One thing all AD, PD and LBD folks share as the dementia worsens is an alteration or modification of not just how we perceive the world around us but how we recall memories as well. In my case, I am lucky the changes in perception have been thus far limited to auditory, taste and smell-based phantoms. I have seen no aliens so far.
That is not to say all is great because one thing that is ham-stringing any attempt at normalcy is the fact that of late I have been plagued with phantom short-term or working memories. I can recall events and things I did yesterday in incredible detail that never happened.
In my parents' day, this would have just been shuffled off to anything from old-age to lunacy on the part of the patient. And the patient would have few ways to know if what he or she is recalling is real or not. Not so today; today almost everything we do (or don't do) leaves a digital trail or fingerprint. So when I have these detailed memories, first thing I do is check to see if they really happened. More and more, they simply have not.
When that happens enough, it makes my already shaky hold on reality a little more tenuous but it also makes planning to do anything more complex than taking out the trash hopelessly impossible. Not keeping details in your head is one thing but not being able to trust any of them, you get caught up in a lather-rinse-repeat cycle of needing to re-confirm everything you have done so you have some clue what it is that you need to do next.
And lately, if this gets too chaotic, if it seems too hopeless to try and sort out the details of what you are trying to do, I give up. Do something simpler, something that can be started and completed in a single session. I am accustomed to doing bigger things so this is a bitter but necessary bit of medicine.
This really has the effect of even further detaching you from the reality shared by the rest of the planet. It is a one-way ticket and you can't change the seating; all you can do is buckle up and enjoy the ride.