Chapter 9 – Wakefulness And Sleep

Question 1

Self-generated rhythm that lasts about a year

Answer 1

Endogenous circannual rhythm

Example: the migratory patterns of birds

Question 2

Self-generated rhythm that lasts about a day

Answer 2

Endogenous circadian rhythm

Example: the wake-sleep rhythms of humans that follow a 24 hour schedule

We have a circadian rhythm’s in our eating and drinking, urination, secretion of hormones, sensitivity to drugs, and body temperature

Question 3

Describe the circadian rhythm for human emotion

Answer 3

We have circadian rhythm’s in mood.

Most individuals in one study showed increases in positive mood from waking until late afternoon, and then a slight decline from then to bedtime.
Most people recorded their most pleasant mood around 5 PM, and their least pleasant mood at around 5 AM.

Question 4

What evidence indicates that humans have an internal biological clock?

Answer 4

People who have lived in an environment with a light-dark schedule much different from 24 hours fail to follow that schedule and instead become wakeful and sleepy on about a 24 hour basis

Question 5

Stimulus that resets the circadian rhythm

Answer 5

Zeitgeber

Question 6

Describe various forms of zeitgeber

Answer 6

Light is the dominant one for land animals, and the tides are important for many marine animals.

Others include exercise, arousal of any kind, meals, the temperature of the environment, and to a lesser degree social stimuli.

Question 7

Why do people at the eastern edge of Germany awaken earlier than those at the western edge on their weekends and holidays?

Answer 7

The sunrise is about half an hour earlier at the eastern edge than at the western edge. Evidently, the sun controls waking-sleeping schedules even when people follow the same clock time for their work schedule

Question 8

A disruption of circadian rhythms due to crossing time zones

Answer 8

Jet lag

Question 9

Do most people find it easier to adjust to crossing time zones going East or west? (Jet lag)

Answer 9

Most people find it easier to adjust to crossing times zones going west then east. Going west, we stay awake later at night and then awaken late the next morning, already partly adjusted to the new schedule. We phase-delay our circadian rhythm’s. Going east, we phase-advance to sleep earlier and awaken earlier. Most people find it difficult to go to sleep before their bodies usual time and difficult to wake up early the next day.

Adjusting to jet lag is often stressful. Stress elevates blood levels of the adrenal hormone cortisol, and many studies have shown that prolonged elevations of cortisol damage neurons and hippocampus, a brain area important for memory

Question 10

Describe the sleep duration of people who sleep irregularly, including shift workers.

Answer 10

Their duration of sleep depends on when they go to sleep. When they have to sleep in the morning or early afternoon, they sleep only briefly, even if they have been awake for many hours.
Many shift workers adjust incompletely and working at night does not reliably change the circadian rhythm because most buildings use artificial lighting, which is only moderately effective in resetting the rhythm.

People adjust best to night work if they sleep in a very dark room during the day and work under very bright lights at night

Question 11

Part of the hypothalamus; provides the main control of the circadian rhythms for sleep and body temperature

Answer 11

Suprachiasmatic nucleus or SCN

It gets its name from its location just above or supra the optic chiasm

After damage to the SCN, the body’s rhythms become a erratic

Question 12

What evidence strongly indicates that the suprachiasmatic nucleus produces the circadian rhythm itself?

Answer 12

SCN cells produce a circadian rhythm of activity even if they are kept in a cell culture isolated from the rest of the body. Also, when hamsters received transplanted SCN neurons, there circadian rhythm followed the pattern of the donor animals

Question 13

How does light reset the biological clock?

Answer 13

A branch of the optic nerve, the retinohypothalamic path, conveys information about light to the SCN. The axons comprising that path originate from special ganglion cells that respond to light by themselves, even if they do not receive input from rods or cones.

These special ganglion cells are located mainly near the nose, not evenly throughout the retina. They respond to light slowly and turn off slowly when the light ceases. Therefore, they respond to the overall average amount of light, not to instantaneous changes in light.

