Summary and Key Terms

What Is Consciousness?

States of consciousness vary over the course of the day and throughout our lives. Important factors in these changes are the biological rhythms, and, more specifically, the circadian rhythms generated by the suprachiasmatic nucleus (SCN). Typically, our biological clocks are aligned with our external environment, and light tends to be an important cue in setting this clock. When people travel across multiple time zones or work rotating shifts, they can experience disruptions of their circadian cycles that can lead to insomnia, sleepiness, and decreased alertness. Bright light therapy has shown to be promising in dealing with circadian disruptions. If people go extended periods of time without sleep, they will accrue a sleep debt and potentially experience a number of adverse psychological and physiological consequences.

Sleep and Why We Sleep

We devote a very large portion of time to sleep, and our brains have complex systems that control various aspects of sleep. Several hormones important for physical growth and maturation are secreted during sleep. While the reason we sleep remains something of a mystery, there is some evidence to suggest that sleep is very important to learning and memory.

Stages of Sleep

The different stages of sleep are characterized by the patterns of brain waves associated with each stage. As a person transitions from being awake to falling asleep, alpha waves are replaced by theta waves. Sleep spindles and K-complexes emerge in stage 2 sleep. Stage 3 and stage 4 are described as slow-wave sleep that is marked by a predominance of delta waves. REM sleep involves rapid movements of the eyes, paralysis of voluntary muscles, and dreaming. Both NREM and REM sleep appear to play important roles in learning and memory. Dreams may represent life events that are important to the dreamer. Alternatively, dreaming may represent a state of protoconsciousness, or a virtual reality, in the mind that helps a person during consciousness.

Sleep Problems and Disorders

Many individuals suffer from some type of sleep disorder or disturbance at some point in their lives. Insomnia is a common experience in which people have difficulty falling or staying asleep. Parasomnias involve unwanted motor behaviour or experiences throughout the sleep cycle and include RBD, sleepwalking, restless leg syndrome, and night terrors. Sleep apnea occurs when individuals stop breathing during their sleep, and in the case of sudden infant death syndrome, infants will stop breathing during sleep and die. Narcolepsy involves an irresistible urge to fall asleep during waking hours and is often associated with cataplexy and hallucination.

Other States of Consciousness

Hypnosis is a focus on the self that involves suggested changes of behaviour and experience. Meditation involves relaxed, yet focused, awareness. Both hypnotic and meditative states may involve altered states of consciousness that have potential application for the treatment of a variety of physical and psychological disorders.

Key Terms

alpha wave
type of rbrain wave characteristic during the early part of NREM stage 1 sleep, which has fairly low amplitude and a frequency of 8–12 Hz
beta wave
type of brain wave characteristic during wakefulness, which has a very low amplitude and a frequency of 13–30 Hz
biological rhythm
internal cycle of biological activity
lack of muscle tone or muscle weakness, and in some cases complete paralysis of the voluntary muscles
circadian rhythm
biological rhythm that occurs over approximately 24 hours
cognitive-behavioural therapy
psychotherapy that focuses on cognitive processes and problem behaviours that is sometimes used to treat sleep disorders such as insomnia
collective unconscious
theoretical repository of information shared by all people across cultures, as described by Carl Jung
awareness of internal and external stimuli
delta wave
type of brain wave characteristic during stage 3 NREM sleep, which has a high amplitude and low frequency of less than 3 Hz
evolutionary psychology
discipline that studies how universal patterns of behaviour and cognitive processes have evolved over time as a result of natural selection
tendency to maintain a balance, or optimal level, within a biological system
state of extreme self-focus and attention in which minimal attention is given to external stimuli
consistent difficulty in falling or staying asleep for at least three nights a week over a month’s time
jet lag
collection of symptoms brought on by travel from one time zone to another that results from the mismatch between our internal circadian cycles and our environment
very high amplitude pattern of brain activity associated with stage 2 sleep that may occur in response to environmental stimuli
latent content
hidden meaning of a dream, per Sigmund Freud’s view of the function of dreams
lucid dream
people become aware that they are dreaming and can control the dream’s content
manifest content
storyline of events that occur during a dream, per Sigmund Freud’s view of the function of dreams
clearing the mind in order to achieve a state of relaxed awareness and focus
hormone secreted by the endocrine gland that serves as an important regulator of the sleep-wake cycle
study that combines the results of several related studies
sleep disorder in which the sufferer cannot resist falling to sleep at inopportune times
night terror
sleep disorder in which the sleeper experiences a sense of panic and may scream or attempt to escape from the immediate environment
non-REM (NREM)
period of sleep outside periods of rapid eye movement (REM) sleep
one of a group of sleep disorders characterized by unwanted, disruptive motor activity and/or experiences during sleep
pineal gland
endocrine structure located inside the brain that releases melatonin
psychological dependence
emotional, rather than a physical, need for a drug which may be used to relieve psychological distress
rapid eye movement (REM) sleep
period of sleep characterized by brain waves very similar to those during wakefulness and by darting movements of the eyes under closed eyelids
REM sleep behaviour disorder (RBD)
sleep disorder in which the muscle paralysis associated with the REM sleep phase does not occur; sleepers have high levels of physical activity during REM sleep, especially during disturbing dreams
restless leg syndrome
sleep disorder in which the sufferer has uncomfortable sensations in the legs when trying to fall asleep that are relieved by moving the legs
rotating shift work
work schedule that changes from early to late on a daily or weekly basis
state marked by relatively low levels of physical activity and reduced sensory awareness that is distinct from periods of rest that occur during wakefulness
sleep debt
result of insufficient sleep on a chronic basis
sleep rebound
sleep-deprived individuals will experience shorter sleep latencies during subsequent opportunities for sleep
sleep regulation
brain’s control of switching between sleep and wakefulness as well as coordinating this cycle with the outside world
sleep spindle
rapid burst of high frequency brain waves during stage 2 sleep that may be important for learning and memory
(also, somnambulism) sleep disorder in which the sleeper engages in relatively complex behaviours
stage 1 sleep
first stage of sleep; transitional phase that occurs between wakefulness and sleep; the period during which a person drifts off to sleep
stage 2 sleep
second stage of sleep; the body goes into deep relaxation; characterized by the appearance of sleep spindles
stage 3 sleep
third stage of sleep; deep sleep characterized by low frequency, high amplitude delta waves
stage 4 sleep
fourth stage of sleep; deep sleep characterized by low frequency, high amplitude delta waves
drug that tends to increase overall levels of neural activity; includes caffeine, nicotine, amphetamines, and cocaine
suprachiasmatic nucleus (SCN)
area of the hypothalamus in which the body’s biological clock is located
theta wave
type of brain wave characteristic of the end of stage 1 NREM sleep, which has a moderately low amplitude and a frequency of 4–7 Hz
state of requiring increasing quantities of the drug to gain the desired effect
characterized by high levels of sensory awareness, thought, and behaviour
variety of negative symptoms experienced when drug use is discontinued


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Introduction to Psychology Copyright © 2021 by Southern Alberta Institution of Technology (SAIT) is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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