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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 wakefulness. In humans, this cycle takes 70 to 110 minutes (90 ± 20 minutes). [1] Within the sleep of adults and infants there are cyclic fluctuations between quiet and active sleep.
While sleep differs from wakefulness in terms of the ability to react to stimuli, it still involves active brain patterns, making it more reactive than a coma or disorders of consciousness. [1] Sleep occurs in repeating periods, during which the body alternates between two distinct modes: REM and non-REM sleep.
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 ]
Dr. Michael Breus, Ph.D., a board-certified sleep specialist in Los Angeles, first introduced the four chronotypes based on sleep-wake patterns seen in certain animals.
Sleep apnea (or sleep apnoea in British English; /æpˈniːə/) is a sleep disorder characterized by pauses in breathing or instances of shallow or infrequent breathing during sleep. Each pause in breathing, called an apnea, can last for several seconds to several minutes, and may occur 5 to 30 times or more in an hour.
Studies have shown that maintaining normal sleep and circadian rhythms is important for many aspects of brain and health. [135] A number of studies have also indicated that a power-nap, a short period of sleep during the day, can reduce stress and may improve productivity without any measurable effect on normal circadian rhythms.
Additionally, education about normal patterns of the sleep-wake cycle may alleviate anxiety in some patients. [1] For patients with severe depression resulting from the fear of having insomnia, electroconvulsive therapy appears to be a safe and effective treatment. [7]
The cyclic alternating pattern (abbreviated CAP) is a pattern of two long-lasting alternate electroencephalogram (EEG) patterns that occur in sleep. [1] It is a pattern of spontaneous cortical activity [ 2 ] which is ongoing and occurs in the absence of sensory stimulation .