Chapter 2

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, this 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, these 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 (MDMA)

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 hallocinations

LSD

a powerful hallucinogenic drug; also known as acid (lysergic aid diethylamide)

THC

the major active ingredient in marijuana; triggers a variety of effects, including mild hallocinations

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

corpus callosum

the large band of neural fibers connecting the two brain hemispheres and carrying messages between them

split brain

a condition resulting from surgery that isolates the brain’s two hemispheres by cutting the fibers (mainly those of corpus callosum) connecting them

consciousness

our subjective awareness of ourselves and our environment

cognitive neuroscience

the interdisciplinary study of the brain activity linked with cognition (including perception, thinking, memory, and language)

dual processing

the principle that information is often simultaneously processed on separate conscious and unconscious tracts

blindsight

a condition in which a person can respond to a visual stimulus without consciously experiencing it

parallel processing

processing many aspects of a problem simultaneously; generally used to process well-learned information or to solve easy problems

sequential processing

processing one aspect of a problem as a time; generally used to process new information or to solve difficult problems

behavior genetics

the study of the relative power and limits of genetic and environmental influences on behavior

heredity

the genetic transfer of characteristics from parents to offspring

environment

every nongenetic influence, from prenatal nutrition to the people and things around us

chromosomes

threadlike structures made of DNA molecules that contain the genes

DNA

deoxyribonucleic acid - a complex molecule containing the genetic information that makes up the chromosomes

genes

the biochemical units of heredity that make up the chromosomes; segments of DNA capable of synthesizing proteins

genome

the complete instructions for making an organism, consisting of all the genetic material in that organism’s chromosomes

identical (monozygotic) twins

develop from a single fertilized egg that splits in two, creating two genetically identical organisms

fraternal (dizygotic) twins

develop from separate fertilized eggs; they are genetically no closer than ordinary brothers and sisters, but they share a prenatal environment

heritability

the proportion of variation among individuals in a group that we can attribute to genes; the heritability of a trait may vary, depending on the range of populations and environments studied

interaction

the interplay that occurs when the effect of one factor (such as environment) depends on another factor (such as heredity)

molecular genetics

the subfield of biology that studies the molecular structure and function of genes

molecular behavior genetics

the study of how the structure and function of genes interact with our environment to influence behavior

epigenetics

“above” or “in addition to” (epi) genetics; the study of environmental influences on gene expression that occur without a DNA change

evolutionary psychology

the study of the evolution of behavior and the mind, using principles of natural selection

natural selection

the principle that inherited traits that better enable an organism to survive and reproduce in a particular environment will (in competition with other trait variations) most likely be passed on to succeeding generations

mutation

a random error in gene replication that leads to a change

social script

a culturally modeled guide for how to act in various situations

lesion

tissue destruction; a naturally or experimentally caused destruction of brain tissue

EEG (electroencephalogram)

an amplified recording of the waves of electrical activity sweeping across the brain’s surface; these waves are measured by electrodes placed on the scalp

MEG (magnetoencephalography)

a brain imaging technique that measures magnetic fields from the brain’s natural electrical activity

CT (computed tomography) scan

a series of x-ray photographs taken from different angles and combined by computer into a composite representation of a slice of the brain’s structure

PET (positron emission tomography) scan

a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task

MRI (magnetic resonance imaging)

a technique that uses magnetic fields and radio waves to produce computer-generated images of soft tissue; show brain anatomy

fMRI (functional MRI)

a technique for revealing bloodflow and, therefore, brain activity by comparing successive MRI scans; show brain function as well as structure

brainstem

the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions

medulla

the base of the brainstem; controls heartbeat and breathing

thalamus

the brain’s sensory control center, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

reticular formation

a nerve network that travels through the brainstem into the thalamus and plays an important role in controlling arousal

cerebellum

the “little brain” at the rear of the brainstem; functions include processing sensory input, coordinating movement output and balance, and enabling nonverbal learning and memory

limbic system

neural system (including the amygdala, hypothalamus, and hippocampus) located below the cerebral hemisphere; associated with emotions and drives

amygdala

two lima-bean-sized neural clusters in the limbic system; linked to emotion

hypothalamus

a neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward

hippocampus

a neural cluster located in the limbic system; helps process for storage explicit (conscious) memories of facts and events

cerebral cortex

the intricate fabric of interconnected neural cells covering the cerebral hemispheres; the body’s ultimate control and information-processing center

frontal lobes

the portion of the cerebral cortex lying just behind the forehead; involved in speaking and muscle movements and in making plans and judgment

parietal lobes

the portion of the cerebral cortex lying at the top of the head and toward the rear; receives sensory input for touch and body position

occipital lobes

the portion of the cerebral cortex lying at the back of the head; includes areas that receive information from visual fields

temporal lobes

the portion of the cerebral cortex lying roughly above the ears; includes the auditory areas, each receiving information primarily from the opposite ear

motor cortex

an area at the rear of the frontal lobes that controls voluntary movements

somatosensory cortex

an area at the front of the parietal lobes that registers and processes body touch and movement sensations

association areas

areas of the cerebral cortex that are not involved in primary motor of sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking

plasticity

the brain’s ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience

neurogenesis

the formation of new neurons

neuron

a nerve cell; the basic building block of the nervous system

cell body

the part of a neuron that contains the nucleus; the cell’s life-support center

dendrites

a neuron’s often bushy, branching extensions that receive and integrate messages, conducting impulses toward the cell body

axon

the neuron extension that passes messages through its branches to other neurons or to muscles or glands

myelin sheath

a fatty tissue layer segmentally encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one node to the next

glial cells

cells in the nervous system that support, nourish, and protect neurons; they also play a role in learning, thinking, and memory

action potential

a neural impulse; a brief electrical charge that travels down an axon

threshold

the level of stimulation required to trigger a neural impulse

refractory period

in neural processing, a brief resting pause that occurs after a neuron has fired; subsequent action potentials cannot occur until the axon returns to its resting state