Consequences: first, many people who are blind because of damage to the rods and cones nevertheless have enough input to the melanopsin-containing ganglion cells to entrain their waking and sleeping cycle to the local pattern of sunlight. Second, it was formerly puzzling that bright light aggravates migraine headaches even for many blind people. The explanation is that the melanopsin-containing ganglion cells send input to the posterior thalamus, which is part of the pathway producing pain in migraines

Question 14

How do the proteins TIM and PER relate to sleepiness in Drosophila (fruit flys)?

Answer 14

The proteins TIM and PER remain low during most of the day and begin to increase toward evening. They reach higher levels at night, promoting sleep. They also feed back to inhibit the genes that produce them, so that their level declines toward morning

Question 15

Proteins in Drosophila that promote sleep and inactivity

Answer 15

TIM and PER

Mammals have three versions of the PER protein and several proteins closely related to TIM and the others found in flies. People with a particular PER mutation have been found to have a circadian rhythm shorter than 24 hours, as if they were moving about a time zone West every day. People with a different mutation are normal in most regards except that there alertness deteriorate substantially if they are deprived of a good nights sleep

Question 16

And endocrine gland located just posterior to the thalamus that releases the hormone melatonin

Answer 16

Pineal gland

The pineal gland secretes melatonin mostly at night, making a sleepy at that time. When people shift to a new time zone and start following a new schedule, they continue to feel sleepy at their old times until the melatonin rhythm shifts.

Melatonin secretion starts to increase about two or three hours before bedtime. Taking a melatonin pill in the evening has little effect on sleepiness because the pineal gland produces melatonin at that time anyway. However, people who take melatonin at other times become sleepy within two hours. A moderate dose of melatonin in the afternoon phase-advances the clock. It makes the person get sleepy earlier in the evening and wake up earlier the next morning. A single dose in the morning has little effect, although repeated doses can phase-delay the clock, causing the person to get sleepy later than usual at night and awaken later the next morning

Question 17

Hormone that influences both circadian and circannual rhythms

Answer 17

Melatonin

Question 18

An extended period of unconsciousness with a low level of brain activity

Answer 18

Coma

Caused by head trauma, stroke, or disease

In contrast to coma, sleep is a state that the brain actively produces, characterized by decreased response to stimuli. It is possible to awaken a sleeping person but not someone in a coma. A person in a coma has a low level of brain activity throughout the day, and little or no response to stimuli, including those that are ordinarily painful. Any movements are purposeless and not directed toward anything

Question 19

Condition in which someone has decreased brain activity and alternates between wakefulness and sleep but shows only limited responsiveness, such as increased heart rate in response to a painful stimulus

Answer 19

Vegetative state

Question 20

Condition of decreased brain activity with occasional, brief periods of purposeful actions and limited speech comprehension

Answer 20

Minimally conscious state

Question 21

Condition with no sign of brain activity and no response to any stimulus

Answer 21

Brain death

Question 22

A combination of EEG and eye movement records

Answer 22

Polysomnograph

Question 23

A steady series of brain waves at a frequency of 8 to 12 per second that are characteristic of relaxation

Answer 23

Alpha waves

Question 24

12 to 14 Hz brain waves in bursts that last at least half a second

Answer 24

Sleep spindle

Question 25

A sharp brain wave associated with temporary inhibition of neuronal firing

Answer 25

K-complex

Question 26

Stages 3 and 4 of sleep, which are occupied by slow, large-amplitude brain waves

Answer 26

Slow-wave sleep SWS

Question 27

Describe the different stages of sleep

Answer 27

Relaxed awake: an EEG shows a steady series of alpha waves at a frequency of 8 to 12 per second. These waves are characteristic of relaxation

Stage 1: The EEG is dominated by irregular, jagged, low-voltage waves. Overall brain activity is less than in relaxed wakefulness but higher than other sleep stages.
Stage 2: prominent characteristics – sleep spindles and K-complexes. A sleep spindle consists of 12 to 14 Hz waves during a burst that lasts at least half a second. Sleep spindles result from oscillating interactions between cells in the thalamus and cortex. A K-complex is a sharp wave associated with temporary inhibition of neuronal firing.

