Oh yeah, I have been sleep deprived so much that the things that I said made no sense. I still formulated sentences but they did not have any meaning. In fact, I noticed this myself and I was like "fuck, what I just said made no sense". This happened a few times. It is a pretty interesting experience.
I had the same experience after almost 4+ days going without sleep. A friend came to check up on me after I fell asleep, I woke up and started telling him a whole story that made no sense, but I said it with such importance that for a week he was asking me to explain to him what I meant...which I don't remember exactly, but it was important.
So, sleep deprivation leads to temporary schizophrenia? Who could have foreseen this?
Sleep scientists and drill instructors!
This sometimes happens to me when I get a migraine.
A sentence can be coherent in the formulaic sense, but complete nonsense as far as words. I immediately notice that it's incorrect, but I don't have the ability to fix it at that moment.