What Is Sleep?

Every night we as humans follow a curious ritual.  As the daylight turns to darkness, a sensitive biological clock alerts the brain to send a chemical response throughout our body…

We change into comfortable clothing, perhaps open up a good book to read or watch a little TV  to wind down the day.  We recount the days events, as we make our way into our beds, cozy up under our sheets and comforters, and let our eyes slowly close…our minds wandering, imagining, thinking….drifting…

Our body becomes motionless, and our eyes roll from side to side.  As the minutes fly by, eventually our eyes begin dancing and darting, rapidly moving as witnesses to mysterious and strange things called dreams.  Our minds enter a highly active state — just as active as the waking hours actually — and we travel to strange and amazing places, exploring the deepest parts of our minds that aren’t normally as accessible to us during the day.

It’s almost as if our mind travels through some sort of portal, a wormhole to a strange dimension so to speak, curiously similar to our daily life as we know it, yet still very different.  The funny thing is, when we’re dreaming, we don’t know we’re dreaming…

To us, in that moment, what we are experiencing is real

Hours later, the sun rises and our brains excrete another chemical, and it’s as if we travel back through the portal, back into “reality,” our eyes open and we’re awake again…

The kicker is when we wake up we usually don’t remember a thing.

So what just exactly is sleep?

It’s a complicated question as it turns out.  Utterly beguiling to humans for thousands of years, sleep is far more than the state of merely not being “awake.”

The state of sleep, and particularly dreams, have long played an important role for ancient people.

Many cultures believed that sleep is a “little death,” and that death is a “long” sleep.  And some even go so far as to say that the soul leaves the body during the night and returns to the body when we wake up.  Many cultures to this day consider the dream world to be every bit as real and important as the waking world.  Other cultures believe that dreams provide guidance for daily life, and that the dreamer has to act out the dream upon awakening to remain safe and healthy.

The ancient Greeks believed that Hypnos was the god of sleep, and Thanatos was the god of death, and the two gods were believe to be the twin offspring of the night.  Often they were depicted as young babies, each one suckling on a breast of Mother Night.

image of hypnos god of sleep

“Hypnos – God of Sleep”

In the fifth century B.C. Alcmaeon hypothesized that sleep was caused by blood filling the brain vessels, and people woke when the blood left their brain.  Plato and Aristotle believed that “vapors” from food decomposing in the stomach rose to the brain to cause sleep.  In fact, even in the 18th century, the most popular theory was that blood flowed to the head and put pressure on the brain, causing sleep, much like Alcmaeon believed over 2000 years earlier.

Thanks to sleep research and specialized machines, we now have a much clearer definition of sleep.

What we know is that sleep is essential for our health, and we know that the state of sleep is unique in that it creates a perceptual wall between the conscious mind and the outside world.  Another defining feature of sleep is that it is immediately reversible.  Even when someone is deeply asleep, intense and persistent stimulation will always awaken the sleeper.  If not, the person is not asleep, but unconscious or dead.

Sleep occurs naturally, and is also characterized by electrical changes in the brain, which scientists can measure using machines called electroencephalographs, or EEG’s.  These machines can detect brain waves, and they measure and plot them much like how a polygraph is used as a lie detector.

Advances in science have moved us beyond the theories of the past, and we can now detect the inner workings of the sleeping brain.  Scientists have discovered a pattern of brainwaves that are repeatable and predictable, and have divided them up into different stages of sleep.

There are 5 stages of sleep during the night, known as stage 1, stage 2, stage 3, and stage 4 sleep, and another distinct stage called REM (Rapid Eye Movement) which does not take place during any of the other stages.

I’ll talk a bit more about the stages of sleep in another post…until then, sleep well!

– Sean

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