Psychology MCAT Practice Exam 2026 - Free Practice Questions and Study Guide for Aspiring Psychologists.

During REM (Rapid Eye Movement) sleep, the brain exhibits a pattern of activity that is similar to a waking state, characterized primarily by the presence of beta waves. These waves are high-frequency brain waves associated with alertness and cognitive functioning, indicating that during REM sleep, the brain is active and engaged in processes such as dreaming.

In contrast, delta waves are associated with deep sleep, theta waves with light sleep and certain meditative states, and alpha waves with relaxed, calm states while awake. The unique characteristics of REM sleep, including rapid eye movements, increased heart rate, and vivid dreaming, correlate strongly with the presence of beta waves in the EEG readings. This connection highlights that although the body may be in a state of muscle atonia, the brain is quite active during this phase of sleep.