During REM sleep, which of the following physiological changes occurs?

During REM sleep, there are several key physiological changes that occur, making this option accurate. One of the hallmark features of REM sleep is increased brain activity, which becomes more similar to wakefulness, as evidenced by EEG patterns that reflect this heightened activity. This stage is often associated with vivid dreaming due to this brain engagement.

Additionally, muscle atonia is a significant characteristic of REM sleep. This temporary paralysis of most voluntary muscles prevents individuals from acting out their dreams, providing a protective mechanism. Irregular breathing is also prominent during this phase, where respiratory patterns can change unpredictably as opposed to the more rhythmic breathing observed in other sleep stages.

These changes—heightened brain activity, muscle atonia, and irregular respiratory patterns—illustrate the unique physiological state associated with REM sleep, distinguishing it from other sleep stages and contributing to the complexity of sleep architecture.