The Mind's Machine: Chapter 10

Biological Rhythm

a regular fluctuation in any living process

Circadian Rhythm

a pattern of behavioral, biochemical, or physiological fluctuation that has a 24-hour period

Ultradian

referring to a rhythmic biological event with a period shorter than a day, usually from several minutes to several hours long

Infradian

referring to a rhythmic biological event with a period longer than a day

Free-Running

referring to a rhythm of behavior shown by an animal deprived of external cues about time of day

Period

the interval of time between two similar points of successive cycles, such as sunset to sunset

Phase Shift

a shift in the activity of a biological rhythm, typically provided by a synchronizing environmental stimulus

Entrainment

the process of synchronizing a biological rhythm to an environmental stimulus

Zeitgeber

Literally "time-giver" (in German). The stimulus (usually the light-dark cycle) that entrains circadian rhythms.

Suprachiasmatic Nucleus (SCN)

a small region of the hypothalamus above the optic chiasm that is the location of a circadian clock

Melatonin

an amine hormone that is secreted by the pineal gland at night, thereby signaling day length to the brain

retinohypothalamic pathway

the route by which specialized retinal ganglion cells send their axons to the suprachiasmatic nuclei

Melanopsin

a photopigment found in those retinal ganglion cells that project to the suprachiasmatic nucleus

Electroencephalography (EEG)

a recording of gross electrical activity of the brain via large electrodes placed on the scalp

rapid eye movement (REM) sleep

Also called paradoxical sleep. A stage of sleep characterized by small-amplitude, fast-EEG waves, no postural tension, and rapid eye movements. REM rhymes with "gem."

Non-REM sleep

Sleep, divided into stages 1-3, that is defined by the presence of distinctive EEG activity that differs from that seen in REM sleep.

Desynchronized EEG

Also called beta activity. A pattern of EEG activity comprising a mix of many different high frequencies with low amplitude.

Alpha Rhythm

A brain potential of 8-12 Hz that occurs during relaxed wakefulness

Vertex Spike

a sharp-wave EEG pattern that is seen during stage 1 sleep

Stage 1 Sleep

the initial stage of non-REM sleep, which is characterized by small-amplitude EEG waves of irregular frequency, slow heart rate, and reduced muscle tension

Stage 2 Sleep

a stage of sleep that is defined by bursts of EEG waves called sleep spindles

Sleep Spindle

A characteristic 12-14 Hz wave in the EEG of a person said to be in stage 2 sleep.

K Complex

a sharp negative EEG potential that is seen in stage 2 sleep

Stage 3 Sleep

Also called slow wave sleep (SWS). A stage of non-REM sleep that is defined by the presence of large amplitude, slow delta waves.

Delta Wave

The slowest type of EEG wave, about 1 per second, characteristic of stage 3 sleep

Nightmare

a long, frightening dream that awakens the sleeper from REM sleep

Night Terror

a sudden arousal from stage 3 sleep that is marked by intense fear and autonomic activation

Sleep Deprivation

the partial or total prevention of sleep

Sleep Recovery

The process of sleeping more than normally after a period of sleep deprivation, as though in compensation

Fatal Familial Insomnia

An inherited disease that causes people in middle age to stop sleeping, which after a few months results in death

Ecological Niche

the unique assortment of environmental opportunities and challenges to which each organism is adapted

Isolated Brain

an experimental preparation in which an animal's brainstem has been separated from the spinal cord by a cut below the medulla

Isolated Forebrain

an experimental preparation in which an animal's nervous system has been cut in the upper midbrain, dividing the forebrain from the brainstem

Basal Forebrain

A ventral region in the forebrain that has been implicated in sleep

Tuberomammillary Nucleus

A region of the basal hypothalamus, near the pituitary stalk, that plays a role in generating slow wave sleep

General Anesthetic

a drug that renders an individual unconscious

Reticular Formation

Also called reticular activating system. An extensive region of the brainstem (extending from the medulla through the thalamus) that is involved in arousal

Locus Coeruleus

a small nucleus in the brainstem whose neurons produce norepinephrine and modulate large areas of the forebrain

Narcolepsy

A disorder that involves frequent, intense episodes of sleep, which last from 5 to 30 minutes and can occur anytime during the usual waking hours.

Cataplexy

sudden loss of muscle tone, leading to collapse of the body without loss of consciousness. Sometimes a component of narcoleptic attacks

Orexin

Also called hypocretin. A neuropeptide produced in the hypothalamus that is involved in switching between sleep states, in narcolepsy, and in the control of appetite.

Sleep Paralysis

a state, during the transition to or from sleep, in which the ability to move or talk is temporarily lost

Sleep Enuresis

Bed-Wetting

Somnambulism

Sleep walking

REM Behavior Disorder (RBD)

a sleep disorder in which a person physically acts out a dream

sleep-onset insomnia

Difficulty falling asleep

Sleep-maintenance insomnia

difficulty staying asleep

Sleep State Misperception

Commonly, the perception of not having been asleep when in fact the person has been. It typically occurs at the start of a sleep episode.

Sleep Apnea

A sleep disorder in which respiration slows or stops periodically, waking the sleeper. Excessive daytime sleepiness results from the frequent nocturnal awakening

Sudden Infant Death Syndrome (SIDS)

Also called crib death. The sudden, unexpected death of an apparently healthy human infant who simply stops breathing, usually during sleep.