Physiology The slow wave sleep predominating in first one third of night sleep is feature of which phase of sleep? A NREM stage 3 and 4 B NREM stage 1 and 2 C NREM stage 1 D REM 💡 Explanation The slow wave sleep predominating in first one third of night sleep is feature of which phase of sleep? ✓ Correct Answer: A. NREM stage 3 and 4