How are memories stored in the brain?
In: Biology
My knowledge is a bit dated these days but I studied a lot of developmental neurobiology in school and while the answer is largely “we don’t exactly know” (unless some major breakthroughs have occurred since I left school) leaving it at “we don’t know” is a vast oversimplification.
Disclaimer: I’m not saying any of this is exactly right, this is just the best I can remember about what I learned and put together that made sense to me during my education.
So the simple question itself is kind of too overly broad to easily address as memory is really kind of a catch all term for a lot of different things. Like an abstract memory, a concept like something you learned in school, might bear very little resemblance in how it is formed and retrieved (or even thought about) vs an visceral emotional experience you have associated with a certain smell, though they could both be described as “memories”.
One is a lot easier to study (the smell response) because you have a simple cause and effect situation, we have a comparably good understanding of how olfactory sensation, experiential associations, and how the limbic system responds to certain signals/conditions.
I think my point is that a “memory” isn’t so much a tangible thing like data on a hard drive, as it is a web of inbuilt or learned abstract and concrete associations that all build together via networking like legos to form unique memories.
Personally I have always thought that might be why recalling certain memories seems to frequent trigger others that you wouldn’t otherwise have remembered. Because they share some base constituent concept, association, object, or experience.
For example a particular memory of riding in a boat might be built up of millions of smaller memories and associations that interweave into a narrative conceptual fabric. At the most basic language level, we can map the association of the word “boat” with the concept of a boat as one simplified memory (which we can see how aphasias interrupt recall where a person knows what a boat is but can’t remember the right word for it). Then the image of your experience on that boat might be a construct of your visual cortex. The memory of your emotional state might involve an entirely different area/system, same with your recall of individual events that happened, and your ability to recall them in a coherent chronology.. it gets mind boggling convoluted and interconnected.
Edit: understanding the specifics of dendritic sensitization, competitive inactivation or inhibition, synaptic pattern generators, a billion other neurological widgets and how they change through use, doesn’t really help to understand what memories are, where they are stored and how they are recalled. Because when you’re looking at that level, it’s a Forrest vs tree situation where the tree is ultimately what makes up a Forrest, but a single tree doesn’t by itself tell you much about the Forrest and it’s ecosystem. So at lower levels you have to change your question to “which tiny part of the memory?” for it to make sense.
Edit2: Even just the concept of “remembering” easily gets really into the weeds when you think about it. Like many memories are memories of memories. In the boat example, you can know you went on a boat ride like you would recall to answer “what did you do last weekend”. But this is far different than “remembering” as in closing your eyes and trying to re-experience what you can recall from you senses and the chronological stream of events or conversations you had on your boat day. “Remembering” gets’s really “meta” fast.
Edit3: there are even more kinds of remembering like muscle memory. This is just one specific form of it, but when you try to do something for the first time (say playing the drums) you are going to light up your motor cortex trying to coordinate your movements. But through repetition your cerebellum will actually take up the load by simplifying small collections of movements (like the necessary state for opposing muscle groups and movements that frequently occur temporarily proximate to each other). Simplifying here but then your higher brain only has to signal “play jazz pattern on ride cymbal” and your cerebellum does the coordinated heavy lifting for you. Your motor cortex and mind are largely freed up to pay attention to additional things and stimulus you would have had to previously ignore. This is called cerebellum patterning and plays a large role in your learning to walk without having to concentrate on it. My point, and yes I am somewhat speculating here, with this is that other parts and structures in your brain probably do similar functions by reducing experienced events/stimulus/responses/environmental or emotional states into small functional blocks to speed up and simplify processing and keep functional recall tracked. This leads back to my Lego block analogy.
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