Psychology Sensation: Vision, Audition, Smell, Taste, and Pain

Vision

The sense that detects light (electromagnetic radiation, roughly 400 to 700 nm) and builds images of the world from it.

Retina

The light-sensitive neural tissue lining the back of the eye.

Rods

Photoreceptors specialized for dim light.

Cones

Photoreceptors for bright light, fine detail, and color.

Rhodopsin

The light-sensitive pigment in rods, made of opsin plus retinal.

Cone opsins (photopsins)

The pigments in cones, each tuned to a different range of wavelengths.

Dark current

The steady inward flow of positive ions (Na⁺ and Ca²⁺) through cGMP-gated channels in photoreceptors in darkness.

Transduction

Conversion of a physical stimulus (light, sound, chemicals, and so on) into an electrical signal in a sensory receptor cell.

Center-on / Center-off / Center-surround

Receptive-field organization of retinal ganglion cells and LGN cells.

LGN (lateral geniculate nucleus)

A thalamic relay that receives input from the retina and sends it to the primary visual cortex.

Primary visual cortex (V1)

The first cortical area to process vision, in the occipital lobe.

Retinotopic

Organized as a spatial map of the retina and visual field.

Feature selectivity

The property that different neurons respond only to specific features.

Simple cells

V1 neurons that respond to an oriented bar or edge at a specific position in the visual field.

Complex cells

V1 neurons that respond to an oriented bar or edge anywhere within their receptive field.

Dorsal stream

The 'where/how' pathway from the occipital lobe to the parietal lobe.

Ventral stream

The 'what' pathway from the occipital lobe to the temporal lobe.

SCN (suprachiasmatic nucleus)

A small area of the hypothalamus that acts as the body's master circadian clock.

Blind spot

The spot on the retina where the optic nerve exits (the optic disc).

Akinetopsia

Motion blindness, the inability to perceive movement.

Prosopagnosia

Face blindness, the inability to recognize faces despite otherwise normal vision.

Hemi-neglect

A neglect syndrome in which a person ignores one side of space or their own body.

Capgras delusion

The false belief that a familiar person has been replaced by an impostor.

Fregoli delusion

The false belief that different people are actually one person in disguise.

Visual snow

A condition in which people see persistent static or tiny flickering dots across their whole visual field.

Color blindness

Reduced ability to tell certain colors apart, usually from a missing or altered cone pigment.

Amplitude

The height of a sound wave, which corresponds to loudness.

Phase

The position within a wave's cycle at a given moment.

Tonotopic

Organized by sound frequency, so neighboring locations respond to neighboring frequencies.

Pinna

The visible outer part of the ear, which collects sound and funnels it into the ear canal.

Eardrum (tympanum)

The membrane that vibrates when sound arrives and separates the outer ear from the middle ear.

Ear bones (malleus, incus, stapes)

The three tiny middle ear bones that pass and amplify vibrations from the eardrum.

Oval window

The membrane at the entrance to the cochlea that transfers vibrations into the cochlear fluid.

Cochlea

The fluid-filled, snail-shaped structure of the inner ear that converts sound vibrations into neural signals.

Hair cells

The sensory receptor cells of the cochlea.

Tectorial membrane

A gelatinous membrane above the hair cells.

Depolarization and VOCs

When stereocilia bend, K⁺ enters and depolarizes the hair cell.

Odorants

Airborne chemical molecules that we detect as smells.

Olfactory epithelium

The tissue in the upper nasal cavity that contains the olfactory receptor neurons.

Olfactory receptor neurons (ORNs)

Sensory neurons whose cilia carry odorant receptors.

Olfactory bulb

The brain structure at the base of the forebrain that receives input from ORNs.

Glomerulus (glomeruli)

Spherical clusters in the olfactory bulb where ORN axons converge.

Mitral cells

The main output neurons of the olfactory bulb.

GPCRs (G-protein-coupled receptors)

Receptors that span the membrane seven times.

Taste buds

Clusters of taste receptor cells that detect chemicals such as sweet, sour, salty, bitter, and umami.

Anterolateral pathway

The ascending spinal pathway that carries pain and temperature information.

Nociception

The detection and neural processing of harmful or potentially harmful stimuli.

A fibers (Aδ)

Thin myelinated nerve fibers that conduct quickly and carry sharp, well-localized pain.

C fibers

Unmyelinated nerve fibers that conduct slowly and carry dull, burning, poorly localized pain.

First pain

The fast, sharp, well-localized pain felt right after an injury.

Second pain

The slower, dull, aching or burning pain that follows and lingers.

TRP channels (transient receptor potential)

Ion channels in sensory neurons that respond to temperature and chemicals.

Enkephalin

An endogenous opioid peptide that reduces pain transmission.

Sensitization

Increased responsiveness of pain pathways after injury or repeated stimulation.

Phantom pain

Pain felt in a limb or body part that has been amputated or lost.

Ascending tracts

Spinal cord pathways that carry sensory information up to the brain.

Descending tracts

Pathways that run from the brain down the spinal cord.