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ZOOL 342 > LGN to V1 > Flashcards

LGN to V1 Flashcards

1
Q

What kind of cells mediate surround inhibition?

A

horizontal cells

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2
Q

Describe the events that occur when light hits an ON center. What kind of bipolar cell is involved? depolarization or hyperpolarization?

A
  1. light hits photoreceptor
  2. photoreceptor becomes hyperpolarized, releasing LESS glutamate, causing LESS inhibition of the D-bipolar cell
  3. D-bipolar cell depolarizes through LOSS OF INHIBITION
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3
Q

Describe the events that occur when light hits the OFF surround. What kind of cells are involved? depolarization or hyperpolarization?

A
  1. light hits photoreceptor
  2. photoreceptor becomes hyperpolarized, releasing LESS glutamate, causing LESS inhibition of the horizontal cells
  3. horizontal cells hyperpolarize, and are inhibited from releasing GABA (inhibitory transmitter) onto photoreceptors (i.e. stop hyperpolarization of photoreceptors)
  4. glutamate is released from photoreceptors (causing inhibition)
  5. D-bipolar cell hyperpolarizes
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4
Q

Describe the events that occur when light hits an OFF center. What kind of bipolar cell is involved? depolarization or hyperpolarization?

A
  1. light hits the photoreceptor
  2. photoreceptor becomes hyperpolarizes, releasing LESS glutamate, causing LESS excitation of the H-bipolar cell
  3. H-bipolar cell hyperpolarizes
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5
Q

What is the only difference between H-bipolar cells and D-bipolar cells?

A

D-bipolar cell receptors = metabotropic
H-bipolar cell receptors = ionotropic

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6
Q

Describe the events that occur when light hits an ON surround/annulus. What kind of cells are involved? depolarization or hyperpolarization?

A
  1. light hits photoreceptor
  2. photoreceptor becomes hyperpolarized, releasing less glutamate, causing LESS inhibition of the horizontal cells
  3. horizontal cells hyperpolarize, and are inhibited from releaseing GABA onto photoreceptors
  4. glutamate is released from photoreceptors
  5. H-bipolar cells depolarize
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7
Q

TRUE or FALSE: there are only 2 types of amacrine cells: starburst and A2.

A

FALSE: many types. at least 40

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8
Q

What type of vision are amacrine cells important for?

A

scotopic vision

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9
Q

What is scotopic vision?

A

vision under low-light conditions

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10
Q

Which cells do cones mainly feed? rods?

A

cones = H bipolar cells (an also D)
rods = D bipolar cells + amacrine cells

(hint: roDs = D bipolar cells)

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11
Q

What do starburst amacrine cells do?

A

help with motion detection in vision

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12
Q

What is the start and end structure of the geniculo-strate pathway?

A

LGN to visual cortex (V1)

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13
Q

TRUE or FALSE: LGN projects contralaterally to the visual cortex

A

FALSE: it projects ipsilaterally to the cortex

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14
Q

Which visual field is represented in the right LGN? Which side of the cortex does this visual field project to?

A

LEFT visual field –> RIGHT LGN -(ipsilateral)-> RIGHT visual cortex

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15
Q

Which percentage of the optic nerves are crossed? uncrossed?

A
  • 55% crossed (nasal hemiretina)
  • 45% uncrossed (temporal hemiretina)
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16
Q

TRUE or FALSE: majority of the optic nerves do not cross the optic chiasm.

A

FALSE: majority are crossed (55%)

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17
Q

TRUE or FALSE: binocular overlap is greater in rats than in primates

A

FALSE: greater in primates

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18
Q

What percentage of optic nerves are crossed in rodents? Why?

A

90% crossed because of laterally placed eyes

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19
Q

Which layers of LGN are magnocellular? parvocellular? receive input from the contralateral eye? the ipsilateral eye?

A
  • magnocellular: 1 and 2
  • parvocellular: 3-6
  • contralateral eye: 1,4,6
  • ipsilateral eye: 2,3,5
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20
Q

What are konicellular layers?

A

white bands in the LGN

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21
Q

draw the LGN and label the layers as parvocellular, magnocellular, contralateral eye or ipsilateral eye

A

slide10

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22
Q

Label a drawing of the visual field, the optic tracts, and the LGN to demonstrate that adjacent points in the visual field are represented by adjacent neurons in the LGN.

A

slide11

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23
Q

TRUE or FALSE: the receptive fields in the LGN are the same as the ones in the RGCs

A

TRUE

24
Q

What kind of receptive fields does the LGN have?

