Sensation and Perception Course Review Flashcards

Comprehensive vocabulary flashcards covering the perceptual process, psychophysical methods, neural firing, eye structure and disorders, retina mechanics, and receptive fields.

Perceptual Process

The multi-step sequence that transforms environmental stimuli into internal sensory experiences, recognition, and behavioral responses.

Environmental Stimulus

All objects, energy, and physical events present in the surrounding world available for an observer to perceive.

Stimulus on the Receptors

The specific reflection or representation of an environmental stimulus formed directly on sensory receptor cells, such as an optical image on the retina.

Transduction

The transformation of environmental physical energy, such as light or sound, into electrical neural signals by sensory receptor cells.

Neural Processing

The transmission and alteration of electrical signals through networks of interconnected neurons leading toward brain centers.

Perception

The conscious sensory experience resulting from neural processing of incoming environmental information.

Recognition

The cognitive ability to categorize and assign identity or meaning to a perceived sensory stimulus.

Action

Motor activities and physical movements executed in response to the perception and recognition of environmental stimuli.

Bottom-Up Processing

Perceptual processing built directly from incoming sensory data received from environmental stimuli and receptors.

Top-Down Processing

Perceptual processing guided by cognitive factors such as existing knowledge, memories, expectations, and context.

Sensation

The initial elementary process of detecting raw physical stimuli by sensory organs prior to perceptual processing.

Psychophysical Level of Analysis

A research approach examining the quantitative relationship between physical stimulus characteristics and an observer's perceptual experience.

Physiological Level of Analysis

A research approach examining the relationship between physical stimuli or perceptual experiences and internal biological/neural responses.

Absolute Threshold

The minimum stimulus energy necessary for an observer to detect a stimulus.

Gustav Fechner

The scientist who developed classical psychophysical methods to measure the quantitative relationships between stimuli and perceptions.

Method of Limits

A psychophysical procedure in which stimuli are presented in ascending or descending intensity order to find detection threshold crossovers.

Ascending Trial

A test sequence in the Method of Limits starting with an undetectable stimulus intensity that increases incrementally until detected.

Descending Trial

A test sequence in the Method of Limits starting with an easily detectable stimulus intensity that decreases incrementally until no longer detected.

Method of Adjustment

A psychophysical procedure where the participant continuously adjusts stimulus intensity until it is barely detectable.

Method of Constant Stimuli

A psychophysical procedure presenting 5 to 9 stimulus intensities in random order repeatedly to identify the intensity detected $50\%$ of the time.

Forced Choice Procedure

A psychophysical technique presenting structured intervals or locations—one containing the stimulus and one without—to eliminate participant response bias.

Difference Threshold

The smallest detectable difference between two physical stimuli; also called the Just Noticeable Difference (JND) or Differenz Limen (DL).

Ernst Weber

The 19th-century researcher who discovered that the difference threshold is proportional to the magnitude of the standard stimulus.

Weber's Law

The relationship stating that the difference threshold ($DL$) equals a constant ($K$) multiplied by standard stimulus intensity ($S$): $DL = K \times S$.

Recognition Testing

A psychophysical measurement method assessing a subject's ability to correctly name or classify presented visual or sensory items.

Reaction Time

The time delay between stimulus onset and the execution of an observer's physical or verbal response.

Stroop Test

A task measuring reaction time and cognitive interference when stating the font color of words printed in conflicting color names.

Phenomenological Report

A qualitative assessment method where individuals describe their first-person perceptual experiences in verbal form.

Neuron

A specialized nerve cell that processes and transmits electrical and chemical signals within the nervous system.

Dendrites

Branching neuron structures that receive incoming chemical or physical signals from neighboring cells.

Soma

The cell body of a neuron containing its metabolic machinery and nucleus.

Axon

The long extension of a neuron that conducts electrical action potentials toward axon terminals.

Resting Potential

The negative electrical charge of an inactive neuron axon membrane relative to the extracellular space, ranging from $-60\,mV$ to $-80\,mV$.

Depolarization

The initial phase of an action potential caused by sodium ($\text{Na}^+$) influx, shifting membrane potential toward positive values.

Hyperpolarization

A transient state following repolarization where membrane voltage becomes more negative than resting potential due to potassium ($\text{K}^+$) outflow.

Action Potential

An all-or-none electrical impulse propagating down an axon at speeds up to $100\,m/s$ without decreasing in magnitude.

Refractory Period

The post-firing recovery phase during which an axon cannot initiate a second action potential.

Sodium-Potassium Pump

A membrane mechanism that active-transports sodium ($\text{Na}^+$) ions out of and potassium ($\text{K}^+$) ions into the cell to maintain resting potential.

Saltatory Conduction

The rapid transmission of action potentials along myelinated axons by jumping between non-insulated Nodes of Ranvier.

Nodes of Ranvier

Unmyelinated gaps along an axon membrane rich in ion channels where action potentials are regenerated.

Myelin Sheath

A fatty layer surrounding axons that speeds electrical conduction through passive insulated flow.

All-or-None Law

The principle stating that an action potential fires at constant amplitude whenever axon threshold is reached, regardless of stimulus strength above threshold.

Single Cell Recording

A physiological recording method placing a microelectrode inside or near a single axon to measure individual action potential firing rates.

Wavelength

The physical distance between consecutive wave crests of light, determining perceived hue or color.

Nanometer

A unit of length equal to $10^{-9}\,m$, used to specify light wave dimensions.

Visible Light Spectrum

The band of electromagnetic radiation detectable by the human eye, spanning wavelengths from $400\,nm$ to $700\,nm$.

Amplitude (Light)

The height of a light wave from baseline to peak, dictating perceived brightness.

