PSYC 476 Exam 1

What is sleep?

A reversible behavioral state of low attention to the environment, usually with relaxed posture and minimal movement.

What is polysomnography (PSG)?

The gold-standard objective sleep measurement that combines recordings such as EEG, EOG, EMG, heart rate, and breathing.

What does EEG measure in sleep research?

Brain waves recorded at the scalp.

What does EOG measure?

Eye movements.

What does EMG measure?

Muscle movement/activity.

What are key limitations of PSG?

It is expensive, inconvenient, usually requires an overnight lab study, and may not generalize perfectly to typical sleep.

What is actigraphy?

A method, usually using a wrist device, that infers sleep from wrist activity; some devices also measure light exposure and daily activity.

Why is actigraphy less informative than PSG?

It cannot identify sleep cycles/stages as PSG can.

What are the two broad types of sleep?

REM sleep and NREM sleep.

How many NREM stages are described in the slides?

Three.

About how long is a typical adult sleep cycle?

About 90 minutes.

How does time spent in sleep stages change across a night?

The amount of time in each stage varies as the night progresses.

Is sleep simply a shutdown of the brain?

No. Brain function during sleep differs from waking; some processes are reduced, others are active or work differently.

What sleep functions were listed?

Energy conservation, predator avoidance, restoring bodily resources, and memory consolidation.

What unusual sleep pattern do dolphins show?

They have no REM sleep and have slow-wave sleep in one hemisphere at a time.

Who was Hypnos (Somnus)?

The ancient Greek/Roman god of sleep; the word hypnotism derives from his name.

What early Greek explanation of sleep did Alcmaeon propose?

Sleep occurred when blood filled brain vessels; waking occurred when blood left them.

What did Plato and Aristotle propose caused sleep?

Vapors from food decomposition in the stomach rose to the brain; Aristotle thought waking came when digestion was complete.

How did many 19th-century theories characterize sleep?

As the brain shutting down, often as an intermediate state between wakefulness and death.

What did Richard Caton discover in 1875?

Spontaneous electrical activity in the brain, using rabbits and monkeys.

What did Hans Berger contribute to sleep science?

He showed that human brains have spontaneous electrical activity recordable from the scalp, leading to EEG.

What is Nathaniel Kleitman known as?

The Father of Sleep Research.

What did Kleitman establish?

The first laboratory devoted solely to sleep research, at the University of Chicago in the early 1920s.

Who discovered rapid eye movements in 1952?

Eugene Aserinsky, a graduate student working with Nathaniel Kleitman.

What did William C. Dement contribute to sleep science?

He discovered and named sleep stages in 1957, advanced sleep research, education, and policy, and is considered the Father of Sleep Medicine.

When was the Sleep Research Society formed?

1961.

What important melatonin discovery occurred in 1963?

Melatonin was shown to be synthesized in the pineal gland and to respond to light.

What is the per gene?

A gene identified in 1971 as a component of the biological clock.

What brain structure was identified as the biological clock site in 1972?

The suprachiasmatic nucleus (SCN).

Why was 1975 a major year for sleep medicine?

Key sleep organizations and meetings formed, including the AASM and ASDC, and narcolepsy received major attention.

What is the AASM?

The American Academy of Sleep Medicine, a professional society for the medical subspecialty of sleep medicine; Dement was a founder.

What is the MSLT?

The Multiple Sleep Latency Test, developed by Mary Carskadon and William Dement in the late 1970s/early 1980s.

Who was Mary Carskadon?

A sleep researcher mentored by Dement who developed the MSLT and whose research and advocacy helped support later school start times.

What treatment did NIH identify as the treatment of choice for insomnia?

Cognitive behavioral therapy (CBT).

What are the major components of the limbic system emphasized in the slides?

Limbic cortex, hippocampus, amygdala, parts of the hypothalamus, and portions of frontal cortex.

What functions is the limbic system important for?

Motivation, emotion, and memory.

What structures are included in the brainstem review?

Medulla, pons, cerebellum, midbrain, reticular formation, and raphé.

What did von Economo infer from patients with midbrain-diencephalic damage?

