Trigg wrote an article for MMA Junkie today on "flash knock outs" You can check out the article from mmajunkie.com :
http://mmajunkie.com/news/4153/frank-trigg-on-flash-knockouts.mma
I have attended a few seminars on concussions, speaking with top Dr's and a few pro football players on the topic I feel that anyone who fights or trains should look into the subject and be familiar with the symptoms of a concussion. As Trigg brought up, flash KO's are serious buisness. Every "flash KO" is considered a concussion in medical terms.
From the Mayo clinic-
Usually caused by a blow to the head, concussions don't always involve a loss of consciousness. In fact, most people who have concussions never black out. Many people have had concussions and not realized it. But every concussion, no matter how mild, injures your brain. This injury needs time and rest to heal properly. Luckily, most concussions are mild and people usually recover fully.
For sure, I definitely have had both, I've been unconscious 3 times, once from a water ski when I hit a sick jump and when I came down the ski whacked me in the back of the head/neck. I woke up face down in the water, couldn't feel my toungue for a week. Before that it was a concrete wall I dove into head first, before that, the ground, I slipped on some ice and hit the back of my head jumping up on a curb in 1st grade on my way home from school.
Getting rocked/dropped by a strike that doesn't ko you definietly doesn't leave you as groggy or make you feel tired like a ko concussion. I probably shouldn't fight, I've had about 40 concussions, pretty much all sports related.
The silliest thing is when people (fighters or ug'ers) act like flash ko's are real finishes or stoppages.