With the development of electricity, our environments went from 12 hour days of light, reliant primarily on sunlight, to 24 hours of available light in our indoor spaces. This has increased further with the development of the internet and our use of computers, television, smart phones, etc. The industrial revolution also has given us shift work that disturbs our sleep. We all know how important a good nights sleep is but what exactly is sleep and why is it so important for optimal function?
Stages of Sleep
Stage One – The lightest stage of sleep. Eye movements will be slow. This is the drowsy stage where you can easily be disrupted. Muscle tone and brain activity begins to slow from the awake stage. In this stage, people can experience the sensation of falling or hypo-tonic muscle jerks.
Stage Two – In this stage, awaking does not occur as easily. Slow eye movements stop and brain activity slows further with bursts of rapid activity. The rapid activity bursts are thought to protect the brain from awakening. In this stage body temperature decreases and heart rate slows.
Stage Three – This is deep non REM sleep, known as “dead to the world” sleep. This consists of slow brain waves called delta waves. This is the restorative stage of sleep where the body heals both physically and psychologically. In this stage waking up is rare. Sleepwalking, sleep talking, and night terrors occurs in this sleep stage. During this sleep, stage the body release growth hormone to help repair the stresses of the day.
Rapid Eye Movement Sleep – This is the dreaming stage of sleep. The brain activity is increased when compared to that of stage two and three. Awakening can occur more easily in this stage. Waking up in this stage leaves you feeling sleepy and groggy. During this stage heart rate and blood pressure increase. Body temperature become harder to regulate. This is when vivid dreams occur. If woken during this stage you are able to recall dreams easier. Muscle paralysis occurs in this stage to prevent the body from acting out dreams and injuring ones self.
Sleep begins in stage one and then cycles into stage two then three and back through two then one, followed by REM sleep. This cycle can take 90 to 120 minutes to progress through. Adults will have about five cycles through the night. In earlier cycles stage three, deep sleep takes more time in the cycle. Later in the sleep cycles (earlier morning) stage two and REM dominate.
Sleep and Optimal Learning
Many studies have revealed a relationship between memory, learning and REM sleep. When learning procedural memory tasks such as math, sleep can have an impact on how you retain that learning. When you learn new complex procedural memory tasks, the night after you learn, there will be an increase in brain activity during REM sleep. This also occurs in the third and fourth night after learning but not in the second night of sleep. Interrupting REM sleep in the first, third and fourth night can therefore have an impact on one’s ability to recall and perform new learned tasks.
When learning new physical skills such as, how to tie your shoe, skate, ski, any sport, or musical instrument, stage two sleep is most important for learning. Stage two sleep is concentrated in the latter half of sleeping, so early morning. When learning new athletic skills waking up too early in the morning can have a negative impact on retention of new skills.
Causes of REM Sleep Disturbance
Now we know how important sleep is for the brain to learn, here are some main causes of REM sleep disturbance:
Booze is a substance known to directly disrupt REM sleep. It affect learning new information and alcohol consumption can interfere with retention of information. Studies show that students consuming alcohol on the weekends when learning in post secondary institutions will have decreased learning and retention.
Another impact on REM sleep, and thus learning, is shifting your sleep schedule. If you delay going to bed by 4 hours, you will not have the same REM sleep. We are creatures of habit and sleep routine is no different. Your body gets REM sleep when it expects it. People who have shifting sleep schedules will have challenges when learning and processing new complex information. When learning new physical skills such as, how to tie your shoe, skate, ski, any sport, or musical instrument, stage two sleep is most important for learning. Stage two sleep is concentrated in the latter half of sleeping, so early morning. When learning new athletic skills waking up too early in the morning do to shift work can have a negative impact on retention of new skills.
Activity Fact: There is also a strong relationship with sleep and pain processing. People with poor quality of REM sleep have a higher chance of also experiencing chronic pain.