In which stage of sleep are delta waves predominantly present?

Delta waves are predominantly present in the N3 stage of sleep, which is also known as slow-wave sleep or deep sleep. This stage is crucial for restorative processes in the body, including physical recovery and growth, as well as memory consolidation. During N3, the brain exhibits high-voltage, low-frequency delta waves, which are indicative of deep restorative sleep.

In contrast, the other stages of sleep, such as N1 and N2, are characterized by lighter sleep and different types of brain wave activity, including alpha and theta waves. REM sleep is marked by rapid eye movements and is associated more with dreaming, with brain activity resembling that of wakefulness, but primarily exhibiting theta waves and sawtooth waves rather than delta waves. This differentiation in brain wave patterns across sleep stages is essential for understanding the overall sleep architecture and the various functions that different stages serve.