But to keep it simple: read, do puzzles, stay active, do not drink or do drugs heavily. ——
Everybody already has a genetic makeup that limits their health—especially the brain—to a preset level. Some people suffer from infantile amnesia—basically not remembering early developmental stages (2-4) and preadolescent (~10 y/o); other’s claim to remember their birth (which is silly since ability to form memories is 2 y/o+). Some have the luxury of having strong working memory^1—a fancy word for temporary memories—but suffers from lackluster short-term memory.
I’m sure you get the point I was trying to make with that mediocre explanation.
tldr: You can not change your brain to not have dementia if your genetic makeup says so. You can however delay the onset possibly by keeping your brain active on a daily basis.
Have you spoke about it at great lengths when older? Is it often brought up about how they took the cast off? If so, you’re looking at the idea of explicit (declarative) memory—the storing of facts and events. If over the years you are constantly reminded of this event, it is more than likely that you’re trying to generate a (possible semi-accurate) image or memory of that particular event.
As far as your second comment goes, mother tongue and languages are different all together. When you learn as a yongue age, your cerebral cortex is still developing and your mind is absorbing everything like a sponge. As you learn these words, continue to use them, that language and those procedures are going to get stored in your long-term memory and then you’ll be able to recite all of these words and form sentences without thinking twice—something we would call implicit memory which helps us with procedure memories (riding a bike, writing, etc.).
Some people may be able to produce a bicycle in more details than others but that depends on how developed and healthy their brain is to use their executive functions. Without knowing all of the subjects medical history—early dementia, strokes, all the good stuff- and current health, it’d come as no surprise that even consciously we cannot produce true representations of what we saw.
Police sketches from eye witnesses may be a good thing to look at when thinking of producing images from memory. Some people have better brain health and are able to utilize many different high and low-level functions to produce more accurate descriptions. Others not so much.