Kong transistor or a Space Invaders transistor. This is hilarious. Thanks for sharing this. It brightened my day.
tardismechanic 5y ago
Getting "ExpiredTokenThe provided token has expired.Request signature expired at: 2021-06-11T11:10:33+00:00"
- Kim_Bruning 5y ago
  https://www.biorxiv.org/content/10.1101/055624v2.full.pdf https://www.biorxiv.org/content/10.1101/055624v2.full.pdf This should be a more permanent link I hope.

nobrains 5y ago

Its just moving from short term memory to long term memory.

pvaldes 5y ago

"Stupid article tries again to make fun of smart people" THAT would be a great title. They are trying to sell this idea all the time.

slver 5y ago
They're not trying to make fun of smart people, they're trying to basically to Shyamalan the research, so every next paragraph wows you with its unexpected plot twists.

slver 5y ago

Imagine if we discover most of the brain's functionality isn't in the brain or any other identifiable part of the body. Rather the brain just connects to something else, that's outside the known timespace.

9wzYQbTYsAIc 5y ago

The real question here is: what insights do computing professionals, whom work with neural networks or parallel distributed processing as their day job, bring to the table? The sort of reasoning that neuroscientists are struggling with is that very same kind of reasoning that computer scientists and practitioners use when thinking about ANN/PDP and deep learning.

benlumen 5y ago

Isn't Neuralink (and other brain interfaces, I assume) also based on the idea that you can pinpoint which neurons are responsible for each function in the brain? If I've read the article correctly, it seems to suggest that they're a moving target. How can permanent implants interface with a moving target? Might the entire Neuralink concept be based on a flawed assumption?

FatalLogic 5y ago
Perhaps the brain will naturally adjust to Neuralink, and similar technology, via a feedback loop that would tend to keep the Neuralink-monitored neurons more static?

jonnycomputer 5y ago

I find the whole spin of this article a little odd. Isn't it enough to talk about how interesting representational drift is without spinning fairy tales about science?

billytetrud 5y ago
I would really like to find a way to incentivize journalists to stop doing that kind of thing. Artistically misleading people shouldn't be seen as acceptable in factual journalism. This should have been rejected and rewritten.

andred14 5y ago

In summary: "Lifeforms are dynamic and sometimes behave unpredictably" Wow great work! BTW is it just me that finds the implantation of things into the brains of test animals to be cruel? Do we really not have better things to do?

philprx 5y ago

Wear management and prevention? just like in SSD ;-)

croehrig 5y ago

TLDR: Representation of the world doesn't seem to be locked to specific neurons or groups of neurons; over time, they drift around to completely different groups of neurons. Someone here likened it to how programs can move around in computer memory. If neurons are the "silicon of the brain" or the "PHY" layer, the biggest problem in neuroscience IMHO is that we have virtually no understanding of what is the next layer up, (i.e. the "logical layer"). What is the equivalent of program counters, CPU instructions, etc. in the brain? The brain is a nonlinear recurrent dynamical system and we are really in the dark as to how to break the dynamics down into understandable subcomponents. To get an idea of the complexity, this paper by Randall Beer analyzes the possible behaviours of 1 and 2 neuron circuits: Beer, R. D. (1995). On the Dynamics of Small Continuous-Time Recurrent Neural Networks. Adaptive Behavior, 3(4), 469–509. doi:10.1177/105971239500300405 Obviously this kind of analysis doesn't scale to 10^10 neurons.

boringg 5y ago

What I like about this, and what I like about existence in general is: While we continue to learn new things sometimes rapidly sometimes slowly, there is so much we truly don't know and it's both frightening and exciting. Constantly updating our priors. What I don't like: so many humans think they know everything or at least position themselves that way. FYI this isn't an attack on experts.

i5heu 5y ago
In my experience people that call themselves “expert” think they know everything. So no hot take there.

darkerside 5y ago

What is so confusing about this? The first time I read a book, it impacts me in a certain way. Every successive time, it hits me differently. I take different life experiences to it, and I understand it more deeply because I've read it before. Why would a smell be any different? Each time I smell an apple, or taste wine, or examine a painting, I am a different person, and I also discover more nuance about the subject.

Voloskaya 5y ago
That your brain continually learns and evolves is not surprising at all. What is surprising is that the location of the subset of neurons that reacts to a specific thing (say the smell of wine) changes over time. So neurons that were used to identify the smell of wine at time T, might be doing something completly unrelated 6 months later, and the task of identifying wine smell is now handled by another subset of neurons in the brain. It is surprising and on the surface seems ineficient since your brain has to continually transfer knowledge from one region to another rather that just ajusting the existing region to new learnings.
- rantwasp 5y ago
  we are making a big assumption here: that neurons have tasks and are responsible for X. What if a neuron (actually a cortical column) could learn thousands of X and fire only when specific environmental conditions are met? What if you constantly wire and rewire the connections between neurons? What if multiple areas can do some thing and they arrive at a conclusion through consensus? what if your brain can predict a lot of things and just discards sensory input when it matches the expected prediction?

makz 5y ago

Doesn’t the brain rearrange itself during sleep?

airhead969 5y ago

My bet is reinforcement decay and strengthening exists to promote novelty rewards. Smell 1000 roses, it's a big "meh" but the identification of them becomes easier and better with strengthened pathways. This would be adaptive for the organism to: 1. seek new, potentially-massive rewards, stimulation rather than do the same thing over and over again without ever trying anything new 2. improve processing of stimuli that are more frequent

derefr 5y ago

It’s good to study the piriform cortex to understand memory formation / neuroplasticity, as (IIRC) it’s one of the most primitive “plastic” parts of the brain. In some species (e.g. fruit flies) the piriform cortex is the only part of the brain that changes at all after birth; i.e. it’s the only place where learning could possibly be going on. So, even if the it’s not intimately linked with human memory, the piriform cortex may be the origin of the cellular template that later diverged into whichever other brain tissues are responsible for other types of memory.

adenozine 5y ago

That little line is so toxic and terrible. If my boss came round and said, "This is adenozine, he's supposed to know what's going on," I'd be pissed. That's just dumping blame.

wizeman 5y ago

How do they know that it's not the neurons who are themselves slowly drifting position over those timescales?

RocketSyntax 5y ago

yes, it is. it adapts. firings get less strong as we get used to stimulus, and neurons that fire together wire together. so different connections form on more important info.