TarkanX
Although we are the smartest living species in the world, our brain has some flaws, memory for example. Usually when we remember something, that memory depends on how motivated we are to remember it. If we don't care about that memory, then we'll forget it, and the statements of "Memory always stays in the brain, it's all just dormant" is false. Once that memory has been used and you don't have any purpose of remembering that memory, it fades away.