Understanding Sleep Paralysis

In your dreams, you’re the star of your own movie—and your subconscious often has you performing stunts that would put Tom Cruise to shame. But even if you’re swinging around the top of the Burj Khalifa in your dream, you stay put in real life. This is thanks to a little thing called sleep paralysis, which keeps you locked in place while you slumber so you don’t hurt yourself. Until recently, scientists understood little about how sleep paralysis works; figuring it out could shed light on disorders such as narcolepsy and REM sleep disorder, and researchers at the University of Toronto might be close to understanding how the phenomenon occurs.

For healthy people, sleep paralysis occurs during REM (Rapid Eye Movement) sleep, and they are blissfully unaware that it’s even happening. But for some narcoleptics, falling asleep or waking up makes sleep paralysis kick in, creating a terrifying state where the mind is awake, but the body cannot move. The paralysis can last several seconds or even minutes, with rare cases lasting for hours.

To get a better understanding of what causes sleep paralysis in REM, Patricia Brooks and John Peever at the University of Toronto monitored the electrical activity in rats’ facial muscles, triggered by trigeminal motor neurons sending messages to the brain (basically, they looked at what causes sleeping rats to chew while asleep). In an effort to stop sleep paralysis, they blocked the neurotransmitters they thought were responsible for the phenomenon—ionotropic GABAA/glycine receptors—but sleep paralysis still occurred. Next, Peever and Brooks tried blocking the GABAA/glycine ionotropic receptors and the metabotropic GABAB—which did, in fact, stop sleep paralysis, meaning that both gamma-aminobutyric acid (GABA) and glycine must be present and working together to cause sleep paralysis.

“Understanding the precise mechanism behind these chemicals’ role in REM sleep disorder is particularly important because about 80 percent of people who have it eventually develop a neurodegenerative disease, such as Parkinson’s disease,” Peever says. “REM sleep behavior disorder could be an early marker of these diseases, and curing it may help prevent or even stop their development.”