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aNeuro Exam 3- Lindsey's > Vision > Flashcards

Flashcards in Vision Deck (114):
1

The output neurons of the retina, the retinal ganglion cells, group together at ______.

the optic disk

2

____ are larger in the periphery of the retina..

Receptive fields

3

What happens after the 2 optic nerves converge @ the optic chiasm?

half of the axons from each eye cross to the other side and continue on as the optic tract

4

What do rods mediate?

black/white; light/dark vision

5

What does activation of transducing cause?

activation of cGMP phosphodiesterase (PDE)

6

What coordinates head and eye movements? Where is this structure located?

the superior colliculus; on the dorsal surface of the midbrain

7

These are central regions of the hypercolumns where color information is deciphered.

blobs

8

These cells capture photons of light and convert them into an electrical signal.

photoreceptor cells

9

What determines cortical wiring?

genetics

10

This is a .2mm wide region where acuity is the greatest.

the fovea

11

The period of time when the connections can be altered by visual experience is called ____.

the critical period (or sensitive period)

12

What is the dorsal parallel pathway?

  • from V1 dorsally --> parietal lobe
  • spatial vision
  • passes thru the thick stripe region of V2 and thru V5

13

What are binocular cells sensitive to?

depth perception

14

Layers 1, 4, and 6 of the lateral geniculate nucleus (LGN) of the thalamus receive input from the ______.

contralateral eye

15

What does the postsynaptic cell release to the presynaptic cell? When can the presynaptic cell take it up?

trophic factors; only when it's been recently active

16

_____ have donut-shaped receptive fields and come in on-center and off-center types.

Ganglion cells

17

Layers 3-6 of the lateral geniculate nucleus (LGN) of the thalamus receive inputs from the _____.

parvocellular ganglion cells

18

How many rods are in the human retina?

100 million

19

Category 4 ocular dominant cells are ____ driven.

equally (from both sides)

20

What do cones mediate?

color vision

21

What is hierarchical processing in the eye?

several cells with similar but spatially offset receptive fields converge on a higher order cell to create an altogether new type of receptive field

22

Beyond the lateral geniculate nucleus (LGN) of the thalamus, the axons fan out into the ______ to the visual cortex.

optic radiations

23

Receptive fields are larger in the ______ of the retina.

periphery

24

Each hypercolumn is divided into 2 parts, one half for each eye, called _____.

ocular dominance columns

25

What do complex cells do?

abstract for position

26

In the dark, the concentration of cGMP is ____, causing the nonselective cation channels to stay _____.

high; open

27

Layers 1 and 2 of the lateral geniculate nucleus (LGN) of the thalamus receive inputs from the _____.

magnocellular ganglion cells

28

What are the features of the parvocellular ganglion cells.?

object vision- color, form, detail high acuity --> fine detail small receptive fields not responsive to motion color vision (input from cones) layers 3-6 of the LGN

29

What are the 2 primary parallel pathways through the ascending visual system?

  1. the dorsal pathway
  2. the ventral pathway

30

What are the features of the magnocellular ganglion cells.?

spatial vision- motion and depth low acuity (crude) large receptive fields responsive to motion no color vision (input from rods) layers 1 and 2 of the LGN

31

V5 is often called the _____.

middle temporal (MT)

32

What is a hypercolumn?

  • a microregion of V1
  • 1mm
  • 10,000 LGN axons
  • 6 layers

33

Which parts of the eye provide the focusing (refractive) power?

cornea (2/3) and lens (1/3)

34

Name the ganglion cell type: object vision- color, form, detail high acuity --> fine detail small receptive fields not responsive to motion color vision (input from cones) layers 3-6 of the LGN

parvocellular ganglion cells

35

Bipolar cells always make ____ synapses on ganglion cells.

excitatory

36

Light --> hyperpolarize photoreceptor --> ?

less NT release

37

What 2 synapses in the eye are always excitatory?

  1. surround photoreceptors --> horizontal cell synapse
  2. bipolar cell --> ganglion cell synapse

38

This is a microregion of V1 that is 1mm and contains 10,000 LGN axons in 6 layers.

a hypercolumn

39

How many photoreceptors does the optic disk contain?

none

40

Each microregion of V1 is called a _____.

hypercolumn

41

Where are cones concentrated?

in the fovea

42

The ______ cells group together at the optic disk forming the optic nerve.

retinal ganglion

43

Where are horizontal cells found?

surrounding the receptive fields

44

These cells abstract for position.

complex cells

45

This is a ganglion cell excited by light in their center and inhibited by light in the periphery.

on-center ganglion cell

46

Layers ____ of the lateral geniculate nucleus (LGN) of the thalamus receive inputs from the parvocellular ganglion cells.

