i remembered having a migraine-like headache (right brain headache) the 1st time I PRed or after a long break. I was then PRing a technical book on biochemistry, which is almost 1200 pages long. it took me about an hour and i did have a headache.
last month, after a break of more than a month, i started PRing again and surely, i got a headache, which disappears soon. the next day i PR again and got a headache again, but less intensely this time. from the third day onwards, everything was fine.
i reckoned that it has something to do with hyperactivation of your brain to process the information. well, i'm not a neurologist or a psychiatrist to accertain this... I'm only a molecular biologist.
