Being an "aging brain" myself I can totally relate to this. I've been a relatively obsessive photographer (i.e. visual diary) since digital cameras were practical, i.e. over 25 years now. 238K photos in the collection so far, and I can actually find things in it.
And I've more than once found that an anecdote I've been telling has been incorrect, precisely in a "melded memories" kind of way. It happened at this sort of gathering which were usually held for that reason so X was involved... and then finally look at the old pictures and there's no sign of X. It is literally the brain invoking "lossy compression" to make it all fit, just like certain web services that let you upload pictures without limit might reduce old ones, that hardly anyone ever looks at any more, to lower quality to limit storage bloat.
Of course any married man can confirm that this only applies to men. Women's memories are flawless. If they claim that they remember a conversation exactly, word for word, 20 years later, who's to prove them wrong?
I think that's because memories really are highly compressed, with the average complex memory (of a grand day out, for example) being compressed into at most a paragraph of text's worth of information. Everything else is made up of context.
For example, having no photographic memory, I can remember the general "feel" of the innards of an antique shortwave receiver I used to have as a kid. But almost all of that is context. I know what canned octal base vacuum tubes and big tuning capacitors look like, what sort of components were in the big band selector "sled" (for geeks: This was an NC2-40D) and so on. So I can "zoom in" on the coarse memory by just filling in details that are generic, not specific. And these details may be from different sources than the original memory too.
And so the brain needs to remember - if one is not faceblind, which in fact I am - just the overall geometry of someone's face, and all the other stuff can be filled in as needed (how they look when they smile or are anxious etc.) Compression, compression. We have a lot to learn from nature. Note that a faceblind person does this too, of course - just not with a geometrically exact visualization of that person's face, just one with the correct "feel".
And that's also why synthetic memories can be formed so easily. You really don't have to insert much. The brain infers the rest as needed.
This of course applies to my (sarcastic) description of women's memory too. A given conversation is compressed to a small amount of memory, a significant part of which is the "feel" of the conversation rather than the actual words. So of course the memory is not word-for-word exact. But, let's just say, a subset of persons, a majority of which may or may not be female, does not acknowledge this and insists that the (reconstructed) sequence of words is exactly what was said 20 years ago.
I went under for 2 different surgeries. One of them I had post surgery complications. Years later, we needed to know the year I had the complications. I remembered the surgery, simply look it up and ta-da I got the date.
Except, my wife thought it was the other surgery. And insisted. I was incredulous and angry. I literally nearly died during the complications. I think I would remember the surgery it was from. And it definitely wasn’t from my vasectomy. I decided to make a stand.
I found the oxygen sensor we purchased for the event. Found to manufacture date. It was after her event. So it was physically impossible have the o2 sensor before her event. Wasn’t good enough. Maybe the date was wrong.
I finally went to the hospital and got the records. I was right. My wife simply could not or would not acknowledge it.
I spent the majority of my marriage being “the forgetful one”. And here was a single case where I was right and she had memory issues. And she could not simply say “oops, I got it wrong”. I began to doubt her memory and thought maybe I was being gaslit sometimes.
It was a very influential event in the course of our marriage. I lost a lot of respect for her and began to wonder what our future would be like.
We were divorced within a year.
Not only this, but other things too. But this was a big part of it.
Given the number of neurons, hash collisions are inevitable? /s
Our model of the world, and this includes "memories" is very highly compressed, and extremely lossy. We reconstruct everything from what neurons activate when we recall something, so it can also be like a corrupted zip, where we don't access everything required in the moment. This can be affected by sleep, stress, hormones, etc.
What is quite interesting is when we try and recall something and can't, but the subconscious processing continues and you recall it later.
Perhaps the rate of occurrence changes, but everybody does this at every age. When even our experience is an interpretation of the real world, our memories are even less accurate.
Just throwing out an idea: I recently stumbled upon an old-school website where someone is uploading a photo of their day (almost) every single day since 1998.
Came across screen captures of the original Everquest (SO COOL) and other games, photos of anime/cosplay events, city shots, family, friends, etc. Really fun for them, and fun for people who like me who still enjoy surfing the web.
When my mom was still alive and relatively new to a smartphone (at age 80) I decided to send her some sort of relevant picture every day via Whatsapp, to get her used to communicating that way. Sometimes it was a real stretch to come up with something. But yes, this forces you to evaluate your life from that viewpoint "surely something was interesting today? Let's keep a picture of it". Even if it's just what I'm having for lunch that day.
I'm not sure if you are in this demographic, but a lot of people I know born in 1999-2003 or so in the US used snapchat as a primary method of communication for many years, and a large part of it was keeping up "snap streaks" of sharing one photo a day with many different friends.
This is one thing for all of the pairs of genuine friends doing this, but I also have two friends who I introduced to each other exactly once, and who have never spoken since, who have a 6 year snap streak together, and both of whom have streaks like that with dozens of other people, many of whom are virtually strangers.
That is interesting. For a streak to count, do you have to both send out your own, and open incoming images? I wonder how much you could tell about someone if you had a 6 year snap streak with them. Would they be more like a friend, or an awkward relative with whom you seldom meet and have little in common?
Both of you have to send them to the other person as a specific recipient (so not just putting it on your story). I'm not sure about opening them.
For the two friends I'm thinking of, my impression is that they don't know each other any better through snapchat than they do from me knowing both of them and mentioning them to each other (they live 1000 miles apart and only met once). I guess the best I can say is that I would be comfortable seating them at the same table at my hypothetical wedding. Same vibe as my cousin I have on Facebook but have only really met twice in the last decade.
Everquest looked sooooo good back then. Man! No more Meridian 59!
Why did you have to destroy my memories? :)
It's like looking at the first DivX encoded movie that was soooooo good vs. VideoCD/LaserDisc. And then you look at it today and it's so damn blocky and also in that tiny resolution. Ugh!
>I don’t think the sexist comment at the end is appropriate for HN
I don't think the ageist comment in the headline is appropriate anywhere.
It is well known that memories and perceptions at every age are largely constructed more as "what makes sense" ("no, a gorilla did not run across the basketball court") than "as recorded" recordings.
> Of course any married man can confirm that this only applies to men.
My first read of this headline was to observe that people seem to get more comfortable stereotyping people different from them as they age. Thanks for the datum.
I wonder how much of this is directly related to age (biological aging), and how much is just someone's brain becoming "full" due to more memories getting added every year?
It seems that memories must be stored as embeddings with single multi-neuron assemblies (cortical columns?) storing multiple embeddings as a kind of contents-addressable memory that is able to keep memories distinct due to the very high dimensional space (# neurons per assembly) being used. However, you'd expect that at some point if you store too many memories in a single assembly the recall accuracy is going to go down.
You'd expect that with big brains being so costly, evolution has only equipped us with brains big enough to store a lifetime of memories, so it would be odd if memory didn't suffer as we get old.
To make a computer analogy, it's a bit like a hash table getting too full. Say you had a hash table without any overflow mechanism... up to a point recall may still be pretty good, but as the table gets closer to full there will be more hash collisions and likelyhood of "false recall". Obviously the brain is not a computer, but the analogy may hold up reasonably well if you consider the hash table keys and values as embeddings and the store operation being an embedding merge rather than overwrite.
The brain does not have the Von Neumann bottleneck. Unlike most current digital systems, the brain doesn’t have a separate memory registry it needs to pull from.
Engrams, that is, the physical trace of a memory, are not stable through life. They start out in the hippocampus, but as the stimulus recedes in time without reinforcement, it moves away.
No evidence exists though that the memory is encoded in one set of cells. This spatial segregation of memory is the worst hangover from the “brain is a computer” analogy. Even if it is, why in the world would it be like our digital devices which specifically have the Von Neumann bottleneck? In biology, memory and processing are not segregated.
There’s growing evidence the memory is much more distributed over the network, and is recomposed based on salience overlap with a new stimulus.
Another factor to keep in mind is circadian rhythms. There’s growing evidence for how much the memory system and timekeeping system overlap, at a molecular level. Every neuron (and other cell) has an intrinsic clock that ticks at roughly 24 hours, and continues to do so even in total darkness.
When you encode the memory has a lot to say, based on your chronotype, on how and how well you will remember it. Same with learning: there’s a time of day based variation.
Sleep, and dreaming, is when these memories seem to get replayed and critical features and connections are incorporated into the system and its regime, awaiting the right triggers to access a state similar to when the memory formed.
I’m stitching across a lot of different research, and I want to be clear many aspects of this system are not yet fully worked out.
But what we do know points to a system that works with different physical and algorithmic priors, and the dynamics are sharply distinct from current digital computers.
Hijacking your post with a dubious segue because I’m itching to bounce these thoughts off somebody:
I’ve been consuming a lot of talks / writing recently about “enactive” pictures of how our brains function. From what I gather, recent studies have called into question the entire idea of real world concepts being “represented” by an area of the brain at all. While it’s true that atandard fMRI-style snapshots of brain activity are semi-stable over the course of a short experiment, it’s not true over longer timeframes. The response to the same stimulus will change over time. They refer to this as “representational drift” in the literature, and some people are using this to bolster theories of mind that they consider non-representational. They instead emphasize the brain as a kind of dynamical system that learns to “resonate” with the world to pull itself back into homeostasis. The focus shifts away from facts and memories as data, and sees neuronal plasticity more as a mechanism for tuning the brain’s resonant frequencies. This obviously places high importance on the spiking, recurrent nature of actual neurons, as opposed to the neurons-as-functions / back-propagation / ML approach.
