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Neuroscience > Week 2 - Central Visual Processing I > Flashcards

Week 2 - Central Visual Processing I Flashcards

1
Q

what does retinotopy and receptive field refer to?

A

the faithful spatial representation of visual space/position from the retina

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2
Q

what does intensity and luminance refer to?

A

photons absorbed/transduced by photo-pigments, rods VS cones

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3
Q

what does differential spectral absorption refer to?

A

3 cone types and color opponency

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4
Q

what does spatial contrast refer to?

A

center-surround receptive fields and edge-detection

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5
Q

what does ON vs OFF refer to for the retina?

A

positive and negative signs of contrast, luminance increments and decrements

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6
Q

what aspects of vision do these contrasts refer to?

  • spatial
  • cone
  • temporal
  • ocular
A
  • form/contour
  • color
  • motion
  • 3D/depth
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7
Q

how does info from the retina get to the LGN? what happens with this information?

A

visual pathway

  • optic nerve –> optic chiasm –> optic tract –> LGN
  • -some may go from OT to hypothalamus, pretectum, or superior colliculus
  • if pupils must be dilated/constricted, then LGN –> pretectum –> Edinger-Westphal nucleus –> CN III (pregang para) –> ciliary ganglion –> postgang para –> ciliary muscles to constrict (if relax, then dilate)
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8
Q

what is the hypothalamus for?

A

regulation of circadian rhythms

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9
Q

what is the pretectum for?

A

reflex control of pupil and lens

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10
Q

what is the superior colliculus for?

A

orienting the movements of head and eyes

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11
Q

what are the first neurons to get bilateral visual input?

A

striate cortex (NOT LGN); until then, signals are kept separate

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12
Q

what visual defect do you get if the right optic nerve is cut?

A

left eye: normal

right eye: totally blind

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13
Q

what visual defect do you get if the optic chiasm is cut?

A

left eye: temporal side blind
right eye: temporal side blind

(b/c nasal retina = temporal vision, which crosses; temporal retina = nasal vision, which stays on the same side)

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14
Q

what visual defect do you get if the right optic tract is cut?

A

left eye: temporal side blind

right eye: nasal side blind

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15
Q

what visual defect do you get if the right optic radiations are cut?

A

left eye: one of the temporal quarters is bind

right eye: one of the nasal quarters is blind

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16
Q

what visual defect do you get if the right striate cortex is cut?

A

left eye: most of temporal side is blind, but macular sparring
right eye: most of nasal side is blind, but macular sparring

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17
Q

from the LGN, where do fibers representing the superior and inferior visual fields go?

A

superior visual field = inferior retinal quadrants
-travel through temporal lobe, and are more susceptible to damage via Meyer’s loop

inferior visual field = superior retinal quadrants
-travel through parietal lobe, and less susceptible to damage via Baum’s loop

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18
Q

what is the primary visual cortex (and other names for it)? what is right next to it?

A

Visual area 1 (V1)
-AKA striate cortex or Brodman’s area 17

right next to V2 = extra-striate cortex = Brodman’s area 18

19
Q

what is the Magnocellular pathway?

A

M-channel
-parasol cells in retina send info through to ventral LGN (1 contralateral, 1 ipsilateral) to ventral primary visual cortex

20
Q

what is the Parvocellular pathway?

A

P-channel

-midget cells in retina send info through to dorsal LGN (2 contralateral, 2 ipsilateral) to dorsal primary visual cortex

21
Q

what are the differential specializations of P and M pathways for

  • color
  • luminance contrast
  • spatial acuity
  • temporal resolution
A

P: color, low luminance, high spatial acuity, low temporal resolution (speed/movement)

M: no color, high luminance contrast (fine shades of gray), low spatial acuity, high temporal resolution (speed/movement)

22
Q

what are common properties of receptive fields in retina and LGN (for both M, P, and K-channels)

A
  • center-surround (spatially opponent) organization (usually)
  • mix of cells with on- and off-center
  • retinotopically (spatially) ordered and specific
  • maybe color-opponent (red/green or blue/yellow)
23
Q

where do LGN inputs enter and terminate?

