When does RAPID EYE MOVEMENT occur in the Sleep Cycle? After Stage IV After Stage I After Stage II After Stage III

Rapid Eye Movement (REM) sleep is a distinct phase of the sleep cycle characterized by vivid dreaming, increased brain activity, and rapid movements of the eyes. Understanding where REM fits into the sleep architecture is essential for comprehending how our bodies rest and rejuvenate. ### **Sleep Stages Overview:** 1. **Stage I (N1):** - **Description:** Light sleep, transition between wakefulness and sleep. - **Characteristics:** Slow eye movements, reduced muscle activity. 2. **Stage II (N2):** - **Description:** Slightly deeper sleep than Stage I. - **Characteristics:** Presence of sleep spindles and K-complexes. 3. **Stage III (N3):** - **Description:** Deep sleep, also known as slow-wave sleep. - **Characteristics:** Extremely slow brain waves (delta waves), difficult to awaken. 4. **Stage IV (N4):** - **Description:** Continuation of deep sleep. - **Characteristics:** Similar to Stage III but with even deeper brain wave activity. 5. **REM Sleep:** - **Description:** Active brain state, dreaming occurs. - **Characteristics:** Rapid eye movements, increased brain activity, muscle atonia (paralysis). ### **When Does REM Occur?** In the traditional classification of sleep stages (which includes Stage IV), REM sleep typically **follows Stage IV** in the sleep cycle. This means that after progressing through the deeper stages of non-REM sleep (Stages I-IV), the body transitions into REM sleep. This cycle usually repeats multiple times throughout the night, with REM periods becoming longer in the latter half of the sleep period. ### **Answer:** **After Stage IV**