Chapter 13: Why Do We Sleep and Dream?

Fatal familial insomnia

A sleep disorder where sleeping stops altogether. Contributes to death after a number of months without sleep. Caused by prions.

If the activity of the cholinergic projection is blocked by drugs or by lesions to the cells of the basal forebrain, the waking EEG normally recorded from an immobile rat is replaced by EEG activity resembling that of _____ sleep.

NREM

NREM Sleep and Explicit Memory: During _____ sleep, if an animal was just doing a task that would involve place cell, the correlations between the place cell activity during the task and the ______ sleep is present.

NREM NREM

The _____ of REM sleep is produced by the MPRF through a pathway that sends input to the subcoerulear nucleus located just behind it.

atonia

Another proposed cause of narcolepsy in humans is an _____ reaction: the immune system attacks and kills orexin cells.

autoimmune

The MPRF also excites _____ motor nuclei to produce rapid eye movements and other twitches.

brainstem

Retinohypothalamic tract activates the _____ cells - they are not rhythmic, but they entrain the shell neurons, which are rhythmic.

core

The activity of nearly every cell in our body has a _____ rhythm.

daily

In NREM sleep, body temperature _____, heat rate and blood flow _____, body weight decreases from water loss in perspiration, and growth hormone levels _____. We also toss and turn a lot in bed. Talking or sleepwalking also occurs in NREM sleep.

declines decrease increase

Electrodes placed on neck muscles provide an _____ (EMG).

electromyogram

Electrodes located near the eyes provide an _____ (EOG) to record eye movements.

electrooculogram

Hamsters: during the dark, the pineal gland secretes melatonin; during the light, it does not. When the melatonin levels are low, the gonads _____, and when the level is high, the gonads _____. The SCN thus controls the pineal gland's sway over the gonads.

enlarge shrink

The property that allows a biological clock to be _____ explains how circadian rhythms synchronize with seasonal changes in day-night duration. E.g., an entrained biological clock allows animals to synchronize daily activity across seasonal change in light at the poles.

entrained

Animals living in polar regions have to cope with _____ seasonal fluctuations in daily temperature, light, and food availability.

greater

In the first two years of life, REM sleep is about _____ of sleep time. By middle age, it is only about 10% of sleep time.

half

Evidence of the SCN's role in circadian rhythms now comes from additional lines of evidence (1 of 5): If the suprachiasmatic nuclei are selectively damaged, animals still eat, drink, exercise, and sleep but at _____ times.

haphazard

Almost all organisms have biological clocks that synchronize behavior to the temporal passage of a read lady and make predictions about tomorrow.

i.e. it is not just to do with light - if light is taken away, there is still a biological clock running.

Basal forebrain system nor the median raphe system: as long as one system is producing waking EEG, rats can learn simple tasks. If both are destroyed, there is no longer an ability to display _____ behavior.

intelligent

REM sleep is _____ eventful than NREM sleep. Our eyes move; our fingers, toes, and moths twitch; and males have penile erections. Still, we are paralyzed, as indicated by atonia.

less

Evidence of the SCN's role in circadian rhythms now comes from additional lines of evidence (2 of 5): If a form of glucose is tagged with a radioactive label, taken up by metabolically active cells, and trapped in them but not used by them, cells that are more active will subsequently emit more radioactivity. When this tracer is injected into rodents, more is found in the SCN after injections given in the light period of the light-dark cycle than in the dark period. This experiment demonstrates that suprachiasmatic cells are more active during the _____ period.

light

Evidence of the SCN's role in circadian rhythms now comes from additional lines of evidence (3 of 5): Recording electrodes placed in the SCN confirm that neurons in this region are more active during the _____ period of the cycle than during the _____ period.

light dark

SCN neurons are _____ from one another - each is rhythmic, but the period of some cells differ. Rhythmic activity must be sent to the cells to synchronize their activity in relation to each other.

separated

The SCN is entrained by light, which in turn drives a number of _____ _____.

slave oscillators

Melatonin promotes _____ and influences the PNS as well as other physiological events in the body.

sleep

Untreated _____ _____ can cause high blood pressure and other cardiovascular diseases, memory problems, weight gain, impotence, headaches, and brain damage due to oxygen insufficiency.

