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67 Cards in this Set
- Front
- Back
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What is the wavelength range of visible light? What color is at the low end and what is at the high end? |
400 (violet) - 700 (red) nm |
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What are the 3 perceptual dimensions of light? |
Hue Brightness Saturation |
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Wavelength determines what perceptual dimension of light? |
Hue
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Light can also vary in intensity. What perceptual dimension of light does this correspond to? |
Brightness |
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The relative purity of the light that is being perceived is it's ______ |
saturation |
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If all the radiation is of one wavelength, the perceived color is pure aka fully saturated. Conversely is the radiation contains all visible wavelength, it produces no sensation of _____. Why? |
hue because all the wavelength are interfering so we get white |
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What is the primary pathway of the visual system to the primary visual cortex? |
Retina --> Optic nerve (2nd cranial nerve)--> optic tract --> Lateral geniculate nucleus of the thalamus --> Primary visual cortex |
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The eyes are suspended in the ____ and held in place by 6 _____ muscles attached to the tough outer coat of the eye called the _____ |
Orbits, extraocular, and sclera |
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Why can't we see out eyeball muscles? |
They attachments are hidden behind the conjunctiva which merges with the inside of the eyelid |
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What is the jerky eye movement called when you scan a scene in front of you or are in REM |
saccadic movements |
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Only by performing a _____ can you prevent saccadic movements. What is cooperative movement between the eyes called? |
pursuit movement which is like looking at your finger as you move it around. Cooperative movement is convergence movement |
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The ____ is the outer layer of the eye and is transparent. The ___ regulates the amount of light that enters, which is an opening in the pigmented ring of muscles situated behind the cornea called the ____ |
cornea, pupil (or aperture), iris |
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What structure is located immediately behind the iris? What muscles are used to manipulate its shape? This manipulation occurs in order to permit the eye to focus images of near or distant objects on the _____, a process called ______ |
The lens is situated behind the iris and it's shape can be altered by the ciliary muscles which attach to the outer edge of the lens which is a process known as accommodation. |
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Light passes through the clear gelatinous substance called the ______ ______ before falling on the ____ the interior lining of the back eye where the photoreceptors are found. What type of photoreceptor dominates in the eye? Which photocepetor is the source of visual sharpness/acuity |
vitreous humor, retina 120 million rods > 6 million cones Cones are source of acuity |
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What region of the retina mediates the most acute vision. What feature of this region allows for this? |
The fovea only contains cones which confer an ability to discriminate light of different wavelengths |
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Where do the axons that convey visual information gather and leave the eye? Where do they leave to? Why does this produce a blind spot? |
The optic disk is where the axons gather together and leave the eye through the optic nerve. This leads to a blind spot because no receptors are located there. |
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The retina consists of several layers of neurons and photoreceptors. What are the 3 main layers starting from the back of the eye horizontally to the 2nd cranial nerves. How many total layers are there? |
Photoreceptive layer --> Bipolar layer --> Ganglion layer Retina consists of 10 layers and cells total |
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The retina contains 2 sets of cells that transmit information parallel to the surface of the retina, combining messages from adjacent photoreceptors. What are these cells called? |
Horizontal cell and amacrine cells |
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Photopigments are embedded in the membrane of the _____. They consist of 2 parts, a ___ protein and a ____lipid |
lamellae, opsin protein, 11-cis retinal lipid |
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The _____ cell is the innermost layer of the retina and the _____ layer is the outermost. Light travels down through even the innermost layer. |
Ganglion cell is the innermost layer Photoreceptors are the outermost layer |
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What 2 photoreceptors are found in the retina. Which is not found in the fovea? |
Cones are mostly concentrated in fovea but can be found in periphery of retina. Rods are only in the periphery |
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There are 3 isoforms of ___ opsin derived from vitamin ___. |
cone opsin derived from vitamin A |
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Light causes conformation changes in rhodopsin, thus activating transducin whose net effect it to _______ which results in ___ of Na+ channels and _______ of the photoreceptor cell |
Transducin's net effect is to reduce cGMP which results in closure of the photoreceptor Na+ channels and hyperpolarization |
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Describe bipolar and photoreceptor cells' polarizations in the dark. Why? |
Photoreceptors are depolarized thanks to cGMP, firing releasing glutamate which hyperpolarizes the ON bipolar cells and depolarizes the OFF bipolar cells |
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What is the effect of light on the polarization of photoreceptor and bipolar cells? |
Photoreceptors hyperpolarize due to absence of cGMP thanks to transducin stimulated degradation. Bipolar ON cells become depolarized whereas the OFF cells become hyperpolarized due to the absence of glutamate being produced by depolarized photoreceptors |
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The different quantitative relationships between cones and ganglion cells vs rods and ganglion cells explains the fact that our foveal vision is very acute but our peripheral is much less precise. Why? |
Foveal: There is 1 cone per ganglion cell, Peripheral: Many rods converge on a single ganglion |
