Chapter 10 Flashcards & Key Terms

accommodation
The process of focusing by the ciliary muscles and the lens to form a sharp image on the retina.
amacrine cells
Specialized retinal cells that contact both the bipolar cells and the ganglion cells, and are especially significant in inhibitory interactions within the retina.
amblyopia
Reduced visual acuity that is not caused by optical or retinal impairments.
ataxia
An impairment in the direction, extent, and rate of muscular movement.
bipolar cells
A class of interneurons of the retina that receive information from rods and cones and pass the information to retinal ganglion cells.
blind spot
The portion of the visual field from which light falls on the optic disc. Because there are no receptors in this region, light striking it cannot be seen.
brightness
One of three basic dimensions of light perception, varying from dark to light.
ciliary muscle
One of the muscles that controls the shape of the lens inside the eye, focusing an image on the retina.
complex cortical cell
A cell in the visual cortex that responds best to a bar of a particular size and orientation anywhere within a particular area of the visual field.
cones
A class of photoreceptor cells in the retina that are responsible for color vision.
cornea
The transparent outer layer of the eye, whose curvature is fixed. It bends light rays and is primarily responsible for forming the image on the retina.
extraocular muscle
One of the muscles attached to the eyeball that control its position and movements.
extrastriate cortex
Visual cortex outside of the primary visual (striate) cortex.
fovea
The central portion of the retina, packed with the most photoreceptors and therefore the center of our gaze.
ganglion cells
A class of cells in the retina whose axons form the optic nerve.
horizontal cells
Specialized retinal cells that contact both the receptor cells and the bipolar cells.
hue
One of three basic dimensions of light perception, varying around the color circle through blue, green, yellow, orange, and red.
iris
The circular structure of the eye that provides an opening to form the pupil.
lateral geniculate nucleus (LGN)
The part of the thalamus that receives information from the optic tract and sends it to visual areas in the occipital cortex.
lateral inhibition
The phenomenon by which interconnected neurons inhibit their neighbors, producing contrast at the edges of regions.
lens
A structure in the eye that helps focus an image on the retina.
magnocellular
Of or consisting of relatively large cells.
mirror neuron
A neuron that is active both when an individual makes a particular movement and when that individual sees another individual make that same movement.
myopia
Nearsightedness; the inability to focus the retinal image of objects that are far away.
occipital cortex
Also called visual cortex. The cortex of the occipital lobe of the brain.
ocular dominance column
A region of cortex in which one eye or the other provides a greater degree of synaptic input.
ocular dominance slab
A slab of visual cortex, about 0.5 mm wide, in which the neurons of all layers respond preferentially to stimulation of one eye.
off-center bipolar cell
A retinal bipolar cell that is inhibited by light in the center of its receptive field.
off-center ganglion cell
A retinal ganglion cell that is activated when light is presented to the periphery, rather than the center, of the cell’s receptive field.
off-center/on-surround
Referring to a concentric receptive field in which the center inhibits the cell of interest while the surround excites it.
on-center bipolar cell
A retinal bipolar cell that is excited by light in the center of its receptive field.
on-center ganglion cell
A retinal ganglion cell that is activated when light is presented to the center, rather than the periphery, of the cell’s receptive field.
on-center/off-surround
Referring to a concentric receptive field in which the center excites the cell of interest while the surround inhibits it.
opponent-process hypothesis
The theory that color vision depends on systems that produce opposite responses to light of different wavelengths.
opsin
One of the two components of photopigments in the retina.
optic chiasm
The point at which the two optic nerves meet.
optic disc
The region of the retina devoid of receptor cells because ganglion cell axons and blood vessels exit the eyeball there.
optic nerve
Cranial nerve II; the collection of ganglion cell axons that extend from the retina to the optic chiasm.
optic radiation
Axons from the lateral geniculate nucleus that terminate in the primary visual areas of the occipital cortex.
optic tract
The axons of retinal ganglion cells after they have passed the optic chiasm; most terminate in the lateral geniculate nucleus.
orientation column
A column of visual cortex that responds to rod-shaped stimuli of a particular orientation.
parvocellular
Of or consisting of relatively small cells.
photon
A quantum of light energy.
photopic system
A system in the retina that operates at high levels of light, shows sensitivity to color, and involves the cones.
photoreceptor adaptation
The tendency of rods and cones to adjust their light sensitivity to match ambient levels of illumination.
photoreceptors
Neural cells in the retina that respond to light.
primary visual cortex (V1) or striate cortex
Also called area 17. The region of the occipital cortex where most visual information first arrives.
pupil
The aperture, formed by the iris, that allows light to enter the eye.
quantum (pl. quanta)
A unit of radiant energy.
range fractionation
A hypothesis of stimulus intensity perception stating that a wide range of intensity values can be encoded by a group of cells, each of which is a specialist for a particular range of stimulus intensities.
receptive field
The stimulus region and features that affect the activity of a cell in a sensory system.
refraction
The bending of light rays by a change in the density of a medium, such as the cornea and the lens of the eyes.
retina
The receptive surface inside the eye that contains photoreceptors and other neurons.
retinal
One of the two components of photopigments in the retina.
rhodopsin
The photopigment in rods that responds to light.
rods
A class of light-sensitive receptor cells (photoreceptors) in the retina that are most active at low levels of light.
saturation
One of three basic dimensions of light perception, varying from rich to pale.
scotoma
A region of blindness caused by injury to the visual pathway or brain.
scotopic system
A system in the retina that operates at low levels of light and involves the rods.
simple cortical cell
Also called bar detector or edge detector. A cell in the visual cortex that responds best to an edge or a bar that has a particular width, as well as a particular orientation and location in the visual field.
spatial-frequency filter model
A model of pattern analysis that emphasizes Fourier analysis of visual stimuli.
spectrally opponent cell
A visual receptor cell that has opposite firing responses to different regions of the spectrum.
trichromatic hypothesis
A hypothesis of color perception stating that there are three different types of cones, each excited by a different region of the spectrum and each having a separate pathway to the brain.
visual acuity
Sharpness of vision.
visual field
The whole area that you can see without moving your head or eyes.
wavelength
The length between two peaks in a repeated stimulus such as a wave, light, or sound.
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