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Delta wave activity, correlating with slow-wave (deep) sleep, in particular shows regular oscillations throughout a good night's sleep. Secretions of various hormones , including renin , growth hormone , and prolactin , correlate positively with delta-wave activity, while secretion of thyroid-stimulating hormone correlates inversely. [ 3 ]
The electrical activity seen on an EEG represents brain waves. The amplitude of EEG waves at a particular frequency corresponds to various points in the sleep-wake cycle, such as being asleep, being awake, or falling asleep. [18] Alpha, beta, theta, gamma, and delta waves are all seen in the different stages of sleep.
Slow-wave sleep (SWS), often referred to as deep sleep, is the third stage of non-rapid eye movement sleep (NREM), where electroencephalography activity is characterised by slow delta waves. [ 2 ] Slow-wave sleep usually lasts between 70 and 90 minutes, taking place during the first hours of the night. [ 3 ]
Night terrors tend to happen during periods of arousal from delta sleep, or slow-wave sleep. [ 8 ] [ 7 ] Delta sleep occurs most often during the first half of a sleep cycle, which indicates that people with more delta-sleep activity are more prone to night terrors.
Known as slow-wave sleep or stage 3 non-REM sleep, this is the deepest stage of sleep and the hardest to wake up from. Brain activity slows down, muscles and bones strengthen, hormones regulate ...
Most of the activity in Stage II is in the 3–6 Hz range. Stage III and IV sleep are defined by the presence of delta frequencies and are often referred to collectively as "slow-wave sleep". Stages I–IV comprise non-REM (or "NREM") sleep. The EEG in REM (rapid eye movement) sleep appears somewhat similar to the awake EEG.
The delta waves have been shown to be generated by recurrent connections within the cerebral cortex. During slow wave sleep, the cortex generates brief periods of activity and inactivity at 0.5–4 Hz, resulting in the generation of the delta waves of slow wave sleep.
Sleep stages are characterized by spectral content of EEG: for instance, stage N1 refers to the transition of the brain from alpha waves (common in the awake state) to theta waves, whereas stage N3 (deep or slow-wave sleep) is characterized by the presence of delta waves. [107] The normal order of sleep stages is N1 → N2 → N3 → N2 → REM.