Definitions

Dream; vision.

[From Old English swefn (sleep, dream, vision).]

"[The queen] went in to the Sultan and assured him that their daughter
had suffered during all her wedding-night from swevens and nightmare."
The Arabian Nights (translated by Richard Francis Burton); 1885.

Source: AWAD 

Lychnobite (LIK-nuh-byt) noun

One who works at night and sleeps during the day.

[From Greek lychnos (lamp) + bios (life).]

"Before the enfeebled of the dull-eyed lychnobite of the press could succumb to its influence, the cheerful voice of the magician awoke him." Observer Journal (Dunkirk, New York); Nov 5, 1887.

Source: A.W.A.D. 

Hypnopompic (hip-no-POM-pik) adjective

Pertaining to the semiconscious state before waking.

[From Greek hypnos (sleep) + pompe (sending away).]

"In my customarily prolonged hypnopompic condition on Saturday morning,
I became aware that there was a government 'initiative' about passports."
Bryan Appleyard; My Life As a Sock Puppet; New Statesman (London, UK);
Feb 26, 2007.

Source: A.W.A.D. 

Soporose (SOP-uh-ros) adjective

Sleepy; in an unusually deep sleep.

[From Latin sopor (a deep sleep). Ultimately from the Indo-European root swep-
(to sleep) that is also the source of insomnia, hypnosis, and somnambulate
(to walk in sleep).]

"We have a world-class orchestra and a world-class young conductor in
Esa-Pekka Salonen. Let's develop a world-class audience to enjoy their
music. This can be done by making certain that difficult music is heard
at concerts before the old chestnuts lull the 'music lovers' into their
customary soporose state."
On a Dissonant Note; Los Angeles Times; Sep 18, 1999.

Source: A.W.A.D.

Diurnation (dy-uhr-NAY-shuhn) noun

The habit of sleeping or being dormant during the day.

[From Latin diurnus (daily), from dies (day).]

"Many others hide away in the daytime, an adaptation called diurnation."
Neil Champion; Deserts; Black Rabbit Books; 2007.

Source: A.W.A.D.

Somniloquy (som-NIL-uh-kwee) noun

The act or habit of talking while asleep.

[From Latin somnus (sleep) + loqui (to speak).]

Today's word in Visual Thesaurus: http://visualthesaurus.com/?w1=somniloquy

"Somniloquy can occur in all stages of sleep (both dream and nondream
sleep), though individuals awakened while talking in their sleep will
often recall dreaming. Sleep talking usually does not result in
significant problems for individuals; however, it may be embarrassing
if noted by family or friends."
Sleep Talking Usually Not Serious; The Cincinnati Post; May 4, 2004.

Source: A.W.A.D.

In Freud's theory, the Dream-Work is the mechanism that distorts a dream's content, so as to conceal an unacceptable wish from the dreamer's conscious mind.  Freud discusses four major dream-work mechanisms:  condensation, displacement, considersations of representability, and secondary revision, which give dreams their bizarre, often disjointed character.

Source:

Freud, The Interpretation of Dreams 

One of the two types of dream according to Artemidorous.  Dreams of Oneiros foretell the future. 

Source:

Artemidorous, The Interpretation of Dream 

One of the two types of dreams, according to Artemidorious.  Enhypnion dreams reflect the present state of the dreamer, and nothing more. 

Source:

Artemidorous:  The Interpretation of Dream 

Also known as "somniloquy." Sleeptalkers utter speech or sounds while asleep, without any awareness of doing so.  Sleeptalking can occur in NREM and REM sleep.  It is extremely common in children, less common in adults.  Sleeptalking is often associated with sleep deprivation, and so may have some of the same root causes as sleepwalking. 

Dement, The Promise of Sleep 

This is the goal of every dream, according to Freudian dream theory.  A dream is a manifestation of a wish being satisfied.  It may be a simple wish, easily recognized, such as in the so-called "dreams of convenience": the body needs to urinate in the night, and so the sleeper dreams of relieving himself.  But most dreams represent disguised wishes--unconscious desires that the conscious mind cannot accept, and so it is twisted into the bizarre narrative of a dream.  Freud's method of dream interpretation consists of revealing the fulfilled wish at the source of every dream.

Source:

Freud, The Interpretation of Dreams 

Also known as somnambulism, this parasomnia occurs in NREM sleep.  The sleepwalker's brain is in fact passing back and forth between sleep and partial wakefulness.  The primitive parts of the brain are aroused, but higher level cognition remains in a deep sleep state.  Many sleepwalkers will be unable to open doors, etc.  Sleepwalking is common in children and may arise from increased sleep debt as children shift from napping to one period of consolidated sleep.  Unlike popular conceptions, the sleepwalker is not in the process of acting out a dream.  (See REM behavior disorder.)

