Live data from Hacker News

Aging brains blend memories together instead of just forgetting them

studyfinds.com

131–140 of 145 posts

Re: Aging brains blend memories together instead of just forgetting them

#131

Earlier quoted context omitted.

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…

> 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. Yes, like basic reading without digging into details. You must have heard about HM, since you’re saying all this. But here’s the facts: When H.M.’s remote memories were probed carefully, they turned out to be gist-li…

> If your model is correct, it needs to account for those facts.

Let me make it simple for you.

We have a finite number of neurons in our brain, as do birds, and our brain is attempting to store an ever growing number of memories in those. And, no, this is not a digital computer (is your reading comprehension really so bad?).

Nobody, including you, knows exactly where different types of memory are stored, and for my argument it makes no difference. What does make a difference is how they are represented, which I am suggesting is sparse embeddings.

So far, you've been ignoring my actual argument and instead responding to various strawmen of your own making, so it's not clear if you even understand what a sparse embedding is.

If you do understand, then it should be obvious that it makes no difference whether the neurons comprising this embedding space are in the hippocampus, cortex/pallium or anywhere else. Clearly you do NOT understand, since you bring up bird brains (pallium vs cortex) and want to argue about location of storage (hippocampus vs elsewhere) as if it made a difference to MY argument.

My argument (if you care to respond to it, which so far you have not) is that when sparse embeddings have little to no overlap, then associative recall by a similar pattern will work reliably, but when multiple embeddings have too much in common then recall will suffer as multiple embeddings will match.

Hint: if you think this has anything to do with digital computers then you have misunderstood and need to go back and re-read more carefully, or google for any terms you do not understand.

Re: Aging brains blend memories together instead of just forgetting them

#132
post #130

Earlier quoted context omitted.

For a lot of people, I think religion provides this basis or promise of harmony with the world, in a simplified way that stipulates what you should or shouldn't do and how things work, and those people find comfort in having these clear "rules"; we want to be able to rely on our understanding of the world, so that we can act within it with confidence, or faith. Ultimately, the "god" that is present in many religions…

If "god" is synonymous with the absolute truth of how the universe works then it can't address moral issues at all, since you can't prove an "ought" like "people shouldn't stab people" from an "is" like "stabbing hurts people and may kill them". You need to add extra axioms like "hurting people ought to be minimized". The universe (and its intrinsic functions) holds no special value for people or trees or life in gen…

> All our moral codes and social norms we live by are purely human invention

I'd say much of it is selected for by evolution. e.g. Most animals don't fight or kill more than they need to since this is not optimal - risk of personal injury and depleting a food resource (there are exceptions of course such as the fox in the henhouse), and this is so universal it seems it has to have a genetic basis.

Re: Aging brains blend memories together instead of just forgetting them

#133
post #130

Earlier quoted context omitted.

For a lot of people, I think religion provides this basis or promise of harmony with the world, in a simplified way that stipulates what you should or shouldn't do and how things work, and those people find comfort in having these clear "rules"; we want to be able to rely on our understanding of the world, so that we can act within it with confidence, or faith. Ultimately, the "god" that is present in many religions…

If "god" is synonymous with the absolute truth of how the universe works then it can't address moral issues at all, since you can't prove an "ought" like "people shouldn't stab people" from an "is" like "stabbing hurts people and may kill them". You need to add extra axioms like "hurting people ought to be minimized". The universe (and its intrinsic functions) holds no special value for people or trees or life in gen…

>All our moral codes and social norms we live by are purely human invention, derived from things that happen to work to produce a somewhat functioning society.

Religious people would disagree, and the evidences are all to see, hear and ponder from their sacred holy books. But the main questions are that which holy books are truly sacred, meaning that purely and utterly God words. Otherwise it's human innovation/exaggeration or something in between (i.e corrupted God words).

Based on these holy books, religious people adhere and follow their prophets teachings and actions to the best of their ability since the prophets are their fellow human beings and not angels send from the heavens.

Re: Aging brains blend memories together instead of just forgetting them

#134

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 dimensiona…

Am neurobiologist and I don't buy the "full" argument, its much more likely a brain aging thing. The brain, before your born, in GW25 (gestational week 25) has finished growing all the neurons you're basically [we can talk about this later perhaps] going to have for the rest of your life. At GW25 current estimates say you have ~86 billion neurons. Now the timing for this next part is a bit unsure but your body doesn'…

But couldn't, and wouldn't you expect, both things to be true?

Existing memories may be degrading as a result of ongoing neuron death and synapse pruning, but at the same time our "storage capacity" (neurons+synapses) is essentially fixed or decreasing, and new memories are going to increasingly be competing with existing ones.

Presumably there is at least some connection between our neuron + synapse counts and species longevity. If we had evolved to live longer then one might naively expect us to have more neurons/synapses to support life-long learning and memories, although you could also argue that, for example, episodic memories too far back are not useful to remember, so maybe there is a cap to how much episodic memory capacity we need, and the complexity of the evolutionary niche we inhabit also limits the amount of declarative knowledge we need to store.

