Non-rapid eye movement sleep; encompasses all sleep stages except REM sleep is called:

• A. NREM sleep
• B. REM sleep
• C. Paradoxical sleep
• D. REM rebound

Answer: (A)

Non-rapid eye movement sleep is the portion of sleep that includes all stages except REM. It covers light sleep (N1), deeper sleep with sleep spindles and K-complexes (N2), and slow-wave, deep sleep (N3). In NREM, brain activity slows and the body is relatively still, with less vivid dreaming compared to REM. REM sleep is the phase with rapid eye movements, vivid dreams, and near-complete muscle relaxation. The term paradoxical sleep refers to REM sleep, not to non-REM, and REM rebound describes increased REM after deprivation. So the sleep state that encompasses all stages other than REM is non-rapid eye movement sleep.