In a Roundabout Way

How Do We Fall Asleep?

Falling asleep is a routine yet mystifying process. Like trying to see the 3D image in a Magic Eye poster, the more you focus on it, the less likely it is to happen. It shies away from scrutiny and is best approached with an air of detached disinterest; so, though most of us fall asleep every night, we can’t say exactly howwe do it.

Even neuroscientists are still struggling to understand the mechanisms the brain uses to switch from a state of wakefulness to unconscious sleep, but research reveals that the transition is a lot more gradual and tumultuous than the flip of a light switch.

According to recent work by neuroscientists at Washington University in St. Louis, during the pre-sleep stage of the process — the period when you’re in bed with the lights off and your eyes closed, slowly “letting go” of the trials of the tribulations of the day — your brain waves exhibit what’s known as alpha activity, typically associated with quiet wakefulness.

“It is in this period that the brain progressively disengages from the external world,” Linda Larson-Prior and her colleagues wrote in a 2011 paper. “Subjects slowly oscillate between attending to external and internal thoughts, with the majority of internal thoughts being autobiographical or self-referential in nature.”

Then, at some crucial moment, you enter the transitional sleep stage, known as stage 1. Brain waves slow down, shifting to a form known as theta-band activity, but are still punctuated by brief bursts of alpha activity. These hiccups give you the sense that you’re still awake, said Scott Campbell, director of the Laboratory of Human Chronobiology at Weill Cornell Medical College, citing a landmark sleep study performed in the 1960s. “Investigators asked subjects aroused out of various stages of sleep whether they considered themselves asleep. Only about 10 percent of those aroused from stage 1 said that they had been asleep.” [Continue Reading]