sleep apnea

Neither the basal forebrain system nor the median raphe system is responsible for behavior. In fact, if both structures are pharmacologically or surgically destroyed, a rat can still stand and walk around. Its EEG, however, permanently resembles that of a _____ animal.

sleeping

Sleeping State: Delta (δ) rhythm: "_____ brain wave activity pattern associated with deep sleep." Also called slow-wave sleep: NREM sleep

slow

Drowsy State: EEG indicates that beta wave activity in the neocortex gives way to _____ EEG wave activity. Amplitude _____, and frequency is _____: theta (θ) rhythm.

slower increases lower

Waking State: EEG is _____-amplitude, and _____-frequency. Known as a _____ rhythm.

small high beta

The _____ nucleus excites the magnocellular nucleus of the medulla, which sends projections to the spinal motor neurons to inhibit them so that paralysis is achieved during the REM sleep period.

subcoerulear

The SCN is usually entrained by morning and evening light, but can also be from _____ changes in light.

sudden

Only a _____ lesion will stop circadian rhythms.

suprachiasmatic

The SCN has a _____-located core, and a _____-located shell.

ventrally dorsally

Humans generate alpha rhythms in the _____ cortex, and they stop abruptly if a relaxed person opens their eyes.

visual

The midbrain structure the median raphe contains serotonin (5-HT) neurons whose axons also project diffusely to the cortex, where they also stimulate cortical cells to produce a _____ EEG.

waking

Cutting the brainstem behind the RAS showed that the RAS was the source of _____, and sensory stimulation produces _____ because it activates the RAS neurons.

waking waking

The basal forebrain contains large cholinergic cells. These neurons secrete acetylcholine (ACh) from their terminals onto cortical neurons to stimulate a ______ EEG (_____ rhythm).

waking beta

There are three contemporary explanations for sleep:

- as adaptive - as restorative - as supportive for memory

To test if a rhythm is produced by a biological clock, there are three tests that can be given:

1. Continuous light. 2. Continuous dark. 3. Be choice of the participant.

REM Sleep Deprivation: two main effects:

1. Participants show an increased tendency to enter REM sleep in subsequent sleep sessions, so awakenings must become more and more frequent. 2. After REM deprivation, participants experience REM rebound, showing more than the usual amount of REM sleep in the first available sleep session.

The SCN clock entrains slave oscillators through a remarkable array of pathways (4):

1. SCN neurons send axonal connections to nuclei close by in the hypothalamus and thalamus. These nuclei in turn connect extensively with other brain and body structures, to which they pass on the entraining signal. 2. The SCN connects with pituitary endocrine neurons to control hormone release. A wide range of hormones circulates through the body to entrain many body tissues and organs. 3. The SCN also sends indirect messages to autonomic neurons in the spinal cord to inhibit the pineal gland from producing the hormone melatonin, which influences daily and seasonal biorhythms. 4. SCN cells themselves release hormones. Silver and colleagues (1996) used a transplantation technique in which encapsulated SCN cells were transplanted into hamsters that had received SCN lesions. Even though the transplanted cells did not make axonal connections, they restored many circadian behaviors, indicating that some SCN signals must be hormonal and travel through the bloodstream.

Aschoff and Weber - allowed people to select their light-dark cycle and studied them in a bunker with no cues from the outside. They controlled when they slept - turning the lights on and off. They found that the sleep-wake cycle followed a _____-_____-hour period, so the people went to bed later, and woke up later each day. By the end of 25 days, they were sleeping 12 hours later than when they started. Example of a free-funning rhythm.

25-27

SSRIs suppress REM sleep either partially or completely. Only about _____% of people on SSRIs display REM sleep behavioral disorder, characterized by agitated movements, as if the sleep were acting out dreams.

6

BRAC lasts about _____ minutes in humans.

90

Synchronizing Biorhythms at a Molecular Level: 4. Decay:

After they play their inhibitory role, the PERCRY proteins decay. Then the CB dimer resumes its activity, the Per and Cry genes resume expression, and the 24-hour cycle begins anew.

