Eli5 How is it possible for people to forget things they studied for years?


Like highschool or even university level studies where someone actually studies and understands their subjects then finds himself a few years later with ZERO memory of the things he studied? where does the information go? is it lost forever?

In: 5

When you learn a skill, it’s like muscle memory. If you learn how to throw a ball, you practice for years, you remember to throw a ball. If you don’t throw a ball for five years, it takes a couple minutes to get back to throwing the ball like you did after practicing for years, because even if it was muscle memory, the pathways created to do that task haven’t been used in so long that they have to either be reignited, or recreated.

Re the “is it lost forever” part of the question, my dad’s family spoke Polish at home growing up, but in adulthood four of the six kids lost their Polish except for a few isolated phrases. When his brother was dying of Alzheimer’s, he talked to himself in Polish all day long and seemed to have lost his English. So all those years the Polish was still in there somewhere, although he could neither speak nor comprehend it.

The information is there, but it becomes misfiled in a way. The indexing in our brain is not like a hard drive and if we don’t keep accessing the memory, at some point the triggers that lead to that memory get weaker and the memory is ‘lost’ until something causes it to pop back

You ever smell something or hear something and a memory suddenly pops into your head you didn’t really ‘remember’ until that very moment?

Another similar scenario, you walk into a room and forgot why you walked into there? You didn’t forget, but the memory of the reason is inaccessible to you because you lost the ‘index’ to that memory. So you retrace your steps in an effort to find the ‘index’ and when you look at the the cats bowl again, it pops into your head, “I needed to get a bottle of water.”