My mind’s not made up on how interesting and revolutionary this approach is / isn’t. The distinction seems to be about whether learning is more like “writing to disk” or “tuning a PID controller” - but in either case, the world is leaving a stateful imprint on your brain that will impact how it processes future data. Is that important to understanding how brains work, or is it just semantics?
Some years ago, I heard a retired Lutheran priest ponder, in radio, about the concept of a prayer, and whether, as an edge case, an unborn child could be able to pray, with the child of that age having no understanding on the required concepts. This is apparently one of those questions that people ponder under the umbrella of philosophy of religion. His conclusion was that prayer was about harmonizing one's self with the universe. It's a beautiful thought, (and I think religions, of all kinds, are really good at providing the fertile ground for thoughts like these).
It's akin to how the saying goes, that when we argue, we need to reach the same wavelength where the other one is to reach an understanding.
In communication studies or sociology or linguistics or one of those fields, there's the idea that communication is about making pacts about meanings, and finding the common ground to understand and delimit the message.
In a sense, from that basing, one could argue that understanding can be seen as an act of harmonizing. I think there's something universal in it.
Ooh thanks for the hijack! It’s so much easier to talk to someone who isn’t stuck in a picture of the brain from the 1980s.
Yes, I fall more towards the camp that a lot of our cognitive models, built from times when we didn’t have the resolution of understanding we have of the capacity of even a single neuron, and before we knew how astrocytes played a role, suffer from being an abstraction describing an abstraction. They are not tethered in the dynamics of the molecules and cells that give rise to the behavior, but rather from an interpretation of observed behavior.
This paper from the field of chronobiogy is one I’d recommend that helpfully contrasts this:
>In circadian research, the models are not proposals regarding the basic architecture of circadian mechanisms; rather, they are used to better understand the functioning of a mechanism whose parts, operations, and organization already have been independently determined. In particular, circadian modelers probe how the
mechanism’s organized parts and operations are orchestrated in real time to produce dynamic phenomena—what we have called dynamic mechanistic explanation.
And what you’re describing, the enactivist description of cognition, (and 4E cognition more broadly as a framework), is one way the neuroscience community is trying to move past these issues.
Few things that give me confidence these are the right track:
1. Circadian rhythms are evolutionarily ancient. Bacteria have em. Plants have em. But different molecular tools shape very different clocks, though the same 24 hour cycle is being tracked.
2. The way these rhythms are generated is not through some central system that broadcasts the information to other regions. Instead, it’s instantiated in every cell in the body, and the behavioral rhythm is due to the synchrony between cells. Resonance absolutely plays a role, and has been well documented. The brains role, via the suprachiasmatic nucleus or SCN, is to orchestrate this synchrony, but it is not the source of the rhythms.
3. This slow rhythm definitely regulates cognition (time of day effects in learning, memory formation, recall etc are well documented), but turns out, the molecular mechanisms by which the clock responds to light hugely overlap with the molecular mechanisms of learning in the synapse, and even more recent work has shown clock proteins are actually in the synapses and synaptic activity affects the clock.
All this points to nested oscillators with cross frequency coupling, and even better, because this is all grounded in actual molecular dynamics, there’s plenty of falsifiability. The phase amplitude links are best established for the faster rhythms, the famous “brain waves”. Highly recommend György Buzsáki‘s work on this:
What’s missing is going down into lower frequency rhythms, and testing how exactly they all couple. We have a lot of the pieces, but no single experimental paradigm that has looked at the full sweep over different times in the same organism. It’s not easy to do, but we’ll get there.
Clock disruption, depending on how you do it, has huge impacts on time perception, cognition, memory, aging AND consciousness. As that data and evidence gets more and more saturated, I hope we see more studies account for chronotype and the internal dynamical state of their test subjects when assessing outcomes.
Obviously I’m biased (also did chronobiology in school), but hopefully I’ve left you curious. Happy to answer more questions all this may have set off.
Thanks for your response, very intriguing! I have some controls background, and there’s something tantalizing about the idea that perhaps we need to be looking at the brain in frequency space, as it were. Are you aware of reservoir computing and do you see it playing a part in this?
> The brain does not have the Von Neumann bottleneck
Obviously not, which is why I didn't say it did!
However, if you want to identify where long-term memories are stored, then that is in the cortex, but it should go without saying that this doesn't make the cortex the storage component of a von-Neumann architecture!
> No evidence exists though that the memory is encoded in one set of cells
I'm not sure what you are trying to say.
Memories are presumably stored as embeddings - a distributed representation, and an episodic memory may well be stored as "chained together" episodic "scenes/chunks" where each chunk recalls the next.
However, a distributed representation isn't the same as a holographic one, and any redundancy may well still be localized within given cortical columns, so I think you may be wrong if you are saying that individual memories/chunks are not confined to one set of cells (some localized neural assembly such as a cortical column).
> Obviously not, which is why I didn't say it did!
But you sneak it into your assumptions on what a memory must be.
> However, if you want to identify where long-term memories are stored
And why do you assume there is a specific “where” for the memory?
> then that is in the cortex
There’s good deal of evidence disproving this in the way you’re stating this. The cortex is involved in sensing, and yes, the sensory information associated with a memory will recruit appropriate cortical cells. This doesn’t mean the memory resides in the cortex. And detailed episodic recall keeps recruiting the hippocampus even for old memories, which is odd if the memory were somehow only in the cortex.
> I'm not sure what you are trying to say.
Let me restate what I’m saying then:
There are four claims bundled together in the way you were describing biological memory: that a specific ensemble is activated when a given memory forms; that it’s the same ensemble that gets activated over time when that memory is retrieved; that it’s spatially compact, like a column in region of the brain; and that this ensemble it’s dedicated to that memory, or similar memories .
The first is well supported. An engram, a network of neurons, is indeed activated when a memory first forms, and gets stabilized due to repeated stimulus. Re-activating these neurons in a different context can make the subject (a mouse) behave as it would if it had contextual signals to evoke said memory.
However:
1. This engram is not in one particular part of the brain. There’s a cortical part that overlaps the sensory regions that were involved. But plenty of other regions are part of the engram
2. There’s turnover, over the course of weeks, when the specific cells involved in the engram drift, while the behavior remains stable.
3. The same synapses participate in many memories.
> Memories are presumably stored as embeddings
No. Let’s consider songbirds, which are an excellent worked out example (in an animal without the complex columnar cortical architecture mammals show, by the way).
What’s learned is a temporal sequence, with neurons in a nucleus in their brains each firing one brief burst at a fixed point in the motif, so the content of the memory is its dynamics rather than any value. The circuit that evaluates the match against the tutor template is the same circuit generating the output being evaluated. Song degrades overnight during sleep replay and recovers the next day, and in seasonal species the song nuclei change size across the year with neurons added and lost while the song persists. There’s no read that leaves the item untouched, no persistent address, and no substrate holding still. “Stored as” imports all three.
And it goes below the neuron or synapse. Hearing a tutor song drives immediate early gene expression that habituates with familiarity, and singing drives large transcriptional changes in the song nuclei that differ by social context for the same motor output. Since transcription runs on minutes to hours and the proteins turn over, any persistent state has to be actively regenerated rather than deposited.
TLDR: the memory isn’t a static store. There’s no persistent “location” for it, distributed or otherwise, though specific locations can be in the chain that’s activated for retrieval/production. Instead, memory, over time, is driven by a dynamical regime that adjusts its dynamics to account for the temporal pattern in the salient stimulus.
Nothing, down to the epigenetic changes in the chromatin of these neurons, can be seen as “the” location of “a” memory, especially over time.
> if you are saying that individual memories/chunks are not confined to one set of cells (some localized neural assembly such as a cortical column).
If someone's hippocampus is destroyed, they lose the ability to form new (episodic) memories, and may lose some more recent old ones, but they certainly do not lose older ones. This is basic knowledge.
> and that this ensemble it’s dedicated to that memory, or similar memories
No - that's the exact opposite of what I said. My whole point was that a cortical column is NOT dedicated to a single memory (we'd run out of memory!), but rather acts as an embedding space containing many (sparse) embeddings.
Due to the size of the embedding space and sparsity of individual embeddings, there is little chance of much overlap between embeddings and therefore associative recall is reliable. When there are too many memories stored using the same set of neurons, then there will be non-trivial overlap between embeddings (this is the definition of "too many" / "full") and associative recall becomes unreliable.
Note incidentally that this explanation holds regardless of whether distributed embeddings are stored in a more localized area (or areas - visual, auditory, etc components) or more globally distributed. At the end of the day evolution has equipped us with a right-sized brain, and an individual that outlives the useful life it is adapted for can expect to experience memory failures.
