My experience of being sleep deprived is that my memory starts going downhill -- I feel like I have difficulty recalling what happened on days where I was running on little sleep, even after I have had good rest. It's as though those memories weren't properly stored and just disappeared.
I did several days straight without sleep and got mildly delusional. I remember sitting up, thinking about something (can't remember what) and then a minute later realized I was just thinking complete nonsense and got up to work.
