Visual System II and III

1. 1The receptive field of an individual sensory neuron is the [blank_start]particular region of sensory space[blank_end] (eg the visual field, or body surface) in which [blank_start]a stimulus affects the firing[blank_end] of that neuron.

   1. Aparticular region of sensory space
   2. Ba stimulus affects the firing
2. 2Receptive fields in the retina are [blank_start]circular[blank_end] in shape and defined in terms of [blank_start]degrees of visual space[blank_end] (from hundredths of a degree in the fovea to tens of degrees in the periphery).

   1. Acircular
   2. Bdegrees of visual space
3. 3Ganglion cell receptive fields are [blank_start]circular[blank_end], with [blank_start]antagonistic[blank_end] (opponent) responses between [blank_start]center and surround[blank_end], ie the show [blank_start]center surround[blank_end] organization

   1. Acircular
   2. Bantagonistic
   3. Ccenter and surround
   4. Dcenter surround
4. 4Receptive fields are either "[blank_start]on-center[blank_end]" or "[blank_start]off-center[blank_end]"

   1. Aon-center
   2. Boff-center
5. 5The two types of center-surround receptive fields exhibited by retinal ganglion cells are created in a two step process:
   - First, the [blank_start]opponent center surround aspect[blank_end] is created by mutual inhibition among photoreceptors that is produced by [blank_start]horizontal cells[blank_end]
   - Second, the [blank_start]on- and off- center aspect[blank_end] is created by [blank_start]bipolar cells[blank_end] which show opposite responses to the Glu released by their receptor (Ie [blank_start]bipolar[blank_end] cells express different Glu receptors)

   1. Aopponent center surround aspect
   2. Bhorizontal cells
   3. Con- and off- center aspect
   4. Dbipolar cells
   5. Ebipolar
6. 6Ganglion cells inherit the on- and off-center aspect of their receptive field responses from [blank_start]bipolar[blank_end] cells.

   1. Abipolar
7. 7On-center bipolar cells have [blank_start]metabotropic glu receptors[blank_end] (activation of which leads to K+ efflux). Thus, on-center bipolar cells respond best when their receptor input releases [blank_start]less Glu[blank_end].

   1. Ametabotropic glu receptors
   2. Bless Glu
8. 8Off-center bipolar cells have [blank_start]ionotropic Glu receptors[blank_end] (activation leads to Na+ influx). Thus, off-center cells respond best when their photoreceptor input releases [blank_start]more Glu[blank_end].

   1. Aionotropic Glu receptors
   2. Bmore Glu
9. 9Ganglion cells (and their bipolar inputs) respond weakly if a stimulus activates their [blank_start]entire receptive field[blank_end].

   1. Aentire receptive field
10. 10Ganglion cells are sensitive to spectral contrasts by virtue of their opponent, center surround organization. The on and off center responses create a [blank_start]push-pull system[blank_end] that provides [blank_start]sensory redundancy[blank_end] and [blank_start]decreases[blank_end] sensitivity to common rate changes (eg due to body temperature).

    1. Apush-pull system
    2. Bsensory redundancy
    3. Cdecreases

11. 11Ganglion cells with inputs mainly from rods (in peripheral retina) are sensitive to [blank_start]light and dark[blank_end]

    1. Alight and dark
12. 12Ganglion cells with inputs primarily from cones (in the fovea) are sensitive to [blank_start]color contrasts[blank_end]

    1. Acolor contrasts
13. 13Most ganglion cells with cone inputs are [blank_start]color-opponent[blank_end]. The two types of color-opponent cells are:
    - [blank_start]red-green[blank_end]
    - [blank_start]blue-yellow[blank_end] (where [blank_start]yellow[blank_end] sensitivity is created by the sum of inputs from [blank_start]red and green cones[blank_end])

    1. Acolor-opponent
    2. Bred-green
    3. Cblue-yellow
    4. Dyellow
    5. Ered and green cones
14. 14M cells:
    - [blank_start]peripheral[blank_end] retina (~100,000)
    - [blank_start]large[blank_end] cell bodies and large RFs
    - [blank_start]coarse[blank_end] resolution
    - [blank_start]inputs[blank_end] from 1000s of rods and cones: convey light vs dark information
    - [blank_start]rapid[blank_end] adaption and conduction of APs
    - [blank_start]Motion[blank_end] response better than stationary
    - optimized for [blank_start]large-scale, low-contrast moving pattern[blank_end]s

