In polysomnography, which of the following combinations of findings CORRECTLY identifies REM sleep?
- A Low-voltage mixed-frequency EEG, REMs on EOG, lowest skeletal muscle tone on chin EMG, penile tumescence ✓
- B High-amplitude delta EEG, absence of REMs, lowest muscle tone, reduced heart rate variability
- C Sleep spindles and K-complexes on EEG, REMs on EOG, normal muscle tone, arousal threshold highest
- D Alpha activity on EEG, burst-suppression pattern, REMs, and highest arousal threshold
Explanation
REM sleep is characterized by: (1) low-voltage, mixed-frequency EEG resembling waking (hence 'paradoxical sleep'), (2) rapid eye movements on electro-oculography, (3) active suppression (atonia) of postural muscles detected by chin EMG — this is mediated by brainstem glycinergic/GABAergic projections to motor neurons, (4) penile tumescence and clitoral engorgement, and (5) irregular heart rate and breathing. High-amplitude delta EEG (option B) is N3. Sleep spindles and K-complexes (option C) define N2. Alpha with burst-suppression (option D) is pathological EEG, not sleep.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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Written and medically reviewed by the StethoPrep medical team.