Unit 1B Vocab: Sleep, Dreams, & Psychoactive Drugs

Stimulants

A type of psychoactive drug that increases activity in the central nervous system, enhancing alertness, energy, and mood. Common examples include caffeine and cocaine.

Depressants

Psychoactive drugs that slow down central nervous system activity, reducing arousal and stimulation. They can induce relaxation, drowsiness, and impaired coordination—alcohol is a common example.

Hallucinogens

Psychoactive drugs that alter perception, mood, and thought by affecting sensory and cognitive processes. They can cause hallucinations and distort reality—marijuana is a common example.

Opioids

A class of psychoactive drugs that reduce pain and produce euphoria by acting on the brain’s endorphin receptors. They carry a high risk of tolerance, dependence, and addiction—heroin is a common example.

Tolerance

A reduced response to a drug after repeated use, requiring higher doses to achieve the same effect. It reflects the body's adaptation to the substance over time.

Addiction/dependence

A condition in which a person compulsively uses a substance despite harmful consequences, often accompanied by physical or psychological reliance. Dependence typically involves tolerance and withdrawal symptoms when the substance is reduced or stopped.

Withdrawal symptoms

Physical or psychological effects that occur when a person stops using a drug they’ve become dependent on. These symptoms vary by substance and can include anxiety, nausea, irritability, or cravings.

REM (paradoxical sleep)

A sleep stage characterized by rapid eye movement, vivid dreaming, and brain activity resembling wakefulness, while the body remains physically paralyzed. It's called "paradoxical" because the brain is active but the muscles are immobile.

REM rebound

The tendency for REM sleep to increase following periods of sleep deprivation. It reflects the brain’s need to recover lost REM sleep, often resulting in more intense and vivid dreams.

Activation-synthesis theory

A biological explanation of dreaming that suggests the brain creates stories to make sense of random neural activity during REM sleep. Dreams are seen as the mind’s attempt to synthesize internal signals into coherent experiences.

Consolidation theory

A cognitive explanation of dreaming that proposes sleep—especially REM—helps strengthen and stabilize memories. It suggests that dreams play a role in organizing and integrating new information into long-term storage.

Circadian Rhythm

The body’s internal biological clock that regulates sleep-wake cycles and other physiological processes on a roughly 24-hour schedule. It’s influenced by environmental cues like light and temperature.

NREM 1

The lightest stage of non-REM sleep, where a person drifts in and out of consciousness and may experience hypnagogic sensations. Brain activity begins to slow, and it's easy to be awakened from this stage.

NREM 2

A deeper stage of non-REM sleep marked by sleep spindles and K-complexes, which help block external stimuli and support memory consolidation. Body temperature drops and heart rate slows, making it harder to wake up than in NREM 1.

NREM 3/4

The deepest stages of non-REM sleep, also called slow-wave sleep, marked by delta brain waves and minimal responsiveness to external stimuli. These stages are critical for physical restoration, immune function, and memory consolidation.

Hypnogogic sensations

Vivid sensory experiences—such as floating, falling, or seeing flashes—that occur during the transition from wakefulness to sleep, especially in NREM 1. They reflect the brain’s shift into altered consciousness.

Why we sleep: memory consolidation and restoration

Sleep plays a critical role in strengthening memories and repairing the body. REM and deep NREM stages help organize learned information and restore physical and cognitive function.

Sleep apnea

A sleep disorder where breathing repeatedly stops and starts during sleep, often due to airway obstruction. It disrupts sleep quality and can lead to daytime fatigue and serious health issues.

Narcolepsy

A chronic sleep disorder marked by overwhelming daytime drowsiness and sudden sleep attacks. It often includes cataplexy—brief loss of muscle control triggered by strong emotions—and is linked to disrupted regulation of REM sleep.

REM sleep behavior disorder

A condition where people physically act out vivid dreams during REM sleep due to lack of normal muscle paralysis. It can involve talking, kicking, or flailing and is linked to neurological disorders.

Somnambulism

A disorder where a person walks or performs complex behaviors while in deep NREM sleep, typically NREM 3.

Transduction

The process of converting one form of energy into another. In sensation, it refers to how sensory receptors transform physical stimuli (like light, sound, or pressure) into neural signals the brain can interpret.

Absolute threshold

The minimum level of stimulation needed for a person to detect a stimulus 50% of the time. It marks the boundary between undetectable and detectable sensory input.

Just-noticeable difference

The smallest change in a stimulus that a person can detect 50% of the time. It reflects our sensitivity to differences like noticing when a light gets slightly brighter or a sound slightly louder.

Weber’s Law

The relationship between actual and perceived differences in stimulus intensity.

Sensory adaptation

When sensory receptor cells are constantly stimulated, they undergo a loss of sensitivity to stimuli.  

Sensory interaction

A principle that states one sense can influence another.

Synesthesia

When your brain processes multiple unrelated senses at the same time, causing you to experience more than one.

Closure as it relates to the blindspot

Closure is a principle where the brain fills in missing visual information to perceive a complete image. It helps us "see" a whole object even when part of it is missing—like when the blind spot in our retina lacks visual input, but our brain fills in the gap using surrounding context.

Accommodation

This is the process by which the eye’s lens changes shape to focus on objects at different distances. The lens flattens for far objects and curves for near ones, helping create a clear image on the retina.

