By day, Mike Doyle is a mild-mannered bank executive who lives with his wife in a suburb of Minneapolis.
By night, he wanders the house in a deep slumber, acting out his strangest and wildest dreams.
"I ran down the hallway and jumped from the top step and landed somewhere near the bottom," Doyle said. "I got up and went back to bed and the following morning I didn't realize what I had done, until I sat down on the wooden chair in the kitchen. And I thought I was gonna die because of how bad it hurt to sit."
Doyle is among millions of Americans -- as many as 4 percent -- who suffer from parasomnias: unpleasant and unwanted behaviors during deep sleep.
"What happens with parasomnias is that the brain tells the body to move, to walk, to have sex, to eat, to become aggressive, to become violent," explained Dr. Carlos Schenck, a sleep disorder specialist and the author of "Sleep: The Mysteries, The Problems, and the Solutions." "It's the brain that directs the muscles in the rest of the body to engage in these activities." (For more information on sleep disorders and on Dr. Schecnk's new book on parasomnias, visit http://www.parasomnias-rbd.com).
Schenck has catalogued a range of parasomnias in the documentary "Sleep Runners," including those who eat in their sleep.
"A woman with sleep eating, every time she eats a bit of her brownie, she extends the pinky of her hand and nibbles on it and that's no way that she would ever do that in the daytime," said Schenck. "The sleep-eaters generally have partial awareness of what they're doing, but they don't know the full extent until the next morning when with horror they see all that they consume and also they are really very disgusted with how they ate, such as spaghetti and meatballs with their bare hands or they make a tuna fish sandwich loaded with salt and pepper or they'll even make a cat food sandwich."
A cat food sandwich? It turns out that's the least of it.
"They butter cigarettes. They put coffee grounds, Coca-Cola, egg shells in a blender and they blend it all together and drink it," he said. "It's bizarre."
Sometimes the behavior can be quite violent.
"You'll see a Japanese man acting out a Samurai warrior dream," said Schenck.
Another man in the documentary is seen suffering from a sleep terror, and responds by punching his pillow and growling.
"I think it's the fight or flight response that suddenly out of deepest sleep you encounter a major threat and you have to respond by either running away or fighting against the threat," said Schenck.
The parasomnias are considered a brain dysfunction, not a mental illness. Schenck said that "most parasomnias can be diagnosed and effectively treated, and most parasomnias are not a function of a daytime psychiatric disorder."
Some people with the condition are reluctant to seek treatment because they fear the stigma, he added.
The more violent episodes -- occurring during the dream stage of sleep known as rapid eye movement or REM -- can be a precursor to brain diseases including Parkinson's.