A

they enter V1 and terminate in layer 4

-comes in eye-specific way, so columns are either contralateral or ipsilateral

24
Q

what does flattening the neocortex show us?

A

it’s a thin layer of simple monocular cells organized into ocular dominance columns and orientation columns

  • at the very top they become complex (binocular) cells
  • it has a very highly conserved laminar architecture with canonical spread
25
Q

how does most cortical circuitry run? what are some examples?

A

vertically, across cell layers

  • ex) monocular inputs from LGN (K, P, or M channels)
  • ex) resident cells (output to higher areas like V2, or feedback output to LGN)
26
Q

what does the Hubel/Wiesel Serial Model show us?

A

orientation tuning

  • certain cells will respond to light bars in a certain orientation (horizontal, vertical, diagonal) with more APs than other orientations; unique to cell
  • there’s a hierarchial/serial elaboration of higher order receptive field properties
27
Q

what is the hierarchial elaboration of form/receptive fields for isolated and combined?

A

isolated: white spots (retina) –> bars (V1)
combined: white/black spots (retina) –> sinusoidal gratings (V1) –> non-cartesian gratings (V2) –> 3D shape primitives (V4) –> faces/objects (temporal)

28
Q

what is color vision based on? what does this mean?

A

cone-opponency (2 color opponent mechanisms)

  • R/G (red VS green) and B/Y (blue VS red/green)
  • can’t see red w/o absence of green
29
Q

what are double-opponent receptive fields?

A

encode both spatial and chromatic contrast

  • both spatial and spectral attributes of stimulus contribute to receptive field
  • visual system is constructed to extract and emphasize contrasts
30
Q

what do Type I vision cells show?

A

R+ center, G- periphery

  • spatial opponency
  • weak color bias
  • retina = midget system
  • LGN = P-pathway
  • V1 = P-pathway and CO blobs
31
Q

what do Type II vision cells show?

A

R+ and G- center only

  • chronatic opponency
  • no spatial opponency
  • retina = unknown
  • LGN = P-pathway
  • V1 = P-pathway and CO blobs
32
Q

what do double opponent vision cells show?

A

R+ and G- center, R- and G+ periphery

  • chromatic opponency
  • spatial opponency
  • not in retina or LGN
  • V1 = P-pathway and CO blobs
  • V2 = thin stripes and higher cortex
33
Q

how do cells change throughout cortical circuitry?

A

increasing sophistication of receptive field properties through cortical circuitry
-Type I –> Type II –> double opponent

34
Q

how is V1 organized functionally? what would vertical VS oblique (horizontal) electrode penetration do?

A

in cortical columns

  • vertical: cells are all the same orientation and ocular dominance
  • horizontal: progression of orientation
35
Q

how are CO blob and interblob cells tuned?

A

CO: color tuned (from K pathway)
interblob: orientation tuned

36
Q

what are the 3 “dimensions” of retinotopy? what parameters do they help for vision?

A 
orientation (horizontally) - form
CO blobs (vertically) - color
ocular dominance (diagonally) - depth
37
Q

what does a hypercolumn refer to?

A

complete set of all possibilities for a given parameter (ocular dominance, orientation, etc.)
-AKA collection of cortical columns whose receptive field properties span entire range of possibilities for a given point in visual space

38
Q

what are the V2 parameters and what do they correspond to?

A

thick - orented, disparity, motion, depth
pale - oriented, end-stopped, form
thin - unoriented, color

39
Q

what is the object discrimination task used for? what “question” does this ask?

A

bilateral lesion of temporal lobe leads to behavioral deficit in a task that requires discrimination of objects
-“what” - temporal

40
Q

what is the landmark discrimination task used for? what “question” does this ask?

A

bilateral lesion of parietal lobe leads to behavioral deficit in a task that requires discriminations of locations
-“where” - parietal

41
Q

what is parietal neglect?

A

hemispatial/hemiagnosia neglect

-will ignore the complete left side of the body and drawings

42
Q

what is the parietal path for V2?

A

V2 –> MT (via dorsal/spatial vision pathway) in parietal lobe
-asks “where”

43
Q

what is the temporal path for V2?

A

V2 –> V4 via ventral (object recognition) pathway in temporal lobe
-asks “what”

Neuroscience (39 decks)

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