I was recently reading about a phenomenon called terminal lucidity, where a person suffering from mental decline such as Alzheimer's spontaneously improves, recognizing loved ones, retrieving memories, and being able to carry on conversations. It's called "terminal" because the person usually dies within hours or days. If this is a real phenomenon, then it's amazing to think that at least some of the people who suffe…
It isn't a monotonic decline with memories disappearing forever. It is like wave upon wave of changing capacity at different time scales. The general trend is deterioration, but there are frequent periods that can almost seem like remission.
There is a well known daily cycle referred to as "sundowning", where the sufferer tends to come unraveled later in the day. The next morning, they'll be more functional.
Later in the progression, you can see much higher frequency variations. Like periods of disorientation and confusion interspersed with periods of lucidity all within a single sitting or conversation.
In those periods of greater lucidity, recall of the past can be more accurate. General listening comprehension, speaking, and logical thought also seem more normal.
Edit to add: I sometimes wonder if the belief in terminal lucidity is one of those logical fallacies which support lots of superstitions. Are we just fixating on the final wave in this chaotic wave train, and forgetting all the other waves that happened before it? Or is it that more caretakers are engaged and observing these waves towards the end, e.g. because the patient is known to be in the terminal phase..?