Flashcards
Cortical Anatomy
Cards in this deck (31)
- 1Who initiated the early definitive works on visual processing via research on the cat visual cortex?Hubel and Wiesel
- 2Explain retinotopic mapping. What does it allow us to do?Each area of the visual field stimulates an exact receptive field on the retina, and causes stimulation of a predictable area of the cortex.
Maintains the integrity of information of specific areas of each retina, all the way to the visual cortex, contributing to retinal correspondence - 3Information collected by the retina can be divided into which two behaviours?90% - image forming (visual perception and visual motor behaviour) and 10% - non-image forming (eye movement, pupil responses, curcadian rhythyms, neuroendocrine functions, optokinetic refelxes)
- 4How many different types of ganglion cells are there? What % of these cells collect information for visual image formation15; 90% of cells collect image forming information
- 5In the visual pathway, rudimentary sorting of light begins where?At the retina (rods and cones into movement, and form and colour, respectively)
- 6What are the 3 classes of image-forming ganglion cells? Which of these forms the majority of the ganglion image forming cells?Parvocellular (P) cells - transmit colour and form information; respond to high spatial and low frequency
Magnocellular (M) cells - transmit motion and spatial relationship information; respond to high temporal frequency and low contrast thresholds
K (koniocellular) cells - transmit specific information about blue-yellow colour componency
Majority of image forming cells are P cells - 7Explain in one sentence what the different cells in the retina respond to/functionRods and cones respond to light stimulation, but retinal ganglion cells respond to the difference in contrast information that the photoreceptors transmit to them through the actions of the amacrine and horizontal cells.
- 8What is the main function of the LGN?To regulate the flow and strength of visual signals sent to V1
- 9Which layers of the LGN recieve information from which eye?Layers 2, 3, 5 are from the ipsilateral eye
Layers 1, 4, 6 are from the contralateral eye - 10What happens with information at the LGN? What happens to M, P, and K pathways here?THe LGN does very little processing, but it starts the sorting process.
The M, P, and K pathways remain divided in the LGN and flow out as such - 11What types of information does the LGN send out to V1?spatial frequency, temporal frequency, brightness, and colour contrast
- 12Which Broadmann's areas are involved in the early processing of vision?BA 8 (eye movment) 17 (V1 - primary vision), 18 & 19 (V2 and V3 - secondary vision)
- 13The bulk of efferent axonal output from the LGN terminates where?Within V1 (the primary visual cortex)
- 14How far in the visual pathway do the photoreceptor connections remain stable? Why is this important?The connections from the PRs remain stable all the way through the visual system until they reach the cortex.
Important because this allows us to stimulate any portion of the visual pathway and reliably locate the retinal receptor and the corresponding cortical location - 15How many fundamental layers are there in the visual cortex? At which layer does information from the LGN arrive?6; layer 4 c
- 16What are the ocular columns of the visual cortex important for?Binocularity; they bring the information from the corresponding points in each eye into columns side by side for comparison
- 17Where does information from V1 go?1. Dorsal stream: The "where" pathway
- Spatial, motion and, position information, and 3D picture formation goes to the parietal lobe
- via M cell pathway: has a rapid response time for tracking and motion perception (contour/local stereopsis, extrafoveal stimulation)
2. Ventral stream: The "what" pathway
- object recognition and color coding information is sent to the temporal lobe
- via the slower P pathway (global stereopsis/Random dot; central foveal stimulation) - 18What is the brain area most important for motion and depth and plays a role in static stereopsis created by retinal disparity?V5. Receives M and P information from V1 and information from V2
- 19What brain area has neurons selective for basic stimulus parameters, including binocular disparity?V3
- 20What brain area provides stereoacuity via cells selective for bioncular disparity?V4 (ventral stream -- what pathway)
- 21What is the measure of visual direction and stereoscopic depth perception in dynamic conditions? Why is this important?Motion in depth; important because this means that Random dot stereopsis (global) may be processed differently than contour stereopsis (local)
- 22Explain how Random Dot and contour stereopsis processing differ, and how this relates to the where and what pathwaysRandom dot stereo is about fine discrimination. It’s a point to point comparison to gain spatial information. It’s a slow process. We might say that it is a “static” phenomenon, and it is handled by the parvocellular pathway. This makes sense – p cells in the retina are smaller and packed into the foveal area. We know that the fovea is responsible for fine vision.
Contour stereopsis is about monocular clues blending with binocular parallax. It is a quick process because it takes only a couple of point comparisons in combination with monocular clues. It functions well with quick moving, very disparate images. This process is carried by the magnocellular stream – large cells in the retina collect lots of information in a coarse sampling, and quickly transport it to cortex. These retinal cells are extrafoveal. This stream transmits information much quicker than the p pathway. This pathway provides the sense of near and far – the information gathered from just before and just after Panum’s fusional area (PFA). - 23Does stereopsis require a corpus callosum?Stereopsis does not count on the transfer of information from one side of the brain to the other within the corpus callosum as many other human functions do.
The corresponding retinal points ensure that as long as information from overlapping fields is present (chiasmal transfer), there will be stereopsis. - 24Where is the first point where information from right and left eyes is compared? How is this done?The primary visual cortex (V1) is the first point where information is compared (blended). It has laters and columns to complete this process
- 25What are the 3 important areas that binocular input travels to, in the form of disparity?MT (V5): The area most important for motion in depth (dorsal stream) and plays role in static stereopsis created by retinal disparity
V3: has neurons selective for basic stimulus parameters, including binocular disparity
V4: brain area provides stereoacuity via cells selective for binocular disparity (ventrla stream) - 26Define receptive fieldThe area where the presentation or removal of a visual stimulus will cause cellular activation
- 27What is the function of the horizontal cells?Lateral inhibition of the rods/cones (inhibt the acitvity of neighbouring cells to increase acuity of sensory signals)
- 28Which cells make up a bipolar cell's receptive field?PRs and horizontal cells
- 29What is the function of amacrine cells?By connecting the bipolar cells with ganglion cells, they provide an alternative, indirect path between them.
- 30How large are the receptive fields in the fovea?since there are 1 - to - 1 connections, the receptive fields are one foveal cone large (30 seconds of arc)
- 31In the optic chiasm, what % of fibres cross over to the opposite optic tract?52% (nasal fibres)
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- 1º ano Orthoptics review - Year 1 (Module 1) Flashcards on Cortical Anatomy, created by Suh Dude on 22/09/2021.
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