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Aging brains blend memories together instead of just forgetting them

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

#71

Post by RankingMember »

MarkusWandel wrote: post #60
YesBox wrote: post #58

Earlier quoted context omitted.

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 Everqu…

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 hav…

What a beautiful little habit to have with a parent

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

#72

Post by SkyPuncher »

HarHarVeryFunny wrote: post #23

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…

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.

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

#73

Post by HarHarVeryFunny »

randomImmigrant wrote: post #53
HarHarVeryFunny wrote: post #45

Earlier quoted context omitted.

> 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…

> 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 info…

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).

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

#74

Post by Fr0styMatt88 »

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.

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

#75

Post by D-Machine »

thesz wrote: post #49
HarHarVeryFunny wrote: post #23

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…

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 h…

"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!

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

#76

Post by randomImmigrant »

chermi wrote: post #61
randomImmigrant wrote: post #31

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…

> 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.

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

#77

Post by unregistereddev »

dan-bailey wrote: post #43
jakzurr wrote: post #42

Earlier quoted context omitted.

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…

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.

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

#78

Post by HarHarVeryFunny »

LorenPechtel wrote: post #65
HarHarVeryFunny wrote: post #23

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…

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.

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

#79

Post by chermi »

randomImmigrant wrote: post #76
chermi wrote: post #61

Earlier quoted context omitted.

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…

> 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 physic…

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/

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

#80

Post by boothby »

MarkusWandel wrote: post #50

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 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.

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