What Is REM Sleep? Definition and Benefits

During REM sleep, brain wave activity increase, as measured on an electroencephalogram (EEG).

• N1 sleep shows slowing of the normal alpha wave pattern noted during the awake state.
• N2 sleep introduces K waves - long, high voltage waves - lasting up to 1 second, and sleep spindles - periods of low voltage and high-frequency spikes.
• N3 sleep is characterized by delta waves, or high voltage, slow and irregular activity. 
• During REM sleep, sleep patterns show low voltage and fast waves, some alpha waves, and muscle twitch spikes associated with transmitted rapid eye movement. 

The most vivid dreams occur during REM sleep. These dreams are often elaborate and emotional experiences that include sadness, anger, apprehension or fear.  A person can more readily recall a dream when they awake from REM sleep. However, the purpose of dream content is not currently understood.

Sigmund Freud suggested dreams were a representation of unconscious thought. Another hypothesis proposes that dreams are a random brain activity during REM sleep and not a meaningful experience.

Non-REM sleep is necessary in order to survive. Mild sleep deprivation increases the risk of chronic health conditions and severe sleep deprivation can lead to hallucinations or death.

However, the benefits of REM sleep remain inconclusive. Studies show no obvious adverse effects when participants were deprived of REM sleep.

• Hypothesized benefits suggest certain negative behaviours which should be unlearned are rehearsed through dreams.
• REM sleep is proposed to help transfer memories from the hippocampus to the cerebral cortex.