Which feature is most characteristic of REM sleep?

Which feature is most characteristic of REM sleep?

• A. No eye movements
• B. Delta waves with high amplitude
• C. Sleep spindles and K-complexes
• D. Rapid eye movements, EEG similar to wakefulness, and muscle atonia.

Answer: (D)

REM sleep is defined by three hallmark features: rapid eye movements, EEG activity that resembles wakefulness (low-amplitude, mixed-frequency), and almost complete muscle atonia. The rapid eye movements reflect bursts of activity in brainstem circuits controlling eye muscles during vivid dreaming. The wake-like EEG indicates active cortical processing, even though you’re asleep. The muscle atonia comes from brainstem pathways that inhibit motor neurons, so the body stays still despite dreams. This combination sets REM apart from other sleep stages, such as deep non-REM sleep with high-amplitude delta waves or stage 2 non-REM sleep characterized by sleep spindles and K-complexes, and from non-eye-movement periods where eye activity is minimal.

REM sleep is defined by three hallmark features: rapid eye movements, EEG activity that resembles wakefulness (low-amplitude, mixed-frequency), and almost complete muscle atonia. The rapid eye movements reflect bursts of activity in brainstem circuits controlling eye muscles during vivid dreaming. The wake-like EEG indicates active cortical processing, even though you’re asleep. The muscle atonia comes from brainstem pathways that inhibit motor neurons, so the body stays still despite dreams. This combination sets REM apart from other sleep stages, such as deep non-REM sleep with high-amplitude delta waves or stage 2 non-REM sleep characterized by sleep spindles and K-complexes, and from non-eye-movement periods where eye activity is minimal.