It's been noted in birds that hippocampus size seems highly correlated with the species memory capacity - but specifically for memory of seasonal seed hiding locations, where the bird only needs memory capacity for the number of seeds (can be 10's of thousands) hidden in a single season - they presumably reuse this hippocampal memory capacity each season, and forget the last season.

Have there been any studies relating brain size / memory capacity to the need of a species for lifelong memory?

Re: Aging brains blend memories together instead of just forgetting them

#135

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 dimensiona…

> 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 It hasn’t, and rightfully so. I don’t think there’s any evolutionary advantage in remembering the first steps you did or the first time you drank milk, for example, and indeed, nobody remembers those. A brain that remembers where the berries grew last year, where that cosy cave is…

Right, I really meant as an upper bound, not as sufficient to memorize everything you ever see or do.

Re: Aging brains blend memories together instead of just forgetting them

#136
post #79

Earlier quoted context omitted.

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 abo…

I’m not sure what you think I’m arguing against but saying that it matches with one of the cognitive models du jour is… odd. The problem with the hopfield model is it simplifies the brain too much. The base unit is “the neuron”. Ok… but what about the Astrocyte? Mathematically you can write it as a different kind of neuron. Or ignore it. But why, as a biologist, must I buy this model which ignores the third partner o…

I mean with respect to your other thread too, where you seem to argue/believe academia has no idea about your brand new dynamical distributed view. I pointed to a really old paper with a self-admitted extremely simple model to point out that one of your specific insights over the field re. memory not being a memory stick is ancient and that your arrogance wrt being certain that your notion of memory is so novel that you weren't even sure there was a definition of capacity for distributed memory.

I intentionally gave older books and papers. I very clearly understand as does everyone in the field that they are not current or complete. But that awareness is precisely my point.

"Are you saying the brain is a Hopfield network, and that’s it? Because later you indicate otherwise. Kinda confused what I’m to make of it." You being confused by that is kind of my point, it shows the projection you're applying to the entire field. I understand models are wrong and iterative. I also understand the parts that survive, survive in the literature and the field at large. For example, the PNAS paper that showed "hey we think memory is distributed, right? Here's a simple model showing how memory might roughly be stored and recalled via these very simple dynamics over this very simple model. That's cool. Let's build on it." Did I make it clear enough yet that it was simple and wrong? Do you thus believe it wasn't valuable? I guess that would match your confident opinion that the whole field is dummies and of course those dummies cited an incorrect model so much.

If you stopped with saying "we know memory isn't a memory stick and here's the well-established evidence", then I'd fully agree with "Ok, but my argument wasn’t with the OP mentioning capacity, but with their analogy." and would've said nothing. Instead your posture was "I know some specifics based on recent findings that aren't obviously incorporated as of now into the current understanding -- which I refuse to read because it doesn't address precisely this thing only I understand(1) -- , so here is my theory that is certainly novel don't dare try to point me to preexisting literature that might help me refine my theory."

To be clear, I want everyone to explore their ideas and think it's great that you doubt things. But I don't like someone claiming superiority over a field they refuse to understand. And if your doubt something maybe you should check first if there's anyone else doubting it. (Hint: not only did everyone doubt it, they knew it was wrong and they're all actively working on using that doubt to improve it.) Of course a theory that predates a discovery doesn't cover that discover. Of course a simple model of memory isn't a complete model of memory, that was in fact the point! The notion of distributed memory and how it could feasibly work according to dynamics is made more precise than ever before to that time in that paper (among others). And of course it's outdated. But it contains a more precise statement and falsifiable statement of "memory is complicated dynamics and those dummies don't know and also that book is stupid because it doesn't cover X(2,3)" your theory espouses. My issue is with the arrogance and certainty you know best while refusing to actual understand what others think. And thus give no credit to. Science is iterative. Someone has an idea, builds a simple model as proof of concept. Someone else builds on that model precisely where it has holes (whose precise shape only present itself after new experiments motivated in part by the obviously wrong and simplified model and other attempts to break the model). Repeat. Built on the shoulders.. etc.

"Why’s it non-falsifiable? If you do find a single computational paradigm that explains all brain dynamics we can measure, then you have falsified the hypothesis that it’s an integration of multiple computational types.". I said non-falsifiable AND well-accepted. Non-falsifiable was the wrong word. What if I instead said trivially falsified and also adds nothing not known except to the layman who posits an analogy they clearly aren't sure of? Its non-falsifiable relative to the current state of the field, which I now know you're not interested in, because it says nothing not already stated more precisely, as of like 40 years ago.

(1) "As a rule I’ve stopped giving too much time to models that predate the last decades actual mechanistic facts. They’re fun curiosities, but hard to take seriously anymore. Here especially, the absence of astrocytes in the picture makes it hard to buy they have anything real to say about the mechanics at play. " In response to a book that has a lot to say about your new and novel dynamical theory.

