K-Complexes and Spindles

K-Complexes and Spindles

One of the components of contemporary scientific sleep research is the classification of stages of sleep according to certain physiological indicators, such as brain wave patterns, which are measured with an electroencephalogram, or EEG. Someone drifting off to sleep, in what is referred to as Stage 1 sleep, is really in a transitional state between sleeping and wakefulness. It is not until the EEG machine begins recording patterns referred to as transient sleep spindles and K complexes that one has entered the sleeping state proper. These two patterns characterize what is called Stage 2 sleep. Spindles are half-second (or longer) bursts of EEG activity measuring 12 to 14 Hz. K-complexes are half-second (approximately) wave patterns with a “well-delineated negative component immediately followed by positive deflection” (Anch et al., p. 28—see Sources). Sleepers are in Stage 2 sleep just before and just after rapid eye movement (REM) sleep, which is the stage of sleep during which our most vivid dreams occur.