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 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

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.

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.

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.

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.

Compacting ———-~~~~~~~ 40%

Clearly the hash table is filling up so you get more hash collisions.

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.

Huffman Coding! :-)

It's interesting to compare and contrast LLMs and biological brains. Both use a form of "compaction".

FYI this is LLM slop. Consider the information to be entirely unfounded.

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.

/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.