Smoothing the Rugged Brow of Night

Although we spend, on average, one third of our lives sleeping, very few people understand how this dream-enchanted state works. Contrary to the public’s prevalent opinion, sleep researchers—scientists devoted to figuring out the why, when, what, and how’s of sleep—believe that sleep is much more than the brain’s strategy of shutting down to rest when it becomes too tired to function.

The first step in figuring out how sleep works is defining what sleep is. According to Dr. David Bliwise, an Emory University sleep scientist, there are three ways to determine whether a person is asleep: self-reporting (asking the person, “Where you sleeping?”), behavioral observation (asking an observer, “Was the person sleeping?”), and physiological criteria (using machine measurements to answer, “Is this person asleep?”).

Many clues to the puzzle of sleep’s inner-workings lie in the physiological criteria used to record sleep. Three main measures are used: brain waves (abbreviated as EEG), eye movements (also known as EOG), and muscle tension (often labeled as EMG).

Together, these three measurements are used to determine human being’s distinct stages of consciousness and unconsciousness—awake, sleep stages 1 through 4, and rapid eye movement (also known as active sleep, in which we most often dream). Throughout an average evening, we spend about two to five percent of the night in the initial, just-fallen-asleep stage, also known as Stage 1 sleep. Stage 1 slowly segues into Stage 2, where we spend about 45-55% of our resting hours. The body then enters “slow wave” sleep stages (Stage 3 and 4). The third and fourth stages are named for the approximately 13-23% of the time we sleep when our brain activity dramatically decreases. After drifting through these stages, the body returns to Stage 2 in preparation for the final Stage 5, or REM Sleep. The body stays in this final stage, in which the brain switches from Stage 2 to Stage 5, for 20-25% of an average night’s sleep.

Title is adapted from John Milton’s Penseroso (1880: 1608-1676.


	click here for author biography Although we spend, on average, one third of our lives sleeping, very few people understand how this dream-enchanted state works. Contrary to the public’s prevalent opinion, sleep researchers—scientists devoted to figuring out the why, when, what, and how’s of sleep—believe that sleep is much more than the brain’s strategy of shutting down to rest when it becomes too tired to function. The first step in figuring out how sleep works is defining what sleep is. According to Dr. David Bliwise, an Emory University sleep scientist, there are three ways to determine whether a person is asleep: self-reporting (asking the person, “Where you sleeping?”), behavioral observation (asking an observer, “Was the person sleeping?”), and physiological criteria (using machine measurements to answer, “Is this person asleep?”). Many clues to the puzzle of sleep’s inner-workings lie in the physiological criteria used to record sleep. Three main measures are used: brain waves (abbreviated as EEG), eye movements (also known as EOG), and muscle tension (often labeled as EMG). Together, these three measurements are used to determine human being’s distinct stages of consciousness and unconsciousness—awake, sleep stages 1 through 4, and rapid eye movement (also known as active sleep, in which we most often dream). Throughout an average evening, we spend about two to five percent of the night in the initial, just-fallen-asleep stage, also known as Stage 1 sleep. Stage 1 slowly segues into Stage 2, where we spend about 45-55% of our resting hours. The body then enters “slow wave” sleep stages (Stage 3 and 4). The third and fourth stages are named for the approximately 13-23% of the time we sleep when our brain activity dramatically decreases. After drifting through these stages, the body returns to Stage 2 in preparation for the final Stage 5, or REM Sleep. The body stays in this final stage, in which the brain switches from Stage 2 to Stage 5, for 20-25% of an average night’s sleep. Title is adapted from John Milton’s Penseroso (1880: 1608-1676.