Unit 1, Part 2: Sleep and Sensation (CED Aligned)

consciousness

our subjective awareness of ourselves and our environment.

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.

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. (Also called hypnic sensations.)

delta waves

the large, slow brain waves associated with deep sleep.

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 one's dream.

dream

a sequence of images, emotions, and thoughts passing through a sleeping person's 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 stimuli.

perception

the process by which our brain organizes and interprets sensory information, enabling us to recognize objects and events as meaningful.

bottom-up processing

information processing that begins with the sensory receptors and works up to the brain's 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.

absolute threshold

the minimum stimulus energy needed to detect a particular stimulus 50 percent of the time.

subliminal

below one's absolute threshold for conscious awareness.

priming

the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response.

difference threshold

the minimum difference between two stimuli required for detection 50 percent of the time.

weber's 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.

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 eye's 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. they are necessary for peripheral and twilight vision.

cones

retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. they 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 "blind" spot because no receptor cells are located there.

fovea

the central focal point in the retina, around which the eye's cones cluster.

young-helmholtz trichromatic theory

the theory that the retina contains three different types of color receptors- one most sensitive to red, one to green, one to blue- which, 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.

audition

the sense or act of hearing.

pitch

a tone's experienced highness or lowness; depends on frequency.

cochlea

a coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through the cochlear fluid trigger nerve impulses.

sensorineural hearing loss

the most common form of hearing loss, caused by damage to the cochlea's 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.

place theory

in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated. (Also called place coding.)

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. (Also called temporal coding.)

gate-control theory

the theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain. The "gate" 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 sensing 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 its taste.