PSY100H1 Chapter Notes - Chapter 4: Syllogism, Sleep Disorder, Sleep Deprivation

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Published on 14 Mar 2016
Chapter 4: The Mind and Consciousness
What Is Sleep?
A common misperception is that the brain shuts itself down during sleep and no
longer processes information about the external world
Many brain regions are more active during sleep than during wakefulness
It is even possible that some complex thinking, such as working on difficult
problems, occurs in the sleeping brain
The conscious experience of the outside world is largely turned off, but to some
extent people remain aware of their surroundings, as when sleeping parents sense
their baby rustling in the crib
The average person sleeps around eight hours per night, but individuals differ
tremendously in the number of hours they sleep
Sleep Is an Altered State of Consciousness:
When you sleep, you are not conscious
Your mind is at work, analyzing potential dangers, controlling bodily movements,
and shifting body parts to maximize comfort
Invented in the 1920s, the electroencephalograph, or EEG, a machine that
measures the brain’s electrical activity, revealed that a lot goes on in the brain
during sleep
When people are awake, their brains’ neurons are extremely active, as evidenced
by short, frequent, desynchronized brain signals known as beta waves
When people close their eyes and relax, brain activity slows and becomes more
synchronized, a pattern that produces alpha waves
Stages of Sleep:
As you drift off to sleep, you enter stage 1, characterized by theta waves, from
which you can be aroused easily
In this light sleep, you might see fantastical images or geometric shapes; you
might have the sensation that you are falling or that your limbs are jerking
As you progress to stage 2, your breathing becomes more regular, and you
become less sensitive to external stimulation
Although the EEG would continue to show theta waves, it would also show
occasional bursts of activity called sleep spindles and large waves called k-
Some researchers believe that these are signals from brain mechanisms involved
with shutting out the external world and keeping people asleep
Two findings – that abrupt noise can trigger k-complexes; and that as people are
and sleep lighter, their EEGs show fewer sleep spindles – indicate that the brain
must work to maintain sleep
The progression to deep sleep occurs through stages 3 and 4, which are marked by
large, regular brain patterns called delta waves
This period is often referred to as slow-wave sleep
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People in slow-wave sleep are very hard to wake and often very disoriented when
they do wake up
REM Sleep:
After about 90 minutes of sleep, the sleep cycle reverses, returning to stage 3 and
then to stage 2
At this point, the EEG suddenly shows a flurry of beta wave activity that usually
indicates an awake, alert mind
The eyes dart back and forth rapidly beneath closed eyelids, and for these rapid
eye movements this stage is called REM sleep
It is sometimes called paradoxical sleep because of the paradox of a sleeping
body with an active brain
Some neurons in the brain, especially in the occipital cortex and brain stem
regions, are more active during REM sleep than during waking hours
But while the brain is active during REM episodes, most of the body’s muscles
are paralyzed
At the same time, the body shows signs of genital arousal
As morning approaches, the sleep cycle becomes shorter, and the sleeper spends
relatively more time in REM sleep
Sleep Disorders:
Insomnia is a sleep disorder in which people’s mental health and ability to
function are compromised by their inability to sleep
Some people experienced pseudoinsomnia, in which they basically dream they are
not sleeping
A major cause of insomnia is worrying about sleep
Recent research demonstrates that the preferred treatment for insomnia is
cognitive-behavioural therapy, which helps people overcome their worries about
Sleep apnea is a disorder in which a person stops breathing for temporary periods
while asleep, resulting in a loss of oxygen and sleep disruption
Sleep apnea is most common among middle-aged men and is often associated
with obesity
People with sleep apnea are often unaware of their condition since the main
symptom is loud snoring and they do not remember their frequent awakenings
during the night
Narcolepsy is a sleep disorder in which people fall asleep during normal waking
The most widely used treatments for this condition are drugs such as the stimulant
A sleep disorder that is roughly the opposite of narcolepsy is REM behaviour
disorder, in which the normal paralysis that accompanies REM sleep is disabled
so that people act out their dreams while sleeping
This rare disorder is caused by a neurological deficit and is most often seen in
elderly males
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Unlike REM behaviour disorder, sleepwalking is a relatively common behaviour
that occurs during stage 4 sleep
Technically called somnambulism, sleepwalking is most common among young
children and typically occurs within the first hour or two after falling asleep
During an episode, the person is glassy-eyed and seems disconnected from other
people and/or the surroundings
Sleep Is an Adaptive Behaviour:
Researchers have proposed three general explanations for sleep’s adaptiveness:
restoration, circadian cycles, and facilitation of learning
Restoration and Sleep Deprivation:
According to the restorative theory, sleep allows the brain and body to rest and to
repair themselves
Sleep deprivation is also dangerous and potentially disastrous because it makes
people prone to microsleeps, in which they fall asleep during the day for periods
ranging from a few seconds to a minute
Sleep deprivation might serve one very useful purpose, however: helping people
overcome depression
Circadian Rhythms:
Brain and other physiological processes are regulated into patterns known as
circadian rhythms
The circadian rhythm theory proposes that sleep has evolved to keep animals
quiet and inactive during times of the day when there is greatest danger, usually
when it is dark
According to this theory, animals need only a limited amount of time each day to
accomplish the necessities of survival, and it is adaptive for them to spend the
remainder of the time inactive, preferably hidden
Facilitation of Learning:
Scientists have also proposed that sleep is important because it is involved in the
strengthening of neural connections that serve as the basis of learning
The general idea is that circuits wired together during the waking periods are
consolidated, or strengthened, during sleep
Both slow-wave sleep and REM sleep appear to be important for learning to take
place, but evidence indicates that people are especially likely to perform better if
they dream about the task while sleeping
Sleep and Wakefulness Are Regulated by Multiple Neural Mechanisms:
A tiny structure in the brain called the pineal gland secretes melatonin, a hormone
that travels through the bloodstream and affects various receptors in both the body
and the brain
Bright light suppresses the production of melatonin, whereas darkness triggers its
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