PSYCHOLOGY OF EMOTIONS

Detailed explanation-1: -These four sleep stages are called non-rapid eye movement (non-REM) sleep, and its most prominent feature is the slow-wave (stage IV) sleep. It is most difficult to awaken people from slow-wave sleep; hence it is considered to be the deepest stage of sleep.

Detailed explanation-2: -Stage 3 and 4 sleep, the most restorative stages, are known as deep sleep. We need about one and a half to two hours of deep sleep a night. In stage 3, very slow brain waves called delta waves are interspersed with smaller, faster waves. By stage 4, the brain almost exclusively produces delta waves.

Detailed explanation-3: -Stage 4 is an even deeper sleep where the brain waves further slow and sleepers are very difficult to wake. It’s believed that tissue repair occurs during the stage of sleep and that hormones are also released to help with growth.

Detailed explanation-4: -Delta waves are associated with the deep sleep stages: stage 3 and REM. During stage 3, less than half of brain waves consist of delta waves, while more than half of brain activity consists of delta waves during REM sleep.