The difference in EEG patterns that occur during sleep has made it possible to divide sleep into the five different stages:
             This is when we are first beginning to fall asleep. At this stage we start to see a reduction in the frequency of alpha waves. These are then replaced by low voltage slow theta waves accompanied by slow rolling eye movements. The heart rate begins to slow and the muscles begin to relax, and at this stage it is very easy to be woken up. This state is similar to deep relaxation, so we not even aware that we are falling asleep. Stage one counts for more or less 5% our total sleep during the night and within 5 to 10 minutes, we enter stage 2.
             In stage two, we still get theta waves and what are also called K complexes and sleep spindles. Sleep spindles are sudden and intense bursts of electrical activity that last for a second or two. K complexes are also sudden and sharp waves of a longer frequency, these are often but not always triggered by noises. They naturally occur at a rate of one per minute. Some researchers believe that sleep spindles and K complexes help us disconnect from the outside world (noises, etc). This stage lasts only for a few minutes.
             After about a total of fifteen minutes, we are ready to enter stage 3. Our bodies and minds are relaxed and our heartbeat and respiration are slow and regular. When we enter Stage 3, our brain activity becomes synchronized. This means that big groups of cells are firing at about the same time. This unified activity in the brain is represented in the EEG recordings by large waves called delta waves. Delta waves are the slowest and strongest waves that our brain produces. Stage 3 is made up of about 20-50% delta waves.
             Stage Four or "Slow Wave Sleep"
             Stage 4 is all delta activity. It is extremely difficult now to wake someone up from the 4th stage of sleep. However, if awakened the person seem confused and disorientated. During sta...