Aging Brains Blend Memories Together Instead of Just Forgetting Them
New brain-imaging research reveals that aging brains don't simply forget; they blend memories together. Scanning adults aged 18 to 74, researchers found that older adults' hippocampal activity during recall, instead of faithfully replaying specific memories, predicted cross-category errors—like mistaking a scene for an object. This 'category-level misbinding' suggests a shift from precise memory replay to a broader, less accurate process, offering a new explanation for age-related memory mix-ups.
Their brains were retrieving too broadly rather than not at all.
- rectang
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.
- MarkusWandel
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?
- HarHarVeryFunny
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.
- delichon
I was positive that I remembered an old hobbit woman scowling and calling Gandalf a storm crow, in the films. Then I found a clip of the scene and it just wasn't in there. It was actually Théoden who said that. But the version in my head is better, so if I make such mistakes please don't correct me.
- sorenKaram
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.