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71 Cards in this Set
- Front
- Back
Sensitivity |
ability to detect dimly lit objects |
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Acuity |
ability to see details of objects |
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Ciliary Muscles |
ligaments holding lens in place, helps lens refract light, bringing close object into focus |
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Accommodation |
Process of adjusting lens to bring images into focus on retina.
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Binocular Disparity |
Difference in position of same image on two retinas; larger for close objects - use degree of binocular disparity to construct 3D perception |
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Receptors |
Specialized cells, receive chemical, mechanical, or radiant signals from the environment ; proteins that contain binding sites for particular neurotransmitters. |
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Horizontal Cells |
Types of retinal neurons whose specialized function is lateral communication. |
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Bipolar Cells |
Bipolar neurons that form the middle layer of the retina. |
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Amacrine Cells |
Type of retinal neurons - specialized function of lateral communication. |
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Retinal Ganglion Cells |
Retinal neurons whose axons leave the eyeball and form the optic nerve. |
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Blind Spot |
Area on the retina where the bundle of axons of the retinal ganglion cells penetrate the receptor layer and leave the eye as the optic nerve. |
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Fovea |
Central indentation of the retina, which is specialized for high-acuity vision. |
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Completion |
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. |
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Surface Interpolation |
Process by which the visual system perceives large surfaces, by extracting information about edges and from it, inferring the appearance of adjacent. |
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Cones |
Visual receptors in the retina that mediate high acuity colour vision in good lighting. |
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Rods |
Visual receptors in the retina that mediate achromatic, low-acuity vision under dim light. |
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Duplexity Theory |
Theory that cones and rods mediate photopic and scotopic vision, respectively. |
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Photopic Vision |
Cone-mediated vision, which predominates when lighting is good. |
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Scotopic Vision |
Rod-mediated vision, predominates in dim light. |
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Photopic Spectral Sensitivity Curve |
Graph of the sensitivity of cone-mediated vision to different wavelengths of light. |
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Scotopic Spectral Sensitivity Curve |
Graph of sensitivity of rod-mediated vision to different wavelengths of light. |
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Purkinje Effect |
In intense light, red and yellow wavelengths look brighter than blue or green wavelengths of equal intensity; in dim light, blue and green wavelengths look brighter than red and yellow wavelengths of equal intensity. |
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Fixational Eye Movements |
Involuntary movements of the eyes (tremor, drifts, and saccades) that occur when person tried to fix their gaze on a point. |
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Saccades |
Rapid movements of the eyes between fixations. |
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Transduction |
Conversion of one form of energy to another. |
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Rhodopsin |
The photopigment of rods. |
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Absorption Spectrum |
Graph of the ability of a substance to absorb light of different wavelengths. |
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Retina-geniculate-striate Pathways |
Major visual pathway from each retina to the striate cortex (primary visual cortex) via the lateral geniculate nuclei of the thalamus. |
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Primary Visual Cortex |
Area of cortex that receives direct input from the lateral geniculate nuclei (aka striate cortex). |
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Lateral Geniculate Nuclei |
Six-layered thalamic structures that receive input from the retinas and transmit structure that receive input from the retinas and transmit their output to primary visual cortex. |
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Retinotopic |
Organized, like the primary visual cortex, according to a map of the retina. |
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Parvocellular Layers |
Layers of the lateral geniculate nuclei that are composed of neurons with small cell bodies; top four layers (called P layers). |
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Magnocellular Layers |
Layers of the lateral geniculate nuclei composed of neurons with large cell bodies; the bottom two layers (called M layers). |
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Contrast Enhancement |
Intensification of the perception of edges. |
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Lateral Inhibition |
Inhibition of adjacent neurons or receptors in a topographic array. |
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Receptive Field |
Area of the visual field within which it is possible for the appropriate stimulus to influence the firing of a visual neuron. |
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On-center Cells |
Visual neurons respond to lights shone in the center of their receptive fields with "on" firing to lights shone in the periphery of their fields with "off" firing. |
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Off-center Cells |
Visual neurons that respond to lights shone in the center of their receptive fields with "off" firing and to lights shone in the periphery of their fields with "on" firing. |