    1. Aperipheral
    2. Blarge
    3. Ccoarse
    4. Dinputs
    5. Erapid
    6. FMotion
    7. Glarge-scale, low-contrast moving pattern
15. 15P cells:
    - [blank_start]central[blank_end] retina (esp. fovea) (~1 million)
    - [blank_start]small[blank_end] cell bodies and small RFs
    - [blank_start]Fine[blank_end] resolution
    - inputs from ~ [blank_start]1 cone[blank_end] - convey color
    - [blank_start]slow[blank_end] adaption and conduction of APs
    - [blank_start]stationary[blank_end] targets better than moving
    - optimized for [blank_start]small-scale high contrast fine patterns[blank_end]

    1. Acentral
    2. Bsmall
    3. CFine
    4. D1 cone
    5. Eslow
    6. Fstationary
    7. Gsmall-scale high contrast fine patterns
16. 16Optics of eye project [blank_start]reversed and upside-down image[blank_end] of monocular visual field onto each retina

    1. Areversed and upside-down image
17. 17Optic nerves exit each eye and project [blank_start]bilaterally[blank_end] to the [blank_start]lateral geniculate nucleus (LGN)[blank_end] of the (visual) thalamus.

    1. Abilaterally
    2. Blateral geniculate nucleus (LGN)
18. 18Fibers from [blank_start]temporal hemi retina[blank_end], which views the contralateral half of a monocular visual field, projects to [blank_start]ipsilateral LGN[blank_end].

    1. Atemporal hemi retina
    2. Bipsilateral LGN
19. 19Fibers from the [blank_start]nasal hemi retina[blank_end], which views the ipsilateral half of a monocular visual field, cross the midline ([blank_start]decussate[blank_end]) in the [blank_start]optic chiasm[blank_end], and project to [blank_start]contralateral LGN.[blank_end]

    1. Anasal hemi retina
    2. Bdecussate
    3. Coptic chiasm
    4. Dcontralateral LGN.
20. 20LGN on each side projects [blank_start]ipsilaterally[blank_end] to the [blank_start]primary visual cortex.[blank_end]

    1. Aipsilaterally
    2. Bprimary visual cortex.
21. 21Information from each visual hemi field processed in [blank_start]contralateral[blank_end] hemisphere of [blank_start]visual cortex[blank_end].

    1. Acontralateral
    2. Bvisual cortex
22. 22Approx [blank_start]90[blank_end]% of retinal ganglion cells project to the LGN. The remainder (not M or P cells) project to the [blank_start]hypothalamus[blank_end], [blank_start]pre-tectum[blank_end], and [blank_start]superior colliculus[blank_end].

    1. A90
    2. Bhypothalamus
    3. Cpre-tectum
    4. Dsuperior colliculus
23. 23Primate LGN is organized into [blank_start]6[blank_end] distinct layers (laminae):
    - Layers 1 and 2: [blank_start]Magnocellular[blank_end] - large cells, input from M-RGCs
    - Layers 3-6: [blank_start]Parvocellular[blank_end] - small cells, input from P-RGCs

    1. A6
    2. BMagnocellular
    3. CParvocellular
24. 24LGN cells in each layer are [blank_start]monocular[blank_end] because they receive RGC input from hemi retina of [blank_start]only one eye[blank_end]:
    - Layer 1, 4, 6: [blank_start]contralateral nasal[blank_end] hemi retina
    - Layer [blank_start]2, 3, 5[blank_end]: ipsilateral temporal hemi retina

    1. Amonocular
    2. Bonly one eye
    3. Ccontralateral nasal
    4. D2, 3, 5
25. 25Each lamina is [blank_start]retinotopically organized[blank_end] (adjacent points of the visual field are represented in adjacent regions). Each point in contralateral visual space is [blank_start]precisely aligned[blank_end] across layers (with the fovea over-represented).

    1. Aretinotopically organized
    2. Bprecisely aligned
26. 26Laminae are [blank_start]retinotopic[blank_end]: orderly space map of [blank_start]contralateral[blank_end] visual hemi field in [blank_start]each layer[blank_end] of LGN

    1. Aretinotopic
    2. Bcontralateral
    3. Ceach layer
27. 27Cells are [blank_start]monocular[blank_end]: segregation of [blank_start]RGC input[blank_end] from each eye in [blank_start]overlapping laminae[blank_end] of LGN

    1. Amonocular
    2. BRGC input
    3. Coverlapping laminae
28. 28Receptive fields are [blank_start]circular/opponent[blank_end], similar to the RGC inputs

    1. Acircular/opponent
29. 29[blank_start]Visual cortex[blank_end] includes many interconnected cortical areas processing visual information in the [blank_start]occipital, parietal, and temporal lobes[blank_end]. Primate visual cortex occupies more than [blank_start]50[blank_end]% of the neocortex, reflecting importance of vision for behavior.

