A 35-year-old patient undergoing EEG monitoring shows high-amplitude, low-frequency (1-4 Hz) waves during sleep. This EEG pattern corresponds to:
- A REM sleep with vivid dreaming
- B Stage N3 (slow-wave sleep) with delta waves ✓
- C Stage N1 sleep with theta waves and occasional vertex sharp waves
- D Stage N2 sleep with sleep spindles and K-complexes
Correct answer: B. Stage N3 (slow-wave sleep) with delta waves
Explanation
Delta waves (frequency 1-4 Hz, amplitude >75 µV) are the hallmark of Stage N3 (slow-wave sleep, SWS). SWS is considered the most restorative phase of sleep and predominates in the first third of the night. Stage N1 shows low-amplitude mixed frequency waves and theta activity (4-7 Hz). Stage N2 is characterized by sleep spindles (12-14 Hz) and K-complexes. REM sleep shows low-amplitude, mixed-frequency waves similar to wakefulness with saw-tooth waves. Growth hormone secretion peaks during SWS.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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Written and medically reviewed by the StethoPrep medical team.