Staged 3 and 4: heart rate, breathing rate, and brain activity decrease, while slow, large-amplitude waves become more common. By stage four, more than half the record includes large waves of at least a half second duration. These two stages constitute slow-wave sleep SWS

REM Or paradoxical sleep: EEG shows a regular, low-voltage fast waves that indicate increased neuronal activity. In this regard, REM sleep is late. However, the postural muscles of the body including those of the head, are more relaxed than in other stages, and in this regard it is deep sleep. Heart rate, blood pressure, and breathing rate are more variable than in stages two through four. REM sleep combines deep sleep, light sleep, and features that are difficult to classify as deep or light.

Question 28

What do long, slow waves on an EEG indicate?

Answer 28

Long, slow waves indicate a low level of activity, with much synchrony of response among neurons

Question 29

Sleep that is deep in some ways and light and others

Answer 29

Paradoxical sleep

Discovered by accident by French scientist Michelle Jouvet who was trying to test the learning abilities of cats after removal of the cerebral cortex. During certain periods of apparent sleep, the cats brain activity was relatively high, but their neck muscles were completely relaxed.

Question 30

Sleep stage with rapid eye movement, high brain activity, and relaxation of the large muscles

Answer 30

Rapid eye movement or REM sleep

In the US, to researchers were observing I movements of sleeping people as a means of measuring depth of sleep, assuming that eye movements would stop during sleep. After repeated careful measurements they concluded that periods of rapid eye movement occur during sleep.

Question 31

Stages of sleep other than REM

Answer 31

Non–rapid eye movement sleep NREM

Question 32

Describe the speed of progression through the different sleep stages

Answer 32

When you fall asleep, you start in stage 1 and slowly progressed to stages 2, 3, and 4 in order, although loud noises or other intrusions can interrupt the sequence. After about an hour of sleep, you begin to cycle back from stage 4 through stages 3, 2, and then REM. The sequence repeats, with each cycle lasting about 90 minutes.
Early in the night, stages three and four predominate. Toward morning, REM occupies an increasing percentage of the time.

Question 33

How can an investigator determine whether a sleeper is in REM sleep?

Answer 33

Examine EEG pattern and I movements

EEG shows irregular, low-voltage fast waves that indicate increased neuronal activity.

Question 34

During which part of a night sleep is REM most common?

Answer 34

REM becomes more common toward the end of the night’s sleep

Question 35

A structure that extends from the medulla into the forebrain; controls motor areas of the spinal cord and selectively increases arousal and attention in various forebrain areas

Answer 35

Reticular formation

A cut through the midbrain decreases arousal by damaging the reticular formation.

Question 36

Part of the reticular formation that contributes to cortical arousal

Answer 36

Pontomesencephalon

These neurons receive input from any sensory systems and generate spontaneous activity of their own. Their axons extend into the forebrain, releasing acetylcholine and glutamate, which excites cells in the hypothalamus, thalamus, and basal forebrain. Consequently, this area maintains arousal during wakefulness and increases it in response to new or challenging tasks.
Stimulation of this area awakens a sleeping individual or increases alertness in one already awake, shifting the EEG from long, slow waves too short, high-frequency waves

Question 37

A small structure in the pons that emits bursts of impulses in response to meaningful events, especially those that produce emotional arousal.

Axons here release norepinephrine widely throughout the cortex, so this tiny area has a huge influence. Anything that stimulates this area strengthens the storage of recent memories and increases wakefulness

Answer 37

Locus coeruleus

Question 38

Neurotransmitter that increases wakefulness and arousal

Answer 38

Orexin or hypocretin

Question 39

Area anterior and dorsal to the hypothalamus; includes cell clusters that promote wakefulness and sleep

Answer 39

Basal forebrain

Question 40

The hypothalamus has several axon pathways that influence arousal. Describe three

Answer 40

1. One pathway releases the neurotransmitter histamine, which produces excitatory effects throughout the brain. Cells releasing histamine are active during arousal and alertness, and are less active when you are getting ready for sleep and when you have just awakened in the morning.
   Antihistamine drugs, often used for allergies, counteract this transmitter and produce drowsiness. Antihistamines that do not cross the blood-brain barrier avoid that side effect
2. Another pathway, mainly from the lateral and posterior nuclei of the hypothalamus, releases a peptide neurotransmitter called either orexin or hypocretin. The axons releasing orexin extend to the basal forebrain and other areas, where they stimulate neurons responsible for wakefulness. This neurotransmitter is not necessary for waking up, but it is for staying awake. Staying awake depends on orexin, especially toward the end of the day.
3. Other pathways from the lateral hypothalamus regulate cells in the basal forebrain. These cells provide axons that extend throughout the thalamus and cerebral cortex, and some release acetylcholine, which is excitatory and tends to increase arousal. Acetylcholine is released during wakefulness and REM sleep, but not during slow-wave sleep. During wakefulness, acetylcholine sharpens attention – it increases the accurate, reliable detection of sensory stimuli

Question 41

Why do most antihistamines make people drowsy?

