EEG Recordings During Wakefulness and Sleep

Brain waves, as measured by the frequency and amplitude of electrical activity, change over the course of the normal circadian rhythm. Beta waves are predominant during wakefulness, but give way to alpha waves during periods of calm and as we drift into sleep. Theta waves are characteristic of stage 1 sleep. As we reach stage 2 sleep, the amplitude (height) of brain waves increases. During deep sleep (stages 3 and 4), the brain waves are at their highest amplitude. During REM sleep, they appear similar to the brain waves occurring when we are awake.