Question
A polysomnography technologist is reviewing 30-second epochs from an overnight study and needs to correctly assign each epoch to a sleep stage before the clinician interprets the report. Which combination of channels does the technologist rely on to distinguish N1, N2, N3, and REM sleep from one another?
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Sleep stage is scored from the combined pattern across EEG, EOG, and chin EMG, not any single channel alone. N1 shows low-amplitude mixed-frequency EEG with slow eye movements and only slightly reduced muscle tone; N2 requires sleep spindles or K-complexes on EEG; N3 requires at least 20% of the epoch to show high-amplitude slow-wave (delta) activity; and REM shows low-amplitude mixed-frequency EEG with rapid eye movements on EOG alongside the lowest chin EMG tone of the night, reflecting REM-related muscle atonia. Reading only EEG would miss the atonia that confirms REM, and reading only EMG would miss the spindles that confirm N2.
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