In the following video, John Brenkus submits to a choke hold (specifically a "rear naked choke") by BJ Penn in order to understand the effects of a choke hold on the human brain:
The effects, according to the video: - Blood flow to the brain is cut by 13% due to the hold - Vision problems are the thing Brenkus notices most. Color vision shuts off, then black and white - By 8 seconds in, his frontal cortex shuts down. - By 9 seconds he is completely unconscious.
It takes about 3 seconds for his brain to come back to life once the choke hold is released and normal blood flow returns to his brain.
What do you do if you get caught in one of these choke holds? You can try this technique to release the attacker:
Choking is obviously useful as a weapon, but some people use choking as part of a relationship. If you search on "erotic choking" or "erotic asphyxiation" you can learn about other uses for oxygen depletion in the human brain. It is thought that David Carradine may have died in this way.