Sleep is a behavior but not distinguished by movement. During wakefulness the eeg of a normal person shows two basic patterns of activity. Alpha activity: smooth electrical activity of 8 12 hz recorded from the brain, generally associated with a state of relaxation: more prevalent when eyes are closed. When we get drowsy and the transition from wakefulness to sleep occurs we show theta activity: eeg activity of 3. 5 to 7 hz that occurs intermittently during early stages of slow-wave sleep and rem sleep. Eeg becomes irregular with mixture of theta activity, sleep spindles, and. K complexes: sleep spindles are short burst of waves (12 14 hz) which occur 2 to 5 times a minute during stages 1 4 of sleep. The sleep of older people contains fewer sleep spindles. Represents the activity of a mechanism that is involved in keeping a person asleep: k-complexes are sudden, sharp waveforms which are found in stage 2 only.