Recognise the paradox: in REM sleep the EEG looks just like the alert waking state, low voltage and fast, even though the person is deeply asleep and skeletal muscles are paralysed. The tracing marked here is desynchronised with saw-tooth waves, the signature of REM.
Map the stages quickly. Stage 1 has theta waves and vertex sharp transients. Stage 2 is identified by sleep spindles and K complexes. Stage 3, slow wave sleep, is dominated by tall delta waves. REM stands apart with beta and reappearing alpha activity, ponto-geniculo-occipital spikes and rapid eye movements on the electrooculogram. The awake-pattern-during-sleep appearance in the image is therefore REM sleep.
Ref: Arvind Arora Review of Physiology, pg 204-205.