(2) A hole it couldn't cover because the experiments and techniques didn't exist at that time. But they knew their theory wasn't complete. They were sharing what was learned up to that point especially the parts that seemed to generalize and survive specifics. That is, an incomplete model they knew was incomplete. But which I promise would help advance your journey.

(3) "Instead, memory, over time, is driven by a dynamical regime that adjusts its dynamics to account for the temporal pattern in the salient stimulus." Which is true and everyone in the field agrees with. And everyone agrees current models don't fully account for everything. Hence their continuing efforts to improve them by accounting for new findings.

Re: Aging brains blend memories together instead of just forgetting them

#137
post #61

Earlier quoted context omitted.

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 cel…

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…

Perhaps undiscussed in the paper is how the blending of memories may also be better. If evolutionary pressure encourages the structure of brain to optimise for accurate prediction, not memory, then it is quite possible that older individuals may be making better predictions than younger ones, in situations where they don't remember the details...

Re: Aging brains blend memories together instead of just forgetting them

#138
post #79

Earlier quoted context omitted.

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 abo…

I’m not sure what you think I’m arguing against but saying that it matches with one of the cognitive models du jour is… odd. The problem with the hopfield model is it simplifies the brain too much. The base unit is “the neuron”. Ok… but what about the Astrocyte? Mathematically you can write it as a different kind of neuron. Or ignore it. But why, as a biologist, must I buy this model which ignores the third partner o…

> Ok, but my argument wasn’t with the OP mentioning capacity, but with their analogy. Am I not allowed to break down that analogy with evidence?

If someone makes an analogy between aspects of A and B, then there is an implicit assumed shared understanding that A & B are DIFFERENT, and what is being pointed out is that they nonetheless may be considered as having something, typically fairly abstract, in common.

Calling a horse's reins as analogous to a cars steering wheel doesn't mean that the person making the analogy can't tell a horse from a car - that would be a very dumb take. A reasonable criticism might be "it's an imperfect analogy since the reins also act as the brake".

If you disagree with an analogy, then you need to address the analogy, not do the dumb take of "a horse is not a car" ("a brain is not a computer").

So, yes, you're "allowed" to "break down" (criticize) the analogy, but please don't just do the dumb take. So, hash key collisions are not analogous to associative recall and sparse embedding overlaps in what way?

Re: Aging brains blend memories together instead of just forgetting them

#139

Earlier quoted context omitted.

> 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. Yes, like basic reading without digging into details. You must have heard about HM, since you’re saying all this. But here’s the facts: When H.M.’s remote memories were probed carefully, they turned out to be gist-li…

> If your model is correct, it needs to account for those facts. Let me make it simple for you. We have a finite number of neurons in our brain, as do birds, and our brain is attempting to store an ever growing number of memories in those. And, no, this is not a digital computer (is your reading comprehension really so bad?). Nobody, including you, knows exactly where different types of memory are stored, and for my…

Sliding past the mistakes pointed out, shifting goalposts and trying to recover I see.

Let’s say I’m a complete moron and don’t know what a sparse embedding is.

Pretty please, can you define it for me and then tell me, in detail, where in whatever region of the brain you think this is going on… how is it going on?

Explain how “memories must be stored as embeddings with single multi-neuron assemblies (cortical columns?) storing multiple embeddings as a kind of contents-addressable memory”

You have moved past the cortical column. But still seem to be insisting it’s a bunch of neurons, somewhere… or has that also conveniently changed? Whatever your current position is, please go ahead and explain what components of what cells or otherwise are involved in this process you’re describing.

Re: Aging brains blend memories together instead of just forgetting them

#140

Earlier quoted context omitted.

I’m not sure what you think I’m arguing against but saying that it matches with one of the cognitive models du jour is… odd. The problem with the hopfield model is it simplifies the brain too much. The base unit is “the neuron”. Ok… but what about the Astrocyte? Mathematically you can write it as a different kind of neuron. Or ignore it. But why, as a biologist, must I buy this model which ignores the third partner o…

> Ok, but my argument wasn’t with the OP mentioning capacity, but with their analogy. Am I not allowed to break down that analogy with evidence? If someone makes an analogy between aspects of A and B, then there is an implicit assumed shared understanding that A & B are DIFFERENT, and what is being pointed out is that they nonetheless may be considered as having something, typically fairly abstract, in common. Callin…

> Calling a horse's reins as analogous to a cars steering wheel doesn't mean that the person making the analogy can't tell a horse from a car

When a person says “I crashed the car because my steering wheel tore, like reigns tear”, they are overfitting their analogy, and it’s perfectly fine to point out the structural and physical differences that make the analogy useless for the question at hand.

You have dismissed the biology that shows the problems with your analogy as immaterial. And continue to insist it’s the right one for the question at hand. This is a pretty pickle, because no facts can shake you from your certainty that you're right.

You seem in love with your analogy no matter how incorrect it is. And I have no problem with that. But when you put half baked biological claims to support it, I’ll point it out. If that’s too much for you to bear, maybe come up with better analogies?

Post reply on HN