When Sleep Problems Become Legal Problems, Neuroscience Can Help

"I always thought about . . . the possibility . . . like, what if I would have hurt my wife or one of my kids or something. I wouldn't be able to live with that," says Voegtli, now 63. "That's why I never had a gun in the house." In 1989, Schenck diagnosed Voegtli with sleepwalking and sleep terrors—frightened, hyperaroused behavior during sleep—and prescribed a nightly dose of an antipanic drug called clonazepam (Klonopin), which has cured his long-standing sleep problem.

Sometimes parasomnias do lead to something darker. A young Canadian man, Kenneth Parks, was acquitted for the 1987 murder of his mother-in-law using the "sleepwalking defense." He arose from sleep one night, drove 14 miles to the house of his in-laws—with whom he was said to be close—and strangled his father-in-law until the man passed out. He bludgeoned his mother-in-law with a tire iron and stabbed them both with a kitchen knife. The woman died; the man barely survived. Parks then arrived at a police station, reportedly confused over what had transpired. Police noted something odd: He appeared oblivious to the fact that he'd severed the tendons in both hands during the attack. That analgesia, along with other factors, including a strong family history of parasomnias, led experts to testify that Parks had been sleepwalking during the attack. Not conscious, not responsible, not guilty.

What explains such parasomnias? In the '70s, it was believed that all complex behaviors arising from sleep were some form of sleepwalking and that in adults, they were all indicative of serious underlying psychiatric disease. Not so, found Mahowald and Schenck; psychiatrically healthy adults could indeed do strange things at night. "Sleep is not a whole-brain phenomenon," says Mahowald. Neurophysiologic studies of sleepwalkers, for example, have shown that during sleepwalking episodes, brain-wave patterns indicate a state of neither full sleep nor full wakefulness: Part of the brain can be awake while the other part is asleep. In sleepwalkers, the part that's shut down governs judgment, says Schenck. "Their eyes are open, they can negotiate the environment; they can see their car keys, grab them, then go drive an automobile," he says. "The problem is, they don't consider the consequences."

They also don't feel pain. That explains how people can go on barefoot forays in the snow without awakening, even as their skin blackens and blisters from frostbite. "If the part [of the brain] that's awake can generate complex motor behaviors, yet the part that's asleep is the part that's normally laying down memories, monitoring what we're doing, then you have a situation where you can have extraordinarily complex behaviors without conscious awareness," says Mahowald. Like murder.

And the more closely the doctors examined these complex nighttime behaviors, the more they saw they weren't all forms of sleepwalking. There's REM sleep behavior disorder (RBD), for instance, which affects mostly men, age 50 and up. Unlike sleepwalking, RBD occurs during rapid-eye-movement sleep, the stage where most dreaming takes place. It's also the stage in which people should be paralyzed, a protective mechanism to guard against dream enactment.

The doctors noticed, however, that some people could leave the paralysis of REM sleep and become free to act out their dreams: dreams of running on a football field, then colliding with reality, into a dresser; dreams of diving through a window, then soaring headfirst into a wall. By following a group of their RBD patients, the doctors made a remarkable discovery. More than 75 percent of them went on to develop Parkinson's or Lewy body disease, which causes dementia. They now consider RBD an early harbinger of neurodegenerative disorders. (In other patients, RBD seems to be associated with antidepressant use, Mahowald says.)