The SCN rhythm is not learned. When animals are raised in constant darkness, their behavior still becomes rhythmic. It also continues with generations.

Aka - there is a genetic component to it.

Relaxes State _____ rhythm: "_____, extremely _____ brain waves with a frequency ranging from 7 to 11 Hz."

Alpha (α) large regular

Sleep Paralysis

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

Dream theory: 1. Dreams as Meaningless Brain Activity: _____-_____ approach that centers on the activation-synthesis hypothesis.

Bottom-up This hypothesis is that dreams are personal in that memories and experience are activated, but they have no meaning. They just happen and there is no underlying meaning or representation of the dream.

Sleep-deprived people often take microsleeps:

Brief sleep period lasting a second or so - common when driving long distances.

REM Sleep Behavioral Disorder

Characterized with REM sleep without atonia - happens when people take antidepressant drugs like SSRIs. People with this condition will behave as though they are acting out their dreams.

Peribrachial area

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

Drug dependence insomnia

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.

E cells

Control evening activity; they need evening light for entrainment.

M cells

Control morning activity; they need morning light for entrainment.

Ultradian rhythms

Cycles less than a day, e.g., human eating cycle.

Infradian rhythms

Cycles longer than a day, e.g., a menstrual cycle.

Circadian rhythms

Daily rhythms, e.g., human sleep-wake cycles.

Entrain

Determine or modify the period of a biorhythm.

Insomnia

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

Hypnogogic hallucination

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

Zeitgeber

Environmental event that entrains biological rhythms.

Light pollution

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

Cats with lesions in the subcoerulear nucleus display a remarkable behavior when they enter REM sleep. Rather than stretching out in the atonia that typically accompanies REM sleep, the cats he was studying stood up, looked around, and made movements of catching an imaginary mouse or running from an imaginary threat. Apparently if cats with damage to this brain region dream about catching mice or escaping from a threat, they are now acting out their dreams.

Fact

Cognitive behaviour and emotional behaviour also synchronize with circadian periods. E.g., fear is more common at night time.

Fact

Humans' sleep is about between that of omnivores and carnivores.

Fact

Restless leg syndrome: people with RLS experience unpleasant sensations in the legs - usually in the calf area - described as creeping, crawling, tingling, pulling, or pain. One or both legs may be effected.

Fact

Sleep deprivation does not seem to have adverse physiological consequences, but it is associated with poor cognitive performance.

Fact

When people are isolated in quiet rooms, they sleep less, not more. This refutes the idea that sleep is merely when we have nothing better to do.

Fact

REM sleep

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

Jet lag

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

Consolidation phase

Forges a relatively permanent representation of memory - depends on biochemical and genetic activity.

_____ mobilize glucose for cellular activity to support arousal responses in the SNS.

Glucocorticoids

Place cell

Hippocampal neuron maximally responsive to specific locations in the world.

Seasonal Affective Disorder (SAD)

In SAD, low levels of sunlight in the winter do not entrain the circadian rhythm. Consequently, a person's biorhythm becomes a free-running rhythm. The perception of longer nights by the circadian pacemaker stimulates wanting more sleep. If this want is not satisfied, cumulative sleep deprivation can result.

Synchronizing Biorhythms at a Molecular Level: 1. Transcription

In the cell nucleus three Period genes (Per1, Per2, Per3) and two Cryptochrome genes (Cry1, Cry2) are transcribed into Per1, Per2, and Per3 messenger RNA and Cry1 and Cry2 mRNA.

Sleep apnea

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

Episodic memory

Includes conscious information such as our autobiographical memories and knowledge of facts.

Implicit memory

Includes unconscious processes such as motor skill learning.

Chronotype

Individual differences in circadian activity. E.g., night owls or early birds.

Biorhythms

Inherent timing mechanism that controls or initiates biological processes.

Atonia

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

Reticular activating system (RAS)

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.

The _____ sends projections to excite basal forebrain cholinergic neurons, resulting in an activated EEG recorded from the cortex.

MPRF

Suprachiasmatic nucleus (SCN)

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

Labile phase

Memory is encoded - fragile and must compete with existing memories and the addition of new memories.

