The ability to detect the presence of dimly lit objects.
The ability to see the details of objects.
The eye muscles that control the shape of the lenses.
The process of adjusting the configuration of the lenses to bring images into focus on the retina.
The difference in the position of the retinal image of the same object on the two retinas
Cells that are specialized to receive chemical, mechanical, or radiant signals from the environment.
Type of retinal neurons whose specialized function is lateral communication
Bipolar neurons that form the middle layer of the retina
A type of retinal neuron whose specialized function is lateral communication.
Retinal Ganglion Cells
Retinal neurons whose axons leave the eyeball and form the optic nerve.
The area on the retina where the bundle of axons of the retinal ganglinon cells penetrate the receptor layer and leave the eye as the optic nerve.
The central indentation of the retina, which is specialized for high-acuity vision.
The visual system's automatic use of information obtained from receptors around the blind spot, or scotoma, to create a perception of the missing portion of the retinal image.
The process by which the visual system perceives large surfaces, by extracting information about edges and from it, inferring the appearance of adjacent surfaces.
The visual receptors in the retina that mediate high-acuity color vision in good lighting.
The visual receptors in the retina that mediate achromatic, low-acuity vision in dim light.
The theory that cones and rods mediate photopic and scotopic vision, respectively.
Cone-mediated vision, which predominates when lighting is good.
Rod mediated vision which predominates in dim light.
The half of each retina next to the nose.
The half of each retina next to the temples.
Photopic Spectral Sensitivity Curve
The graph of the sensitivy of cone-mediate vision to different wavelenghts of light.
Scotopic Spectral Sensitivity Curve
The graph of the sensitivity of rod-mediated vision to different wavelengths of light.
In intense light, red and yello wavelenghts look brighter than blue or green wavelengths of equal intensity. In dim light the opposite is true.
Fixational Eye Movements
Involuntary eye movements of the eyes that occurs when a person tries to fix their gaze.
The rapid eye movements between fixations.
The conversion of one form of energy to another.
The photopigment of rods.
A graph of the ability of a substance to absorb light of different wavelengths.
The major visual pathway from each retina to the striate cortex (primary visual cortex) via the lateral geniculate nuclei of the thalamus.
Primary Visual Cortex
The area of the cortex that receives direct imput from the lateral geniculate nuclei (striate cortex).
Lateral Geniculate Nuclei
The six-layered thalamic structures that receive imput from the retinas and transmit their output to the primary visual cortex.
Organized, like the primary visual cortex, according to a map of the retina.
The layers of the lateral geniculate nuclei that are composed of neurons with small cell bodies; the top four layers (P layers).
The layers of the lateral geniculate nuclei that are composes of neurons with large cell bodies; the bottom two layers (M layers).
The intensification of the perception of edges.
The visual receptors of the horseshoe crab.
Inhibition of adjacent neurons or receptors in a topographic array.
The area of the visual field with which it is possible for the appropriate stimulus to influence the firing of a visual neuron.
Involving only one eye.
Visual neurons that respond to lights shown in the center of their receptive fields with "on" firing and to lights shone in the periphery of their fields with "off" firing.
Visual neurons that respond to lights shown in the center of their receptive fields with "off" firing and to lights shone in the periphery of their fields with "on" firing.
Neurons in the visual cortex that responds maximally to straight-edge stimuli in a certain position and orientation.
Neurons in the visual cortex that responds optimally to straight-edge stimuli in a certain orientation in any part of their receptive field.
The difference in the position of the retinal image of the same object on the two retinas.
The theory that the relative amount of activity produced in three different classes of cones by light determines its perceived color (trichromatic theory)
The theory that a visual receptor or a neuron signals one color when it responds in one way (eg. Increasing its firing rate) and signals the complementary color when it responds in the opposite way.
Pairs of colors that produce white or gray.
The tendency of an object to appear the same color even with the wavelengths of light that it reflects change.
Land's theory that the color of an object is determined by its reflectance, which the visual system calculates by comparing the ability of adjacent surfaces to reflect short, medium, and long wavelengths.
Dual-opponent Color Cells
Neurons that respond to the differences in the wavelengths of light stimulating adjacent areas of their receptive field.
An enzyme present in particularly high concentrations in the mitochondria of dual-opponent color cells of the visual cortex.
Peglike, cytochrome oxidase-rich, dual-opponent color columns.
Secondary Visual Cortex
Areas of the cerebral cortex that receive most of their input from primary visual cortex.
Visual Association Cortex
Ares of cerebral cortex that receive input from areas of secondary visual cortex as well as from secondary cortex of other sensory symptoms.
The band of tissue in the occipital lobe that surrounds the primary visual cortex and contains areas of secondary visual cortex.
The cortex of the inferior temporal lobe, in which is located an area of secondary visual cortex that is involved in object recognition.
Posterior Parietal Cortex
A area of association cortex that receives input from the visual, auditory, and somatosensory systems and is involved in the perception of spatial locations and guidance of voluntary behavior.
An area of blindness produced by damage to, or disruption of, an area of the visual system.
The procedure used to map scotomas.
Having a scotoma that covers half the visual field
The ability to perceive one's experiences, typically inferred from the ability to verbally describe them.
The ability of some patients who are blind as a consequence of cortical damage to unconsciously see some aspect of their visual enviornments.
The group of visual pathways that flows from the primary visual cortex to the dorsal prestriate cortex to the posterior parietal cortex. According to one theory, its function is the control of visually guided behavior
The group of visual pathways that flows from the primary visual cortex to the ventral prestriate cortex to the inferotemporal cortex; accordig to one theory, its function is conscious visual perception
"Where" versus "What" Theory
The theory that the dorsal stream mediates the perception of where things are and the ventral stream mediates the perception of what things are.
"Control of Behavior" vs. "Conscious Perception" Theory
The theory that the dorsal stream mediates behaviorial interactions with objects and the ventral stream mediates conscious perceptions of objects.
Visual agnosia for faces.
An inability to consciously recognize sensory stimuli of a particular class that is not attributable to a sensory deficit or to verbal or intellectual impairment.
A failure to recognize visual stimuli that is not attributable to sensory, verbal, or intellectual impairment.
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