neurobio 916 ch 10 of Bear's book: the central visual system part 3 (retinofugal projection optic n

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mikepl103
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269454
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neurobio 916 ch 10 of Bear's book: the central visual system part 3 (retinofugal projection optic n
Updated:
2014-04-07 09:55:32
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neurobio 916 10 Bear book central visual system part retinofugal projection optic nerve chiasm hemifield tectum LGN retinotopy interblob 23
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2014,biology,neurobiology
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neurobio 916 ch 10 of Bear's book: the central visual system part 3 (retinofugal projection, optic nerve, optic chiasm, visual hemifield, optic tectum, LGN, retinotopy, interblob) #23
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  1. As a microelectrode advances radially (perpendicular to the surface) from one layer to the next, what happens to the preferred orientation of the neurons?
    As a microelectrode advances radially (perpendicular to the surface) from one layer to the next, the preferred orientation remains the same for all the selective neurons encountered from layer II down to laer VI. Hubel and Wiesel called such a radial column of cells an orientation column
  2. As a microelectrode advances tangentially (parallel to the surface) through the cortex in a single layer, what occurs to the preferred orientation of hte neurons?
    As a microelectrode advances tangentially (parallel to the surface) through the cortex in a single layer, the preferred orientation progressively shifts. We now know, from the use of a technique called optical imaging, that there is a mosaiclike pattern of optimal orientations in striate cortex. If an electrode is passed at certain angles through this mosaic, the preferred orientation rotates like the sweep of the minute hand of a clock, from the top of the hour to ten past to twenty past, and so on. I fthe elctrode is moved at other angles, more sudden shifts in preffered orientation occur. Hubel and Wiesel found that a complete 180 degree shift in preferred orientation required a traverse of about 1 mm, on average, within layer III
  3. describe direction selectivity
    many v1 receptive fields exhibit direction selectivity; they respond when a bar of light at the optimal orientation moves perpendicular to the orientation in on e direction but not in the opposite direction.
  4. true or false? Direction- selective cells are a subset of the cells that are orientation selective
    true
  5. what are simple cells?
    simple cells are orientation-detecting cortical neurons and they have a receptor field elongated along a particular axis, with an ON-center or OFF-center region flanked on one or both sides by the antagonistic surround. This linear arrangement of ON and OFF areas is analogous to the concentric antagonistic areas seen in retinal and LGN receptive fields. One gets the impression that the cortical neurons receive a converging input from three or more LGN cells with receptive fields that are aligned along one axis. the segregation of ON and OFF regions is a defining property of simple cells
  6. what are complex cells?
    complex cells give ON and OFF responses to stimuli throughout the receptive field; they do not have distinct ON and OFF regions and are therefore not considered simple cells
  7. true or false, simple and complex cells are typically monocular and sensitive to stimulus orientation
    false, simple and complex cells are typically binocular and sensitive to stimulus orientation
  8. true or false, interblob neurons have all or some of these properties: binocularity, orientation selectivity, and direction selectivity?
    true
  9. what makes blob cells different from interblob cells
    most blob cells are wavelength sensitive and monocular, ad they lack orientation and direction selectivity.
  10. blob cells receive input from where?
    blobs receive input directly from the koniocellular layers of the LGN and magnocellular and parvocellular input via layer IVC.
  11. the visual responses of blob cells most resemble thos of ...
    the visual responses of blob cells most resemble those of the koniocellular and parvocellular input
  12. true or false? blobs contain the great majority of color-sensitive neurons outside layer IVC
    true
  13. which LGN cells exhibit color opponency?
    koniocellular layer cells and some parvocellular layer cells
  14. how are receptive fields transformed at each of the synaptic relays that connect an M type retinal ganglion cell to a neuron in the striate cortical layer IVB?
    the magnocellular pathway begins with M type ganglion cells of the retina with large, monocular, center-surround receptive fields. These cells project to the magnocellular layers of the LGN that also have large, monocular, center-surround receptive fields. The magnocellular LGN layers project to layer IVCαof the striate cortex where the monocular, center-surround receptive field properties are retained. Finally, neurons in layer IVCα project to the layer IVB. The pyramidal cells in the layer IVB have binocular receptive fields that are elongated rather than circular. These receptive fields can be either simple or complex. Many of them are orientation-selective and direction-selective, but not wavelength-sensitive
  15. Which pathway, magnocellular or parvocellular, provides a greater percentage of the input to the striate cortex? What are the two analyses of the visual world that are involved with these pathways?
    The parvocellular pathway provides the greatest percentage of input to the striate cortex. This pathway contains neurons with sustained responses, small receptive fields, and fewer direction selective neurons. It originates with P-type retinal ganglion cells that project to parvocellular LGN neurons, which in turn project to layer IVCb in striate cortex. This pathway is thought to be involved in the analysis of object shape. The magnocellular pathway contains neurons with transient responses, large receptive fields, and the highest percentage of direction-sensitive neurons. It originates with M-type retinal ganglion cells that project to magnocellular LGN cells, which in turn project to layer IVCa of striate cortex. This pathway is thought to be involved in the analysis of object motion and the guidance of motor actions.
  16. which pathway (magnocellular, parvocellular, or nonM-nonP) provides the greatest percentage of direction sensitive neurons?
    magnocellular

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