I'm not sure why you bring up bird brains, and specifically bird songs(!), but FWIW it seems that their short term memory likely works similarly to our own in as much as it is based on the hippocampus, with a very strong correlation between bird hippocampus size and memory capacity (ability to memorize 10's of thousands of hidden seed locations in some species). Some birds such as crows certainly have long term memory where I'd guess those may have migrated to their pallium, but we're discussing human memory here (or at least I thought we were).
None of that changes whether there is a physical capacity, which I think was the larger point? There is no reason to believe distributed memory doesn't suffer from the capacity component of the bottleneck. In fact iirc there was some late 80s/early 90s papers on the memory capacity of NN. Btw I would advise against the absolute statement that there's absolute segregation of memory and processing.
I guess my point is the brain not being "von Neumann" in architecture or digital is not proof that isn't a "computer" of some sort.
> None of that changes whether there is a physical capacity, which I think was the larger point?
Capacity in what sense? Are we saying it’s X MB of data the brain can store? That claim is steeped in assumptions.
On the other hand, no one is claiming the brain has infinite memory or anything. And it’s certainly not a very accurate memory system. I’m arguing against “capacity” being understood as “these specific physical components located here and here we can ID store memories, and can get crowded with too many memories” sense.
This most particularly fails because not all memory is even identical in the brain, whether we mean the physical changes associated, the topology of the information, or how it’s activated.
> There is no reason to believe distributed memory doesn't suffer from the capacity component of the bottleneck.
I didn’t know there was a capacity component to the bottleneck, only a bandwidth one.
All I’m trying to say is that analogy to current typical memory storage systems to explain the brains memory processes is not helpful.
> I guess my point is the brain not being "von Neumann" in architecture or digital is not proof that isn't a "computer" of some sort.
Indeed, since the word computer was first used for humans. But what kind of computer matters enormously. Ising machine? Quantum+classical stack? Reservoir computer? All those frameworks have processes in the brain they can point to as homology.
Which points to a possibility: maybe the brain is multiple types of computers interacting. And the physical realization of these computing architectures aren’t spatially separated but thread through each other in the biochemistry and physical dynamics of cells.
https://www.pnas.org/doi/pdf/10.1073/pnas.79.8.2554 in a very precise sense going back a long time. I don't really know who you're arguing against or refuting? You seem to be touching on some pretty well accepted ideas.
"All I’m trying to say is that analogy to current typical memory storage systems to explain the brains memory processes is not helpful." Again, my impression is that the original author's idea was about capacity in general, then he gave an analogy. The analogy was wrong, but your reply went way beyond his specific analogy to the extreme of discarding memory itself as useful concept. To be clear, I agree that it is distributed and lossy and time-dependent. I agree it is not just a simple read-off of a static chunk with a fixed address.
"Which points to a possibility: maybe the brain is multiple types of computers interacting. And the physical realization of these computing architectures aren’t spatially separated but thread through each other in the biochemistry and physical dynamics of cells."
I would say that is both non-falsifiable and well-accepted.
This is really fascinating. The actual mechanisms of the human mind are distinct from computer systems, yet there are some parallels.
There are some hints that increased memory access times scale with the amount of information the brain has stored vs the more typical narrative that aging decreases the capabilities of the brain.
> Our results indicate that older adults'; performance on cognitive tests reflects the predictable consequences of learning on information-processing, and not cognitive decline. We consider the implications of this for our scientific and cultural understanding of aging.
"His memory was so powerful that he could still recall decades-old events and experiences in the smallest details. After he discovered his own abilities, he performed as a mnemonist; but this created confusion in his mind. He went as far as writing things down on paper and burning it, so that he could see the words in cinders, in a desperate attempt to forget them. Some later mnemonists have speculated that this was a mentalist's technique for writing things down to later commit to long-term memory. Reportedly, in his late years, he realized that he could forget facts with just a conscious desire to remove them from his memory, although Luria did not test this directly."
I believe that one need to have superhuman memorization abilities to have definite confusion due to too much remembered. More trivial explanation of this effect in normal ageing persons is age-related brain shrinkage.
> Obviously the brain is not a computer,
Our brain consists of approximately 86 billions quantum computers [2] controlling tens-of-thousands chemical neural networks with at least 10 coefficients, communicating [4] using lasers [5] (coherent light is laser light).
Well, sure, it's a computer of sorts, although in the abstract sense of being able to perform computations so is our liver, so perhaps not a very useful concept.
What I meant (as I assume you realize) was "not a von Neumann architecture computer", but I'd also fairly confidently assert that it's not a quantum computer either.
Our ANN model of a neuron is obviously too simple (especially being a synchronous model, not a real-time asynchronous one), but it's hard to imagine that all of the classical chemistry, let alone quantum, details are important. It's necessarily built out of chemistry, but selection is happening at the level of behavior - presumably depending only on a much higher level set of abstract capabilities (ability to learn, etc), not the exact details of chemistry.
The success of LLMs, a crude prediction mechanism built atop a crude ANN, does tend to support the idea that low level details don't matter. Timing will matter if we want to go beyond LLMs to AI that can learn time-based things and not just sequence order, but how much else will matter remains to be seen!
I suspect the anxiety of being unable to forget things has an inherent selection bias. You will only stress over the things you can't forget, the things you have forgotten you won't stress over...
Generally claims of eidetic memories are overstated, doubly for older claims, but Nigel Richards memorized a French dictionary in 9 weeks, over 6k words a day, x2 including the alphagram.
I consider myself to have a decent memory, but that is 200x what I'd think myself capable of, assuming I want to retain it all at the end of the 9 weeks.
Our brain consists of approximately 86 billions quantum computers [2] controlling tens-of-thousands chemical neural networks with at least 10 coefficients
By that logic, a Blackwell GPU contains 208 billion quantum computers.
Each transistor is a quantum mechanical system and takes hundreds of model parameters to describe. So apparently a GPU is a 208-billion-node quantum supercomputer.
"The brain is not a computer" != "Parts / aspects of the brain do computation".
"A computer" in the first statement is IMO obviously intended in the common usage sense of the term, i.e. the brain is not a desktop computer or smartphone, or Turing machine, or etc, and thinking of it like these things will cause more error than insights. Also, billions of interlinked mini bio quantum computers arguably produce something with emergent properties and behaviour much, much more complex than "a computer". I am with GP, the analogy to "a computer" is not super helpful here unless you highly restrict the meaning.
But yeah, the Shereshevsky case is a super interesting one, thanks for linking!
You are wrong, as I didn't limit the analogy specifically to desktop computers only, try reading the rest of what I wrote. The original analogy was obviously hedging against simplistic brain-computer analogies (GP could be read as: "the brain is not a simplistic computer"), so the response demanding to "live with that" citing computational aspects of the brain was misguided and arrogantly wrong.
Multiple other responses also point out the definition given leads to absurdities / triviality (the liver is a computer in this context), so the "correction" with citations is both inept and inapt.
I see it differently: as a teen, I could remember the exact word for lots of things, I could recall numbers and data with high precision. Nowadays, I'm pretty bad at all those things, but I can very well understand metaphors and connects concepts from wildly different topics — which I couldn't back then.
I see this kind of "interconnecting ideas" of my current years as somewhat connected with "fuzzy memory". It's like, when I retrieve data, it's not as precise, and sometimes I get neighbouring data, but that can actually of use.
I feel like I feel this increasingly as I age. I used to be able to remember nuanced details of API and computer systems. Now, so many of those memories simply get stored as “FLAG: double check the docs” (because I’ll forget).
I’m a lot better at assessing things from a high level, knowing where to find the information I need, and knowing how to assess it for accuracy - but I can’t remember details anymore. Books become summaries. Trips become a few key snapshots representing the trip.
I don't think there is a "full" state, but watching the changes as the years go by I have thought of collisions. Not really like a hash table, though--most collisions are with things that would be filed together. I think it's more like the brain returns a random item matching the category. Brains are expensive, memory that gets fuzzy with age is probably the better choice than trying to feed a brain that does better.
Yes, evolution is not going to penalize everyone with a "100-year brain" when the rest of our body seems optimized for something more like a 30-40 year lifespan. Evolution is all about propagating your genes, and not too many 100-year olds are going to be doing that!
In any case, fuzzy associative recall is really the "design spec" for a brain, so semi-graceful degradation and fuzzy recall comes for free.
I'm not sure if old-age memory unreliability is totally random - I would not expect it to be. I'd expect these associative recall failures to happen when there are too many memories partially matching the same "key" (activation pattern), which presumably happens mostly when they do have something in common.
The paper certainly has its limitations. Only 61 participants, with almost nobody between 30 and 50, so we shouldn’t read the age trend as a decline across lifespan. What’s more interesting than the title suggests (and I find the title forcing the conclusion a bit) is that the attention measures were not linked to age or the brain patterns at all.
Then again, i'm 45 and I've been losing my keys and my IDs since I was 20
The entire article is AI-generated.I wish such sources would include the prompting used as well as the model so a (human) reader can better evaluate the document.
> This process includes multiple checks using different LLM platforms, human editorial verification, and cross-referencing with original sources to ensure accuracy and eliminate false information, misleading content, fabricated content, bias, and unreasonable speculations or editorialization
Gonna chuck a thought for you all. In social situations there is someone who talks alot and I think they are able to do so because they have lots of stories they can recall in good detail (maybe not perfect) but 20 year old event they are describing better than I can describe last week. Now I assume they don't have that rare calendar level memory but they do have a huge storage of stories and events. I am pretty jealous tbh!
