Long term memory and sleep

One thing that bothers me with long-term memory is the need to review the flashcards or mental palaces or other memory structures. Most memory experts I know use spaced repetitions constantly. Since I use slightly different tools, I use spaced repetitions only for very specific issues, and when I use it I do not like it. What does that mean, why does it happen, and to which extent can this effect be avoided?

What happens when we sleep

When we sleep, we write down some of the day’s memories into our long-term memory. The memories quite often are created in a small area of the brain called hippocampus. They need to be written to some part of the brain near hippocampus to create space for the newer memories. The older memories we do not use often get pushed further into deeper corners of the brain. Each time a memory is pushed it can be rewritten, modified or even forgotten. The memories we use often and the memories that are required to generate new memories stay near the hippocampus relatively intact, while less important memories fade away. The process is very similar to computer processors working with several levels of cache. The better we sleep, the fewer error will happen during this stage, the better will be the integrity of the relevant memories. To counter this caching effect of the brain, we need either to use (or review) the memories we want to preserve or create new memories that are deeply linked to the memories we want to preserve.

Typical memorization process

When we see memory masters do their thing, we are exposed only to a small part of the process. Remembering thousands of details for a couple of hours is a complex task, remembering the same amount of details for months and years is a monumental task. For example, if we use a memory palace with 5 houses, 5 rooms per house, 10 details per room, we generate an itinerary of 250 items. We play it in our heads according to all the memory palace rules (for example this), and we can replay the itinerary an hour later. If we do not replay it in our heads using spaced repetitions, we will probably forget it the following day. So in the evening, we write down some key events to remind us the itinerary and for the next couple of days we need to replay this itinerary using spaced repetitions. Then we need to replay it occasionally so we do not forget it. So we try to fall in love with our itineraries, otherwise, this review process will get too damn boring.

Variations of classical memorization

So the next question: what happens if we use a different method of memorization? I do not play FPV shooters (video games where the perspective changes) because they may me nauseous. Since the process of navigation in mental palaces in 3D makes me feel vertigo, I do not use classical mental palaces. I do use a complex variation of a mental palace with imaginary landscapes and PAO, but (in all honesty) I prefer mindmaps with animations/cartoons.

The mindmaps I use enable complex manipulations of abstract notions, sometimes in several layers of hierarchy. I can use it to memorize complex texts and ideas. The navigation is very simple and very fast since I use the face of a clock to navigate each node. Some nodes open up to further mindmaps, some nodes open up to animations with several complex objects etc. If I want to remember some specific information, say 4 slides with 4 objects having 4 details each, I can encode the animation pretty fast. I do need to write down some highlights and review the animations just like other people review memory palaces. Fortunately, I enjoy the reviewing process very much. But do I need to review the whole mindmap?

Multiple exposures similar content

Typically I do not review my mindmaps, not because they are so good, but because they interplay with other mindmaps I create during the next day. It is much easier to connect different mindmaps with each other then it is connecting mental palaces. Some nodes of new mindmaps can connect to nodes in existing mindmaps. By studying consistently the same sort of articles or the same language, I consistently refer to the same mindmaps, making each mindmap stronger. Also, when I review my animations I try to see what they connect to and make the nearby mindmaps stronger. If these connections are interesting, they can be further reinforced by associations I call “logical markers”.

A different strategy with a similar effect is using two sorts of mnemonics, for example combining mental palace with rhyme or major method. Then if one of the results disappears during the sleep, the other method will provide enough clues to recover the details of the damaged mnemonic. This is a classical dual coding method. The time required to create two mnemonics is probably much lower than the time required to review the same mnemonic over and over, so reducing the number of reviews significantly is important.

How long is long-term memory

Even with multiple exposures and spaced repetition over several months, the memory will probably deteriorate over several years. If we do not speak a language for 20 years we lose it. I used to speak Ukrainian 30 years ago. Did not use it since till a year ago. At first, I did not understand anything, after a couple of days, some words slowly came back, like pieces of a puzzle, far from complete. I know that if I need, I can relearn the language very fast since I used to speak it and the mental templates are in place, yet I do not have a sufficient incentive.

The mental templates are more resilient than specific facts. The connectivity patterns of the neurons probably deteriorate slower than the relevant memories (We do know that old people can generate pattern-specific memories as accurately as young). This is one of the reasons we put so much focus on linking: linking is slightly more resilient in the long run.

The conclusions

I have several takeaways for you:

  1. Sleep well to preserve memory integrity.
  2. Generate multiple exposures to the important memories, for example studying consistently the subject or reviewing subject notes.
  3. Generate multiple representations of the memories, using notes or different mnemonic methods.
  4. We are much better remembering memory patterns than remembering specific facts. Even if we forget some facts, we can easily relearn.
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