Answer 41

Two paths from the hypothalamus – one to the basal forebrain and one to the pontomesencephalon – use histamine as their neurotransmitter to increase arousal. Antihistamines that cross the blood-brain barrier block those synapses

Question 42

What would happen to the sleep-wake schedule of someone who lacked orexin?

Answer 42

Someone without orexin would alternate between brief periods of waking and sleeping

Question 43

Describe the role of GABA during sleep and the inhibition of brain activity

Answer 43

GABA is the brains main inhibitory transmitter. It is responsible for sleep.

During sleep, activity of neurons decrease, but by less than we might expect. Spontaneously active neurons continue to fire at close to their usual rate, and neurons in the brain sensory areas continue to respond to sounds and other stimuli. Nevertheless, we are unconscious. The reason is that GABA inhibits synaptic activity. When a neuron is active, the increased GABA levels cut the Activity short and prevent axons from spreading stimulation to other areas. Connections from one brain area to another become weaker, and when stimulation doesn’t spread, you don’t become conscious of it.

Because sleep depends on GABA-mediated inhibition, it can be local within the brain. That means he might have substantial inhibition in one brain area and not so much in another. In cases when different brain areas wake up and go to sleep at different times, this can cause phenomenons such as sleepwalking and waking up and not being able to move your arms or legs.

Question 44

What would happen to the sleep-wake schedule of someone who took a drug that blocked GABA?

Answer 44

Someone who took a drug that blocked GABA would remain awake. Tranquilizers put people to sleep by facilitating GABA

Question 45

Someone who has just awakened sometimes speaks in a loose, unconnected, illogical way. How could you explain this finding?

Answer 45

People often awaken from REM period, because REM is abundant toward morning when people usually awaken. Different brain areas don’t wake up all at once. Shortly after awakening, parts of the brain may still be in a REM-like state, and thinking may have an illogical, dreamlike quality

Question 46

A distinctive pattern of high-amplitude electrical potentials that occur first in the pons, then in the lateral geniculate, and then in the occipital cortex

Answer 46

PGO waves

Question 47

Describe brain function in REM sleep

Answer 47

During REM sleep, activity increased in the pons, which triggers the onset of REM sleep, and the limbic system, which is important for emotional responses. Activity decreased in the primary visual cortex, the motor cortex, and the dorsolateral prefrontal cortex but increased in parts of the parietal and temporal cortex.

REM sleep is associated with a distinctive pattern of high-amplitude electrical potential is known as PGO waves, for pons-geniculate-occipital. Waves of neural activity are detected first in the pond, shortly afterward in the lateral geniculate nucleus of the thalamus, and then in the occipital cortex.

REM sleep apparently depends on the relationship between the neurotransmitter serotonin and acetylcholine. Injections of the drug carbachol, which stimulates acetylcholine synapses, quickly move a sleeper into REM sleep. Serotonin and norepinephrine interrupt REM sleep.

Researchers interested in the brain mechanisms of REM used a PET scan to determine which areas increased or decreased in activity – required injecting a radioactive chemical and had the participants remain motionless by attaching their heads firmly to masks that did not permit any movements.

