Sleeping is something that we all do every night. We all have experienced waking up earlier than usual and being grumpy or sleeping long than usual and waking up tired. We have also all have had dreams that we have forgotten or that we remembered and they make no logical sense. Sleep as defined by Webster’s Dictionary is the natural periodic suspension of consciousness during which are bodies are restored.
To begin the study of sleep, first we need to know why we get tired. The first reason we get is the homeostat pressure to sleep that builds up while you are awake. This builds up in a linear manner based on how long you are awake and how active you are when you are awake (Marano 2003). The reason that you do not continually get more and more tired as the day goes on is because of the circadian rhythm. “The circadian rhythm is a naturally occurring 24-hour cycle” that your body goes through daily. Circadian is taken from the Latin words circa and dies which mean about and days respectively (Schacter 2009 p. 191). The circadian rhythm is essentially your body’s clock. This process goes through a cycle of activeness and sleepiness and is affected by lightness and darkness. This is one of the reasons why it is more common to sleep during the night and be awake during the day. The circadian rhythm also explains why you are more alert at certain times of the day then at others. Humans tend to be most alert around dinner time from six P.M to eight P.M, then they start to get drowse. We also become the sleepiest in the early morning from four A.M to six A.M before starting to become more alert (Marano 2003). A perfect example of this is when I have work at five in the morning and decide to stay up all night so I do oversleep I will be dead tired when I first arrive but while be alert around eight or so.
Now that we know what makes us tired, let us move on to the stages of sleep. Before you fall asleep your brain is producing beta waves. As you get more drowse the brain starts producing alpha waves which are much slower. At this point you may experience hypnagogic hallucinations. Your brain waves then switch to theta waves in the first stage of sleep. This is a very light sleep that only last for five to ten minutes. After this you move on to stage two were your brain starts to produce wanes known as sleep spindles. These are rapid moving, rhythmic brain waves. In stage three you switch over into a deeper sleep and delta waves begin to appear. Stage four, much like stage three, has delta waves and is a very deep sleep. This stage last roughly 30 minutes. The fifth and final stage of sleep is known as REM sleep. REM, Rapid Eye Movement, is a light sleep with a heightened increase in brain activity. The brain goes through these stages throughout the night in the order of 1, 2, 3, 4, 3, 2, 5, 2, 3, 4, 3, 2, 5, 2, ect (Cherry).
During REM sleep, brain waves are the same beta waves you have when you are awake. This suggests a very high level of brain activity. During this period is also when dreams mostly occur. This was found out in studies that used electrooculograph (EOG) to wake sleepers during REM sleep. These subjects reported to have dreams much more often than subjects who were woken in other stages of sleep (Aserinsky & Kleitman, 1953). EOG is an instrument that measures the movements of the eye (Schacter 2009 p. 191). One of the reasons we have REM sleep is believed to help us retain information (Stickgold 2001 p. 2). Hennevin studied the capability of the brain to encode information during REM sleep in rats. His findings showed that rats would have ponto-geniculo-occipital waves, or PGO, during post training REM sleep and lead to improved task performance (Stickgold 2001 p. 4). Another reason we need REM sleep is to process emotional memories. Dream elements often appear from things that happened while awake as opposed to the entire episodic memory. An