Which brain region is responsible for muscle atonia during REM sleep?

• A. The Pons
• B. The Hippocampus
• C. The Cerebellum
• D. The Thalamus

Answer: (A)

REM sleep muscle atonia is produced by brainstem circuits in the pons that generate and coordinate REM phenomena. During REM, specialized pontine neurons activate pathways that descend to the spinal cord and inhibit motor neurons, effectively paralyzing most skeletal muscles. This safeguard prevents dream actions and allows the brain to explore vivid dreams without moving the body. The hippocampus handles memory consolidation, the cerebellum coordinates movement and learning, and the thalamus modulates sensory relay and arousal. While these areas contribute to sleep physiology in other ways, they do not drive the REM-related muscle paralysis.