Also that skill is probably excellent for interviews which is the ultimate memory test. I.e. Tell me a time when you turned water to wine, plus 5 deeper questions, any hesitation will be chalked ip as suspicious AI use.
For me I either do or I remember which makes performance management and interviews hard for me (as someone vouching for someone as evidence is rare now).
It's interesting for interviews. I assume that people who have somewhat inaccurate memories but with a (possibly subconscious) egotistical filter do much better in interviews than those of us who have more accurate memories of exactly what our contributions to a project were. There are a lot of ways of stretching the truth in your favor, and they all seem much more natural if you really believe them.
My friend recently told me about seeing that an old coworker of hers from 20 years ago described her role as HR manager rather than HR assistant on her LinkedIn. I can easily see how someone with a fallible memory can retroactively exaggerate their title or responsibilities, especially when it's been 20 years.
I have a few friends and family members like that and for the stories which I was present, they always hit the broad strokes, but the finer details get switched around and sometimes the whole story has a major perspective shift.
The concept of memories blending together resonates after watching a recent Kurzgezadt video entitled "How Are Memories Stored Inside Your Brain?". It makes the point that the very act of recalling a memory changes it:
> But memories are not static like photos. Like dioramas made from wax, each time they’re under the spotlight of your attention they can melt and change a tiny bit.
I suspect my oldest memory, of me getting into a booster car seat as a child, is no longer the actual memory, but the accumulated imaginings of me trying to remember that specific memory, masquerading as a memory.
I can't wait to tell my dad about this study. We recently got into a heated debate when he insisted that I was a toddler on a family vacation we were reminiscing about, when in fact I was a teenager on that particular vacation, and he was mashing it together with memories of a different vacation. He is 75 but is in pretty good cognitive health, no signs of dementia besides this unreliable long term memory.
My theory behind this is that when you encounter something new/novel it is distinct enough to remember -- where you were when you learned of 9/11; the days around the start of covid/lockdowns; being in a car accident; getting married; etc..
However, when you experience the same thing repetitively -- having breakfast; getting ready for school/work/etc. -- it doesn't make sense for your brain to remember each of these events as distinct events but to mush them together into a single or combined memory. This may be due to how the brain indexes/references memories and that memories with the same references get combined together.
This is also partly why time appears to go faster when you get older -- the same day-to-day events blend together but the key milestones (holidays, etc.) stick out.
By 'rewritten' do you mean refreshed, like learning material with spaced repetition, or some different/deeper concept? Do we 'move' that information to a different cluster of neurons?
This comes as absolutely no surprise to me -- my mother was recently transferred into memory care, and the changes to her memories are definitely showing some interesting changes. The foremost was that her new "apartment" is shared with one other person, gives off a bit of a dorm room vibe. First day, she was talking about how excited she was to be going back to school and seeing her boyfriends again(?!). I said, "Oh, like Doug? [my dad]". Her response? "Ew. No."
But, she's come around on that, and recently been upset about the affair he's been having (they divorced in 1980), and is irate over him having another kid with his new wife (1983), but isn't surprised that I haven't spoken to him in 12 years. She's never surprised at how I've aged, but doesn't remember her grandkids even exist and insists on meeting them soon (but remembers them when she sees them). Two weeks ago, she called to yell at me for things I did in high school (1990). At this point, I seem to be the anchor for everything recent, but when I'm not around physically, it's scattered everywhere else.
It's hard to write this, but before my grandmother died about 45 years ago, it felt like she'd lost almost all her memories, but was easy to take care of. She was in her late 80's.
My mom & aunt took yearly turns keeping her in their homes. If you kept her away from the stove, she still seemed quite happy helping fix her own breakfast, taking her meds, etc. Give her a warm washrag after, and she'd wipe down the table and then proceed to putter all around the kitchen, wiping and straightening. She preferred cartoons on TV (easier to see, I guess), and was always glad to fold clean towels or clothes, if she had the chance.
Once, she actually recognized me, and remembered my name. It was a very precious 5 minute chat, but then the memories were gone. Still, I'll always remember her that way, because it was just like how I remembered her, when I was a child.
Man, that makes me happy. I'm guessing your grandmother was a very upbeat, happy person who dealt with change well. My mother's the opposite, so now every little thing going wrong is the end of the world. It's rough, but I also get to see these moments where I can see how she was when I was little/before I was born, and those are moments that I do really enjoy.
These stories scare me. I'm happy that you were able to enjoy glimpses of your mother's past.
Mine is showing signs that several of us believe to be dementia, but she refuses to be seen and screened. It has gotten worse over time - repeated conversations, sometimes inside the same phone call, and a shift from "can't remember things if she doesn't write them down" to "needs to ask on multiple occasions because she hasn't remembered to write it down" - but not to the point where she seems to be a danger to herself.
I love my mother, but she is difficult. She also has grown with age. While she is difficult now, she used to be abusive and manipulative. My father would never speak ill of her, but from some things she's said I believe she was worse before she was raising us. If my mother regresses to an earlier state of mind, we will both need professional help. She will need professional care, and I will need help to not internalize the way she treats me.
I have some memories that I know for a fact are wrong in a pretty particular way. They’ve either become attached to the wrong place or the wrong time.
Like I remember a good friend picking me up from my childhood home, yet I didn’t even know that person until I’d long moved out (many years) from that place.
How much of this, I wonder, is a function of the fact that our circadian rhythms get less robust with aging. The circadian clock hugely influences learning and memory processes, gating when you can learn and how much, and shaping the storage and recall also.
We know that with age the amplitude of these rhythms can decrease, as can the synchrony between cells.
This kind of mid-management seems to have at least some circadian component, and it would have been great if they looked to see if the effects were equally bad at all times of day, and knew the chronotype of the participants to use as a reference. I’d love to see if every test participant was tested at their cognitive peak, too.
Anecdatum: I confidently told a woman that her son, who was looking for a research opportunity in Berne, Switzerland, was heading for the birthplace of the World Wide Web, which is actually a couple of hours west and south at CERN.
Worth keeping in mind also is that memories are not a reliable facsimile of objective reality.
Instead, they are selective representations of parts of a subjective experience. It also means that memories aren’t static, but shift over time and can even be imagined.
Compaction is not even an intrinsic function of an LLM, but of it's harness or whatever code is calling it. When an LLM compacts something it's just creating a summary of the previous conversation using the same mechanism that it uses to generate any other text. It doesn't "forget" the text from before the summary, it just no longer receives it when it is invoked.
In contrast, when we forget something we are not summarizing anything, we are just losing the ability to recall something. We might remember what we have forgotten later on, showing that it is still somewhere in the mind, and that the reason we have forgotten it is not necessarily because it has been discarded.
Even then, what this article is talking about is not even normal forgetting as a function of the brain. It's talking about a degenerative and dysfunctional form of memory loss where different memories are confused with each other.
Being an "aging brain" myself I can totally relate to this. I've been a relatively obsessive photographer (i.e. visual diary) since digital cameras were practical, i.e. over 25 years now. 238K photos in the collection so far, and I can actually find things in it.
And I've more than once found that an anecdote I've been telling has been incorrect, precisely in a "melded memories" kind of way. It happened at this sort of gathering which were usually held for that reason so X was involved... and then finally look at the old pictures and there's no sign of X. It is literally the brain invoking "lossy compression" to make it all fit, just like certain web services that let you upload pictures without limit might reduce old ones, that hardly anyone ever looks at any more, to lower quality to limit storage bloat.
Of course any married man can confirm that this only applies to men. Women's memories are flawless. If they claim that they remember a conversation exactly, word for word, 20 years later, who's to prove them wrong?
But did you see the gorilla?
EDIT: https://en.wikipedia.org/wiki/Inattentional_blindness#Invisi...
Can confirm. This "aging brain" regularly and vividly inserts my child into memories created before they existed.
I think that's because memories really are highly compressed, with the average complex memory (of a grand day out, for example) being compressed into at most a paragraph of text's worth of information. Everything else is made up of context.
For example, having no photographic memory, I can remember the general "feel" of the innards of an antique shortwave receiver I used to have as a kid. But almost all of that is context. I know what canned octal base vacuum tubes and big tuning capacitors look like, what sort of components were in the big band selector "sled" (for geeks: This was an NC2-40D) and so on. So I can "zoom in" on the coarse memory by just filling in details that are generic, not specific. And these details may be from different sources than the original memory too.
And so the brain needs to remember - if one is not faceblind, which in fact I am - just the overall geometry of someone's face, and all the other stuff can be filled in as needed (how they look when they smile or are anxious etc.) Compression, compression. We have a lot to learn from nature. Note that a faceblind person does this too, of course - just not with a geometrically exact visualization of that person's face, just one with the correct "feel".
And that's also why synthetic memories can be formed so easily. You really don't have to insert much. The brain infers the rest as needed.
This of course applies to my (sarcastic) description of women's memory too. A given conversation is compressed to a small amount of memory, a significant part of which is the "feel" of the conversation rather than the actual words. So of course the memory is not word-for-word exact. But, let's just say, a subset of persons, a majority of which may or may not be female, does not acknowledge this and insists that the (reconstructed) sequence of words is exactly what was said 20 years ago.
