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Consciousness
Our subjective awareness of ourselves and our environment.
Cognitive Neuroscience
The interdisciplinary study of the brain activity linked with cognition (thinking, knowing, remembering, communicating).
Dual Processing
The principle that information is often simultaneously processed on separate conscious and unconscious tracks.
Blindsight
A condition in which a person can respond to a visual stimulus without consciously experiencing it.
Paralllel Processing
Processing multiple aspects of a stimulus or problem simultaneously.
Sequential Processing
Processing one aspect of a stimulus or problem at a time; generally used to process new information or to solve difficult problems.
Sleep
A periodic, natural loss of consciousnessāas 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 deep sleep.
Suprachiasmatic Nucleus (SCN)
A pair of cell clusters in the hypothalamus that controls circadian rhythm. In response to light, the SCN adjusts 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 affected person 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.
REM Sleep Behavior Disorder
A sleep disorder in which normal REM paralysis does not occur; instead, twitching, talking, or even kicking or punching may occur, often acting out oneās dream.
Dream
A sequence of images, emotions, and thoughts passing through a sleeping personās mind.
REM Rebound
The tendency for REM sleep to increase following REM sleep deprivation.
Sensation
The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
Sensory Receptors
Sensory nerve endings that respond to stimulus.
Perception
The process by which our brain organizes and interprets sensory information, enabling us to recognize ob
Bottom-Up Processing
Information processing that begins with the sensory receptors and works up to the brainās integration of sensory information.
Top-Down Processing
Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.
Transduction
Conversion of one form of energy into another. In sensation, the transforming of physical energy, such as sights, sounds, and smells, into neural impulses the brain can interpret.
Psychophysics
The study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them.
Absolute Threshold
The minimum stimulus energy needed to detect a particular stimulus 50 percent of the time.
Signal Detection Theory
A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise); assumes there is no single absolute threshold and that detection depends partly on a personās experience, expectations, motivation, and alertness.
Subliminal
Below oneās absolute threshold for conscious awareness.
Priming
The activation, often unconsciously, of certain associations, thus predisposing oneās perception, memory, or response.
Difference Threshold
The minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference (JND).
Weberās Law
The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount).
Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Wavelength
The distance from the peak of one light wave or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short gamma waves to the long pulses of radio transmission.
Hue
The dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth.
Intensity
The amount of energy in a light wave or sound wave, which influences what we perceive as a brightness or loudness. Determined by the waveās amplitude (height).
Cornea
The eyeās clear, protective outer layer, covering the pupil and iris.
Pupil
The adjustable opening in the center of the eye through which light enters.
Iris
A ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening.
Lens
The transparent structure behind the pupil that changes shape to help focus images on the retina.
Retina
The light-sensitive back inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.
Accommodation
The process by which the eyeās lens changes shape to focus images of near or far objects on the retina.
Rods
Retinal receptors that detect black, white, and gray, and are sensitive to movement. Necessary for peripheral and twilight vision, when cones donāt respond.
Cones
Retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. Detect fine detail and give rise to color sensations.
Optic Nerve
The nerve that carries neural impulses from the eye to the brain.
Blind Spot
The point at which the optic nerve leaves the eye, creating a ____ because no receptor cells are located there.
Fovea
The central focal point in the retina, around which the eyeās cones cluster.
Young-Helmholtz Trichromatic (Three-Color) Theory
The theory that the retina contains three different types of color receptorsāone most sensitive to red, one to green, one to blueāwhich, when stimulated in combination, can produce the perception of any color.
Opponent-Process Theory
The theory that opposing retinal processes (red-green, blue-yellow, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.
Feature Detectors
Nerve cells in the brainās visual cortex that respond to specific features of the stimulus, such as shape, angle, or movement.
Parallel Processing
Processing multiple aspects of a stimulus or problem simultaneously.
Audition
The sense or act of hearing.
Frequency
The number of complete wavelengths that pass a point in a given time (for example, per second).
Pitch
A toneās experienced highness or lowness; depends on frequency.
Middle Ear
The chamber between the eardrum and the cochlea containing three tiny bones that concentrate the vibrations of the eardrum on the cochleaās oval window.
Cochlea
A coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through the _____ fluid trigger nerve impulses.
Inner Ear
The innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs.
Sensorineural Hearing Loss
The most common form of hearing loss, caused by damage to the cochleaās receptor cells or to the auditory nerve; also called nerve deafness.
Conduction Hearing Loss
A less common form of hearing loss, caused by damage to the mechanical system that conducts sound waves to the cochlea.
Cochlear Implant
A device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea.
Place Theory
In hearing, the theory that links the pitch we hear with the place where the cochleaās membrane is stimulating.
Frequency Theory
In hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch.
Gate-Control Theory
The theory that the spinal cord contains a neurological āgateā that blocks pain signals or allows them to pass on to the brain. The āgateā is opened by the activity of pain signals traveling up small nerve fibers, and is closed by activity in larger fibers or by information coming from the brain.
Gustation
Our sense of taste.
Olfaction
Our sense of smell.
Kinesthesis
Our movement sense; our system for sending the position and movement of individual body parts.
Vestibular Sense
Our balance sense; our sense of body movement and position that enables our sense of balance.
Sensory Interaction
The principle that one sense can influence another, as when the smell of food influences the taste.
Embodied Cognition
The influence of bodily sensations, gestures, and other states on cognitive preferences and judgments.
Psychoactive Drug
A chemical substance that alters the brain, causing changes in perceptions and moods.
Substance Use Disorder
A disorder characterized by continued substance use despite resulting life disruption.
Depressants
Drugs that reduce neural activity and slow body functions.
Tolerance
The diminishing effect with regular use of the same dose of a drug, requiring the use to take larger and larger doses before experiencing the drugās effect.
Addiction
An everyday term for compulsive substance use (and sometimes for dysfunctional behavior patterns, such as out-of-control gambling) that continue despite harmful consequences.
Withdrawl
The discomfort and distress that follow discontinuing an addictive drug or behavior.
Barbiturates
Drugs that depress central nervous system activity, reducing anxiety but impairing memory and judgment.
Opioids
Opium and its derivatives; they depress neural activity, temporarily lessening pain and anxiety.
Stimulants
Drugs that excite neural activity and speed up body functions.
Hallucinogens
Psychedelic drugs 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; often similar to drug-induced hallucinations.