What is a K-complex and which sleep stage does it help justify?

A K-complex is characterized by a sharp upward and downward deflection in the electroencephalogram (EEG) and is predominantly observed during stage 2 of non-rapid eye movement (NREM) sleep. This distinctive waveform often appears in response to external stimuli and serves as a marker of light sleep.

The presence of K-complexes is significant as they indicate the brain's response mechanisms during sleep, functioning to maintain sleep and protect it from disturbances. They are not typically associated with deep sleep, rhythmic brain wave patterns, REM sleep, or stage 1 sleep, making the first description accurate in highlighting both the nature of K-complexes and their correlation with light sleep.