    1. AVisual cortex
    2. Boccipital, parietal, and temporal lobes
    3. C50
30. 30LGN projects to [blank_start]primary visual cortex[blank_end] (aka [blank_start]striate cortex, V1, Brodman's area 17[blank_end]) in the [blank_start]occipital lobe[blank_end] (caudal cortical pole).

    1. Aprimary visual cortex
    2. Bstriate cortex, V1, Brodman's area 17
    3. Coccipital lobe
31. 31Neocortex has [blank_start]6[blank_end] layers labeled [blank_start]I to VI[blank_end] from [blank_start]top (pia surface) to bottom[blank_end].
    - layer [blank_start]IV[blank_end] receives inputs from the thalamus
    - layer [blank_start]interconnected vertically[blank_end], forming cortical columns, the fundamental [blank_start]processing unit of the cortex[blank_end]

    1. A6
    2. BI to VI
    3. Ctop (pia surface) to bottom
    4. DIV
    5. Einterconnected vertically
    6. Fprocessing unit of the cortex
32. 32LGN cells project to [blank_start]lowest part of layer IV (layer IV-C)[blank_end] of striate cortex
    - P and M cells project to [blank_start]different subdivisions of layer IV-C[blank_end]
    - inputs from the two eyes [blank_start]terminate side-by-side[blank_end]

    1. Alowest part of layer IV (layer IV-C)
    2. Bdifferent subdivisions of layer IV-C
    3. Cterminate side-by-side
33. 33V1 is [blank_start]retinotopic[blank_end]; the [blank_start]central[blank_end] (~4 degree) visual space (esp fovea) is heavily over-represented

    1. Aretinotopic
    2. Bcentral
34. 34By and large, the receptive fields of neurons of layer IVC ([blank_start]the input layer[blank_end] of [blank_start]primary visual cortex; striate cortex; V[blank_end]1) are similar to those of their LGN inputs and, in turn, of retinal ganglion cells.

    1. Athe input layer
    2. Bprimary visual cortex; striate cortex; V
35. 35Receptive fields of neurons of layer IVC are
    - [blank_start]monocular[blank_end]
    - [blank_start]circular[blank_end]
    - [blank_start]center-surround[blank_end]

    1. Amonocular
    2. Bcircular
    3. Ccenter-surround
36. 36retinal inputs from the left and right eye (with receptive fields in the same spot in space) [blank_start]remain segregated in the LGN[blank_end] and the input layer of visual cortex (layer IVC)

    1. Aremain segregated in the LGN
37. 37Beyond layer IVC, the signals from the two eyes are [blank_start]combined at the cellular level[blank_end]; that is, neurons in most layers of visual cortex are [blank_start]binocular[blank_end]. However, the input from one eye is usually dominant; the bands of cells extending through the thickness of the striate cortex are called [blank_start]ocular dominance columns[blank_end].

    1. Acombined at the cellular level
    2. Bbinocular
    3. Cocular dominance columns
38. 38Cells in layer IVC are [blank_start]monocular[blank_end] and have receptive fields with [blank_start]opponent center-surround organization[blank_end].

    1. Amonocular
    2. Bopponent center-surround organization
39. 39Many neurons beyond layer IVC are [blank_start]simple[blank_end] cells.
    - [blank_start]rectangular receptive field[blank_end]
    - [blank_start]on and off regions[blank_end], like cells in layer IVC
    - neurons are [blank_start]orientation-selective[blank_end] and location sensitive
    - many are [blank_start]binocular[blank_end]

    1. Asimple
    2. Brectangular receptive field
    3. Con and off regions
    4. Dorientation-selective
    5. Ebinocular
40. 40Simple cells can be constructed simply from the [blank_start]convergence of center surround inputs[blank_end]. [blank_start]Optimal stimulus for their elongated RF[blank_end]: [blank_start]edge, bar, or grating[blank_end] precisely oriented and placed at the [blank_start]boundary[blank_end] of on and off region of RF.

