Night of the Living Dread

Nevermind the childhood assurance that there's nothing in the dark that isn't there in the light. Nighttime scares people.

That's the psychological essence of anxiety-induced insomnia. Once the brain is freed from the preoccupations of waking life, concerns and fears that have been laying dormant come out to play.

This is your brain on fear

For all of its remarkable capabilities, the brain is not so good at distinguishing true threats from irrational fears. Granted, a threat does not have to be physical to be real; we can suffer under fear of embarrassment, fear of failure, or fear of confrontation. Fear of going broke certainly keeps a lot of people tossing and turning.

But because all types of fear—physical or emotional, real or imagined—are processed by the same part of the brain, the body responds to them without much distinction. When stressed about a school exam or a speaking engagement, our breathing gets shallow, the heart speeds up, adrenaline surges and palms get sweaty. These symptoms all bear the marks of going into physical battle, even though the threat faced is strictly emotional.

Though we commonly regard fear as something to conquer, it exists to protect us. Evolution taught the human animal to be afraid of snakes, sharks and bears, and it's in the most animalistic part of the brain—called the primitive brain—that we manage this emotion. Specifically, the limbic system within the primitive brain controls our instinctive survival functions just as it does in all types of mammals (which is why the limbic system is sometimes called the "mammalian brain").

The primitive brain doesn't think, it reacts. Rational thought takes place elsewhere in the brain. So, when we freak out from something that's scary but not immediately threatening—whether it's an infuriated boss or the movie Saw—the unilateral fear response overrides the rational recognition that there's no physical threat. Fear is fear. While the thinking brain says, I know Jigsaw can't reach out of the film to get me, the limbic system says, I won't be going to the bathroom by myself for a while.

When nightmares are acted out

Sleep and fear are renowned bedfellows, and insomnia is just one of the disorders that entangles the two. REM Sleep Behavior Disorder (RBD) has garnered attention from researchers due not only to its dramatic symptoms but because it may provide clues for treating dementia.

It must be haunting and surreal for a patient with RBD to review videotapes of his or her own sleep. While deep in a cycle of REM sleep, they are seen acting out the physical movements of a frightening dream. The motions are not simply aimless thrashes or momentary starts; rather, all of the complex, violent actions of a nightmare are mirrored in the real world—even though the patient remains in a deep sleep. It's a dangerous scene for the person with RBD and for anyone sharing the same bed.

REM is understood to be the phase of sleep with the greatest potential for nightmare imagery, and RBD patients seem to have more than four times the normal frequency of terrifying dreams. Whereas a healthy sleeper will experience motor atonia, or sleep paralysis, during the REM phase, the RBD sleeper doesn't benefit from the same temporary shutdown of brain-to-body connectivity. When researchers observe an RBD episode at a sleep clinic, it's like watching a dream plot unfold.

There haven't been many studies yet on RBD's relationship to neurodegenerative conditions, but some evidence suggests that the sleep disorder may result from degeneration in certain areas of the brain, which is a hallmark of dementia. Further study may yield a better understanding of conditions like Parkinson's Disease.

RBD represents an open pathway between nightmare fears and real life, which sounds as chilling as a supernatural horror film. But what RBD patients experience on those dark nights may shine some light on a disturbing dementia that haunts the waking hours.

More Brain & Body Columns:

• Sleepless Creativity
• The Mysteries of Synesthesia
• His Brain, Her Brain

Search for all Brain & Body columns

Rich Maloof's award-winning writing has covered subjects ranging from soda pop to stem cells. He has written for MSN, CNN, MSNBC, Yahoo!, Women’s Health, and various other publications. He is the published author of 12 books to date, including several instructional titles for musicians. His latest title, This Will Kill You, is being released by St. Martin's Press in May. Rich is a regular contributor to Brain & Body.