This is your Brain on Sleep – Stages of Sleep


Cycling through the Sleep Stages
Part of the Sleep Series

© by Madelyn Griffith-Haynie, CTP, CMC, A.C.T, MCC, SCAC

“Sleep is not a luxury or an indulgence but a
fundamental biological need, enhancing 
creativity,
productivity, mood, and the ability to interact with others.”

~ Russell G. Foster, a leading expert on chronobiology

zzzzz_in bed_blue 298x232Gettin’ those Zzzz’s

Until the mid-twentieth century, most scientists believed that we were asleep for approximately a third of our lives — experienced, primarily, in a uniform block of time that was the opposite of wakefulness.

THAT was pretty much it.

Their assumption was that sleep was a homogeneous state.  It’s most salient feature was considered to be the fact that you were NOT AWAKE.  Duh!

The main side-effect of sleep deprivation, so it was believed at the time, was that you got sleepyOh my.

  • It was assumed that we needed some sort of down-time to recharge our batteries somehow.
  • There was so little curiosity about sleep, very few scientists felt that it was worthy of the time or money for research.

In the 1950s, the breaking news from one of the few sleep labs was that sleep actually consisted of two distinct states:

  1. Rapid eye movement sleep [REM], which distinguished dreaming sleep, according to what they knew at the time
  2. AND . . . the rest of it!
    (imaginatively referred to as “non-rapid eye movement sleep” [NREM])

You probably already know that REM sleep was so named because it was noticed that the eyes moved quickly back and forth under closed eyelids – rather like they might if the sleeper were speed-reading a teeny-tiny English-language book.

BRAINonSleepLooking More Closely

In rapid succession, with the advances of electro-physiological studies, new findings were announced.

These findings came about thanks to the use of technology known as an electroencephalogram [EEG].

An EEG measures the brain’s electrical activity and translates these measurements into a pictographic representation of what we now refer to as brainwaves.

With the help of measuring technology, NREM sleep revealed itself to be composed of a series of distinct stages of what was then presumed to be un-consciousness: NREM1, NREM2, NREM3 and NREM4.
(No prizes for nomenclature creativity were awarded!)

This four stage division became the standard in 1968, what is called the Rechtschaffen and Kales (R&K) standardization.

And then there were three

Almost forty years later, in 2007, non-REM sleep was reduced to three stages by The American Academy of Sleep Medicine [AASM], combining stages 3 and 4. You will still see both classification systems in internet articles and older books.

My personal belief is that R&K Stage-4 sleep, distinct from R&K Stage-3 and more specific than the AASM Stage-3, will prove to be important in research on sleep disorders — so I prefer to pay attention to non-REM sleep in the original four categories rather than the relatively recently collapsed three.

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