Nonrapid Eye Movement (NREM) refers to a stage or phase of sleep characterized by the absence of rapid eye movements and the presence of slow, synchronous brain waves. It is one of the two main categories of sleep, the other being Rapid Eye Movement (REM) sleep. NREM sleep is further subdivided into three stages, namely N1, N2, and N3.
During the N1 stage, which is the transition phase between wakefulness and sleep, the individual experiences drowsiness, a slowing heart rate, and decreased body temperature. This stage typically lasts for a few minutes and is characterized by the presence of theta waves in the brain.
N2 is the stage of light sleep, constituting the largest portion of the sleep period. In this stage, there is a further decrease in heart rate and body temperature, as well as a decrease in muscle activity. Sleep spindles, which are short bursts of brain activity, and K-complexes, which are single large waves, are observed in the EEG during this stage.
N3, also referred to as slow-wave sleep or deep sleep, is the stage where the body experiences the most significant restoration and rejuvenation. It is characterized by slow, high-amplitude delta waves in the brain, and the individual is difficult to awaken. It is during this stage that important processes like tissue growth and repair, energy restoration, and memory consolidation take place.
In summary, NREM sleep is a vital stage of the sleep cycle that includes three stages: N1, N2, and N3. It is characterized by the absence of rapid eye movements, synchronized brain waves with specific frequencies, and varying levels of arousal and restorative processes.
