I remember some theory, though i don't know how well it has been tested, that how braindead you are during the day depends not on how much sleep you got the night before, but on how much sleep you got the night before that. I got about three hours of sleep saturday night in two chunks and felt mentally fine all sunday. I suppose it's possible that i was sleep depped and not running on all wheels, but i _felt_ fine.
So last night i got about fiveish hours of sleep, and my brain is all fuzzy. Strangely i've gotten more work done this morning than on most days but it's all kind of rote stuff and my head feels like crap.
Of course i suppose one could just as easily argue that i didn't get enough sleep either night, however i had some reserves of sleep that kicked into play on sunday but which are exhausted now.