<P> 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 . </P> <P> 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 . </P>

Sleep spindles and k-complexes are most characteristic of which sleep stage ​