Even though I haven't eaten it for over 10 years, I remember the smell and taste of chestnuts vividly so that I can detect it without seeing it visually if I chew it between my teeth. A clear and sharp distinction.

On the other hand, I realize that I forgot almost any notion of mathematics, whereas during my studies, I deeply studied mathematics (algebra, algorithm, probability, statistics, differential calculus, geometry, matrices, sets, etc…).

How come !!! Have I lost my memory of my studies 22 years ago ?!
Why haven't I lost my memory about the chestnut ?!
So there is a difference.

In fact the resolution of a differential equation for example is not a memory object only, but it’s a whole set of reflexes, methodologies, routes, approaches, logics and rules that our brain put in place together in cohesion and certain order to achieve the result.

So we lose a kind of aptitude cognitive memory, a chain of tic-tac between our neurons.

The big question is how we can easily find these habits without moving the wheel from the beginning ???