1.5,1.6a,1.6b

Activation synthesis theory

A theory that dreams are the brain's attempt to make sense of random neural activity during sleep.

consolidation theory

The idea that sleep helps strengthen and stabilize memories, transferring them from short-term to long-term storage.

insomnia

A sleep disorder characterized by difficulty falling asleep, staying asleep, or achieving restorative sleep.

narcolepsy

A sleep disorder marked by sudden, uncontrollable episodes of falling asleep, often directly into REM sleep.

rem sleep behavior disorder

a sleep condition where a person physically acts out vivid dreams with vocalizations and sudden, violent limb movements because normal muscle paralysis during REM sleep fails

sleep apnea

A sleep disorder in which a person temporarily stops breathing during sleep, leading to frequent awakenings and daytime fatigue.

somnambulism

a behavior disorder that causes a person to perform complex activities while remaining mostly asleep (sleep walking)

consciousness

the awareness of our environment and ourselves

circadian rhythm

a 24-hour biological clock that regulates sleep, wakefulness, and other functions.

jet lag

a temporary sleep disorder caused by crossing two or more time zones, which throws your body's internal clock out of sync with local time

eeg patterns

the graphic record of electrical brain wave activity measured by electrodes placed on the scalp

nrem

Sleep stages 1-3 (non-dreaming sleep), involving slower brain activity, deep rest, and physical restoration.

hallucinations

sensory perceptions that occur without any external stimulus, yet feel completely real to the person experiencing them

hypnagogic sensations

bizarre sensory experiences that occur during the transitional state of falling asleep, specifically as a person enters initial NREM Stage 1 sleep

rem

A stage of sleep marked by rapid eye movements, vivid dreams, and brain activity similar to wakefulness; essential for memory consolidation.

rem rebound

The tendency to enter REM sleep more quickly and spend more time in it after being deprived of REM sleep.

suprachiasmatic nucleus

a pair of tiny cell clusters in the hypothalamus of the brain that acts as the body's master biological clock to control the circadian rhythm

dream

sequences of images, emotions, and thoughts—often surreal or hallucinatory—that pass through a sleeping person's mind, most vividly during REM Sleep

sensation

The process of detecting physical energy (stimuli) from the environment and encoding it into neural signals.

absolute threshold

The minimum level of stimulation needed for a person to detect a stimulus 50% of the time.

just noticeable difference

The minimum change in a stimulus that can be detected 50% of the time.

weber's law

The principle that the just noticeable difference (JND) is a constant proportion of the original stimulus intensity.

sensory adaptation

Reduced sensitivity to a constant or unchanging stimulus over time (e.g., no longer noticing a strong smell).

sensory interaction

The principle that one sense can influence another (e.g., smell affecting taste).

synesthesia

A condition where stimulation of one sensory pathway triggers involuntary experiences in another (e.g., "seeing" sounds as colors).

priming

The unconscious activation of certain associations that influence perception, memory, or response (e.g., seeing the word "yellow" makes you quicker to recognize "banana").

transduction

The process of converting physical energy (light, sound, chemicals) into neural impulses.

rods

Photoreceptor cells in the retina: Rods detect black, white and gray; work well in low light but not detail.

cones

Photoreceptor cells in the retina: work well in low light but not detail. Cones detect color and fine detail; function best in bright light.

trichromatic theory

The theory that color vision results from three types of cones sensitive to red, green, and blue light.

opponent-process theory

The theory that color vision is based on opposing pairs of receptors (red-green, blue-yellow, black-white).

after images

visual sensation or illusion that continues to appear in your field of vision even after the original physical stimulus has been removed

ganglion cells

Neurons in the retina that receive information from bipolar cells; their axons form the optic nerve, which carries visual information to the brain.

dichromatism

A vision deficiency in which one type of cone receptor is absent or nonfunctional, leading to difficulty distinguishing certain color pairs (e.g., red-green or blue-yellow).

monochromatism

a person possesses only one type of functioning cone photoreceptor or lacks cones entirely, resulting in an inability to distinguish colors and seeing the world only in shades of black, white, and gray

prosopagnosia

A neurological condition (face blindness) in which a person cannot recognize familiar faces.

blindsight

a condition where a person can respond to visual information without consciously perceiving or being aware of seeing it

cornea

the clear, protective outer layer on the front of the eye that bends light to help focus it

pupil

The adjustable opening in the center of the eye that controls how much light enters.

iris

the ring of muscle tissue that forms the colored portion of the eye and controls the size of the pupil opening

retina

The light-sensitive layer at the back of the eye where sensory receptor cells (rods and cones) convert light into neural signals.

blind spot

The area on the retina where the optic nerve exits the eye; contains no photoreceptors, so no visual information is detected there.

visual nerve

the bundle of ganglion cell axons that carries neural impulses from the retina of the eye to the brain

lens

A transparent structure in the eye that changes shape (accommodation) to focus light on the retina.

accommodation

Modifying existing schemas or creating new ones when new information does not fit existing understanding.

nearsightedness

a vision condition where nearby objects appear clear, but distant objects look blurry because light rays focus in front of the retina rather than directly on it

farsightedness

a vision condition in which faraway objects are seen more clearly than nearby objects because the image of near objects focuses behind the retina rather than directly on it

fovea

The central part of the retina with the highest concentration of cones, responsible for sharp central vision.

photoreceptors

specialized light-sensitive neurons located in the retina that convert light energy into neural impulses