more issues than Time mag
I've experimented recently with overwork.
A few months ago, I decided to test how much sustained (ie. no breaks of greater than 30 seconds), serious thinking I could do: I completed about 3000 grammar problems over two days and then a string of Maths puzzles on the third. Result: a very odd feeling in the top of my head, difficulty in walking upright (ie. I was tending to tilt to one side), nausea when having to process anything even vaguely cerebral for two days afterwards (reading, even watching the telly) and slightly garbled speech. Moral of the story: don't do it again.
A couple of days ago, I tried to test the limits of memorisation on one of those spaced repetition things. 2000 words repped over two days (ie. speeded forced recall). Towards the end of the second round of reps on the second day I was feeling distinctly agitated and it felt like my brain was attempting to escape. Immediately afterwards: the same odd feeling in the top of my head, language incomprehensibilities (slight babbling), bouts of dizziness...BUT, in the evening, improved performance on memory game and more lucid thinking. Also, seem to have memorised about 1400 of the words. Conclusion: no bloody idea.
Totally OT but I notice this exact same thing, and I'm definitely noticing it this weekend (I'm procrastinating like crazy--have 70 stoichiometry calculations to do by Monday, a chem exam on Monday to study for, a chemistry pre-lab assignment due on Wednesday, a 15 page research paper to write by Thursday, a bio lab quiz and written assignment, a bio exam on Friday on Mendelian genetics, mitosis, and meoisis, and miscellaneous other assignments that are going to have to fall by the wayside.)
What I'm finding, and I've always found, is that in situations where I flood my brain with information, I switch back and forth between moments of a feeling sort of like nausea and intense confusion, then moments of clarity when things come together and make sense, then back to the nausea.
At the end of the day here, I have the syndrome you're describing up there. You could call it "overload syndrome". But when things settle down and I go a weekend without having much work, rest a while, I notice a marked improvement in my ability to figure out difficult problems or memorize things or focus intently, etc.