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Lateral inhibition is the reduction in activity of one cell by activity in an adjacent neuron. What is the purpose of this? |
Lateral inhibition increases the contrast and sharpness Ex: In the dark, a small light stimulus will enhance the different photoreceptors (rod cells). The rods in the center of the stimulus will transduce the "light" signal to the brain, whereas different rods on the outside of the stimulus will send a "dark" signal to the brain. |
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Input from the nasal hemiretinas of both eyes ______ at the optic chiasm. Input from the temporal hemiretinas of both eyes _______ at the optic chiasm |
cross contralaterally
Do not cross and remain ipsilaterally |
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Once information has reached the optic tract, the information then stops at the dorsal lateral geniculate nucleus (LGN) of the thalamus. The LGN has ___ layers with ____ types of layer. Each layer type receives input from only 1 eye, thus each eye communicate with the ___ different layers. |
6 layers with 3 types of layers and each eye communities with the 3 different layers |
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The magnocellular level is found in the _____ layers. The outer 4 layers are called the _____ ____. The 3rd set of LGN cells are found ventral to each of the 2 types of cells and are called _____ |
inner 2 layers The outer 3 are called the parvocellular The 3rd set are the konoicellular |
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Why is foveal information relatively largely represented in LGN in comparison with peripheral ganglion cell information? |
The retinotopic projections to LGN and Striate cortex is highly ordered similar to the somatosensory homunculus. So since the fovea processes a lot of data, it is most highly represented (relatively) |
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Describe the receptive field of a ganglion cell. Describe it's stimulation. How does a ON and OFF cell respectively react to light? |
Roughly circular center, surrounded by a ring. Stimulation of the center or surrounding fields had contrary effects -ON cells are excited (increase firing rate) by light falling in the central field and were inhibited by light falling in the surrounding field -OFF cells responded in the opposite manner -When both are stimulated, nothing happens |
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Define the trichromatic theory. |
Any color can be reproduced by mixing various quantities of three colors judiciously selected from different points along the spectrum accounted for by the 3 different cones |
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Define opponent process. What are the color pairs? Where does this process take place? |
color is perceived interms of paired opposites -green vs. red -blue vs. yellow -white/black are colorless. Atthe ganglion cell level, the system responds in an opponent-processfashion |
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Why do we see negative afterimages? |
A given cell might increase its firing rate to yellow light in the center, but decrease it to blue light where yellow in the middle and off is the periphery of the receptive field. This is governed by opponent process pairs. |
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The P(arvocellular) pathway is best for processing ____, ____, and ____ information. Most of the P pathway input comes from ____ cells near the fovea that are sensitive to color. This is contrasted by the M(agnocellular) pathway which is best for _____, _____, and ______ ______. Most of the M pathway input comes from ____ cells |
high acuity, detail, and color. Most of the input comes from X cells Magnocellular is best for broad outlines of shapes, depth, and movement detection. Most of the input comes from Y cells |
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What are x cells and what are y cells? |
-X-cells(ganglion cells near the fovea that are sensitive to colors) -Y-cells (ganglion cells near the periphery that are not sensitive to colors and have large receptive fields) |
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What layer of the striate cortex receives input from the parvocellular and magnocellular layers of the LGN. Where is it sent for analysis after the first stop. |
Layer4c receives input from parvocellular and magnocellular layers, it is then sent to layers above and below 4c |
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What brain structure allows for the combination of several ganglion cells' receptive fields in order to detect features larger than that of a single receptive field? |
Striate cortex aka primary visual cortex aka V1 |
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What are the 4 organizational features of the mammalian primary visual cortex (V1). How many layers does this region have? |
1) Horizontal stratification parallel to the cortex 2) Radial columns perpendicular to the cortex 3) Ocular dominance columns in layer IVc parallel to the cortex 4) Cytochrome Oxidase blobs of layer II, III, V, and VI perpendicular to the cortex 6 principal layers and many sublayers |
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What 5 visual characteristics are processed in the striate cortex? Where are these characteristics processed? |
-Interblob regions process orientation, movement, spatial frequency, and retinal disparity -Color is the only feature processed in the cytochrome oxidase blobs |
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What would we find if we inserted a microelectrode perpendicularly through the radial columns of the visual cortex? What if we went in parallel to the surface of the cortex? |
Perpendicular: all of the neurons that it encounters will have the same orientation preference, regardless of whether they have simple or complex receptive fields Parallel: all of the neurons that it encounters will have different orientation preferences |
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What are the ocular dominance columns on layer IVc in the striate nucleus? |
Regularly spaced bands that represent the nerve endings of the left and right eyes and that they thus alternate between one eye and the other, in a pattern something like a zebra's stripes. Each column responds to one eye. |
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Cytochrome oxidase blobs receive inputs from 2 LGN systems that transmit color. What are these systems, and what colors' info do they respectively transmit? What blobs do these systems project to respectively? |
Parvocellular system projects Red/Green info to blobs that pass through layers V and VI Konoicellular systems projects Blue info to layer blobs that pass through layers II and III |
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What is the function of the M(agnocellular) channel, P(arvocellular)-interblob channel, and blobs in the striate cortex |
