I had a seizure on acid once, only took a total of one hit of paper. the first 1/2 was taken about 3-4 hours before the 2nd 1/2. I was at club arc in nyc (which will be closing shortly), had been going all night just fine (great trip! great visuals! no bad vibes whatsoever!!!) And then out of nowhere i woke up at the bottom of a flight of stairs wiht some security dude sitting next to me, my boyfriend telling me i needed to try and stand up, and my other friends looking on...i had no recollection of what had happened
i was told the story a little bit later: we were all dancing and partying and out of nowhere my friends looked over and i was on the ground having a grand mal seizure....violently shaking, foaming at the mouth, the whole deal. i have NO history of a seizure disorder, this wasn't the first time i had taken acid at a party, and it came completely out of blue!! the only thing i can blame it on are the REALLY intense strobes that arc has. i recently went back for another party and couldnt stay more than 3 hours b/c the strobes were making me dizzy and faint...and i was sober that night.
so yes...brain overload (esp. the sensory overload you have regardless of your surroundings when you drop acid) can cause a seizure. had i not been tripping, the seizure wouldn't ahve happened. but i was, and i seized, and DAMN i was sore for a week.