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One of the important questions in sleep research is clearly defining the sleep state. This problem arises because sleep was traditionally defined as a state of consciousness and not as a physiological state, [14] [15] thus there was no clear definition of what minimum set of events constitute sleep and distinguish it from other states of partial or no consciousness.
In cats, the sleep cycle lasts about 30 minutes, though it is about 12 minutes in rats and up to 120 minutes in elephants (In this regard, the ontogeny of the sleep cycle appears proportionate with metabolic processes, which vary in proportion with organism size. However, shorter sleep cycles detected in some elephants complicate this theory).
Tononi also developed the integrated information theory (IIT): a theory of what consciousness is, how it can be measured, how it is correlated with brain states, and why it fades when we fall into dreamless sleep and returns when we dream. The theory is being tested with neuroimaging, Transcranial magnetic stimulation (TMS), and computer models ...
The sleep cycle of alternate NREM and REM sleep takes an average of 90 minutes, occurring 4–6 times in a good night's sleep. [17] [22] The American Academy of Sleep Medicine (AASM) divides NREM into three stages: N1, N2, and N3, the last of which is also called delta sleep or slow-wave sleep. [23]
Empirically, it is an ultradian rhythm of approximately 90 minutes (80–120 minutes [2]) characterized by different levels of excitement and rest. The cycle is mediated by the human biological clock. It is most readily observed in stages of sleep, for example, rapid eye movement sleep (REM) and the delta activity cycle.
Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals (including humans) and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly. The core body and brain temperatures increase during REM sleep and skin ...
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Minutes Sleepiness 0–5: Severe 5–10: Troublesome 10–15: Manageable 15–20: Excellent A sleep onset latency of 0 to 5 minutes means severe sleep deprivation, 5 to 10 minutes is "troublesome", 10 to 15 minutes indicates a mild but "manageable" degree of sleep debt, and 15 to 20 minutes is indicative of "little or no" sleep debt. [1]: 341–342