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How awake are you?

Your brain wave pattern depends on what you are doing. When you are alert and thinking, your brain is very active and gives a beta-wave EEG pattern. If you close your eyes but stay awake, the EEG shows an alpha wave, while theta and delta waves show you are drowsy or asleep. Different stages of sleep also have different EEG patterns. Strangely enough, REM (rapid eye movement) sleep has an EEG pattern very similar to that of your awake brain - it probably occurs when you are dreaming.

EEGs showing the five stages of sleep.
EEGs showing the five stages of sleep.
BSIP VEM/Science Photo Library

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