What it looks like
N2 is defined by K-complexes (a sharp negative wave followed by a slower positive one, lasting at least 0.5 s, maximal frontocentrally) and sleep spindles (11–16 Hz bursts of at least 0.5 s, maximal centrally). 10
What it means at the bedside
Normal sleep architecture in a comatose or encephalopathic patient is a reassuring background feature. Vertex waves and K-complexes are symmetric and midline; a consistently one-sided "vertex wave" is not one.