4.7 : 睡眠の段階

Sleep progresses through stages, starting with non-rapid eye movement or NREM, and transitioning to rapid eye movement or REM. Each stage is characterized by distinct brain wave patterns and physiological responses.

During the wakefulness stage, the brain exhibits beta waves when an individual is alert and alpha waves when they are relaxed.

Stage 1 of non-REM marks the onset of sleep, transitioning from alpha to theta waves in the brain,  indicating light sleep that is easy to disrupt.

Stage 2 of non-REM sleep deepens relaxation with continued theta waves and features two distinctive brain wave patterns — sleep spindles that aid memory and K-complexes that help stabilize sleep.

Stage 3 of non-REM, or deep sleep, involves slow, high-amplitude delta waves, which are crucial for physical recovery and growth.

The last stage of the sleep cycle, REM sleep, resembles wakefulness with rapid eye movements and vivid dreams, playing a key role in emotional and memory processes.

Typically, an individual experiences 4 to 6 sleep cycles per night, each lasting 90 to 100 minutes.