A

center-surround (like RGCs)

25
Q

TRUE or FALSE: parvo- and magno- layers receive inputs from different types of RGCs

A

TRUE

26
Q

What is another name for midget RGCS? parasol?

A
  • midget RGCs = P ganglion cells
  • parasol RGCs = M ganglion cells
27
Q

Do midget RGCs project to parvo or magnocellular layers of the LGN? Which layer number are these?

A

midget (P) RGCs –> parvocellular (3-6)

hint: P RGCs –> Parvocellular

28
Q

Do parasol RGCs project to parvo or magnocellular layers of the LGN? Which layer number are these?

A

parasol (M) RGCs –> magnocellular (1,2)

hint: M RGCs –> Magnocellular

29
Q

TRUE or FALSE: like RGCs and the LGN, the receptive fields in visual cortical cells are also center-surround

A

FALSE: visual cortex has cells that respond to certain orientations of light (simple, complex, end-stopped cells)

30
Q

According to Hubel and Weisel, what do the receptive field cells in the visual cortex respond to?

A

straight dark line on a light background

31
Q

What are the 3 types of cells in the visual cortex?

A

simple cells, complex cells, end-stopped cells

32
Q

What do simple cells respond to?

A

“bars” of light of a particular orientation (orientation selective)

33
Q

What do complex cells respond to?

A

“bars” of light of a particular orientation, moving in a particular direction (direction selective)

34
Q

What do end-stopped cells respond to?

A

moving “bars” of light of a particular orientation and a particular length (moving “corners”)

35
Q

At what degree is the neural response greatest in simple cells?

A

zero degrees

36
Q

Draw a simple cell receptive field.

A

slide 19

37
Q

draw a complex cell receptive field and demonstrate when it is optimally excitatory.

A

slide 22

38
Q

Draw the complex cell direction tuning curve. At what degrees are there maximal spikes? minimal spikes?

A

90 degrees = maximal spiking; 270 degrees = minimal spiking

39
Q

Draw an end-stopped cell receptive field optimally responding to a bar of light.

A

slide 26

40
Q

What is another name for cells of the visual cortex?

A

edge detectors

41
Q

List the following for a photoreceptor:
- shape of field
- best stimulus
- how good is diffuse light as a stimulus?
- is orientation of stimulus important?

A
  • slide 31
  • light
  • good
  • no
42
Q

List the following for a RGC:
- shape of field
- best stimulus
- how good is diffuse light as a stimulus?
- is orientation of stimulus important?

A
  • center-surround
  • small spot or narrow bar over center
  • moderate
  • no
43
Q

List the following for LGN:
- shape of field
- best stimulus
- how good is diffuse light as a stimulus?
- is orientation of stimulus important?

A
  • center-surround
  • small spot or narrow bar over center
  • poor
  • no
44
Q

List the following for a simple cell:
- shape of field
- best stimulus
- how good is diffuse light as a stimulus?
- is orientation of stimulus important?

A
  • slide 31
  • narrow bar or edges
  • ineffective
  • yes
45
Q

List the following for a complex cell:
- shape of field
- best stimulus
- how good is diffuse light as a stimulus?
- is orientation of stimulus important?

A
  • slide 31
  • bar or edge
  • ineffective
  • yes
46
Q

List the following for an end-stopped cell:
- shape of field
- best stimulus
- how good is diffuse light as a stimulus?
- is orientation of stimulus important?

A
  • slide 31
  • line or edge that stops; corner or angle
  • ineffective
  • yes
47
Q

Which layers of the visual cortex are simple cells found? complex? end-inhibited?

A
  • simple cells = layers 4,6
  • complex and end-stopped cells = layers 2,3,5,6
48
Q

Into which layer does most of the input to the visual cortex go?

A

4C

49
Q

To which layers of the visual cortex does the koniocellular pathway project?

A
  • 4A
  • 2
  • 3
50
Q

To which layers of the visual cortex do the magnocellular layers project?

A
  • 4C-alpha
  • 4B
51
Q

To which layers of the visual cortex do the parvocellular layers project?

A

4C-beta

52
Q

From which paths/layers does the visual cortex receive inputs?

A

koniocellular pathway, magnocellular layers, and parvocellular layers

(LGN?)

53
Q

Which layers of the visual cortex project to other cortical areas?

A
  • 2
  • 3
  • 4
54
Q

Which layers of the visual cortex project to deep brain structures?

A
  • 5
  • 6
55
Q

TRUE or FALSE: both simple and complex cells project to both other cortical areas and deep areas.

A

TRUE

ZOOL 342 (21 decks)

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