We tend to think of being asleep or awake as an either-or prospect: If you’re not asleep, then you must be awake. But sleep disorder specialist and neurologist Guy Leschziner says it’s not that simple.
“If one looks at the brain during sleep, we now know that actually sleep is not a static state,” Leschziner says. “There are a number of different brain states that occur while we sleep.”
As head of the sleep disorders center at Guy’s Hospital in London, Leschziner has treated patients with a host of nocturnal problems, including insomnia, night terrors, narcolepsy, sleep walking, sleep eating and sexsomnia, a condition in which a person pursues sexual acts while asleep. He writes about his experiences in his book The Nocturnal Brain.