Sleep spindle

A Sleep spindle is burst of brain activity visible on an EEG that occurs during stage 2 sleep. It consists of 12-16 Hz waves that occur for 0.5 to 1.5 seconds.

Function
Sleep spindles may represent periods where the brain is inhibiting processing to keep the sleeper in a tranquil state. Along with K-complexes they are defining characteristics of stage II sleep. Sleep spindles (also called sigma waves) indicate the onset of Stage II sleep. They are often tapered at both ends and frequently seen over the central head regions. They may or may not be synchronous, but they should be symmetrical and bilateral.

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