W6 - Vision and Hearing

Sensory transduction

The process by which sensory stimuli are converted into neural signals.

Neural codes

The patterns of neural activity used to represent information in the brain.

Iris

The colored part of the eye that controls the size of the pupil.

Pupil

The opening in the center of the iris that allows light to enter the eye.

Cornea

The transparent outer layer of the eye that begins the process of refraction.

Lens

A flexible structure that changes shape to focus light onto the retina.

Ciliary muscle

Muscle that adjusts the shape of the lens for focusing.

Retina

The light-sensitive layer at the back of the eye containing photoreceptors

Receptor cell

A specialized cell that detects sensory stimuli and converts them into neural signals.

Vitreous humor

The gel-like substance filling the eye that helps maintain its shape.

Optic nerve

The bundle of axons that carries visual information from the retina to the brain.

Optic chiasma

The point where optic nerve fibers partially cross to the opposite hemisphere.

Blind spot

The area of the retina with no photoreceptors where the optic nerve exits.

Macula

The central region of the retina responsible for detailed vision.

Fovea

The small central pit in the macula with the highest concentration of cones.

Refraction

The bending of light as it passes through different media.

Retinex theory

A theory explaining colour constancy based on comparisons across the retina.

Photoreceptors

Cells in the retina (rods and cones) that detect light.

Horizontal cells

Retinal cells that integrate and regulate input from multiple photoreceptors.

Bipolar cells

Retinal neurons that transmit signals from photoreceptors to ganglion cells.

Amacrine cells

Interneurons in the retina involved in complex visual processing.

Ganglion cells

Retinal neurons whose axons form the optic nerve.

Rods

Photoreceptors sensitive to low light and motion but not colour.

Cones

Photoreceptors responsible for colour vision and high acuity.

Lateral inhibition

A process where activated neurons inhibit neighboring neurons to enhance contrast.

Trichromatic theory

The theory that colour vision is based on three types of cones sensitive to red, green, and blue.

Negative colour afterimage

A visual illusion where colours appear reversed after prolonged viewing.

Colour constancy

The ability to perceive consistent colours under varying lighting conditions.

Colour vision deficiency

A reduced ability to distinguish certain colours.

Opponent process (Hering’s) theory

A theory proposing colour vision is based on opposing colour pairs.

Nasal hemiretina

The half of the retina closest to the nose.

Temporal hemiretina

The half of the retina closest to the temples.

Lateral geniculate nucleus

A thalamic relay center for visual information.

Primary visual cortex

The first cortical area that processes visual input (V1).

Magnocellular layers

LGN layers that process motion and coarse detail.

Parvocellular layers

LGN layers that process fine detail and colour.

Koniocellular neurons

LGN neurons involved in additional colour processing pathways.

Aphantasia

The inability to form mental visual images.

Hyperphantasia

Exceptionally vivid mental imagery ability.

Blindsight

The ability to respond to visual stimuli without conscious awareness.

Retinal ganglion cells

Output neurons of the retina that send signals to the brain.

Brightness constancy

The perception of consistent brightness despite changes in lighting.

Secondary visual cortex

Higher visual areas involved in complex processing beyond V1.

Ventral stream

The visual pathway involved in object recognition (“what” pathway).

Inferior temporal cortex

A region involved in complex object and face recognition.

Dorsal stream

The visual pathway involved in spatial processing (“where/how” pathway).

Sensitive period

A developmental window when the brain is especially responsive to experience.

Strabismus

A condition where the eyes are misaligned.

Astigmatism

A refractive error caused by an irregularly shaped cornea or lens

Hypercomplex cell

A visual cortex neuron responsive to complex features like angles and motion.

Receptive fields

The specific region of sensory space a neuron responds to.

Spatial frequency code

The representation of visual patterns based on levels of detail.

Visual gratings

Patterns of alternating light and dark bars used in vision research.

Sinewaves

Smooth, continuous wave patterns used to represent simple visual stimuli.

Square waves

Waveforms with abrupt transitions between high and low values.

Agnosia

The inability to recognize objects despite intact sensory function.

Prosopagnosia

The inability to recognize faces.

Amplitude

The height of a wave, related to intensity or loudness.

Frequency

The number of cycles per second of a wave.

Pitch

The perception of frequency in sound.

Timbre

The quality of a sound that distinguishes different sources.

Tympanic membrane

The eardrum that vibrates in response to sound waves.

Ear canal

The passage that directs sound waves to the eardrum.

Ossicles

Three small bones in the middle ear that amplify sound vibrations.

Inner ear

The structure containing the cochlea and vestibular system.

Oval window

A membrane that transmits vibrations into the cochlea.

Facial nerve

A nerve involved in facial movement and some auditory reflexes.

Auditory nerve

The nerve that carries sound information to the brain.

Cochlea

A spiral-shaped organ that converts sound vibrations into neural signals.

Eustachian tube

A tube that equalizes pressure between the middle ear and throat.

Vestibular canal

A fluid-filled structure involved in balance.

Superior olive

A brainstem structure involved in sound localization.

Cochlear nucleus

The first brainstem relay for auditory information.

Inferior colliculus

A midbrain structure involved in auditory processing.

Medial geniculate body

A thalamic relay for auditory information.

Tonotopic pitch

The spatial arrangement of frequencies along the cochlea

Cortical relay

The transmission of sensory information through cortical areas.

Frequency theory

The idea that pitch is coded by the rate of neural firing.

Volley principle

A theory where groups of neurons fire in alternation to encode high frequencies.

Place theory

The theory that pitch is determined by where the cochlea is stimulated.

Apex

The tip of the cochlea sensitive to low frequencies.

Vestibular system

The system responsible for balance and spatial orientation.

Semicircular canals

Structures that detect rotational head movements.

Kinaesthetic information

Sensory input about body movement and position.

Proprioceptive information

Sensory input about body position and muscle activity.

Otoliths (utricle and saccule)

Structures that detect linear acceleration and gravity.

Midget ganglion cell

A type of retinal ganglion cell involved in high-acuity vision.

Photopigments

Light-sensitive molecules in photoreceptors.

Visual agnosia

The inability to recognize visual objects.

Fusiform gyrus

A brain region involved in face recognition.

Motion blindness

The inability to perceive motion.

Saccades

Rapid eye movements between fixation points.

Amusia

A deficit in music perception.

Tinnitus

The perception of ringing or noise without external sound.

Conductive deafness

Hearing loss due to problems in transmitting sound through the outer or middle ear.

Nerve deafness

Hearing loss caused by damage to the inner ear or auditory nerve