REM is an active and final phase of the four-stage sleep cycle characterised by increased brain activity and autonomic nervous system functions. The brainstem and hypothalamus mostly control this stage of sleep.

Many theories hypothesise that REM sleep is helpful for learning and memory for...

Before REM sleep, the three prior stages of sleep occur progressively slow bodily function and brain activity. These stages are known as non-REM or N1, N2, and N3.

However, during REM sleep, the eyes move rapidly sideways. The heart rate, respiratory rate and blood pressure increase to thei...

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...

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 unde...

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 wh...