The brain thing is called a perception error in my circles (not sure if there is a "correct" term). We actually do it all the time. By the time you finish this sentence your brain will have perceived a completely different syntax. This is because our subconscious (especially in the frontal lobe) perceives more information than our working memory can store. Thus, everything is shortened to save room and we "forget" all the specific details. Because we forgot these details before we recorded them into the working memory, they essential don't exist. And this is why people can swear to an altered event. In their minds, it IS reality. And don't even get me started on the perception of reality itself; just thinking about it makes my head spin. Anyway, you learn something new every day.