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Simple Cells |
Neurons in the visual cortex that respond maximally to straight-edge stimuli in a certain position and orientation. |
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Complex Cells |
Neurons in visual cortex that respond optimally to straight-edge stimuli in certain orientation in any part of their receptive field. |
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Component Theory |
The relative amount of activity produced in three different classes of cones by light determines its perceived colour (AKA trichromatic theory) |
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Opponent-process Theory |
Theory that a visual receptor or a neuron signals one color when it responds in one way (eg, by increasing its firing rate) and signals the complementary color when it responds in the opposite way (eg. by decreasing its firing rate). |
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Complementary Colours |
Pairs of colours that produce white or gray when combined in equal measure; every colour has a complementary color. |
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Colour Constancy |
Tendency of an object to appear the same colour even when the wavelengths of light that it reflects change. |
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Retinex Theory |
Land's theory that colour of an object determined by its reflectance, which the visual system calculates by comparing the ability of adjacent surfaces to reflect short, medium, long wavelengths. |
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Dual-opponent Colour Cells |
Neurons that respond to the differences in the wavelengths of light stimulating adjacent areas of their receptive field. |
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Cytochrome Oxidase |
Enzyme present in part. high concentrations in mitochondria of dual-opponent colour cells of visual cortex. |
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Blobs |
Peglike, cytochrome oxidase-rich, dual-opponent colour columns. |
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Secondary Visual Cortex |
Areas of cerebral cortex that receive most of input from primary visual cortex. |
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Visual Association Cortex |
Areas of cerebral cortex receive input from areas of secondary visual cortex as well as from secondary cortex of other sensory systems. |
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Prestriate Cortex |
The band of tissue in the occipital lobe that surround the primary visual cortex and contains areas of secondary visual cortex. |
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Inferotemporal Cortex |
Cortex of the inferior temporal lobe, which is located in area of secondary visual cortex that is involved in object recognition. |
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Posterior Parietal (association) Cortex |
Area of association cortex that receives input from the visual, auditory, and somatosensory systems and is involved in the perception of spatial location and guidance of voluntary beh. |
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Scotoma |
Area of blindness produced by damage to, or disruption of, an area of the visual system. |
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Perimetry Test |
The procedure used to map scotomas. |
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Hemianopsic |
Having a scotoma that covers half of the visual field. |
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Conscious Awareness |
Ability to perceive one's experiences; typically inferred from the ability to verbally describe them. |
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Blindsight |
Ability of some patients who are blind as a consequence of cortical damage to unconsciously see some aspects of their visual environments. |
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Dorsal Stream |
Group of visual pathways that flow from primary visual cortex to dorsal prestriate cortex to the posterior parietal cortex; one theory states - function is the control of visually guided behaviour. |
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Ventral Stream |
Group of visual pathway that flow from the primary visual cortex to ventral prestriate cortex to the inferotemporal cortex; according to one theory, its function is conscious visual perception. |
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"Where" vs. "What" Theory |
Theory that the dorsal stream mediates perception of where things are and ventral stream mediates perception of what things are. |
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"Control of Behaviour" vs. "Conscious Perception" Theory |
Theory that dorsal stream mediates beh. interactions w/ objects and the ventral stream mediates conscious perception of objects. |
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Prospoagnosia |
Visual agnosia for faces. |
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Agnosia |
Inability to consciously recognize sensory stimuli of a particular class that is not attributable to a sensory deficit or to verbal or intellectual impairment. |
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Visual Agnosia |
Failure to recog. visual stimuli that is not attributable to sensory, verbal, or intellectual impairment. |
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Fusiform Face Area |
Area of human cortex, located at boundary btwn occipital & temporal lobes, that is selective activated by human faces. |
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Akinetopsia |
Deficiency in the ability to perceive motion, often results from damage to dorsal visual pathway. |
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MT Area |
Area of cortex, located near the junction of the temporal, parietal, and occipital lobes, function appears to be the perception of motion. |
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Sensory Feedback |
sensory signals that are produced by a response and are often used to guide the continuation of the response. |
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Frontal Eye Field |
Small area of prefrontal cortex that controls eye movements. |
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Apraxia |
Disorder where patients have great difficulty performing movements when asked to do so out of context but can readily perform them spontaneously in natural situations. |