Final answer:
In REM sleep, there is muscle paralysis while the brain exhibits activity similar to wakefulness, characterizing a state known as paradoxical sleep where dreams are common.
Step-by-step explanation:
In REM sleep, the EEG resembles that of a person who is awake and mentally active. However, during REM sleep, there is paralysis of muscle systems in the body, with the exception of those that enable circulation and respiration. This means that no movement of voluntary muscles occurs in a normal individual during REM sleep, leading to a state often referred to as paradoxical sleep because of the coexistence of active brain waves and inactive muscle tone.
REM sleep, with its rapid eye movement, is also the period when dreaming typically occurs. As opposed to NREM sleep, with its characteristic slow-wave sleep patterns like delta waves, REM stages present brain activity that closely mirrors the active, wakeful state.