NREM sleep
Overview
NREM sleep, or Non-Rapid Eye Movement sleep, is one of the two basic types of sleep. The other type is REM sleep. These two types of sleep are differentiated by the presence or absence of rapid eye movements and the type of brain waves that are observed during sleep. NREM sleep is further divided into three stages: N1, N2, and N3. Each stage represents a different depth of sleep, with N3 being the deepest stage of NREM sleep.
Stages of NREM Sleep
NREM sleep consists of three stages, each characterized by specific brain wave patterns, muscle activity, and eye movements.
N1
The first stage of NREM sleep, N1, is the lightest stage of sleep. It is often referred to as the transition phase between wakefulness and sleep. During this stage, the brain produces high amplitude theta waves, which are slow brain waves. This stage typically lasts for five to ten minutes.
N2
The second stage of NREM sleep, N2, is characterized by sleep spindles and K-complexes. Sleep spindles are bursts of rapid, rhythmic brain activity, while K-complexes are high amplitude patterns of brain activity. Together, these two patterns of brain activity help to inhibit certain perceptions from the external world, thus aiding in sleep.
N3
The third and final stage of NREM sleep, N3, is the deepest stage of sleep. It is during this stage that delta waves, the slowest and highest amplitude brain waves, are produced. This stage of sleep is also referred to as slow-wave sleep or delta sleep. It is the most restorative stage of sleep, during which the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system.
Functions of NREM Sleep
NREM sleep serves several vital functions. It is during NREM sleep that the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system. This stage of sleep is also associated with memory consolidation, during which the brain processes and stores new information from the day. Additionally, NREM sleep is thought to play a role in brain development.
Disorders Associated with NREM Sleep
Several sleep disorders are associated with NREM sleep. These include insomnia, sleep apnea, restless legs syndrome, and nightmare disorder. Each of these disorders can disrupt the normal progression of NREM sleep, leading to poor sleep quality and a variety of health problems.