What is "k-complex"

n. (context electrencephalography English) A (l en waveform) that occurs approxmiately every 60–100 seconds during stage 2 of (l en NREM) sleep, and which consists of a brief negative high-voltage peak (usually >100(l mul µV)), followed by a slower positive complex ~350–550(l mul ms), and at 900ms a final negative peak.

A K-complex is an electroencephalography (EEG) waveform that occurs during stage 2 of NREM sleep. It is the "largest event in healthy human EEG". They are more frequent in the first sleep cycles.

K-complexes have two proposed functions: first, suppressing cortical arousal in response to stimuli that the sleeping brain evaluates not to signal danger, and second, aiding sleep-based memory consolidation.

The K-complex was discovered in 1937 in the private laboratories of Alfred Lee Loomis.