Quote Originally Posted by Wolfwood View Post
Is this from stimulation of the vagus nerve by tightening the upper chest.. or are you referring to something else and more ridiculous?
I had a goofy classmate try to get me to do this back in '91 in Physics class. From what I remember, he wanted me to hyperventilate by breathing in through the nose and out through the mouth for several minutes. Then I was to take a deep breath, lean forward, and clamp off the blood flow in my Carotid arteries in my neck (although at the time he wasn't medically knowledgeable to know what they were called) by placing the palms of my wrists on both sides of my Adam's apple, and wrap my fingers around towards my spinal column. I squeezed my neck... and the room very quickly (and frighteningly) faded out white.

I let go, and I regained sight of my physics teacher and my classmates (much to my relief).