Glossary
A-C | D-F | G-J | K-M | N-P | Q-S | T-Z
- K complex
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An EEG waveform pattern with a distinct shape; associated with N2 (stage 2) sleep.
- Lark
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A term describing individuals who are predisposed to wake early and to be at their best in the morning. Also termed “morning-type.” Contrasts with “owl” (see entry). Such owl and lark predispositions may have a genetic component.
- Leptin
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A hormone that stimulates satiety, and thus decreases appetite. Reduced sleep duration may lead to a reduction in leptin, thereby stimulating appetite. See also ghrelin.
- Melatonin
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A hormone produced by the pineal gland in vertebrates. The secretion of melatonin occurs in a predictable pattern across the day and night, and plasma melatonin concentration is one of the most distinctive circadian rhythms. Melatonin secretion is suppressed by light. Melatonin can assist with sleep onset in humans and may be involved in regulating other circadian rhythms.
- Memory acquisition
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The initial step in memory formation in which newly perceived information is received by the brain.
- Memory consolidation
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The neural processing that occurs after information is initially registered, which contributes to its permanent storage in memory.
- Memory recall
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The ability to access and utilize information stored in the brain.
- Microsleep
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A very brief period of sleep, lasting only a few seconds. Microsleeps occur most frequently when a very sleepy person is trying to stay awake—for example, when driving while sleepy.
- Modafinil
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A central nervous system stimulant that promotes wakefulness. Modafinil is primarily used to treat the symptoms of excessive daytime sleepiness (EDS) in people with narcolepsy. See also excessive daytime sleepiness (EDS) and narcolepsy.
- Motor neuron
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A neuron that conveys signals from the central nervous system to a muscle.
- Multiple sleep latency test (MSLT)
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A sleep laboratory test that consists of a series of 20-minute nap opportunities during the daytime to measure a human’s sleepiness. People who regularly fall asleep in less than 10 minutes, or who enter REM sleep rather than NREM sleep, may suffer from excessive daytime sleepiness and perhaps narcolepsy.