It was with me at the beginning, almost before I was here myself. It will be there at the end, gently easing me closer to the secrets of the universe. It provides escape from daily stress. It makes all my problems disappear, at least for a little while. It helped me grow into what I am today.
It is sleep.
Sleep may seem like nothing—a stretch of blank, empty time. But it works tirelessly behind the scenes to give us what wakefulness cannot. It takes on many guises, molding its shape to meet our needs. We call on it for catnaps during the day for quick revitalization. We allow it to transport us into deep slumber to replenish energy depleted during the day. And as we lie nearly motionless through the night, our guard down, sleep prepares us for tomorrow.
Fade to Black: The Stages of Sleep
There are five stages of sleep, and most of them are repeated during the night. Healthy adults typically go through four to six cycles of these stages before waking in the morning, each lasting around 90 to 110 minutes.
Newborn babies may sleep up to 18 hours a day. Newborn kittens sleep virtually 24 hours a day, and when they grow up they still grab about 16 hours of daily sack time.
Stage 1. Onset: not quite asleep or awake
You know how you sometimes doze off while watching TV? That’s the first stage of sleep. We may go in and out of this phase and not even notice we were unconscious for a moment. Stage 1 is a transition between wakefulness and sleep, lasting five to ten minutes.
Bizarre things can happen during this drowsy phase. I have a habit of falling asleep during the middle third of movies when watching television. Before realizing that I nodded off for a spell, I attempt to fill in the blanks, rationalizing the action onscreen as if I hadn’t missed a minute. Quizzical looks from my wife and daughter as I review the movie afterward make me aware of my inadvertent “intermission.”
Non sequiturs uttered while fading in and out of Stage 1 can be amusing. Once, after falling asleep for a moment on the couch, I said to my wife, “Wrangling with the Holsteins.” (Perhaps I had been dreaming about being a farmer in a barn full of feisty dairy cows.)
Stage 2. Light sleep: not conscious, but easily aroused
About half of our total sleep time is spent in this stage. Body temperature and pulse rates start to drop, blood flow to the brain decreases, and eye movements stop. Each sequence of Stage 2 sleep lasts about 20 minutes.
Stage 3. Deeper sleep
This stage is a transition between light and deep sleep. Very slow delta brain waves begin to appear, and people awakened during this phase tend to be disoriented. Increased blood flow to the muscles and secretion of hormones in Stage 3 help spur cell growth.
Stage 4. Deep sleep
Body repair continues during this phase, which lasts about 30 minutes and is dominated by delta waves. Stage 4 is the most refreshing part of the sleep cycle and the hardest to be awakened from. Most high-level functions of the brain are shut down so more blood can be diverted to the body.
Stage 5. REM sleep
Some people can. It requires being able to block the processing of visual input (this is what happens during hypnosis). Sleepwalkers often have their eyes open as they make their nocturnal rounds.
Here’s where the fun begins. After about 60 to 90 minutes of a sleep cycle, rapid eye movement (REM) sleep takes over. Most dreaming occurs in this stage. While the mind is most active during REM sleep, which lasts about 30 minutes, the body is not. In fact, hormones released during this phase basically paralyze our bodies. It’s a good thing, too—otherwise we might try to act out our dreams!
REM sleep accounts for approximately 20% of our total sleep time. Following this stage, our bodies go back to Stage 1 and proceed through the cycle again.
The Brain’s Changing Tides: Theta, Delta, and REM
Certain types of brain waves are characteristic of each stage of sleep.
- Stages 1 and 5. Theta waves (high-amplitude brain waves associated with deep relaxation)
- Stage 2. Sleep spindles (rapid, short-term brain waves) and K complexes (large waves triggered by stimuli, such as hearing sounds while in bed)
- Stages 3 and 4. Delta waves (deep, slow brain waves associated with deep relaxation as well as healing). High levels of these waves are also seen during meditation.
In Your Dreams!
Exactly what dreams are all about remains subject to debate. Sigmund Freud thought they were expressions of repressed urges and impulses from our unconscious mind, often symbolic because their content would otherwise be too disturbing. Freud also believed that our superego (or conscience) protects us from these disturbing images by making them hard to remember.
Dreams have been considered everything from an escape from the day’s problems to our brain’s attempt to make sense of those problems. Recent research by scientists such as Robert Stickgold, an associate professor at Harvard University Medical School, supports the theory that new connections between our experiences may be formulated as we dream. These formulations may then be stored somewhere in our brain and boost our cognitive functioning, even if we don’t remember the dreams.
Yawning when seeing someone else yawn may be a demonstration of empathy that is rooted in human evolution. “Yawning contagion” doesn’t occur until about age four, when we first start developing social bonds and the ability to empathize with others.
Today’s sophisticated brain scanning is opening up new possibilities in dream analysis. We can now “decode” dreams to determine what types of images they contain, even as the dreamer remains asleep. Since most dreams aren’t remembered, this may greatly expand our dream database and help us recognize common patterns in our nocturnal fantasy lives.
Getting No Sleep Can Be a Death Sentence
Sleep is essential for good health—and it may be essential for life itself. Rats experience a decreased life span—from an average of two to three years down to about five weeks—when deprived of REM sleep. The toll is even greater when they’re not allowed to sleep at all, perhaps because sleep deprivation compromises the immune system.
What’s Your Favorite Part of the Sleep Experience?
For me, the best part of a night’s sleep is the moment right after waking in the morning. That refreshed feeling with a brand-new day waiting for me is like no other.
But right now, I’m feeling a little tired and could go for a catnap. I probably won’t get past Stage 2, but it’s better than nothing.
Related Article
Find Out More
- Amie M. Gordon, “Your Sleep Cycle Revealed,” Psychology Today
- David K. Randall, Dreamland: Adventures in the Strange Science of Sleep (New York: Norton, 2013)
1 Comment
Barbara Botta
Great article. I’ve always been amazed with the whole sleep/ REM thing….how our bodies are preparing us, in silence, for the next day. And dreaming. …don’t get me started on this subject. To this day I have many, many nightly dreams. ..and remember them, too. Freud would have loved to pick my brain. But as far as that great, refreshed feeling one experiences after a great night’s sleep, it’s incomparable. Thanks for this great article, Ed.