Source:

Dement, The Promise of Sleep 

The brain keeps track of the accumulated hours of wakefulness.  One hour of sleep is needed to "pay off" every two hours of wakefulness.  When the sleep debt load is high enough, the brain will essentially force one into sleep, which is what happens when drowsy drivers fall asleep at the wheel.  Although sleep debt must be paid back eventually, there is unfortunately no way to "stockpile" sleep in the event of future shortages.  Dement notes, too, that there have been no studies on long term sleep debt, and so it is unknown whether the brain keeps track of sleep debt past two weeks or so.  And while a large sleep debt can be a very dangerous thing, a small sleep debt is good, because it allows us to fall asleep quickly and stay asleep.  Test subjects with no sleep debt often have difficulty both falling asleep quickly and staying asleep the whole night through.

Source:

Dement, The Promise of Sleep 

One sleep cycle typically consists of a period of NREM followed by a period of REM sleep.   The brain passes through four stages of NREM sleep first, going from light to deep sleep.  Then after coming back up to a brief period of shallow sleep, REM sleep begins.  Each sleep cycle lasts about 90 minutes, and in each successive cycle, the time spent in REM sleep increases and the time spent in NREM decreases.  Towards the end of an 8 hour night's sleep, the sleeper will alternate between REM sleep and the shallow stages of NREM, spending as much as an hour in REM sleep.

Sources:

Dement, The Promise of Sleep

Lavie, The Enchanted World of Sleep 

Apnea means "absence of breath." In sleep apnea, the sleeper stops breathing.  The throat collapses and carbon dioxide builds up in the bloodstream.  The brain awakens the sleeper to breathe, but usually the sleeper falls right back asleep and never realizes what happened.  The cycle can repeat hundreds of times in one night.  Because the normal sleep cycle is interrupted all night long, the victim is unable to reduce his sleep debt.  The most common symptom of sleep apnea is daytime fatigue.  Sleep apnea is also very hard on the cardiovascular system because blood pressure rises each time the brain has to awaken the sleeper to breathe. 

Source:

Dement, The Promise of Sleep 

One of the three types of dreams in the Tibetan Buddhist practice of dream yoga.  Samsaric dreams are ordinary dreams, based on our lives and subject to our emotions, desires, fears, and fantasies.  While lucidity is possible in a samsaric dream, Tenzin Wangyal Rinpoche maintains that unilke dreams of clarity, samsaric dreams do not offer true guidance.  

Source:

Rinpoche, The Tibetan Yogas of Dream and Sleep 

Francis Crick and Graeme Mitchison's theory that the function of REM sleep is to erase potentially damaging brain circuitry: we dream to unlearn undesirable patterns of behavior and to undo faulty neural connections. This would explain why infants spend so much time in REM sleep, and why dreams are so fleeting. Dreams would be meant to be forgotten. One of the implications of this theory is that in recalling, telling, and interpretating our dreams, we would be reversing the reverse learning, and reinforcing the very patterns that the brain has deemed unhealthy.

Source:

Bulkeley, An Introduction to the Psychology of Dreaming

The phase of sleep in which there is no rapid eye movement.  NREM sleep is typically divided into 4 stages, each characterized by a particular brain wave pattern. 

Stage 1 is very light sleep.  Brain waves transition from alpha to theta waves.   Muscles relax.  The sleeper will be easily awakened.

Stage 2 is a bit deeper sleep.  Brain activity shows alpha and theta waves, with two additional disctint patterns emerging:  k-complexes and sleep spindles.  

Stage 3 begins deep sleep.  Brain activity turns to slow delta waves with some theta waves.

Stage 4 is the deepest sleep.  All delta waves.  

For many years scientists believed that NREM sleep was dreamless, and that REM sleep was identical to dreaming.  Much turns on how "dreaming" is defined and understood by researchers and subjects.  Sleepers awakened from NREM sleep typically report experiences closer to thinking than dreaming, although some do report the vivid and complex sorts of dreams that are usually associated with REM sleep.

Source:

Bulkeley, An Introduction to the Psychology of Dreaming

Dement, The Promise of Sleep 

Also known as "paradoxical sleep." REM sleep describes a particular phase in the sleep cycle, which is characterized by rapid eye movement, irregular breathing and heartrate, increased blood flow to the genitals, muscle paralysis from the neck down, and increased brain wave activity.  The brain wave pattern of a sleeper in REM sleep looks remarkably similar to that of a waking person, although the subjective experience is more akin to deep sleep, hence the moniker "paradoxical." The discovery of REM sleep electrified the world of sleep science, indicating that humans experience two unique kinds of sleep every night:  REM and NREM (non-REM).  Although REM sleep is associated with dreaming, scientists do not currently agree that REM sleep and dreaming are identical.

Sources:

Dement, The Promise of Sleep

Lavie, The Enchanted World of Sleep

Bulkeley, An Introduction to the Psychology of Dreaming 

A parasomnia in which the muscle paralysis which normally accompanies REM sleep does not take effect, causing the subject to act out his or her dream.  REM behavior disorder is physically dangerous to the victims and their bed fellows, as their actions tend to be violent.  Middle-aged men are more likely than any other group to suffer from the disorder, which leads scientists to hypothesize that there is a hormonal component to REM behavior disorder.  Another theory holds that the disorder is linked to a problem in the brain stem, due to atrophy or age. 

Source:

Dement, The Promise of Sleep