Bear with me. So for example you forget words in a foreign language or someone’s name… what has happened to the information in your brain? Does it just…disappear after a certain amount of time? Does it get “stored” somewhere else and it just takes longer to retreieve the information after a while? Maybe a bit harder to answer…is there a reason that sometimes the information comes back on its own (you recall it independently) and sometimes you have to relearn things (for example, a foreign language you used to speak and have to learn again after not speaking it for months/years)?
In: 840
The brain “knows things” by connections. A simple example is probably song lyrics – people generally know the verse lyrics in order, but it’s hard to pull specific lines out of order for most. Similarly, the brain and those connections are like a muscle, where frequent and repeated use helps.
Forgetting something means the connection is weak for some reason and just straight up isn’t happening. Remembering later means the connection happened differently. If I forgot to water the garden, maybe if I just slowed down I finally was able to remember it because my brain wasn’t as busy/stressed, or maybe I saw a flower garden on TV, or maybe I saw the hose at the gas pump.
Imagine your brain like a jungle with all these different pathways that you can walk through right? And everytime you do anything (litterally anything even walking) you are doing maitnence to the bridge and trimming leaves and stuff. When you dont keep check on a ceartin path it starts to get overrun and becomes unusable. Now imagine you have a bad habit that you’re trying to break. When you’re breaking the bad habit what youre doing is carving out a new entire path but if you had the choice between walking on a really rough path that barely has room to get through or a path that’s really easy to walk but a bit longer. Which are you choosing? Probably the longer one because it’s easier (that’s the bad habit) so what you want to do is let the easy path get overrun with weeds and become unusable and have the new path get carved out and be a shorter path with better scenery.
Edit: with how long it takes to start forgetting stuff it takes longer for some things. For walking it takes years because every time you take a step you get a repetition that cleans the path polishes it does whatever. When you get a kink in your memory it’s because just a ceartin part is harder to walk through as its overgrown. When you have to relearn a small part in the middle it’s because the middle is overgrown so once it gets cleared out it becomes all available again the entire path
BA in psychology with a focus in cognition. Memory isn’t exactly my area but I have some insights I can offer. This is a really, REALLY interesting question; if you stick with me through this novel, you’ll learn why. **TL;DR at the bottom though.**
The shortest and most honest answer to your question is that we don’t know.
We do not know the exact mechanism of how (or, frankly, if) memories are stored in cells, especially long-term and short-term memory. “Isn’t that all memory?” you ask. It’s actually funny because no, and we do have a bit of an [idea](https://en.wikipedia.org/wiki/Long-term_potentiation) about medium-term memory on the scale of about three weeks. (I know the process is called “long-term potentiation but that refers to a different arena of long- and short-term stuff.)
What we do know a bit about is the psychology of memories and the somewhat more macro-biology of memories, as opposed to the microbiology of memories.
Here’s some of what we do know and how we know it.
**There is no one memory center of the brain when it comes to long-term storage.** Memories—and I’m talking about individual memories here, not different discrete memories—are stored all over the place. A given memory is broken into pieces essentially according to, believe it or not, the sensory modality. How your grandma’s hug physically felt is stored near the sensorimotor cortex. How her perfume smelled is stored near the olfactory cortex. How that weird mole on her neck looked is stored near the visual cortex. Your concern for her mole and how you planned to call the doctor for her is stored near your prefrontal cortex, where higher-level reasoning is done.
**However, memories are “administrated” in the hippocampus**. The hippocampus is sometimes called the “memory center” of the brain, but that’s misleading, since long-term memories aren’t stored there (although it is where the long-term potentiation I mentioned above happens). The hippocampus is kind of like the switchboard when it comes to memories, distributing the various parts of it to the other areas where they’re stored and recombining them when called to be re-experienced.
**Memories are not opened like a file on a computer. They are re-experienced.** When we call up an episodic memory, the neurons same neurons fire that also fired when we were experiencing the event for the first time. When you visualize that mole on your grandma’s neck, your brain is literally rebuilding the experience in your visual cortex largely the same way as when you saw it for the first time.
**Memories tend to fade over time, but the act of remembering something re-writes it into memory.** The neurons in a given “map” firing when you remember the memory creates its own map of the same neurons firing, “darkening the ink” on the original map.
**This is true for explicit (episodic and semantic) and implicit (procedural, associative) memory.** Psychologists divide memory into several types. Explicit memory is made up of memories you would be able to “say” consciously, and is made up of episodic memory (“remembering when”) and semantic memory (“remembering that”). Episodic memory is your memory of learning about cell structure in biology class; semantic memory is remembering that the mitochondria is the powerhouse of the cell. Implicit memory includes several types, but of interest here is procedural memory, which is memory for skills and behaviors that you wouldn’t necessarily be able to verbalize. Last, and perhaps most interesting here, is associative memory. Associative memory, a kind of implicit memory, is where “classical conditioning” happens; it’s essentially a map of which neuron maps often fired together before.
***So now I can answer part of your question!***
While we don’t understand the cellular mechanics of long-term memory storage, we can come up with an explanation of memory “restoration” or “refreshing.”
The hippocampus maps for explicit memories and for associative memories are not necessarily the same maps.
