PSYCHOLOGY OF EMOTIONS

Detailed explanation-1: -Electroencephalography. 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: -Deep, slow brain waves known as delta waves begin to emerge during NREM stage 3 sleep-a stage that is also referred to as delta sleep. This is a period of deep sleep where any environmental noises or activity may fail to wake the sleeping person.

Detailed explanation-3: -NREM sleep is differentiated from rapid eye movement (REM) sleep. View Source because sleepers experience slowed eye movements during NREM sleep. Stage 1 and stage 2 NREM sleep are considered light sleep, while stage 3 NREM sleep is considered deep sleep.

Detailed explanation-4: -Stage 3 lasts only a few minutes and constitutes about 3 to 8 percent of sleep. The EEG shows increased high-voltage, slow-wave activity (Figure 2-2). The last NREM stage is stage 4, which lasts approximately 20 to 40 minutes in the first cycle and makes up about 10 to 15 percent of sleep.