I went under for 2 different surgeries. One of them I had post surgery complications. Years later, we needed to know the year I had the complications. I remembered the surgery, simply look it up and ta-da I got the date.
Except, my wife thought it was the other surgery. And insisted. I was incredulous and angry. I literally nearly died during the complications. I think I would remember the surgery it was from. And it definitely wasn’t from my vasectomy. I decided to make a stand.
I found the oxygen sensor we purchased for the event. Found to manufacture date. It was after her event. So it was physically impossible have the o2 sensor before her event. Wasn’t good enough. Maybe the date was wrong.
I finally went to the hospital and got the records. I was right. My wife simply could not or would not acknowledge it.
I spent the majority of my marriage being “the forgetful one”. And here was a single case where I was right and she had memory issues. And she could not simply say “oops, I got it wrong”. I began to doubt her memory and thought maybe I was being gaslit sometimes.
It was a very influential event in the course of our marriage. I lost a lot of respect for her and began to wonder what our future would be like.
We were divorced within a year.
Not only this, but other things too. But this was a big part of it.
Given the number of neurons, hash collisions are inevitable? /s
Our model of the world, and this includes "memories" is very highly compressed, and extremely lossy. We reconstruct everything from what neurons activate when we recall something, so it can also be like a corrupted zip, where we don't access everything required in the moment. This can be affected by sleep, stress, hormones, etc.
What is quite interesting is when we try and recall something and can't, but the subconscious processing continues and you recall it later.
as you say, everyone does this. you just have the evidence and the humility to admit it.
Perhaps the rate of occurrence changes, but everybody does this at every age. When even our experience is an interpretation of the real world, our memories are even less accurate.
Just throwing out an idea: I recently stumbled upon an old-school website where someone is uploading a photo of their day (almost) every single day since 1998.
Came across screen captures of the original Everquest (SO COOL) and other games, photos of anime/cosplay events, city shots, family, friends, etc. Really fun for them, and fun for people who like me who still enjoy surfing the web.
edit: Screencap of an Everquest screencap for funsies: https://imgur.com/a/HUqc6p5
When my mom was still alive and relatively new to a smartphone (at age 80) I decided to send her some sort of relevant picture every day via Whatsapp, to get her used to communicating that way. Sometimes it was a real stretch to come up with something. But yes, this forces you to evaluate your life from that viewpoint "surely something was interesting today? Let's keep a picture of it". Even if it's just what I'm having for lunch that day.
But she's gone now and so is that habit.
I'm not sure if you are in this demographic, but a lot of people I know born in 1999-2003 or so in the US used snapchat as a primary method of communication for many years, and a large part of it was keeping up "snap streaks" of sharing one photo a day with many different friends.
This is one thing for all of the pairs of genuine friends doing this, but I also have two friends who I introduced to each other exactly once, and who have never spoken since, who have a 6 year snap streak together, and both of whom have streaks like that with dozens of other people, many of whom are virtually strangers.
That is interesting. For a streak to count, do you have to both send out your own, and open incoming images? I wonder how much you could tell about someone if you had a 6 year snap streak with them. Would they be more like a friend, or an awkward relative with whom you seldom meet and have little in common?
Both of you have to send them to the other person as a specific recipient (so not just putting it on your story). I'm not sure about opening them.
For the two friends I'm thinking of, my impression is that they don't know each other any better through snapchat than they do from me knowing both of them and mentioning them to each other (they live 1000 miles apart and only met once). I guess the best I can say is that I would be comfortable seating them at the same table at my hypothetical wedding. Same vibe as my cousin I have on Facebook but have only really met twice in the last decade.
What a beautiful little habit to have with a parent
Everquest looked sooooo good back then. Man! No more Meridian 59!
Why did you have to destroy my memories? :)
It's like looking at the first DivX encoded movie that was soooooo good vs. VideoCD/LaserDisc. And then you look at it today and it's so damn blocky and also in that tiny resolution. Ugh!
I don’t think the sexist comment at the end is appropriate for HN
>I don’t think the sexist comment at the end is appropriate for HN
I don't think the ageist comment in the headline is appropriate anywhere.
It is well known that memories and perceptions at every age are largely constructed more as "what makes sense" ("no, a gorilla did not run across the basketball court") than "as recorded" recordings.
> Of course any married man can confirm that this only applies to men.
My first read of this headline was to observe that people seem to get more comfortable stereotyping people different from them as they age. Thanks for the datum.
I wonder how much of this is directly related to age (biological aging), and how much is just someone's brain becoming "full" due to more memories getting added every year?
It seems that memories must be stored as embeddings with single multi-neuron assemblies (cortical columns?) storing multiple embeddings as a kind of contents-addressable memory that is able to keep memories distinct due to the very high dimensional space (# neurons per assembly) being used. However, you'd expect that at some point if you store too many memories in a single assembly the recall accuracy is going to go down.
You'd expect that with big brains being so costly, evolution has only equipped us with brains big enough to store a lifetime of memories, so it would be odd if memory didn't suffer as we get old.
To make a computer analogy, it's a bit like a hash table getting too full. Say you had a hash table without any overflow mechanism... up to a point recall may still be pretty good, but as the table gets closer to full there will be more hash collisions and likelyhood of "false recall". Obviously the brain is not a computer, but the analogy may hold up reasonably well if you consider the hash table keys and values as embeddings and the store operation being an embedding merge rather than overwrite.
The brain does not have the Von Neumann bottleneck. Unlike most current digital systems, the brain doesn’t have a separate memory registry it needs to pull from.
Engrams, that is, the physical trace of a memory, are not stable through life. They start out in the hippocampus, but as the stimulus recedes in time without reinforcement, it moves away.
No evidence exists though that the memory is encoded in one set of cells. This spatial segregation of memory is the worst hangover from the “brain is a computer” analogy. Even if it is, why in the world would it be like our digital devices which specifically have the Von Neumann bottleneck? In biology, memory and processing are not segregated.
There’s growing evidence the memory is much more distributed over the network, and is recomposed based on salience overlap with a new stimulus.
Another factor to keep in mind is circadian rhythms. There’s growing evidence for how much the memory system and timekeeping system overlap, at a molecular level. Every neuron (and other cell) has an intrinsic clock that ticks at roughly 24 hours, and continues to do so even in total darkness.
When you encode the memory has a lot to say, based on your chronotype, on how and how well you will remember it. Same with learning: there’s a time of day based variation.
Sleep, and dreaming, is when these memories seem to get replayed and critical features and connections are incorporated into the system and its regime, awaiting the right triggers to access a state similar to when the memory formed.
I’m stitching across a lot of different research, and I want to be clear many aspects of this system are not yet fully worked out.
But what we do know points to a system that works with different physical and algorithmic priors, and the dynamics are sharply distinct from current digital computers.
Hijacking your post with a dubious segue because I’m itching to bounce these thoughts off somebody:
I’ve been consuming a lot of talks / writing recently about “enactive” pictures of how our brains function. From what I gather, recent studies have called into question the entire idea of real world concepts being “represented” by an area of the brain at all. While it’s true that atandard fMRI-style snapshots of brain activity are semi-stable over the course of a short experiment, it’s not true over longer timeframes. The response to the same stimulus will change over time. They refer to this as “representational drift” in the literature, and some people are using this to bolster theories of mind that they consider non-representational. They instead emphasize the brain as a kind of dynamical system that learns to “resonate” with the world to pull itself back into homeostasis. The focus shifts away from facts and memories as data, and sees neuronal plasticity more as a mechanism for tuning the brain’s resonant frequencies. This obviously places high importance on the spiking, recurrent nature of actual neurons, as opposed to the neurons-as-functions / back-propagation / ML approach.
My mind’s not made up on how interesting and revolutionary this approach is / isn’t. The distinction seems to be about whether learning is more like “writing to disk” or “tuning a PID controller” - but in either case, the world is leaving a stateful imprint on your brain that will impact how it processes future data. Is that important to understanding how brains work, or is it just semantics?
Some years ago, I heard a retired Lutheran priest ponder, in radio, about the concept of a prayer, and whether, as an edge case, an unborn child could be able to pray, with the child of that age having no understanding on the required concepts. This is apparently one of those questions that people ponder under the umbrella of philosophy of religion. His conclusion was that prayer was about harmonizing one's self with the universe. It's a beautiful thought, (and I think religions, of all kinds, are really good at providing the fertile ground for thoughts like these).
It's akin to how the saying goes, that when we argue, we need to reach the same wavelength where the other one is to reach an understanding.
In communication studies or sociology or linguistics or one of those fields, there's the idea that communication is about making pacts about meanings, and finding the common ground to understand and delimit the message.
In a sense, from that basing, one could argue that understanding can be seen as an act of harmonizing. I think there's something universal in it.
Ooh thanks for the hijack! It’s so much easier to talk to someone who isn’t stuck in a picture of the brain from the 1980s.
Yes, I fall more towards the camp that a lot of our cognitive models, built from times when we didn’t have the resolution of understanding we have of the capacity of even a single neuron, and before we knew how astrocytes played a role, suffer from being an abstraction describing an abstraction. They are not tethered in the dynamics of the molecules and cells that give rise to the behavior, but rather from an interpretation of observed behavior.
