Deep sleep
Medical term · D
Stage of sleep where the brain is less responsive to outside stimuli.
Related terms
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Central (brain) fatigueA lack of concentration or alertness as well as a sense of lethargy and loss of motivation; involves the central nervous system.
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Alpha-delta sleepAbnormal deep sleep; also called non-restorative sleep.
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Delta wavesSlow brain activity that occurs when a person is in deep sleep.
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non-REM sleepThe sleep phase that includes deep sleep, the type considered most important for preventing daytime sleepiness.