consciousness
our subjective awareness of ourselves and our environment
hypnosis
a social interaction in which one person (the hypnotist) suggests to another (the subject) that certain perceptions, feelings, thoughts, or behaviors will spontaneously occur
posthypnotic suggestion
a suggestion, made during a hypnosis session, to be carried out after the subject is no longer hypnotized; used by some clinicians to help control undesired symptoms and behaviors
dissociation
a split in consciousness, which allows some thoughts and behaviors to occur simultaneously with others
sleep
a periodic, natural loss of consciousness — as distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation
circadian rhythm
our biological clock; regular bodily rhythms (for example, of temperature and wakefulness) that occur on a 24-hour cycle
REM sleep
rapid eye movement sleep; a recurring sleep stage during which vivid dreams commonly occur. Also known as paradoxical sleep, because the muscles are relaxed (except for minor twitches) but other body systems are active
alpha waves
the relatively slow brain waves of a relaxed, awake state
NREM sleep
non-rapid eye movement sleep; encompasses all sleep stages except for REM sleep
hallucinations
false sensory experiences, such as seeing something in the absence of an external visual stimulus
hypnagogic sensations
bizarre experiences, such as jerking or a feeling of falling or floating weightlessly, while transitioning to sleep
delta waves
the large, slow brain waves associated with the deep sleep of NREM-3
suprachiasmatic nucleus (SCN)
a pair of cell clusters in the hypothalamus that controls circadian rhythm. In response to light, the SCN causes the pineal gland to adjust melatonin production, thus modifying our feelings of sleepiness
insomnia
recurring problems in falling or staying asleep
narcolepsy
a sleep disorder characterized by uncontrollable sleep attacks. The sufferer may lapse directly into REM sleep, often at inopportune times
sleep apnea
a sleep disorder characterized by temporary cessations of breathing during sleep and repeated momentary awakenings
night terrors
a sleep disorder characterized by high arousal and an appearance of being terrified; unlike nightmares, night terrors occur during NREM-3 sleep, within two or three hours of falling asleep, and are seldom remembered
dream
a sequence of images, emotions, and thoughts passing through a sleeping person's mind
manifest content
according to Freud, the symbolic, remembered story line of a dream (as distinct from its latent, or hidden, content)
latent content
according to Freud, the underlying meaning of a dream (as distinct from its manifest content)
REM rebound
the tendency for REM sleep to increase following REM sleep deprivation
psychoactive drug
a chemical substance that alters perceptions and moods
substance use disorder
a disorder characterized by continued substance craving and use despite significant life disruption and/or physical risk
tolerance
the diminishing effect with regular use of the same dose of a drug, requiring the user to take larger and larger doses before experiencing the drug's effect
withdrawal
the discomfort and distress that follow discontinuing an addictive drug or behavior
depressants
drugs (such as alcohol, barbiturates, and opiates) that reduce neural activity and slow body functions
alcohol use disorder
(popularly known as alcoholism) alcohol use marked by tolerance, withdrawal, and a drive to continue problematic use
barbiturates
drugs that depress central nervous system activity, reducing anxiety but impairing memory and judgment
opiates
opium and its derivatives, such as morphine and heroin; depress neural activity, temporarily lessening pain and anxiety
stimulants
drugs (such as caffeine, nicotine, and the more powerful cocaine, amphetamines, methamphetamine, and Ecstasy) that excite neural activity and speed up body functions
nicotine
a stimulating and highly addictive psychoactive drug in tobacco
cocaine
a powerful and addictive stimulant derived from the coca plant; produces temporarily increased alertness and euphoria
amphetamines
drugs, such as methamphetamine, that stimulate neural activity, causing accelerated body functions and associated energy and mood changes
methamphetamine
a powerfully addictive drug that stimulates the central nervous system, with accelerated body functions and associated energy and mood changes; over time, appears to reduce baseline dopamine levels
Ecstasy
a synthetic stimulant and mild hallucinogen. Produces euphoria and social intimacy, but with short-term health risks and longer-term harm to serotonin-producing neurons and to mood and cognition
hallucinogens
psychedelic ("mind-manifesting") drugs, such as LSD, that distort perceptions and evoke sensory images in the absence of sensory input
near-death experience
an altered state of consciousness reported after a close brush with death (such as cardiac arrest); often similar to drug-induced hallucinations
LSD
a powerful hallucinogenic drug; also known as acid
THC
the major active ingredient in marijuana; triggers a variety of effects, including mild hallucinations