Question 48

Inadequate sleep

Answer 48

Insomnia

If you feel tired during the day, you are not sleeping enough at night. Causes include noise, uncomfortable temperatures, stress, pain, diet, and medications. Can also be the result of epilepsy, Parkinson’s disease, brain tumors, depression, anxiety, or other neurological or psychiatric conditions. Some cases also relate to shift in circadian rhythm’s.
Another cause is the use of tranquilizers as sleeping pills – repeated use causes dependence and an inability to sleep without the pills

Question 49

Impaired ability to breathe while sleeping

Answer 49

Sleep apnea

Consequences include sleepiness during the day, impaired attention, depression, and sometimes heart problems. People with sleep apnoea have multiple brain areas that appear to have lost neurons, and consequently they show deficiencies of learning, reasoning, attention, and impulse control.
Causes: genetics, hormones, old-age deterioration of the brain mechanisms that regulate breathing. Another cause is obesity, especially in middle aged men who have narrower than normal airways and have to compensate by breathing frequently or vigourously and cannot keep up that rate of breathing during sleep.

Question 50

A condition characterized by frequent periods of sleepiness during the day

Answer 50

Narcolepsy

Question 51

A sleep disorder characterized by repeated involuntary movement of the legs and sometimes the arms

Answer 51

Periodic limb movement disorder

Question 52

A condition in which people move around vigourously during REM sleep

Answer 52

REM behaviour disorder

Question 53

Experiences of intense anxiety from which a person awakens screaming in terror; more severe than a nightmare

Answer 53

Night terrors

Question 54

What are the four main symptoms of narcolepsy?

Answer 54

1. Gradual or sudden attacks of sleepiness during the day
2. Locational cataplexy – an attack of muscle weakness while the person remains awake – often triggered by strong emotions, such as anger or great excitement
3. Sleep paralysis – an inability to move while falling asleep or waking up
4. Hypnagogic hallucinations – dreamlike experiences that the person has trouble distinguishing from reality, often occurring at the onset of sleep

Question 55

What kind of people are most likely to develop sleep apnea?

Answer 55

Sleep apnea is most common among people with a genetic predisposition, old people, and overweight middle-aged men

Question 56

What is the relationship between orexin and narcolepsy?

Answer 56

Orexin is important for staying awake. Therefore, people or animals lacking either orexin or the receptors for orexin develop narcolepsy, characterized by bouts of sleepiness during the day

Question 57

Describe the proposed functions of sleep

Answer 57

During sleep, we rest our muscles, decrease metabolism, rebuild proteins in the brain, re-organize synopses, and strength and memories. People who don’t sleep enough have problems with attention, it creates more accidents at work and while driving, and activates the immune system.

One of the main functions of sleep is to save energy: sleep conserves energy during the inefficient times, when activity would be wasteful and possibly dangerous. For example, a mammals body temperature decreases by one or 2°C, which saves a significant amount of energy, and muscle activity decreases

Another important function of sleep is to improve memory

Question 58

What is the function of hibernation?

Answer 58

To conserve energy while food is scarce.

Question 59

Provide evidence that one of the main functions of sleep is to shut down activity at times of relative inefficiency, in effort to save energy

Answer 59

Researchers find little or no sleep in species that are equally effective at all times of the day. For example, certain fish have evolved for life in a cave where day and night have virtually no meaning, because light is always absent and temperature is virtually constant – these fish never sleep apparently

After a dolphin or whale gives birth, mother and baby stay awake for 24 hours a day for the first couple of weeks while the baby is vulnerable. Neither shows any sign of harm from sleep deprivation. Migratory birds sleep less during their migratory season.
Animal species vary in their sleep habits in ways that sense. Grazing animals that need to eat for many hours per day get less sleep than carnivores that can satisfy their nutritional needs with a single meal. Animals on the alert for predators get a little sleep, whereas the predators themselves sleep easily.

Question 60

What kind of animal tends to get more than the average amount of sleep?

Answer 60

Predators get much sleep, and so do species that are unlikely to be attacked during their sleep, such as armadillos

Question 61

What might one predict about the sleep of fish that live deep in the ocean?

Answer 61

The deep ocean, like a cave, has no lights and no difference between day and night. These fish might not need to sleep because they are equally efficient at all times of day and have no reason to conserve energy at one time more than another.

Question 62

Describe sleeping and improved memory

Answer 62

Deprivation of a night sleep interferes with memory tasks.
If people learn something and then go to sleep or take a nap, their memory often improves beyond what it was before their sleep.

Sleep also helps people reanalyze their memories – in one study, people who had just practised a complex task were more likely to perceive a hidden rule after a period of sleeping then after a similar period of wakefulness

Question 63

How does sleeping improve memory?

