Editing Sleep (section)

=== Brain waves in sleep ===
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.<ref>{{citation|vauthors=Borbély AA, Daan S, Wirz-Justice A, Deboer T|title= The two-process model of sleep regulation: a reappraisal|journal= J Sleep Res | volume=25|issue=2|pages=131–43|doi= 10.1111/jsr.12371 |date=14 January 2016 |pmid=26762182|s2cid= 206156163|url= https://www.zora.uzh.ch/id/eprint/121344/1/TPM%20a%20reappraisal%2025-11-15%20Figs%20inserted%20in%20text-2.pdf}}</ref> Alpha, beta, theta, gamma, and delta waves are all seen in the different stages of sleep. Each waveform maintains a different frequency and amplitude. Alpha waves are seen when a person is in a resting state, but is still fully conscious. Their eyes may be closed and all of their body is resting and relatively still, where the body is starting to slow down. Beta waves take over alpha waves when a person is at attention, as they might be completing a task or concentrating on something. Beta waves consist of the highest of frequencies and the lowest of amplitude, and occur when a person is fully alert. Gamma waves are seen when a person is highly focused on a task or using all their concentration. Theta waves occur during the period of a person being awake, and they continue to transition into Stage 1 of sleep and in stage 2. Delta waves are seen in stages 3 and 4 of sleep when a person is in their deepest of sleep.<ref>{{citation|vauthors=Posada-Quintero HF, Reljin N, Bolkhovsky JB, Orjuela-Cañón AD, Chon KH|title=Brain Activity Correlates With Cognitive Performance Deterioration During Sleep Deprivation. |journal=Front. Neurosci. |date= 19 September 2019 |volume=13 |page=1001 |doi=10.3389/fnins.2019.01001|pmid=31607847 |pmc=6761229 |doi-access=free }}</ref>