Which phase of sleep is characterized by increased brain activity and vivid dreams?

The phase of sleep characterized by increased brain activity and vivid dreams is REM Sleep. During this stage, the brain exhibits a high level of activity similar to that observed during waking hours. This is when most dreaming occurs, and it is crucial for various functions including cognitive processes such as memory consolidation and emotional regulation.

In REM Sleep, the body's muscles are typically paralyzed in a state known as atonia, which prevents individuals from acting out their dreams. This unique combination of increased brain activity and muscle relaxation differentiates REM Sleep from other stages, where brain activity is generally lower and dreaming is less vivid or less frequent.

Understanding the characteristics of REM Sleep is vital for recognizing its role in overall sleep architecture and its importance for restorative processes, which is why it stands out among the phases of sleep.