This paper from the field of chronobiogy is one I’d recommend that helpfully contrasts this:
https://www.sciencedirect.com/science/article/abs/pii/S00393...
>In circadian research, the models are not proposals regarding the basic architecture of circadian mechanisms; rather, they are used to better understand the functioning of a mechanism whose parts, operations, and organization already have been independently determined. In particular, circadian modelers probe how the mechanism’s organized parts and operations are orchestrated in real time to produce dynamic phenomena—what we have called dynamic mechanistic explanation.
And what you’re describing, the enactivist description of cognition, (and 4E cognition more broadly as a framework), is one way the neuroscience community is trying to move past these issues.
Few things that give me confidence these are the right track:
1. Circadian rhythms are evolutionarily ancient. Bacteria have em. Plants have em. But different molecular tools shape very different clocks, though the same 24 hour cycle is being tracked. 2. The way these rhythms are generated is not through some central system that broadcasts the information to other regions. Instead, it’s instantiated in every cell in the body, and the behavioral rhythm is due to the synchrony between cells. Resonance absolutely plays a role, and has been well documented. The brains role, via the suprachiasmatic nucleus or SCN, is to orchestrate this synchrony, but it is not the source of the rhythms. 3. This slow rhythm definitely regulates cognition (time of day effects in learning, memory formation, recall etc are well documented), but turns out, the molecular mechanisms by which the clock responds to light hugely overlap with the molecular mechanisms of learning in the synapse, and even more recent work has shown clock proteins are actually in the synapses and synaptic activity affects the clock.
All this points to nested oscillators with cross frequency coupling, and even better, because this is all grounded in actual molecular dynamics, there’s plenty of falsifiability. The phase amplitude links are best established for the faster rhythms, the famous “brain waves”. Highly recommend György Buzsáki‘s work on this:
https://www.jneurosci.org/content/32/2/423.short
What’s missing is going down into lower frequency rhythms, and testing how exactly they all couple. We have a lot of the pieces, but no single experimental paradigm that has looked at the full sweep over different times in the same organism. It’s not easy to do, but we’ll get there.
Clock disruption, depending on how you do it, has huge impacts on time perception, cognition, memory, aging AND consciousness. As that data and evidence gets more and more saturated, I hope we see more studies account for chronotype and the internal dynamical state of their test subjects when assessing outcomes.
Obviously I’m biased (also did chronobiology in school), but hopefully I’ve left you curious. Happy to answer more questions all this may have set off.
Thanks for your response, very intriguing! I have some controls background, and there’s something tantalizing about the idea that perhaps we need to be looking at the brain in frequency space, as it were. Are you aware of reservoir computing and do you see it playing a part in this?
> The brain does not have the Von Neumann bottleneck
Obviously not, which is why I didn't say it did!
However, if you want to identify where long-term memories are stored, then that is in the cortex, but it should go without saying that this doesn't make the cortex the storage component of a von-Neumann architecture!
> No evidence exists though that the memory is encoded in one set of cells
I'm not sure what you are trying to say.
Memories are presumably stored as embeddings - a distributed representation, and an episodic memory may well be stored as "chained together" episodic "scenes/chunks" where each chunk recalls the next.
However, a distributed representation isn't the same as a holographic one, and any redundancy may well still be localized within given cortical columns, so I think you may be wrong if you are saying that individual memories/chunks are not confined to one set of cells (some localized neural assembly such as a cortical column).
> Obviously not, which is why I didn't say it did!
But you sneak it into your assumptions on what a memory must be.
> However, if you want to identify where long-term memories are stored
And why do you assume there is a specific “where” for the memory?
> then that is in the cortex
There’s good deal of evidence disproving this in the way you’re stating this. The cortex is involved in sensing, and yes, the sensory information associated with a memory will recruit appropriate cortical cells. This doesn’t mean the memory resides in the cortex. And detailed episodic recall keeps recruiting the hippocampus even for old memories, which is odd if the memory were somehow only in the cortex.
> I'm not sure what you are trying to say.
Let me restate what I’m saying then:
There are four claims bundled together in the way you were describing biological memory: that a specific ensemble is activated when a given memory forms; that it’s the same ensemble that gets activated over time when that memory is retrieved; that it’s spatially compact, like a column in region of the brain; and that this ensemble it’s dedicated to that memory, or similar memories .
The first is well supported. An engram, a network of neurons, is indeed activated when a memory first forms, and gets stabilized due to repeated stimulus. Re-activating these neurons in a different context can make the subject (a mouse) behave as it would if it had contextual signals to evoke said memory.
However: 1. This engram is not in one particular part of the brain. There’s a cortical part that overlaps the sensory regions that were involved. But plenty of other regions are part of the engram 2. There’s turnover, over the course of weeks, when the specific cells involved in the engram drift, while the behavior remains stable. 3. The same synapses participate in many memories.
> Memories are presumably stored as embeddings
No. Let’s consider songbirds, which are an excellent worked out example (in an animal without the complex columnar cortical architecture mammals show, by the way).
What’s learned is a temporal sequence, with neurons in a nucleus in their brains each firing one brief burst at a fixed point in the motif, so the content of the memory is its dynamics rather than any value. The circuit that evaluates the match against the tutor template is the same circuit generating the output being evaluated. Song degrades overnight during sleep replay and recovers the next day, and in seasonal species the song nuclei change size across the year with neurons added and lost while the song persists. There’s no read that leaves the item untouched, no persistent address, and no substrate holding still. “Stored as” imports all three.
And it goes below the neuron or synapse. Hearing a tutor song drives immediate early gene expression that habituates with familiarity, and singing drives large transcriptional changes in the song nuclei that differ by social context for the same motor output. Since transcription runs on minutes to hours and the proteins turn over, any persistent state has to be actively regenerated rather than deposited.
TLDR: the memory isn’t a static store. There’s no persistent “location” for it, distributed or otherwise, though specific locations can be in the chain that’s activated for retrieval/production. Instead, memory, over time, is driven by a dynamical regime that adjusts its dynamics to account for the temporal pattern in the salient stimulus.
Nothing, down to the epigenetic changes in the chromatin of these neurons, can be seen as “the” location of “a” memory, especially over time.
> if you are saying that individual memories/chunks are not confined to one set of cells (some localized neural assembly such as a cortical column).
That is indeed the case.
If someone's hippocampus is destroyed, they lose the ability to form new (episodic) memories, and may lose some more recent old ones, but they certainly do not lose older ones. This is basic knowledge.
> and that this ensemble it’s dedicated to that memory, or similar memories
No - that's the exact opposite of what I said. My whole point was that a cortical column is NOT dedicated to a single memory (we'd run out of memory!), but rather acts as an embedding space containing many (sparse) embeddings.
Due to the size of the embedding space and sparsity of individual embeddings, there is little chance of much overlap between embeddings and therefore associative recall is reliable. When there are too many memories stored using the same set of neurons, then there will be non-trivial overlap between embeddings (this is the definition of "too many" / "full") and associative recall becomes unreliable.
Note incidentally that this explanation holds regardless of whether distributed embeddings are stored in a more localized area (or areas - visual, auditory, etc components) or more globally distributed. At the end of the day evolution has equipped us with a right-sized brain, and an individual that outlives the useful life it is adapted for can expect to experience memory failures.
I'm not sure why you bring up bird brains, and specifically bird songs(!), but FWIW it seems that their short term memory likely works similarly to our own in as much as it is based on the hippocampus, with a very strong correlation between bird hippocampus size and memory capacity (ability to memorize 10's of thousands of hidden seed locations in some species). Some birds such as crows certainly have long term memory where I'd guess those may have migrated to their pallium, but we're discussing human memory here (or at least I thought we were).
None of that changes whether there is a physical capacity, which I think was the larger point? There is no reason to believe distributed memory doesn't suffer from the capacity component of the bottleneck. In fact iirc there was some late 80s/early 90s papers on the memory capacity of NN. Btw I would advise against the absolute statement that there's absolute segregation of memory and processing.
I guess my point is the brain not being "von Neumann" in architecture or digital is not proof that isn't a "computer" of some sort.
> None of that changes whether there is a physical capacity, which I think was the larger point?
Capacity in what sense? Are we saying it’s X MB of data the brain can store? That claim is steeped in assumptions.
On the other hand, no one is claiming the brain has infinite memory or anything. And it’s certainly not a very accurate memory system. I’m arguing against “capacity” being understood as “these specific physical components located here and here we can ID store memories, and can get crowded with too many memories” sense.
This most particularly fails because not all memory is even identical in the brain, whether we mean the physical changes associated, the topology of the information, or how it’s activated.
> There is no reason to believe distributed memory doesn't suffer from the capacity component of the bottleneck.
I didn’t know there was a capacity component to the bottleneck, only a bandwidth one.
All I’m trying to say is that analogy to current typical memory storage systems to explain the brains memory processes is not helpful.
> I guess my point is the brain not being "von Neumann" in architecture or digital is not proof that isn't a "computer" of some sort.
