Sensory Systems, Psychophysics, and Perception

Comprehensive vocabulary flashcards covering psychophysics, sensory thresholds, visual, auditory, somatosensory, chemical, vestibular, and kinesthetic systems based on lecture notes.

Sensation

The biological process through which sensory receptors and the nervous system detect and represent physical stimulus energy from the environment.

Perception

The cognitive process of organizing, synthesizing, and interpreting raw sensory inputs to construct meaningful internal representations of the external environment, influenced by memory, expectation, and context.

Transduction

The physiological conversion of physical or chemical stimulus energy into electrochemical neural impulses digestible by the central nervous system.

Absolute Threshold

The minimum stimulus intensity required for a sensory system to detect a stimulus at least $50\%$ of the time (e.g., a candle flame at $30\text{ miles}$ / $48.3\text{ km}$, a watch tick at $20\text{ feet}$ / $6.1\text{ m}$, or a drop of perfume diffused across a three-room apartment).

Difference Threshold (Just-Noticeable Difference / JND)

The minimal physical change in stimulus intensity required for an observer to reliably detect a difference between two stimuli $50\%$ of the time.

Weber's Law

The psychophysical principle stating that the difference threshold is not a fixed absolute quantity, but a constant mathematical ratio relative to the intensity of the baseline stimulus: $\frac{\Delta I}{I} = k$, where $\Delta I$ is the JND increment, $I$ is baseline intensity, and $k$ is a constant fraction.

Sensory Adaptation

The progressive reduction in sensory receptor firing rates in response to continuous, unchanging environmental stimulation.

Visible Light Spectrum

The band of electromagnetic radiation detectable by human vision, spanning wavelengths from $380\text{ nm}$ to $750\text{ nm}$.

Accommodation

The visual process in which ciliary muscle contraction modifies the curvature of the transparent lens to focus light from near or far targets onto the retina.

Myopia (Nearsightedness)

A refractive error where the eyeball is excessively long or corneal curvature is too steep, causing the focal point of incoming light to fall in front of the retina.

Hyperopia (Farsightedness)

A refractive error where the eyeball is structurally too short or the cornea is too flat, causing the focal point of incoming light to fall behind the retina.

Rods

Retinal photoreceptors with high sensitivity specialized for scotopic (low-light) vision, peripheral awareness, and motion detection, characterized by low acuity and achromatic vision.

Cones

Retinal photoreceptors concentrated densely in the fovea, specialized for photopic (bright light) vision, color discrimination, and high spatial acuity.

Blind Spot (Optic Disc)

The anatomical region of the retina that completely lacks photoreceptors where ganglion cell axons converge to form the optic nerve and exit the eye.

Trichromatic Theory (Young-Helmholtz)

A theory of color vision operating at the retinal level via three cone types: Short-Wavelength (S-Cones, $\approx 420\text{ nm}$, Blue), Medium-Wavelength (M-Cones, $\approx 530\text{ nm}$, Green), and Long-Wavelength (L-Cones, $\approx 560\text{ nm}$, Red).

Opponent-Process Theory

A theory proposing color vision operates post-photoreceptor level via opposing neuronal channels (Red vs. Green, Blue vs. Yellow, and Black vs. White), in which neural fatigue in one pathway creates complementary negative afterimages.

Dichromatism

A form of color vision deficiency resulting from the absence of one functional cone class.

Monochromatism

The absence of functional cone types (such as rod monochromatism), resulting in total color blindness and perceiving the world entirely in shades of gray.

Blindsight

A condition resulting from primary visual cortex ($V1$) lesions where individuals demonstrate unconscious visual processing via subcortical pathways (retina to superior colliculus) despite conscious blindness.

Prosopagnosia (Face Blindness)

The inability to recognize familiar faces despite intact basic vision, caused by damage to the fusiform face area (FFA) in the inferior temporal cortex.

Auditory Frequency

A sound wave property measured in Hertz ($\text{Hz}$) that dictates perceived pitch, with the human hearing range spanning from $20\text{ Hz}$ to $20{,}000\text{ Hz}$.

Auditory Amplitude

The peak height of a sound wave measured in decibels ($\text{dB}$) that dictates perceived loudness, with intensities of $85\text{ dB}+$ posing a risk of hearing damage.

Ossicles

Three tiny middle ear bones (malleus, incus, and stapes) that amplify kinetic force from the tympanic membrane onto the oval window.

Organ of Corti

A specialized inner ear structure located on the basilar membrane within the cochlea, bearing hair cells that transduce mechanical displacement into action potentials sent along the auditory nerve.

Place Theory

A pitch perception theory stating that perceived pitch depends on the specific location along the basilar membrane undergoing peak displacement, with high frequencies exciting the base and low frequencies exciting the apex.

Frequency Theory

A pitch perception theory stating that the firing rate of the auditory nerve directly matches sound wave frequency, accounting for low frequencies up to $1000\text{ Hz}$.

Volley Principle

The auditory principle stating that staggered ensembles of neurons fire in coordinated volleys to process intermediate frequencies between $1000\text{ Hz}$ and $4000\text{ Hz}$.

Sound Localization

The perceptual determination of a sound's spatial location, derived primarily from Interaural Time Difference (ITD) and Interaural Level Difference (ILD).

Conduction Deafness

Hearing loss caused by structural damage or physical blockage located in the outer or middle ear.

Sensorineural Deafness

Permanent hearing loss caused by damage to cochlear hair cells or the auditory nerve.

Sensory Interaction

The principle that distinct sensory modalities continuously interact to shape perception, such as taste, smell, thermal, and tactile inputs combining into flavor.

Pheromones

Secreted chemical signals that elicit innate behavioral or physiological responses in other individuals of the same species.

Gustation

The chemical sense mediated by taste buds on papillae detecting primary tastes: Sweet, Sour, Salty, Bitter, Umami, and Oleogustus.

Gate Control Theory

A pain modulation model proposing a spinal gating mechanism in the substantia gelatinosa, where small nociceptive fibers ($\text{A-delta} / \text{C}$) open the gate and large mechanoreceptive fibers ($\text{A-beta}$) close the gate.

Phantom Limb Phenomenon

The perception of sensations in an amputated limb, driven by neuroplasticity and cortical reorganization within the primary somatosensory cortex ($S1$).

Vestibular Sense

The sensory system that monitors balance, head position, and spatial orientation via inner ear structures, specifically the semicircular canals and otolith organs.

Semicircular Canals

Inner ear structures that detect rotational (angular) head acceleration across three spatial planes.

Otolith Organs (Utricle and Saccule)

Inner ear structures that utilize calcium carbonate crystals (otoliths) to detect linear acceleration and head tilt relative to gravity.

Kinesthesis (Proprioception)

The sense that tracks the movement, position, and location of body parts using internal mechanoreceptors.

Muscle Spindles

Mechanoreceptors located in skeletal muscles that monitor muscle length and stretch velocity.

Golgi Tendon Organs

Proprioceptive mechanoreceptors located in muscle tendons that monitor tendon tension.

Joint Kinesthetic Receptors

Mechanoreceptors located within joint capsules that monitor joint angles and mechanical pressure.