Sleep

Four stages of sleep are defined electrophysiologically - with some grey areas inbetween: - N1 sleep - N2 sleep - N3 sleep - REM sleep

Sleep stage	Alpha dropout	Vertex waves	K complexes	Sleep spindles	Delta
N1	X	X
N2	X	X	X	X
N3	X	X	X	X
REM	X

Sleep waveforms

Vertex waves

K complexes

Sleep spindles

Posterior occipital sharp transients of sleep (POSTS)