An ascending brainstem input to the forebrain is needed to maintain wakefulness.

What did Bremer's encéphale isolé cats demonstrate?

Cats with spinal cord severed just below the brain were paralyzed but still awake with normal EEG and facial/eye movements.

What did Bremer's cerveau isolé cats demonstrate?

Severing between the superior and inferior colliculi produced a coma, implying arousal influence comes from brainstem below the inferior colliculus.

What is the ascending reticular activating system (ARAS)?

A brainstem arousal system proposed by Moruzzi and Magoun after lesion/stimulation work on the upper reticular formation.

What is the basal forebrain's role in wakefulness?

It is a key wake-promoting relay with cholinergic, GABAergic, and glutamatergic neurons.

Which neurotransmitter is critical in the basal forebrain for maintaining wakefulness and high-frequency EEG rhythms?

GABA.

What is acetylcholine's role in wakefulness?

It supports arousal and attention through wide projections to the cerebral cortex.

What is norepinephrine's role in wakefulness?

NE neurons fire more during wakefulness and support vigilance and arousal.

What is histamine's role in wakefulness?

Histamine increases arousal; antihistamines can induce drowsiness.

What is orexin also called?

Hypocretin.

What does orexin do?

It facilitates alertness/wakefulness, helps switch between sleep states, and has a role in appetite.

What happens when orexinergic neurons are lost?

Narcolepsy can result.

Where are key acetylcholine-producing groups feeding into the ARAS?

The pedunculopontine (PPT) and laterodorsal tegmental (LDT) nuclei of the brainstem.

How does ARAS output activate the cortex?

Through a thalamic route and a posterior-hypothalamic route; output through basal forebrain uses acetylcholine to excite cortex and hippocampus.

What is the locus coeruleus's contribution to wakefulness?

It uses norepinephrine to activate the forebrain and help control what sensory input is attended to.

What does the raphé use to stimulate wakefulness?

Serotonin.

Where are many sleep-promoting neurons located?

In the preoptic hypothalamus and rostral medulla.

What is the VLPO?

The ventrolateral preoptic area: anterior-hypothalamic sleep-active cells that become active at sleep onset and increase activity with sleep depth.

How are VLPO neurons related to sleep deprivation?

They are sensitive to sleep deprivation and are important for recovery sleep.

What is the MnPO's role?

The median preoptic nucleus responds dynamically to homeostatic sleep pressure; GABA supports sleep drive and glutamate supports recovery sleep.

What is the parafacial zone?

A rostral-medulla group of sleep-promoting neurons that increases discharge before NREM onset and may inhibit wake-promoting regions.

What neurotransmitter dominates NREM sleep promotion?

GABA, an inhibitory neurotransmitter that dampens neural activity and reduces arousal.

What is adenosine's overall role in sleep?

It is a somnogen associated with homeostatic sleep pressure that promotes sleep.

How does adenosine promote sleep?

It inhibits wake-promoting neurons, disinhibits VLPO sleep-promoting neurons, and activates sleep-promoting neurons in the nucleus accumbens.

Which adenosine receptor is associated with sleep need?

A1 receptors.

Which adenosine receptor is associated with allowing the brain to sleep?

A2A receptors.

How do adenosine levels relate to wake and sleep?

Glycogen depletion during wakefulness promotes adenosine release; adenosine builds during waking and diminishes during sleep.

How does caffeine affect adenosine?

It competes with adenosine at A1 and A2A receptors, weakening adenosine's sleep-promoting impact.

What does a higher adenosine level at sleep onset predict?

More slow-wave sleep (SWS) and delta waves during sleep.

What is serotonin's proposed role in NREM sleep?

It helps sleep onset by dampening the brain's response to sensory input.

What is glycine's key role in REM sleep?

It helps produce REM muscle paralysis (atonia).

How can SSRIs affect REM sleep?

By altering norepinephrine/serotonin signaling, they can eliminate REM sleep.

Which areas are more active in REM than in waking, according to the slides?

The temporal-occipital junction, posterior pons/midbrain, thalamus, and limbic system.