Answer 63

Patterns recorded in the hippocampus during sleep resemble those that occurred during learning, except that they were more rapid during sleep. The amount of hippocampal activity during sleep correlates with the subsequent improvement in performance. These results suggest that the brain replays it’s daily experiences during sleep.

Sleep also strengthens memory by weeding out the less successful connections – to prevent over activity in the brain, your brain compensates for strengthening some synapsis by weakening others, mostly during sleep. Weakening synapses during sleep emphasizes the ones that were strengthened during wakefulness.

Sleep spindles – waves of activity about 12 to 14 hurts that occur mostly during stage to sleep – indicate an exchange of information between the thalamus and cerebral cortex. In both rats and humans, sleep spindles increase in number after new learning. Spindle activity correlates with nonverbal tests of IQ

Question 64

Does sleep improve memory by strengthening or weakening synapses?

Answer 64

The evidence so far points to weakening the synapses that were not strengthened during the day. Weakening these less relevant synapses enables the strengthened ones to stand out by contrast

Question 65

Describe the functions of REM sleep

Answer 65

As a rule, the species with the most total sleep hours also have the highest percentage of REM sleep. Infants get more REM and more total sleep than adults do, confirming the pattern that more total sleep predicts a higher percentage of REM sleep.

One hypothesis is that REM is important for memory storage, especially for weakening the inappropriate connections. Depriving people of sleep early in the night, which is mostly non-REM sleep, impairs verbal learning such as memorizing a list of words, where is depriving people of sleep during the second half the night, which is more REM, impairs consolidation of learned motor skills. However, many people take antidepressant drugs that severely decreased REM sleep, without incurring memory problems.

Another hypothesis is that REM just shake the eyeballs back-and-forth enough to get sufficient oxygen to the corneas of the eyes, which get oxygen directly from the surrounding air and from the fluid behind them. When the fluid become stagnant as our eyes are motionless during the night, moving the eyes increases the oxygen supply to the corneas. However, many people take antidepressants that restrict REM sleep and they are not known to suffer damage to the cornea

Question 66

What kinds of individuals get more REM sleep than others? Think in terms of age, species, and long versus short sleepers

Answer 66

Much REM sleep is more typical of the young than the old, of individuals who get much sleep than those who get a little, and of species that sleep much of the day

Question 67

Idea that a dream represents the brains effort to make sense of sparse and distorted information

Answer 67

Activation-synthesis hypothesis

Dreams begin with periodic bursts of spontaneous activity in the pons – the PGO waves previously described – that activate some parts of the cortex but not others. The cortex combines this haphazard input with whatever other activity was already occurring and does it’s best to synthesize a story that makes sense of the information.

Question 68

Idea that considers dreams as a type of thinking that occurs under unusual conditions

Answer 68

Clinico-anatomical hypothesis

Like the activation-synthesis theory, emphasizes that dreams begin with arousing stimuli that are generated within the brain combined with recent memories and any information in the brain is receiving from the senses. However, puts less emphasis on the pons, PGO waves, or REM sleep, and regards dream just thinking that takes place under unusual conditions, similar to mind wandering during every day life.
Unusual conditions: the brain is getting little information from the sense organs, the primary visual and auditory areas have lower than usual activity so either brain areas are free to generate images without interference, the primary motor cortex is suppressed arousal cannot lead to action, activity is suppressed in the prefrontal cortex which is important for working memory, and we lose a sense of volition – planning.
Meanwhile, activity is relatively high in the inferior part of the parietal cortex, and area important for visual spatial perception. Fairly high activity is also found in the areas of visual cortex outside V1 – those areas are presumably important for the visual imagery that accompanies most dreams. Also, activity is high in the hypothalamus, amygdala, and other areas important for emotions and motivations.

The idea is that either internal or external stimulation activates part of the parietal, occipital, and temporal cortex. The arousal develops into a hallucinatory perception, with no sensory input from area V1 to override it.

Question 69

What is a key point of disagreement between the activation-synthesis hypothesis and the clinico-anatomical hypothesis?

Answer 69

The activation-synthesis hypothesis puts much more emphasis on the importance of the pons