Hippocampal neuron maximally responsive to specific locations in the world.

Recurring cycle of temporal packets, about 90-minute periods in humans, during which an animal’s level of arousal waxes and wanes.

Brief sleep period lasting a second or so.

Determine or modify the period of a biorhythm.

Time required to complete an activity cycle.

Condition resulting from continuous use of sleeping pills; drug tolerance also results in deprivation of either REM or NREM sleep, leading the user to increase the drug dosage.

Large reticulum (mixture of cell nuclei and nerve fibers) that runs through the center of the brainstem; associated with sleep–wake behavior and behavioral arousal; also called the reticular formation.

Fast brain wave pattern displayed by the neocortical EEG record during sleep.

Nucleus in the pons participating in REM sleep.

Exposure to artificial light that changes activity patterns and so disrupts circadian rhythms.

Fatigue and disorientation resulting from rapid travel through time zones and exposure to a changed light–dark cycle.

Day–night rhythm.

Inability to breathe during sleep, causing a sleeper to wake up to breathe.

Fast brain wave activity pattern associated with a waking EEG.

Atonia and dreaming occurring when a person is awake, usually just falling asleep or waking up.

Organism that is active chiefly during daylight.

Disorder of slow-wave sleep resulting in prolonged inability to sleep.

Prolonged state of deep unconsciousness resembling sleep.

State of atonia, as in REM sleep, occurring while a person is awake and active; linked to strong emotional stimulation.

Environmental event that entrains biological rhythms: German for time giver.

Neural route formed by axons of photosensitive retinal ganglion cells from the retina to the suprachiasmatic nucleus; allows light to entrain the rhythmic activity of the SCN.

Hormone secreted by the pineal gland during the dark phase of the day–night cycle; influences daily and seasonal biorhythms.

Cholinergic nucleus in the dorsal brainstem having a role in REM sleep behaviors; projects to medial pontine reticular formation.

Slow brain wave activity pattern associated with deep sleep.

Rhythm of the body’s own devising in the absence of all external cues.

Two proteins combined into one.

Lacking tone; condition of complete muscle inactivity produced by motor neuron inhibition.

Individual differences in circadian activity.

Master biological clock located in the hypothalamus just above the optic chiasm.

NREM sleep.

Dreamlike event as sleep begins or while a person is in a state of cataplexy.

Combinations of medical disorders, including obesity and insulin abnormalities, that collectively increase the risk of developing cardiovascular disease and diabetes.

Neural system that times behavior.

Slow-wave sleep associated with delta rhythms.

Slow-wave sleep disorder in which a person uncontrollably falls asleep at inappropriate times.

Inherent timing mechanism that controls or initiates biological processes.