Indeed, since the word computer was first used for humans. But what kind of computer matters enormously. Ising machine? Quantum+classical stack? Reservoir computer? All those frameworks have processes in the brain they can point to as homology.
Which points to a possibility: maybe the brain is multiple types of computers interacting. And the physical realization of these computing architectures aren’t spatially separated but thread through each other in the biochemistry and physical dynamics of cells.
https://www.pnas.org/doi/pdf/10.1073/pnas.79.8.2554 in a very precise sense going back a long time. I don't really know who you're arguing against or refuting? You seem to be touching on some pretty well accepted ideas.
"All I’m trying to say is that analogy to current typical memory storage systems to explain the brains memory processes is not helpful." Again, my impression is that the original author's idea was about capacity in general, then he gave an analogy. The analogy was wrong, but your reply went way beyond his specific analogy to the extreme of discarding memory itself as useful concept. To be clear, I agree that it is distributed and lossy and time-dependent. I agree it is not just a simple read-off of a static chunk with a fixed address.
"Which points to a possibility: maybe the brain is multiple types of computers interacting. And the physical realization of these computing architectures aren’t spatially separated but thread through each other in the biochemistry and physical dynamics of cells."
I would say that is both non-falsifiable and well-accepted.
https://mitpress.mit.edu/9780262041997/theoretical-neuroscie... might interest you and on the other end bialek's spikes shows quite a bit actual does happen near the single neuron limit. bialek also does/did a lot of other stuff on capacities and processing you might be interested in. https://mitpress.mit.edu/9780262181747/spikes/
Does this mean we have unlimited memory storage?
This is really fascinating. The actual mechanisms of the human mind are distinct from computer systems, yet there are some parallels.
There are some hints that increased memory access times scale with the amount of information the brain has stored vs the more typical narrative that aging decreases the capabilities of the brain.
> Our results indicate that older adults'; performance on cognitive tests reflects the predictable consequences of learning on information-processing, and not cognitive decline. We consider the implications of this for our scientific and cultural understanding of aging.
[0] https://pubmed.ncbi.nlm.nih.gov/24421073/
A fascinating story of "Patient Sh." [1], the man who did not forget.
[1] https://en.wikipedia.org/wiki/Solomon_Shereshevsky
"His memory was so powerful that he could still recall decades-old events and experiences in the smallest details. After he discovered his own abilities, he performed as a mnemonist; but this created confusion in his mind. He went as far as writing things down on paper and burning it, so that he could see the words in cinders, in a desperate attempt to forget them. Some later mnemonists have speculated that this was a mentalist's technique for writing things down to later commit to long-term memory. Reportedly, in his late years, he realized that he could forget facts with just a conscious desire to remove them from his memory, although Luria did not test this directly."
I believe that one need to have superhuman memorization abilities to have definite confusion due to too much remembered. More trivial explanation of this effect in normal ageing persons is age-related brain shrinkage.
Our brain consists of approximately 86 billions quantum computers [2] controlling tens-of-thousands chemical neural networks with at least 10 coefficients, communicating [4] using lasers [5] (coherent light is laser light). Live with that. ;)> Live with that. ;)
Well, sure, it's a computer of sorts, although in the abstract sense of being able to perform computations so is our liver, so perhaps not a very useful concept.
What I meant (as I assume you realize) was "not a von Neumann architecture computer", but I'd also fairly confidently assert that it's not a quantum computer either.
Our ANN model of a neuron is obviously too simple (especially being a synchronous model, not a real-time asynchronous one), but it's hard to imagine that all of the classical chemistry, let alone quantum, details are important. It's necessarily built out of chemistry, but selection is happening at the level of behavior - presumably depending only on a much higher level set of abstract capabilities (ability to learn, etc), not the exact details of chemistry.
The success of LLMs, a crude prediction mechanism built atop a crude ANN, does tend to support the idea that low level details don't matter. Timing will matter if we want to go beyond LLMs to AI that can learn time-based things and not just sequence order, but how much else will matter remains to be seen!
I suspect the anxiety of being unable to forget things has an inherent selection bias. You will only stress over the things you can't forget, the things you have forgotten you won't stress over...
Generally claims of eidetic memories are overstated, doubly for older claims, but Nigel Richards memorized a French dictionary in 9 weeks, over 6k words a day, x2 including the alphagram.
I consider myself to have a decent memory, but that is 200x what I'd think myself capable of, assuming I want to retain it all at the end of the 9 weeks.
Our brain consists of approximately 86 billions quantum computers [2] controlling tens-of-thousands chemical neural networks with at least 10 coefficients
By that logic, a Blackwell GPU contains 208 billion quantum computers.
Each transistor is a quantum mechanical system and takes hundreds of model parameters to describe. So apparently a GPU is a 208-billion-node quantum supercomputer.
"The brain is not a computer" != "Parts / aspects of the brain do computation".
"A computer" in the first statement is IMO obviously intended in the common usage sense of the term, i.e. the brain is not a desktop computer or smartphone, or Turing machine, or etc, and thinking of it like these things will cause more error than insights. Also, billions of interlinked mini bio quantum computers arguably produce something with emergent properties and behaviour much, much more complex than "a computer". I am with GP, the analogy to "a computer" is not super helpful here unless you highly restrict the meaning.
But yeah, the Shereshevsky case is a super interesting one, thanks for linking!
> "A computer" in the first statement is IMO obviously intended in the common usage sense of the term, i.e. the brain is not a desktop computer
No one has ever thought that a brain is a desktop computer, and that is not the common usage sense of the term in this context.
You are wrong, as I didn't limit the analogy specifically to desktop computers only, try reading the rest of what I wrote. The original analogy was obviously hedging against simplistic brain-computer analogies (GP could be read as: "the brain is not a simplistic computer"), so the response demanding to "live with that" citing computational aspects of the brain was misguided and arrogantly wrong.
Multiple other responses also point out the definition given leads to absurdities / triviality (the liver is a computer in this context), so the "correction" with citations is both inept and inapt.
The book Moonwalking with Einstein covers Patient S and memory in general. It's an enjoyable and quick read on the topic, would definitely recommend.
I see it differently: as a teen, I could remember the exact word for lots of things, I could recall numbers and data with high precision. Nowadays, I'm pretty bad at all those things, but I can very well understand metaphors and connects concepts from wildly different topics — which I couldn't back then.
I see this kind of "interconnecting ideas" of my current years as somewhat connected with "fuzzy memory". It's like, when I retrieve data, it's not as precise, and sometimes I get neighbouring data, but that can actually of use.
I feel like I feel this increasingly as I age. I used to be able to remember nuanced details of API and computer systems. Now, so many of those memories simply get stored as “FLAG: double check the docs” (because I’ll forget).
I’m a lot better at assessing things from a high level, knowing where to find the information I need, and knowing how to assess it for accuracy - but I can’t remember details anymore. Books become summaries. Trips become a few key snapshots representing the trip.
I am not a biologist so I cannot say this authoritatively, but I’m fairly certain that’s not how neuroplasticity works.
I only mentioned neural assemblies storing multiple embeddings - what about that contradicts your understanding of neuroplasticity?
How so?
I don't think there is a "full" state, but watching the changes as the years go by I have thought of collisions. Not really like a hash table, though--most collisions are with things that would be filed together. I think it's more like the brain returns a random item matching the category. Brains are expensive, memory that gets fuzzy with age is probably the better choice than trying to feed a brain that does better.
Yes, evolution is not going to penalize everyone with a "100-year brain" when the rest of our body seems optimized for something more like a 30-40 year lifespan. Evolution is all about propagating your genes, and not too many 100-year olds are going to be doing that!
In any case, fuzzy associative recall is really the "design spec" for a brain, so semi-graceful degradation and fuzzy recall comes for free.
I'm not sure if old-age memory unreliability is totally random - I would not expect it to be. I'd expect these associative recall failures to happen when there are too many memories partially matching the same "key" (activation pattern), which presumably happens mostly when they do have something in common.
The paper certainly has its limitations. Only 61 participants, with almost nobody between 30 and 50, so we shouldn’t read the age trend as a decline across lifespan. What’s more interesting than the title suggests (and I find the title forcing the conclusion a bit) is that the attention measures were not linked to age or the brain patterns at all.
Then again, i'm 45 and I've been losing my keys and my IDs since I was 20
>I find the title forcing the conclusion a bit
The entire article is AI-generated.I wish such sources would include the prompting used as well as the model so a (human) reader can better evaluate the document.
> Reviewed by Patrisha Antonaros
There is a responsible signer.
If you think their method can be improved, write at https://studyfinds.com/contact/
They disclose an "AI policy" - https://studyfinds.com/ai-policy/
> This process includes multiple checks using different LLM platforms, human editorial verification, and cross-referencing with original sources to ensure accuracy and eliminate false information, misleading content, fabricated content, bias, and unreasonable speculations or editorialization
Gonna chuck a thought for you all. In social situations there is someone who talks alot and I think they are able to do so because they have lots of stories they can recall in good detail (maybe not perfect) but 20 year old event they are describing better than I can describe last week. Now I assume they don't have that rare calendar level memory but they do have a huge storage of stories and events. I am pretty jealous tbh!