Purity (Light)

The relative proportion of a single spectral wavelength compared to added achromatic white/black light.

Saturation

The relative vividness or richness of a color hue, controlled by light purity.

Cornea

The clear outer surface covering the front of the eye that provides approximately 80 percent of total optical focusing power.

Sclera

The tough, white outer wall protecting the majority of the eyeball.

Iris

The pigmented muscular ring regulating pupil size to control light entering the eye.

Pupil

The central dark opening in the iris that allows light to reach the internal optics.

Lens

The flexible, transparent structure behind the pupil that fine-tunes image focus on the retina.

Accommodation

The change in lens curvature driven by ciliary muscles to focus objects at various distances.

Ciliary Muscle

Internal eye muscles that adjust lens shape during optical accommodation.

Aqueous Humor

The clear fluid occupying the anterior chamber between the cornea and lens.

Vitreous Humor

The transparent gel filling the large posterior cavity behind the lens.

Retina

The light-sensitive layer lining the back of the eye containing photoreceptor cells and visual processing circuits.

Fovea

The tiny central area of the retina composed entirely of cones, responsible for sharp high-acuity vision.

Optic Disc

The region on the retina where ganglion cell axons bundle together to exit toward the brain, containing no photoreceptors.

Blind Spot

The area of the visual field corresponding to the optic disc where light stimuli cannot be perceived.

Optic Nerve

The nerve pathway formed by about 1 million ganglion cell axons conducting visual signals from retina to brain.

Astigmatism

A refractive vision defect where a misshapen cornea causes light rays to focus unevenly across different orientations, producing blurred images.

Cataracts

A visual disorder caused by clouding of the crystalline lens due to protein buildup, blurring overall vision.

Phacoemulsification

A cataract surgery technique using ultrasonic energy to fragment and remove a cloudy natural lens.

Intraocular Lens

An artificial lens implant placed in the eye capsule to replace a removed cataractous lens.

Dr. Patricia Bath

The ophthalmologist and inventor who created laser phacoemulsification devices for cataract removal.

Myopia

Nearsightedness; a refractive state where parallel light focuses in front of the retina, blurring distant targets.

Hyperopia

Farsightedness; a refractive state where light focuses behind the retina, blurring nearby targets.

Presbyopia

Age-related stiffening of the lens that diminishes accommodation capacity and near focusing ability.

Glaucoma

An eye disease caused by aqueous humor fluid buildup that elevates intraocular pressure, damages the optic nerve, and produces tunnel vision.

Trabecular Meshwork

The porous tissue ring near the anterior chamber through which aqueous humor drains.

Schlemm's Canal

The circular drainage channel collecting aqueous humor from the trabecular meshwork to route it into venous circulation.

Macular Degeneration

A disease destroying the macula and fovea, leading to central vision loss while leaving peripheral vision intact.

Retinitis Pigmentosa

A genetic retinal disease destroying peripheral rods first, causing night blindness and severe tunnel vision.

Photoreceptors

Retinal sensory neurons (rods and cones) containing photopigments that transduce light energy into electrical potentials.

Rods

Photoreceptor cells (~120 million per retina) concentrated in the periphery, providing high sensitivity for dim scotopic vision without color.

Cones

Photoreceptor cells (~5 million per retina) concentrated in the fovea, providing high-acuity photopic daylight and color vision.

Rhodopsin

The visual photopigment located in rod outer segment discs, composed of 11-cis retinal bound to opsin.

Retinal

The light-absorbing Vitamin A derivative molecule within visual photopigments that changes shape upon absorbing light photons.

Opsin

The large protein component bound to retinal within photoreceptor photopigments.

Isomerization

The chemical transformation of 11-cis retinal into all-trans retinal initiated by light photon absorption.

Bleaching (Photopigment)

The separation of retinal from opsin following isomerization, causing the photopigment to lose color and light sensitivity.

Rhodopsin Regeneration

The enzymatic process recombining 11-cis retinal and opsin to restore dark sensitivity to rods.

Erythrolabe

The cone photopigment formed by photopsin I and retinal, absorbing long wavelengths (red light).

Chlorolabe

The cone photopigment formed by photopsin II and retinal, absorbing medium wavelengths (green light).

Cyanolabe

The cone photopigment formed by photopsin III and retinal, absorbing short wavelengths (blue light).

Photopic Vision

Visual perception operating under bright light conditions mediated exclusively by cones.

Scotopic Vision

Visual perception operating under low light conditions mediated exclusively by rods.

Dark Adaptation

The gradual increase in visual sensitivity observed when staying in total darkness.

Dark Adaptation Curve

A graph of visual threshold versus time in darkness showing a fast cone branch and a slow, highly sensitive rod branch.

Rod-Cone Break

The point on a dark adaptation curve around 7 to 10 minutes where rod sensitivity surpasses cone sensitivity.

Purkinje Shift

The shift in peak visual spectral sensitivity from $555\,nm$ (daytime cones) to $507\,nm$ (nighttime rods), making blue/green hues appear brighter at night.

Neural Convergence

The synaptic summation where input from many photoreceptors converges onto a single ganglion cell.

Retinal Ganglion Cells

The final output neurons of the retina whose axons form the optic nerve.

Receptive Field

The specific area on sensory receptors (retina) where stimulation alters the firing rate of a neuron.

Lateral Inhibition

Inhibition transmitted sideways across a neural circuit to suppress neighboring responses, sharpening edge contrast.

Center-Surround Receptive Field

A circular receptive field organization where light on the central area produces the opposite response of light on the surrounding ring.

Simultaneous Contrast

A perceptual phenomenon where an area's perceived brightness is modified by the luminance of its surrounding background through lateral inhibition.