Ellen Vincenti went through a two-and-a-half day stretch she wil never forget. She spent that time stuck in a remote swamp in the woods about 15 miles from her home in Tuftonboro, New Hampshire.
"I managed to get up on a tiny piece of land, but the water was waist-deep around me," said Vincenti.
What was worse was the fact that she has no idea how she got there.
"Saturday night, I kissed my husband goodnight. I took the new medication I was on and said I was going to read until I'm tired. The next thing I knew, it was 5:30 Sunday morning and I was in my car in the middle of the woods," said Vincenti.
Vincenti said she was disoriented at that point, and walked in the direction of the traffic she heard. After that, she said she found herself waist-deep in water.
"I spent Sunday screaming for help, but no help came," she said. She kept on screaming, and help finally came on Tuesday after a woman living nearby heard her.
Vincenti was shaken by the incident but otherwise uninjured. She said her doctor told her the medication she was taking, which she did not want to disclose, was the likely trigger of her nighttime excursion. She also said she has a history of sleepwalking and sleep talking.
Sleepwalking is perhaps the most well-known form of parasomnia -- a disorder that interrupts sleep and often involves disruptive behaviors -- but experts say there are others that can either be very milid or cause severe disturbances. The next few pages feature a closer look at some of these disorders.
The fact that Vincenti somehow got in her car and ended up getting stuck in the woods is uncharacteristic of most sleepwalkers, though experts say it can happen.
"An extreme case is the individual who actually gets out of the house," said Dr. Helene Emsellem, director of the Center for Sleep and Wake Disorders in Chevy Chase, Md.
"In general, the furthest they go is the next room," said Joyce Walsleben, associate professor of medicine at the NYU School of Medicine.
Experts say a number of factors can contribute to sleepwalking, including certain medications, stress and sleep deprivation. It's most common in children between the ages of 8 and 12, and they outgrow it by their early teens.
"It typically happens coming out of deep sleep, so sleepwalkers are half in and half out of arousal," said Walsleben.
People who sleepwalk don't remember what they did during an episode. While most don't involve any serious or life-threatening incidents, there have been a number of high-profile cases of crimes that were committed by people who said they were sleepwalking.
One recent case concluded this past August. A Bloomington, Ill. man was acquitted of sexual assaulting a woman after a party. He said he was sleepwalking and had no memory of the incident.
A London man became an Internet celebrity after his wife posted videos of him talking in his sleep on a blog.
Adam Lennard blurted out things like, "Elephants in thongs are not something you see every day. Enjoy it," and "Vampire penguins. Zombie guinea pigs. We're done for. Done for."
Outbursts like these are characteristic of sleep talking. They can be funny and sometimes graphic.
"You'll wake up for a second and say something," said Walsleben. "It tends to happen in the earlier part of the night when you're going from deep sleep into lighter sleep."