Stage 2 - looks very wide). Then there is a sudden decrease...

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Stage 2 - This stage of sleep is the most prominent stage as we spend the majority of sleep time in it. Approximately 45% of sleep time is spent in Stage 2. Stage 2 is characterized by a mix of Theta, sleep spindles, K-Complexes, & some Delta waves. Look at the image , and you can see all of these different components (although not that well). Let me describe a couple of important ones: 1. Sleep Spindles -- these are short episodes that look (the EEG that is) like small footballs. When looking at the EEG, if you notice an area in which the amplitude (the height of the wave) increases little by little, and the frequency (how close each wave is to the others) decreases slightly, thus giving it the shape of a football, and then goes back to normal, you know you are looking at a spindle. 2. K-Complex -- these are the most sure indicators of stage 2 sleep. When a K-Complex occurs, there is a sudden rise in wave amplitude (height) so the wave goes high above baseline, and sharp decrease in frequency (so the wave
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Unformatted text preview: looks very wide). Then there is a sudden decrease in amplitude (so the wave now goes well below baseline) and then back to baseline. In addition, there is often a little spike in the wave when it is moving from high above baseline to far below baseline that gives it its characteristic "K" shape. If you are monitoring a persons sleeping EEG, sleep spindles are a nice indicator of Stage 2, but when you see K-Complexes, you know the person is definitely in Stage 2. d) Stage 3 - This is the first stage of what is considered "deep sleep" or Slow Wave Sleep (SWS). We spend approximately 7% of our time asleep in this stage, and it is characterized by approximately 20-50% delta waves within minimal amplitude. Although it is a type of deep sleep, many consider this a transition stage (much like Stage 1) between stages 2 & 4. As a result, there has been a push in recent years to eliminate Stages 3 & 4 and replace them with just a single, "Stage 3" sleep....
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