Retinohypothalamic tract

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

______ _____: dreams so vivid that the child continues to experience a dream and the fear after waking. Common in younger children.

Night terrors

Medial pontine reticular formation (MPRF)

Nucleus in the pons participating in REM sleep.

Synchronizing Biorhythms at a Molecular Level: 3. Inhibition:

PERCRY dimers enter the cell nucleus, where they bind to and inhibit the CB dimer (formed by the CLOCK and BMAL proteins). The CB dimer turns on the Enhancer box (Ebox), a part of the DNA that activates transcription of the Period and Cryptochrome genes, so that when the CB dimer is inhibited, the Per and Cry genes are no longer expressed.

Synchronizing Biorhythms at a Molecular Level: 2. Translation:

Ribosomes in the endoplasmic reticulum translate these mRNAs into the proteins PER1, PER2, PER3, and CRY1, CRY2. In the intracellular fluid the proteins form various dimers, or two-protein combinations of PERCRY.

Coma

Prolonged state of deep unconsciousness resembling sleep.

Storage process theories

Propose that brain regions that handle different kinds of memory during waking continue to do so during sleep.

Multiple process theories

Propose that different kinds of memory are stored during different sleep states.

Sequential process theories

Propose that memory is manipulated in different ways during different sleep states.

Recall phase

Puts memory to work at some future time and also integrates it into existing memory stores.

Because children spend much more time in _____ sleep, they have complex dreams filled with emotion and conflict.

REM

During _____ sleep, mechanisms that regulate body temperature stop working and body temperature moves towards room temperate. Waking up from REM sleep may have you feeling cold or hot, depending on the temperature of the room.

REM

The amount of time spent in ______ sleep decreases with age. They are high in infancy, increase during growth spurts, and pregnancy.

REM

The peribrachial area initiates _____ sleep by activating the medial pontine reticular formation.

REM

Basic rest-activity cycle (BRAC)

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

Free-running rhythm

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

NREM sleep

Slow-wave sleep associated with delta rhythms.

Narcolepsy

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

Cataplexy

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

Period

Time required to complete an activity cycle.

Dream theory: 2. Dreams as a Coping Strategy: _____-_____ approach that centers on the coping hypothesis.

Top-down

_____-to-_____ travelling is generally more difficult than _____-to-_____ travelling (need to stay up longer than usual).

West-to-east east-to-west

Lucid dreaming:

When we are aware of our dreams as we dream.

Circannual rhythms

Yearly rhythms, e.g., migratory cycles of birds.

The peribrachial area extends into a more ventrally located nucleus called the _____ _____ _____ _____.

medial pontine reticular formation

RGCs in the retinohypothalamic tract contain the photosensitive pigment _____. These receive light-related signals from the rods and cones that send information to the brain's visual centers. They can also be activated by certain _____ wavelengths directly in the absence of rods and cones.

melanopsin blue

The SCN releases _____ from the pineal gland so that it circulates during the dark phase of the circadian cycle. It also controls the release of glucocorticoids from the adrenal gland so that they circulate during the light phase.

melatonin

REM Sleep and Implicit Memory: On PET scan measures of brain activation, a similar pattern of neocortical activation appeared during task acquisition and during REM sleep. Suggests that much rule learning in both _____ and _____ domains likely is strengthened during sleep, including REM sleep.

motor cognitive

Mice bred without _____ will collapse into cataplexy at random time of activity, like eating.

orexin

Research shows that _____ serves as a signaling molecule to maintain wakefulness. It helps us remain active when awake.

orexin

Evidence of the SCN's role in circadian rhythms now comes from additional lines of evidence (5 of 5): SCN cells removed from the brain and cultured in a dish _____ a periodic rhythm.

retain

Malcolm-Smith:

reward-seeking behavior is as likely to represent a dream's latent content as avoidance behavior is.

Each slave oscillator is responsible for the _____ occurrence of one activity - e.g., eating, drinking, body temperature.

rhythmic

Evidence of the SCN's role in circadian rhythms now comes from additional lines of evidence (4 of 5): If all the pathways into and out of the suprachiasmatic nucleus are cut, SCN neurons maintain their _____ electrical activity.

rhythmic