Also that skill is probably excellent for interviews which is the ultimate memory test. I.e. Tell me a time when you turned water to wine, plus 5 deeper questions, any hesitation will be chalked ip as suspicious AI use.
For me I either do or I remember which makes performance management and interviews hard for me (as someone vouching for someone as evidence is rare now).
It's interesting for interviews. I assume that people who have somewhat inaccurate memories but with a (possibly subconscious) egotistical filter do much better in interviews than those of us who have more accurate memories of exactly what our contributions to a project were. There are a lot of ways of stretching the truth in your favor, and they all seem much more natural if you really believe them.
My friend recently told me about seeing that an old coworker of hers from 20 years ago described her role as HR manager rather than HR assistant on her LinkedIn. I can easily see how someone with a fallible memory can retroactively exaggerate their title or responsibilities, especially when it's been 20 years.
I have a few friends and family members like that and for the stories which I was present, they always hit the broad strokes, but the finer details get switched around and sometimes the whole story has a major perspective shift.
The concept of memories blending together resonates after watching a recent Kurzgezadt video entitled "How Are Memories Stored Inside Your Brain?". It makes the point that the very act of recalling a memory changes it:
https://www.youtube.com/watch?v=PqtggjVAi8M
> But memories are not static like photos. Like dioramas made from wax, each time they’re under the spotlight of your attention they can melt and change a tiny bit.
I suspect my oldest memory, of me getting into a booster car seat as a child, is no longer the actual memory, but the accumulated imaginings of me trying to remember that specific memory, masquerading as a memory.
My earliest memory… turned out to be a videoclip I discovered 20 years later… I really thought I experienced this!
Very poetic metaphor!
I can't wait to tell my dad about this study. We recently got into a heated debate when he insisted that I was a toddler on a family vacation we were reminiscing about, when in fact I was a teenager on that particular vacation, and he was mashing it together with memories of a different vacation. He is 75 but is in pretty good cognitive health, no signs of dementia besides this unreliable long term memory.
My theory behind this is that when you encounter something new/novel it is distinct enough to remember -- where you were when you learned of 9/11; the days around the start of covid/lockdowns; being in a car accident; getting married; etc..
However, when you experience the same thing repetitively -- having breakfast; getting ready for school/work/etc. -- it doesn't make sense for your brain to remember each of these events as distinct events but to mush them together into a single or combined memory. This may be due to how the brain indexes/references memories and that memories with the same references get combined together.
This is also partly why time appears to go faster when you get older -- the same day-to-day events blend together but the key milestones (holidays, etc.) stick out.
We do know that memories get rewritten every time they are remembered
By 'rewritten' do you mean refreshed, like learning material with spaced repetition, or some different/deeper concept? Do we 'move' that information to a different cluster of neurons?
Compacting ———-~~~~~~~ 40%
Retrocompomorphism
Deticulating splines...
This comes as absolutely no surprise to me -- my mother was recently transferred into memory care, and the changes to her memories are definitely showing some interesting changes. The foremost was that her new "apartment" is shared with one other person, gives off a bit of a dorm room vibe. First day, she was talking about how excited she was to be going back to school and seeing her boyfriends again(?!). I said, "Oh, like Doug? [my dad]". Her response? "Ew. No."
But, she's come around on that, and recently been upset about the affair he's been having (they divorced in 1980), and is irate over him having another kid with his new wife (1983), but isn't surprised that I haven't spoken to him in 12 years. She's never surprised at how I've aged, but doesn't remember her grandkids even exist and insists on meeting them soon (but remembers them when she sees them). Two weeks ago, she called to yell at me for things I did in high school (1990). At this point, I seem to be the anchor for everything recent, but when I'm not around physically, it's scattered everywhere else.
It's hard to write this, but before my grandmother died about 45 years ago, it felt like she'd lost almost all her memories, but was easy to take care of. She was in her late 80's.
My mom & aunt took yearly turns keeping her in their homes. If you kept her away from the stove, she still seemed quite happy helping fix her own breakfast, taking her meds, etc. Give her a warm washrag after, and she'd wipe down the table and then proceed to putter all around the kitchen, wiping and straightening. She preferred cartoons on TV (easier to see, I guess), and was always glad to fold clean towels or clothes, if she had the chance.
Once, she actually recognized me, and remembered my name. It was a very precious 5 minute chat, but then the memories were gone. Still, I'll always remember her that way, because it was just like how I remembered her, when I was a child.
Man, that makes me happy. I'm guessing your grandmother was a very upbeat, happy person who dealt with change well. My mother's the opposite, so now every little thing going wrong is the end of the world. It's rough, but I also get to see these moments where I can see how she was when I was little/before I was born, and those are moments that I do really enjoy.
These stories scare me. I'm happy that you were able to enjoy glimpses of your mother's past.
Mine is showing signs that several of us believe to be dementia, but she refuses to be seen and screened. It has gotten worse over time - repeated conversations, sometimes inside the same phone call, and a shift from "can't remember things if she doesn't write them down" to "needs to ask on multiple occasions because she hasn't remembered to write it down" - but not to the point where she seems to be a danger to herself.
I love my mother, but she is difficult. She also has grown with age. While she is difficult now, she used to be abusive and manipulative. My father would never speak ill of her, but from some things she's said I believe she was worse before she was raising us. If my mother regresses to an earlier state of mind, we will both need professional help. She will need professional care, and I will need help to not internalize the way she treats me.
I feel for you. Even though it's entertaining to read, that must be really hard to go through for you.
Sorry to hear that - my dad spent the last few years of his life in a care home, and I can very much relate.
Is so fascinating and horrifying to read this. We still have to learn so much about how the brain works
My dreams imprint stronger than reality. This has the unfortunate effect of sometimes recalling memories as real, when in fact it was all a dream.
Unless the dreams are the reality and the reality is the fake!
That’s also what happens at around ~1200 micrograms
The new version of this tale is that reality is a simulation. Reality being a dream is so 4th Century China
Happened to me, induced chemically when I experimented with lucid dreaming. It was to scary so I stopped it.
I have some memories that I know for a fact are wrong in a pretty particular way. They’ve either become attached to the wrong place or the wrong time.
Like I remember a good friend picking me up from my childhood home, yet I didn’t even know that person until I’d long moved out (many years) from that place.
For those getting locked out due to using an ad blocker: https://archive.ph/rPdSW
And the actual study: https://academic.oup.com/cercor/article/36/7/bhag114/8758582
How much of this, I wonder, is a function of the fact that our circadian rhythms get less robust with aging. The circadian clock hugely influences learning and memory processes, gating when you can learn and how much, and shaping the storage and recall also.
We know that with age the amplitude of these rhythms can decrease, as can the synchrony between cells.
This kind of mid-management seems to have at least some circadian component, and it would have been great if they looked to see if the effects were equally bad at all times of day, and knew the chronotype of the participants to use as a reference. I’d love to see if every test participant was tested at their cognitive peak, too.
Anecdatum: I confidently told a woman that her son, who was looking for a research opportunity in Berne, Switzerland, was heading for the birthplace of the World Wide Web, which is actually a couple of hours west and south at CERN.
I feel that anyone who has cared for someone with progressive brain degeneration has seen this a million times.
My grandmother has dementia, and if you know her you can see exactly which events/memories she's erroneously combining.
Worth keeping in mind also is that memories are not a reliable facsimile of objective reality.
Instead, they are selective representations of parts of a subjective experience. It also means that memories aren’t static, but shift over time and can even be imagined.
I feel like we didn't need a study to tell us this but its always nice when science confirms something we know to be true.
Clearly the hash table is filling up so you get more hash collisions.
This I belive, I used to have intimate knowledge of my niche internet lore and keep learning I am blending years around.
As a person who used to be a super genius then turned 40 and is now only a regular genius aging has been very hard to get used to.
Don’t worry. By 60 you’ll remember being a super genius again — with increasingly convincing evidence.
I think at 60 the definition for super genius just changes to "having regular poops".
It's interesting to compare and contrast LLMs and biological brains. Both use a form of "compaction".
Compaction is not even an intrinsic function of an LLM, but of it's harness or whatever code is calling it. When an LLM compacts something it's just creating a summary of the previous conversation using the same mechanism that it uses to generate any other text. It doesn't "forget" the text from before the summary, it just no longer receives it when it is invoked.
In contrast, when we forget something we are not summarizing anything, we are just losing the ability to recall something. We might remember what we have forgotten later on, showing that it is still somewhere in the mind, and that the reason we have forgotten it is not necessarily because it has been discarded.
Even then, what this article is talking about is not even normal forgetting as a function of the brain. It's talking about a degenerative and dysfunctional form of memory loss where different memories are confused with each other.
That's largely because we intentionally model llm "brains" after the human brain.
Huffman Coding! :-)
Things seen at a distance blend together, as opposed to just disappearing.
So that's an interesting parallel. Says something about memory.
the basins merge
FYI this is LLM slop. Consider the information to be entirely unfounded.
What, the paper from Mekbib and McDonough, or the divulgation from Antonaros?
Supposing it is the submitted (under Antonaros), see https://news.ycombinator.com/item?id=49538906
/compact
This a covert op to buttress LLM support by planting this article and having people say it's just like compacting. The hype is getting more elaborate.