Dr. Mehmet Oz
People spend thousands of hours asleep over the course of their lifetimes, yet scientists have only begun to scratch the surface when it comes to understanding what goes on when a person sleeps. In his book Sleep: The Mysteries, The Problems, and The Solutions, Dr. Carlos Schenck explores the mechanisms behind sleep as well as the disorders that may arise when sleep is disrupted. Dr. Oz talks with Dr. Schenck, a sleep specialist and psychiatrist, about some of his insights into to the study of sleep.

Sleepwalking is a kind of parasomnia, which is defined as any abnormal events, physical or emotional, that accompany sleep. These may include night terrors, dream-enactment, sexual activity while sleeping or any number of other motor activities or emotions that occur during sleep.

Dr. Schenck says that while there is a genetic basis to most cases of sleepwalking, the precipitating factors can be controlled, such as insufficient sleep, irregular sleep/wake hours and either physical or emotional stress. "You really have to learn about yourself, what makes it more likely for you to have an episode of sleepwalking," he says.

Sleep Deprivation
Dr. Schenck says everyone requires different amounts of sleep, though research suggests that on average, most adults need between seven and eight-and-a-half hours of sleep each night. When you wake up feeling refreshed and ready to go, you'll know you've slept enough, he says.

As for catching up on your zzz's, Dr. Schenck says this may work for some people some of the time. What you don't want to do is deprive yourself of sleep, which can lead to loss of memory and cognitive functioning, increased moodiness and depression, and can adversely affect interpersonal relationships and motor skills.

Strategic Napping
According to Dr. Schenck, research has shown that all human beings have a hardwired minor sleep cycle in the early afternoon, between the hours of 1 and 3 p.m., which many cultures have made use of throughout history. Some studies have even linked naps to health and longevity benefits, he says. In modern times, Dr. Schenck says this natural tendency has been overridden in most industrialized countries.