"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 sexually 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."
"If it happens during REM sleep [the stage characterized by rapid eye movements], it could be associated with dreaming," said Dr. Mark Dyken, professor of neurology at the University of Iowa College of Medicine.
Sleep talking can be caused by stress, certain medications and certain mental illnesses. Experts estimate about half of all children between the ages of 3 and 10 talk in their sleep, and about 5 percent of adults do it.
If talk becomes violent, that's a characteristic of a more serious disorder known as REM behavior disorder.
"There will be screaming, yelling, punching and other outbusts, such as flying out of bed or lunging at something," said Walsleben.
REM behavior disorder is most common among older men. It's caused by a deterioration in the brain, Walsleben said.
There are often stories of people who wake up with crumbs in their bed but have no idea how they got there, or people who walk into their kitchen in the morning and find it inexplicably in complete disarray. People may also find that they've eaten bizarre things, like cigarette butts or flour.
Sleep experts believe there are a number of factors that contribute to sleep eating.
"If you go to bed hungry, your stomach is going to win," said Emsellem.
Certain medications can also precipitate sleep eating.
"Ambien is known to increase the risk of nocturnal eating," said Emsellem. She also said selective serotonin reuptake inhibitors -- antidepressants similar to Prozac -- can also lead to sleep eating episodes.
Stress can also play a role, especially if someone is dieting and focused heavily on food during waking hours.
Dyken also suggested the roots of sleep eating are planted during infancy and childhood.
"Parents sometimes feed kids late at night, and they wake up becasue their rhythms are off and have adpated to being hungry at night. It's induced by parents who have been negatively conditioned by a hungry child," said Dyken. "This has developed into a patient wandering around and going to the kitchen."
Sleep deprivation and improper use of sleep medication are two causes experts believe contribute to the phenomenon of texting while asleep.