On EEG, which waveform pattern is characteristically seen during the deepest stage of non-REM sleep (Stage N3, slow-wave sleep)?

• A Alpha waves: 8–13 Hz, high amplitude, over occipital regions
• B Delta waves: <4 Hz, high amplitude, comprising ≥20% of the epoch ✓
• C Beta waves: >13 Hz, low amplitude, widespread
• D Theta waves: 4–8 Hz, low amplitude, frontal predominance

Explanation

Stage N3 (formerly stages 3 and 4) is defined by high-amplitude delta waves (<4 Hz) occupying ≥20% of the 30-second epoch. This is the restorative phase of sleep during which GH secretion peaks, synaptic homeostasis occurs, and cellular repair takes place. Alpha waves characterize relaxed wakefulness with eyes closed; beta waves are seen in alert wakefulness or REM sleep; theta waves mark light non-REM sleep (N1) and drowsiness.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.