What signifies REM sleep in a sleep study?

REM (Rapid Eye Movement) sleep is characterized by specific physiological signs that differentiate it from other sleep stages. The correct indicator of REM sleep is the presence of muscle atonia and rapid eye movements. During this phase, the body experiences a temporary paralysis of most voluntary muscles, which is referred to as muscle atonia. This mechanism prevents individuals from physically acting out their dreams, ensuring safety during sleep. Additionally, the presence of rapid eye movements beneath the eyelids is a hallmark of REM sleep, indicating increased brain activity that resembles that of wakefulness.

While increased heart rate and breathing can occur during REM sleep, they are not definitive features that classify it, as these changes can also be seen during other sleep stages or in response to external stimuli. Deep, restorative sleep typically refers to non-REM sleep stages rather than REM sleep. Frequent awakenings can happen at any point during the sleep cycle and do not specifically denote the REM stage. Thus, muscle atonia and eye movements are the distinct features that clearly signify REM sleep in a sleep study.