Rods

Photoreceptor cells in the retina that are highly sensitive to light, allowing us to see in dim conditions. They don’t detect color or fine detail, but are essential for night and peripheral vision.

Cones

Photoreceptor cells in the retina responsible for color vision and sharp detail. They function best in bright light and are concentrated in the fovea, enabling us to perceive fine visual detail and distinguish between red, green, and blue wavelength.

Trichromatic theory

A theory of color vision stating that the retina has three types of cones, each sensitive to red, green, or blue light. Color perception arises from the combined activation of these cones in varying degrees

Opponent-process theory

A theory of color vision that suggests we perceive color in opposing pairs—red-green, blue-yellow, and black-white. When one color in a pair is activated, the other is inhibited. This explains phenomena like afterimages and why we don’t see reddish-green or bluish-yellow.

Fovea

A small central pit in the retina packed with cones, responsible for our sharpest vision and fine detail. It’s where light is focused when we look directly at something.

Prosopagnosia (face blindness)

A neurological condition where a person has difficulty recognizing faces—even familiar ones. It can result from brain damage or be present from birth, affecting social interactions and memory.

Blindsight

A condition where individuals with damage to the visual cortex can respond to visual stimuli—like detecting movement or location—without consciously seeing them. It reveals that some visual processing occurs outside of conscious awareness

Place theory

A theory of pitch perception stating that different sound frequencies stimulate different locations along the basilar membrane in the cochlea. The brain interprets pitch based on which region is most active.

Frequency theory (with the volley principle)

We hear pitch based on how fast neurons fire, and for higher frequencies, groups of neurons alternate firing to match the sound’s frequency.

Sound localization

The brain’s ability to determine where a sound is coming from, based on differences in timing and intensity between the ears.

Conduction deafness

Hearing loss caused by problems in the outer or middle ear that block sound from reaching the inner ear—like earwax buildup, a ruptured eardrum, or damaged ossicles. It’s often treatable with surgery or hearing aids.

Sensorineural deafness

Hearing loss caused by damage to the inner ear (cochlea) or auditory nerve, often permanent and affecting both volume and clarity. Common causes include aging, loud noise exposure, or genetic factors.

Chemical senses (olfaction + gustation)

These senses detect molecules: smell (olfaction) senses airborne chemicals, and taste (gustation) senses dissolved ones. They work together to create flavor and are closely linked to emotion and memory due to their connection with the limbic system.

Thalamus

The brain’s sensory relay station—it receives incoming sensory information (except smell) and directs it to the appropriate areas of the cortex for processing. It plays a key role in attention, consciousness, and perception.

Pheromones

Chemical signals released by organisms to affect the behavior or physiology of others of the same species. In humans, they may play subtle roles in attraction, mood, and social communication, though their effects are less pronounced than in animals.

Gustatory cells (sweet, sour, bitter, salty, umami, oleogustus)

Specialized taste receptor cells on the tongue that detect five main taste qualities—sweet, sour, bitter, salty, and umami (savory)—plus a sixth, oleogustus, which senses fatty acids. Each type responds to specific chemical compounds, helping us identify nutrients and avoid toxins.

Taste receptors (linked to sensitivity of taste)

Taste receptors on gustatory cells vary in density and responsiveness across individuals, influencing how strongly someone perceives flavors. People with more taste buds (like “supertasters”) experience heightened sensitivity to certain tastes.

Supertasters

People with a higher density of taste buds, making them extremely sensitive to certain flavors.

Nontasters

Individuals with fewer taste buds, making them less sensitive to certain flavors.

Medium tasters

Average taste bud count, moderate sensitivity to flavors.

Pain (gate control theory)

The spinal cord has a “gate” mechanism that can either block or allow pain signals to pass to the brain—non-painful input (like rubbing an injury) can close the gate, reducing the perception of pain.

Phantom limb syndrome

A condition where amputees feel sensations like pain, itching, or movement in a limb that’s no longer there, due to the brain’s continued mapping of the missing body part.

Gustation/olfaction

Taste and smell are chemical senses. Gustation detects dissolved molecules (like sweet or salty), while olfaction detects airborne ones, and together they shape flavor perception and link strongly to emotion and memory.

Afterimages (red/green, blue/yellow, black/white)

When you stare at a color (like red) for a while and then look away, you see its opponent color (like green) due to fatigued photoreceptors—this supports opponent-process theory (red/green, blue/yellow, black/white).

Ganglion cells

Neurons in the retina that receive visual info from bipolar cells and transmit it to the brain via the optic nerve.

Dichromatism

A type of color blindness where one of the three cone types (red, green, or blue) is missing, causing limited color perception—like confusing red with green or blue with yellow.

Monochromatism

A rare form of color blindness where only one type of cone functions—or none at all—resulting in seeing the world in shades of gray.

Vestibular sense (semicircular canals)

Your sense of balance and spatial orientation, controlled by structures in the inner ear—especially the semicircular canals, which detect head rotation and movement. They send signals to the brain to help you stay upright and coordinated.

Kinesthesis

Your sense of body position and movement—kinesthetic receptors in muscles, joints, and tendons let you know where your limbs are and how they’re moving, even without looking.