What’s happening when a memory fades is that the map for your hippocampus to read to put a memory back together is faded really badly. Research suggests that the content of memories is lost very slowly, if at all, but the ability of your hippocampus to reassemble the memory is lost much quicker. It’s almost analogous to losing the pointer file on a hard drive. The data is still there, we just forgot how to find it.
When a memory is recovered, a chain reaction takes place and is triggered by an event. Suppose you forgot about your grandma and the mole incident. The hippocampus map for that episodic memory was lost—or, put better, the ink has faded such that your hippocampus can’t read it anymore. But then one day you’re in the doctor’s office and you get a whiff of the cleaning compound that they used in the hospital where your grandma ended up passing away because of the skin cancer that the mole really was.
The hippocampus sees the activation of the “Cleaning Spray” pattern in the olfactory cortex. Via the associative memory and its neuron maps, it remembers the “Grandma” neurons also firing. The act of remembering Grandma causes your brain to look like you’re experiencing her right now—the same neurons are firing. The hippocampus sees the new pattern of neurons that are a combination of the “Cleaning Spray” and “Grandma” neurons firing, call it the “Cleaning Grandma” pattern, and looks for the map of neurons that fired with the “Cleaning Grandma” pattern last time. Well that’s associated with the “Grandma’s Mole” map. Fire those. What neurons fired with the Grandma’s Mole map? The neurons for making a phone call, fire those too. What neurons fired with the “Grandma’s Mole + Phone Call” map? The neurons for the sensory sensation for a hug, the look of the mole, the smell of her perfume, the “I’ve got to call the doctor soon” planning neurons, the emotions around the hug. FIRE ALL THOSE NEURONS TOO.
And what happens when the neurons fire when a memory is being recalled?
You literally re-experience it.
From adding these various other hippocampus maps together, you have reconstructed what the brain map for the hug looked like. And this compiled map’s neurons are firing. And when a map’s neurons are firing, you are literally re-experiencing the event.
Now you have a new sensory experience of the hug.
Which generates its own memory map that re-darkens the ink on the episodic memory map for the hug.
And the memory of the hug comes rushing back.
The map of the hug was reconstructed out of combining other maps together in a chain reaction.
And this isn’t limited to episodic memory, of course. Procedural and semantic memories are subject to the same thing. Like how to speak a given language.
This process isn’t perfect, though. Not every memory can be reconstructed in this way. Sometimes so many of the maps have faded that there’s no way to rebuild the associations to get at the way the map looked by firing other maps together, or at least there’s no available path to get you there. But it’s almost guaranteed that some of the component maps are intact; you just need to cue them to fire together again—which is why it’ll be much quicker to learn the language again this time around.
Wow, that got intensely long. I may have gotten carried away.
**TL;DR: We don’t know how long-term memories are mechanically stored in cells. However, memories are “maps” of which neurons fired together. Memories are re-experienced when remembered; during remembering, the neurons in the “map” all fire again just like they did when the thing was first experienced. Memories are lost when the “maps” fade over time, but the content of what the maps led to is usually still there. Through associations, remembering Memory A could trigger Memory B because the brain remembers B’s neurons firing the last time A’s fired. Then, the neurons for both A and B are firing, creating a distinct “A + B” pattern, which itself could be associated with Memory C. Eventually, it is possible for the right combination of other maps to re-build to look exactly like what the lost memory’s map looked like, and the memory is recovered.**
I have no institutional background whatsoever.
Memories are categorized into 2. There’s short term and long term memory.
Short term is if you forget, it’s gone. You’re referring to long term memory. In long term, it’s like remembering 1+1, you can do it – instinctively. Sometimes, accessing long term memory can be hazy because you’re either distracted or it’s “archived”.
Like a computer, you have files saved. If those files aren’t used, the computer puts them in archives to save storage and RAM. There’s no need for those files to be readily available if you’re not gonna use em, so it’s archived. Still there, just takes awhile to dig up your archives. That’s why there’s hypnotherapy where they tell you to close your eyes and you can recall incidents vividly.
Sometimes I can’t think of something (usually a random fact that annoys my girlfriend) cause I’m full of useless information. But hours later when I’m not even thinking about it anymore, it will just pop into my head. It’s weird how that works
Somethng important:
You can’t remember everything. Nothing can.
So, short term memory is like RAM in computers. It has to be constantly there for it to work. Same with mid term memory, except it’ll run longer because you’ve gotten used to it for a while.
Long term memory is di- no its not. It’d just take an extremely long time forget, just like the rest.
Neuroscience PhD here! Definitely learned this at some point, but I can’t recall at the moment sorry.
*Edit* Ok fine, short answer – we don’t know. But I like to think of memories like fading tire tracks across our brains. Like tire tracks, memories aren’t specific items so much as a pattern of information that’s represented amid all the rest; your brain is covered over with tracks in all directions.
When you focus on one track in particular you can get into the groove and follow it easily, but as it fades over time you can lose your way.
Of course the brain isn’t a static thing. Depending on the context and what you’re thinking of, different tracks become more or less easy to pick out. That’s why sometimes things will remind you of a lost memory, or it will seem to just pop into your head – some pattern across your brain has snapped back into focus.
Your brain is like a filing system. Certain files you don’t lose track of, certain files you put in the filing cabinet but forget where, and some files are discarded as not important. When you can’t remember something but it’s in the filing cabinet sometimes you will finally connect the pieces and remember where it was filed.
As far as how that works it’s a bit more complex and not fully understood.
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