K-complex
Large amplitude, biphasic EEG waveform lasting at least 0.5 seconds that characterizes stage 2 NREM sleep.
Full Definition
K-complexes are large amplitude, biphasic electroencephalographic waveforms that are one of the defining features of stage 2 non-REM sleep. These waveforms consist of a sharp negative deflection followed by a slower positive component and must last at least 0.5 seconds to meet scoring criteria. K-complexes can occur spontaneously or be evoked by external stimuli such as sounds. They are generated by the cortex and are thought to represent a protective mechanism that helps maintain sleep by preventing arousal from mild sensory stimuli. The presence of K-complexes, along with sleep spindles, distinguishes stage 2 NREM sleep from lighter stage 1 sleep in polysomnographic scoring.
Usage
Usage note: Always hyphenated; capitalize the K.
In Context
- "K-complexes were frequently observed in response to auditory stimuli during stage 2 sleep." — Sleep study interpretation
- "The scoring technician identified numerous spontaneous K-complexes throughout the night." — Polysomnography scoring notes