Brain Waves
Your brain produces electrical impulses all the time. These currents of electricity determine your state of consciousness and we refer to them as brain waves. For the purpose of this book, there is no reason to get very technical about this – a basic understanding will suffice. What you need to know is the fact that your brain emits waves of varying speed and that these brain waves are a measure of brain activity. High, intense, or fast brain waves mean high brain activity, whereas slow brain waves denote low activity. In other words, it is when your brain waves are fast, you feel most alert and energized. As brain wave speed decreases, you will feel less alert. When you are in deep sleep, your brain waves are at their lowest.
Why are Brain Waves Relevant?
Because your brain waves can be manipulated, and chances are that you are interfering with your brain waves every single day. Lifestyles choices such as what you drink during the day or even the way you think influence brain waves. We’ll examine the specific factors that interfere with brain waves in later parts of this book.
The 5 Stages of Sleep
During sleep, your brain waves cycle through five stages of sleep
Stage 1—Drowsiness also Known as Twilight Stage
This is a light sleep, when you drift in and out of sleep and can be easily awakened. Your eyes roll very slowly, muscle activity slows and relaxes, you breathe deeply and slowly, and you may move your limbs for five to 10 minutes. People awakened from Stage 1 sleep often remember fragmented visual images – like daydreaming.
Stage 2—Light Sleep
Now your eye movements stop and brain waves become slower, with occasional bursts of rapid waves called sleep spindles. Your heart rate slows and body temperature decreases.
These first two stages of sleep are of a relatively light quality, called transitional periods.
Stages 3 and 4—Deep Sleep
Almost all your muscles are paralyzed. Your body rejuvenates itself by healing damaged tissue. Blood that is stored in your organs during the day flow to the muscles to replenish them. Your brain predominantly emits delta waves that have low frequency and high amplitude (slow brain waves). You feel well rested after experiencing delta sleep, and it’s very difficult to awaken you during this period. There is no eye movement or muscle activity, and if you are awakened during deep sleep, you do not adjust immediately and often feel groggy and disoriented for several minutes after you wake up. It is very difficult to awaken from deep sleep because you are cut off from the external world. The brain and body are shut down.
Stage 5—REM Sleep, also Known as Paradoxical Sleep
When we switch into REM sleep, our breathing becomes more rapid, irregular, and shallow; our eyes jerk rapidly in various directions; and our limb muscles become temporarily paralyzed. Our heart rate increases, blood pressure rises, and males develop penile erections. When people awaken during REM sleep, they often describe bizarre and illogical tales—dreams. Scientists still don’t quite understand why we dream, but people kept from dreaming develop behavioral and mental problems, so REM sleep is clearly a critical behavior.
Understanding Your Sleep Cycles
It is important to realize that these five stages don’t just occur once per night. Throughout the night, you progress through the five stages like this: 1,2,3,4,3,2,REM,2,3,4,3,2,REM,2,3,2,REM,2,3,2,REM,2,REM,1
Okay, now we know that each cycle occurs several times throughout a normal night. As you may already have figured out, there’s more to it than that. Let me explain: The first sleep cycles each night contain relatively short REM periods and long periods of deep sleep. As the night progresses, REM sleep periods increase in length while deep sleep decreases.
By morning, most sleepers spend almost all of their time in Stages 1, 2 and REM sleep with very little or no deep sleep (Stages 3 and 4). To summarize, while we are asleep, our brains are on a bit of a “roller-coaster” through different stages of sleep. As we drift off to sleep, we first enter Stage 1 sleep. After a few minutes, the EEG changes to Stage 2 sleep, and then Stage 3 sleep, and finally Stage 4 sleep. Then it’s back up again: Stage 3, Stage 2, then a period of REM sleep… then it’s back down again, back up again, and down again! As shown in the figure above, in an 8 hour period of sleep, the brain cycles through these stages about four to five times. During the early part of sleep, deep-sleep periods sometimes last up to one hour, and, REM periods only last a few minutes.
However, as the night progresses and you sleep, your deep sleep periods become much shorter and REM periods grow longer – up to one hour. Think of it this way: during the first half of the night, you obtain most of your deep sleep. You receive most of your dream and light sleep in the second half of the night.
July 9th, 2007 at 12:19 pm
[…] missing core sleep), your sleep will be more restorative because you will more easily enter the deep sleep stage(s). It is a scientifically proven fact that the more prior wakefulness, the more quality […]