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
cataplexy: lack of muscle tone or muscle weakness, and in some cases complete paralysis of the voluntary muscles
central sleep apnea: sleep disorder with periods of interrupted breathing due to a disruption in signals sent from the brain that regulate breathing
circadian rhythm: biological rhythm that occurs over approximately 24 hours
cognitive-behavioral therapy: psychotherapy that focuses on cognitive processes and problem behaviors 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
consciousness: awareness of internal and external stimuli
continuous positive airway pressure (CPAP): device used to treat sleep apnea; includes a mask that fits over the sleeper’s nose and mouth, which is connected to a pump that pumps air into the person’s airways, forcing them to remain open
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 behavior and cognitive processes have evolved over time as a result of natural selection
hallucinogen: one of a class of drugs that results in profound alterations in sensory and perceptual experiences, often with vivid hallucinations
homeostasis: tendency to maintain a balance, or optimal level, within a biological system
insomnia: 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
K-complex: 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
melatonin: hormone secreted by the endocrine gland that serves as an important regulator of the sleep-wake cycle
meta-analysis: study that combines the results of several related studies
narcolepsy: 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
obstructive sleep apnea: sleep disorder defined by episodes when breathing stops during sleep as a result of blockage of the airway
parasomnia: one of a group of sleep disorders characterized by unwanted, disruptive motor activity and/or experiences during sleep
physical dependence: changes in normal bodily functions that cause a drug user to experience withdrawal symptoms upon cessation of use
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 behavior 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
sleep: 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 apnea: sleep disorder defined by episodes during which breathing stops during sleep
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
sleepwalking: (also, somnambulism) sleep disorder in which the sleeper engages in relatively complex behaviors
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
stimulant: drug that tends to increase overall levels of neural activity; includes caffeine, nicotine, amphetamines, and cocaine
sudden infant death syndrome (SIDS): infant (one year old or younger) with no apparent medical condition suddenly dies during sleep
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
wakefulness: characterized by high levels of sensory awareness, thought, and behavior