M-Channel: Analysis of motion P-interblob channel: Analysis of shape Blobs- Color and low spatial frequency |
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What path does magnocellular, parvocellular, and konoicellular cells' info of the thalamic LGN take to terminate in the striate cortex respectively? Which of these systems only exists in primates? |
Magno: LGN layer 1 and 2 --> V1 layer 4c(alpha) Parvo: LGN layers 3-6 --> V1 layer 4c(beta) --> Interblob layer II and III Konoi: LGN to blobs of layer 2/3 --> Only in primates |
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What interblob cells process monocular orientation information? What do they process respectively? |
Simple: Axis of orientation Hypercomplex: Edges and angles |
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What interblob cells process binocular orientation information? What do they process respectively? |
Simple can be monocular and binocular: Axis of orientation Complex: Movement along an axis of orientation |
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Where is the visual extrastraite region, how is it organized? |
V1 projects to over 2 dozen distinct regions that are arranged hierarchically beginning with V1 and passing the results onto "higher" regions for further analysis |
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Define spatial frequency. How would these images look? What kind of spatial frequency contains the most important information in terms of perceiving the shapes of images? |
Spatial frequency of a a sine-wave grating is its variation in brightness measured in cycle per degree of visual angle. High: sharp edges and lots of detail Low: Fuzzy and out of focus, but still provides info about forms and objects. This is the most important! |
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What kind of information do parvocellular neurons convey? |
Information necessary for perception of color and fine details |
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Binocular striate cortex cells respond most vigorously when each eye sees a stimulus in a ________ location. That is, the neurons respond to retinal disparity. This information is needed for ________ vision for 3D scenes. This indicates differences in the _____ of the objects from the observer. |
Different location This is needed for stereoscopic vision aka stereopsis This indicates differences in distance |
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What kind of information do magnocellular neurons convey? |
Information for perception of broad form, movement, depth, and small differences in brightness |
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In what regions of the straite cortex is spatial frequency processed? |
Neurons within the CO blobs responded to low spatial frequencies but were sensitive to small differences in brightness. Outside the blobs, sensitivity to spatial frequency varied with the distance from the center of the nearest blob. Higher frequencies were associated with greater distances. |
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The V1 projects to V2 (visual association cortex), at which point the visual association cortex divides into 2 streams of analysis. What are these streams called, and where do they terminate? |
Ventral Stream terminates in the Inferior temporal cortex Dorsal Stream terminates in the posterior parietal cortex |
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What is the primary function of the dorsal and ventral stream respectively? |
Dorsal provides information that guides navigation and skilled movement directed towards objects aka where the object is Ventral provides visual information about the size, shape, color, texture, and other people aka what an object is |
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The ventral stream receives an equal amount of ______ and ______ input. This then projects to what extrastriate cortex before terminating in the inferior temporal cortex? |
Equal amounts of magnocellular and parvocellular input before projecting to V2, V3, V4, and V5 |
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What area of the extrastraite cortex allows us the ability of color constancy. What is the name of the disorder that yields vision without color when knocking out the visual association cortex? |
Area 4 Achromatopsia is vision without color |
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Visual pattern discrimination and identification of objects are housed together in the inferior temporal cortex. What two structures are responsible for these tasks? |
TEO and TE |
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Problems with analysis of form can be divided into 2 categories, visual agnosia and __________. What are the 2 subcategorizations of visual agnosia and what do they result in? |
Prosopagnosia: Failure to recognize faces Apperceptive visual agnosia: Failure to recognize objects based on their shape but normal visual acuity Associative visual agnosia: Person cannot name what they see |
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Where are the fusiform face area and parahippocampal place area found? What are their roles? |
Fusiform face area is located at the inferior temporal cortex. Recognition of faces. Parahippocampal place area is a region of the medial temporal cortex. Perception of "scenes." |
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What is the motion-sensitive area of the extrastraite visual cortex? Where is it found? Damage to this area results in what disorder? Where does this region get inputs from? |
The area is called the MT(Medial Temporal)/MST(Medial Superior Temporal) aka V5/V5a and found within the inferior temporal sulcus at the end of the dorsal stream. |
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Damage to what area results in akinetopsia? What inputs go to this area? |
Damage to this area results in akinetopsia which is an inability to perceive movement aka optic flow. MT receives input from V1 and superior colliculi of the tectum. V5a aka MST receives input from V5 for further analysis. |
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Area V1, V2, V4, and V8 all respond to color, what is unique about V8? |
V8 will not respond to photographs of objects painted in unnatural colors. Thus V8, is not only involved in color perception, but also with the memories of colors of particular objects. |
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What 2 regions of the brain need to work together to completely identify a human? |
FFA recognizes faces and EBA recognizes bodies, so FFA + EBA allows us to recognize and identify humans and form from motion |
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What is the correlation between the size of the FFA and the person's ability to recognize faces? |
Larger the area, the better you can recognize faces. FFA is enlarged in people wiht william's syndrome |
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What kind of information do konoicellular neurons convey? |
Blue light |
