What is REM sleep primarily characterized by?

REM sleep is primarily characterized by high brain activity and rapid eye movements. During this stage of sleep, the brain exhibits patterns of activity that resemble wakefulness, including increased blood flow and oxygen consumption, which is associated with vivid dreaming. The rapid eye movements are a distinctive feature of REM sleep and are thought to be related to the intense brain activity taking place during this time, often reflecting dream content. This phase of sleep plays a crucial role in processes such as memory consolidation and emotional processing, underscoring its importance in overall cognitive health.

In contrast, the other options describe different aspects of sleep or other sleep stages. Deep and restorative sleep is primarily associated with non-REM stages, specifically stages three and four, where there is a predominance of slow-wave sleep and delta waves. Relaxation and light sleep refer to stages of non-REM sleep that are not characterized by rapid eye movements or the high brain activity seen in REM. Increased delta wave production occurs during deeper stages of non-REM sleep, again illustrating a distinct difference from the characteristics of REM sleep.