    1. Aconvergence of center surround inputs
    2. BOptimal stimulus for their elongated RF
    3. Cedge, bar, or grating
    4. Dboundary
41. 41Response may also be [blank_start]direction and velocity selective[blank_end] for visual stimuli moving across RF of simple cells.

    1. Adirection and velocity selective
42. 42[blank_start]V1[blank_end] neurons show a range of optimal stimulus orientations. As an electrode passes parallel to the surface, the preferred orientation shifts progressively forming [blank_start]orientation columns.[blank_end]

    1. AV1
    2. Borientation columns.
43. 43Cortical modules (or hyper columns) consist of:
    - [blank_start]pairs of ocular dominance columns[blank_end]
    - [blank_start]many orientation coumns[blank_end]
    - [blank_start]blobs and inter blob regions[blank_end]

    1. Apairs of ocular dominance columns
    2. Bmany orientation coumns
    3. Cblobs and inter blob regions
44. 44Higher order neurons that prefer the same orientation as simple cells may also be sensitive to the line [blank_start]over larger areas of visual space[blank_end] (complex cells), to the line's [blank_start]length[blank_end] (hyper complex), and/or to [blank_start]binocular disparity.[blank_end]

    1. Aover larger areas of visual space
    2. Blength
    3. Cbinocular disparity.
45. 45Module is [blank_start]necessary and sufficient[blank_end] for analysis of each point in visual space.

    1. Anecessary and sufficient
46. 46Staining for the mitochondrial enzyme [blank_start]cytochrome oxidase[blank_end] (CO) reveals patches of more (blobs) or less densely labeled cells (inter-blob) in [blank_start]V1[blank_end].

    1. Acytochrome oxidase
    2. BV1
47. 47Blobs most apparent in [blank_start]superficial layers II and III.[blank_end]

    1. Asuperficial layers II and III.
48. 48Both blobs and interblob regions receive their dominant input from [blank_start]P type[blank_end] cells. [blank_start]M type[blank_end] cells project to [blank_start]layer IVB[blank_end] and then out of V1 (to [blank_start]extrastriate cortex[blank_end]).

    1. AP type
    2. BM type
    3. Clayer IVB
    4. Dextrastriate cortex
49. 49Functional significance:
    - neurons in blobs process [blank_start]color[blank_end]
    - neurons in inter blobs process [blank_start]form[blank_end]

    1. Acolor
    2. Bform
50. 50Evidence suggests that there are two major parallel output pathways (streams) from V1 to extrastriate cortex:
    - dorsal: [blank_start]M cells; motion/space[blank_end]
    - ventral: [blank_start]P cells; color and form[blank_end]

    1. AM cells; motion/space
    2. BP cells; color and form
51. 51[blank_start]MST[blank_end] responds best to global motion patterns. Different cells are selective for [blank_start]apparent movement heading[blank_end]. May be important for [blank_start]navigation in space[blank_end], distinguishing [blank_start]self motion from object motion.[blank_end]

    1. AMST
    2. Bapparent movement heading
    3. Cnavigation in space
    4. Dself motion from object motion.
52. 52[blank_start]Parietal[blank_end] cortex lesions lead to selective impairments of spatial processing:
    - akinetopsia: [blank_start]selective inability to perceive motion[blank_end]
    - optic ataxia: [blank_start]impairment of visually guided reaching[blank_end]
    - hemi neglect syndrome: perceptual unawareness of the [blank_start]half of visual space contralateral[blank_end] to the lesion

    1. Aselective inability to perceive motion
    2. Bimpairment of visually guided reaching
    3. Chalf of visual space contralateral
    4. DParietal
53. 53[blank_start]Inferotemporal[blank_end] cortex cells have very large RFs (often bilateral) that include fovea. Large RF may be important for recognizing [blank_start]objects regardless of orientation[blank_end] in space ([blank_start]position invariance[blank_end]).

    1. AInferotemporal
    2. Bobjects regardless of orientation
    3. Cposition invariance
54. 54Specific deficits occur with lesions to ventral stream. Examples:
    - achromatopsia: [blank_start]loss of color vision[blank_end] ([blank_start]V4[blank_end] lesion)
    - prosopagnosia: [blank_start]failure to recognize familiar faces[blank_end] ([blank_start]IT[blank_end] lesion). (may play a role in autism).

    1. Aloss of color vision
    2. BV4
    3. Cfailure to recognize familiar faces
    4. DIT

Descripción

Test sobre Visual System II and III, creado por Hannah Miller el 10/11/2019.

Autor

Hannah Miller

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