Which areas are less active in REM than in waking?

Associative areas in the frontal cortex and forebrain.

Where are REM-on cells located?

On the rostral side of the pons; they are largely glutamatergic.

What is the sublaterodorsal nucleus (SLD) role in REM?

It drives muscle atonia through projections to ventromedial medulla and spinal cord that activate glycinergic premotor neurons and inhibit motor neurons.

What do PB and PC REM pathways do?

The medial parabrachial (PB) and precoeruleus (PC) pathways help desynchronize the cortex by projecting to basal forebrain and intralaminar thalamus.

Where are REM-off cells concentrated?

In the locus coeruleus (norepinephrine) and raphé (serotonin).

How do REM-off cells affect REM-on cells?

They inhibit REM-on cells; their influence weakens through the night as sleep cycles transition between NREM and REM.

What is quiescence?

A state or period of inactivity or dormancy.

What is rest?

Reduced activity without loss of consciousness or greatly reduced responsiveness.

What is torpor?

Decreased physical activity, typically with reduced body temperature and metabolic rate; it may occur daily and is easily aroused from.

What is hibernation?

A state of inactivity and metabolic depression from which an animal is not easily aroused.

What three criteria must be met to identify sleep in other species?

Rapidly reversible immobility, greatly reduced sensory responsiveness, and homeostatic regulation including sleep rebound after sleep loss.

Why must sleep be distinguished from circadian changes in alertness?

Reduced activity can reflect body-clock timing rather than sleep itself.

What is sleep rebound?

An increased drive for sleep after sleep has been lost, showing homeostatic regulation.

What has sleep research found in fruit flies?

Drosophila show a behavioral state that satisfies all behavioral criteria of sleep, though their nervous system differs from humans'.

How can sleep be studied in fruit flies?

By infrared-beam or video actigraphy, local field potentials, calorimetry, and tests of arousal threshold.

What zebrafish observations support sleep-like behavior?

Circadian changes in responsiveness/activity and decreased responses to stimuli after rest deprivation.

What did perch show after deprivation?

An increase in rest behavior, though light used for deprivation may have had stimulatory effects.

What is known about sleep in tree frogs?

Tree frogs sleep, but there is no evidence of REM sleep.

Why did researchers conclude bullfrogs may not sleep?

Bullfrogs were more responsive while inactive than active, suggesting they can rest without losing vigilance.

What is uncertain about reptile REM sleep?

Reports conflict, and REM-like states may occur without eye movements or muscle-tone suppression; episodes must be distinguished from waking.

What kind of sleep do birds show?

Both REM and NREM sleep by electrographic criteria, with shorter REM periods than most mammals.

What is notable about white-crowned sparrows during migration?

They reduce sleep by about two-thirds without reduced task performance, sleep rebound, or rat-like deprivation pathologies.

What do conventional studies show about domesticated land mammals?

Rats, mice, cats, dogs, and monkeys meet the conventional definition of sleep.

How do wild and zoo African elephant sleep times compare?

Wild elephants average about 2.1 hours/day, whereas zoo elephants sleep about 4-5 hours/day.

How do fur seals/sea lions sleep on land versus in water?

On land they show bilateral synchronized EEG and cycle through REM/NREM; in water they show one-hemisphere SWS with the opposite eye closed and reduced REM.

What is unihemispheric slow-wave sleep (USW)?

Slow-wave sleep in one cerebral hemisphere at a time, shown by cetaceans such as bottlenose dolphins and beluga whales.

Why should scientists be cautious when concluding an animal does not sleep?

Sleep varies by species, few species have been thoroughly studied, and inactivity alone is not definitive evidence.

How does human sleep compare with nonhuman primates in the slides?

Humans have comparatively short sleep times and a greater REM proportion.

What sleep patterns are common in primates?

Sleep consolidated into one or two long bouts, reduced total sleep in diurnal species, increased sleep intensity, and social contact during sleep.

Which Neanderthal-linked genes were said to enhance REM processes?

ASB1 and EXOC6; the slides also associate them with increased narcolepsy risk.