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Brainwave entrainment is a colloquialism for 'neural entrainment', [25] which is a term used to denote the way in which the aggregate frequency of oscillations produced by the synchronous electrical activity in ensembles of cortical neurons can adjust to synchronize with the periodic vibration of external stimuli, such as a sustained acoustic ...
Sample hypnogram showing one sleep cycle (the first of the night) from NREM through REM. The sleep cycle is an oscillation between the slow-wave and REM (paradoxical) phases of sleep. It is sometimes called the ultradian sleep cycle, sleep–dream cycle, or REM-NREM cycle, to distinguish it from the circadian alternation between sleep and ...
On the other hand, the amplitude of sleep waves is lowest during wakefulness (10–30μV) and shows a progressive increase through the various stages of sleep. Stage 2 is characterized by sleep spindles (intermittent clusters of waves at sigma frequency i.e. 12–14 Hz) and K complexes (sharp upward deflection followed by slower downward ...
The whole period normally proceeds in the order: N1 → N2 → N3 → N2 → REM. REM sleep occurs as a person returns to stage 2 or 1 from a deep sleep. [20] There is a greater amount of deep sleep (stage N3) earlier in the night, while the proportion of REM sleep increases in the two cycles just before natural awakening. [17]
Some researchers posit that there are at least two forms of alpha waves, which may have different functions in the wake-sleep cycle. Alpha waves are present at different stages of the wake-sleep cycle. [21] The most widely researched is during the relaxed mental state, where the subject is at rest with eyes closed, but is not tired or asleep.
Polyphasic sleep is the practice of sleeping during multiple periods over the course of 24 hours, in contrast to monophasic sleep, which is one period of sleep within 24 hours. Biphasic (or diphasic , bifurcated , or bimodal ) sleep refers to two periods, while polyphasic usually means more than two. [ 1 ]
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 ]
A gamma wave or gamma rhythm is a pattern of neural oscillation in humans with a frequency between 30 and 100 Hz, the 40 Hz point being of particular interest. [1] Gamma rhythms are correlated with large-scale brain network activity and cognitive phenomena such as working memory , attention , and perceptual grouping , and can be increased in ...