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58 Cards in this Set

  • Front
  • Back
What is a sensory receptor?
A specialized neuron that detects a particular category of physical events.
What is sensory transduction?
The process by which sensory stimuli are transduced into slow, graded receptor potentials.
What is a receptor potential?
A slow, graded electrical potential produced by a receptor cell in response to a physical stimulus.
What is hue?
One of the perceptual dimensions of color; the dominant wavelength.
What is brightness?
One of the perceptual dimensions of color; intensity.
What is saturation?
One of the perceptual dimensions of color; purity.
What is vergence movement?
The cooperative movement of the eyes, which ensures that the image of an object falls of identical portions of both retinas.
What is saccadic movement?
The rapid, jerky movement of the eyes used in scanning a visual scene.
What is pursuit movement?
The movement that the eyes make to maintain an image of a moving object on the fovea.
What is accommodation?
Changes in the thickness of the lens of the eye, accomplished by the ciliary muscles, that focus images of near or distant objects on the retina.
What is the retina?
The neural tissue and photoreceptive cells located on the inner surface of the posterior portion of the eye.
What is a rod?
One of the receptor cells of the retina; sensitive to light of low intensity.
What is a cone?
One of the receptor cells of the retina; maximally sensitive to one of three different wavelengths of light and hence encodes color vision.
What is a photoreceptor?
One of the receptor cells of the retina; transduces photic energy into electrical potentials.
What is the fovea?
The region of the retina that mediates the most acute vision of birds and higher mammals. Color-sensitive cones constitute the only type of photoreceptor found in the fovea.
What is the optic disk?
The location of the exit point from the retina of the fibers of the ganglion cells that form the optic nerve; responsible for the blind spot.
What is a bipolar cell?
A bipolar neuron located in the middle layer of the retina, conveying information from the photreceptors to the ganglion cells.
What is a ganglion cell?
A neuron located in the retina that receives visual information from bipolar cells; its axons give rise to the optic nerve.
What is a horizontal cell?
A neuron in the retina that interconnects adjacent photoreceptors and the outer processes of the bipolar cells.
What is an amacrine cell?
A neuron in the retina that interconnects adjacent ganglion cells and the inner processes of the bipolar cells.
What is the lamella?
A layer of membrane containing photopigments; found in rods and cones of the retina.
What is a photopigment?
A protein dye bonded to retinal, a substance derived from vitamin A; responsible for transduction of visual information.
What is opsin?
A class of protein that, together with retinal, constitutes the photpigments.
What is retinal?
A chemical synthesized from vitamin A; joins with an opsin to form a photopigment.
What is rhodopsin?
A particular opsin found in rods.
What is transducin?
A G protein that is activated when a photon strikes a photopigment; activates phosphodiesterase molecules, which destroy cyclic GMP and close cation channels in the photoreceptor.
What is the dorsal lateral geniculate nucleus?
A group of cell bodies within the lateral geniculate body of the thalamus; receives inputs from the retina and projects to the primary visual cortex.
What is the magnocellular layer?
One of the inner two layers of cells in the dorsal lateral geniculate nucleus; transmits information necessary for the perception of form, movement, depth, and small differences in brightness.
What is the parvocellular layer?
One of the four outer layers of cells in the dorsal lateral geniculate nucleus; transmits information necessary for perception of color and fine details.
What is the calcarine fissure?
A horizontal fissure on the inner surface of the posterior cerebral cortex; the location of the primary visual cortex.
What is the striate cortex?
The primary visual cortex.
What is the optic chiasm?
A cross-shaped connection between the optic nerves, located below the base of the brain, just anterior to the pituitary gland.
What is the receptive field?
That portion of the visual field in which the presentation of visual stimuli will produce an alteration in the firing rate of a particular neuron.
What is protanopia?
An inherited form of defective color vision in which red and green hues are confused; "red" cones are filled with "green" cone opsin.
What is deuteranopia?
An inherited form of defective color vision in which hues with short wavelengths are confused; "blue" cones are either lacking or faulty.
What is a negative afterimage?
The image seen after a portion of the retina is exposed to an intense visual stimulus; consists of colors complementary to those of the physical stimulus.
What are complementary colors?
Colors that make white or gray when mixed.
What is a simple cell?
An orientation-sensitive neuron in the striate cortex whose receptive field is organized in an opponent fashion.
What is a complex cell?
A neuron in the visual cortex that responds to the presence of a line segment with a particular orientation located within its receptive field, especially when the line moves peripendicularly to its orientation.
What is sine-wave grating?
A series of straight parallel bands varying continuously in brightness according to a sine-wave function, along a line perpendicular to their lengths.
What is spatial frequency?
The relative width of bands in a sine-wave grating, measured in cycles per degree of visual angle.
What is retinal disparity?
The fact that points on objects located at different distances from the observer will fall on slightly different locations on the two retinas; provides the basis for stereopsis.
What is the cytochrome oxidase (CO) blob?
The central region of a module of the primary visual cortex, revealed by a stain for cytochrome oxidase; contains wavelength-sensitive neurons; part of the parvocellular system.
What is ocular dominance?
The extent to which a particular neuron receives more input from one eye than from the other.
What is blindsight?
The ability of a person to reach for objects located in his or her "blind" field; occurs after damage restricted to the primary visual cortex.
What is the extrastriate cortex?
A region of visual association cortex; receives fibers from the striate cortex and from the superior colliculi and projects to the inferior temporal cortex.
What is color constancy?
The relatively constant appearance of the colors of objects viewed under varying lighting conditions.
What is achromatopsia?
Inability to discriminate among different hues; caused by damage to the visual association cortex.
What is the inferior temporal cortex?
In primates, the highest level of the ventral stream of the visual association cortex; located on the inferior portion of the temporal lobe.
What is visual agnosia?
Deficits in visual perception in the absence of blindness; caused by brain damage.
What is apperceptive visual agnosia?
Failure to perceive objects, even though visual acuity is relatively normal.
What is prosopagnosia?
Failure to recognize particular people by the sight of their faces.
What is associative visual agnosia?
Inability to identify objects that are perceived visually, even thought the form of the perceived object can be drawn or matched with similar objects.
What is the pulvinar?
A large thalamic nucleus that projects to the visual association cortex and may play a role in compensating for eye and head movements.
What is Balint's syndrome?
A syndrome caused by bilateral damage to the parieto-occipital region; includes optic ataxia, ocular apraxia, and simultanagnosia.
What optic ataxia?
Difficulty in reaching for objects under visual guidance.
What is ocular apraxia?
Difficulty in visual scanning.
What is simultanagnosia?
Difficulty in perceiving more than one object at a time.