3-6

47

What does glutamate do to bipolar cells?

it either excites them (off-center) or inhibits them (on-center)

48

What does light do to rhodopsin?

causes it to activate transducin (a G protein)

49

If one eye is deprived from vision, what happens to its synaptic connections in the cortex?

they degenerate and disappear

50

Lesions in V4 can result in ______.

impairments in color discrimination

51

____ is the method by which light is focused on the retina by the cornea and lens.

Refraction

52

If light passes from one medium to another, it is ____.

refracted

53

Intensity corresponds to the perceptual ____ of an object, while wavelength corresponds to _____.

brightness; color

54

Layers 2, 3, and 5 of the lateral geniculate nucleus (LGN) of the thalamus receive input from the ______.

ipsilateral eye

55

What are the wavelength boundaries of the visible light spectrum and what color do they coordinate with?

400nm (blue) --> 700nm (red)

56

Light can be described as having ____ and ____.

wavelength and amplitude (intensity)

57

What are the 3 kinds of human cones?

  1. blue
  2. green
  3. red

58

What does reduced cGMP in the optic disc do?

closes Na channels --> hyperpolarization

59

Most of the bipolar cells in the fovea are connected directly to _____ and indirectly to _____.

direct = one kind of cone in the field center indirect = cones with a different color preference in the field surround

60

The optic nerves from the 2 eyes merge at the ____.

optic chiasm

61

What do photoreceptors release?

glutamate

62

What is the fovea?

a .2mm wide region where acuity is the greatest

63

What are blobs?

central regions of the hypercolumns where color information is deciphered

64

Which synapse in the eye is always inhibitory?

horizontal cell --> photoreceptor synapses

65

In which hypercolumn layer do LGN axons terminate?

layer 4

66

What is the pupil?

the opening thru which light enters the eye

67

Layers _____ of the lateral geniculate nucleus (LGN) of the thalamus receive input from the ipsilateral eye.

2, 3, and 5

68

What is an off-center ganglion cell?

ganglion cell excited by light shining in the periphery and inhibited by light shining in their center

69

Which synapse in the eye can either be excitatory or inhibitory?

synapses with the on- or off-center bipolar cells

70

The lateral geniculate nucleus (LGN) of the thalamus represents the ____ visual field.

contralateral

71

Light absorption causes photoreceptors to ____.

hyperpolarize

72

What input does the lateral geniculate nucleus (LGN) of the thalamus receive?

visual info via the optic tract

73

Layers ______ of the lateral geniculate nucleus (LGN) of the thalamus receive inputs from the magnocellular ganglion cells.

1 and 2

74

Ganglion cells have donut-shaped receptive fields and come in ____ and _____ types.

on-center and off-center

75

Where do ganglion cell axons end?

in the lateral geniculate nucleus (LGN) of the thalamus

76

The longer the period of monocular deprivation during the sensitive period, _____.

the worse the outcome

77

___ and ____ are located together within the same hypercolumn.

Simple and complex cells

78

The retinal ganglion cells group together at the _____ forming the optic nerve.

optic disk

79

What are ocular dominance columns?

each hypercolumn divided into 2 parts, one half for each eye

80

In strabismus, what happens to the bilateral eye inputs?

one eye wins everything and the other loses altogether --> monocular driving of the cells

81

The lateral geniculate nucleus (LGN) of the thalamus is composed of ____ layers.

6

82

What is retinotopic projection?

axons project in an orderly fashion to the cortex

83

___ tend to be found at the borders of the ocular dominance columns.

Binocular cells

84

What is parallel processing?

dimensions of an object are analyzed separately but in parallel, neutral systems and then are later united

85

What is the ventral parallel pathway?

  • from V1 ventrally --> temporal lobe
  • object vision
  • passes thru the stripe and interstripe regions of V2 and thru V4

86

What do bipolar cells synapse with?

ganglion cells

87

What cells in the eye make APs?

ganglion cells

88

_____ is the process by which light is converted into a change in membrane potential by the photoreceptors.

Phototransduction

89

The foveal region occupies nearly ____ of the visual cortex.

1/2

90

How many codes are there in a human retina?

8 million

91

What do photoreceptor cells do?

capture photons of light and convert them into an electrical signal

92

retinal ganglion cells @ optic disk --> optic nerve --> optic chiasm --> optic tract --> ?

lateral geniculate nucleus (LGN) of the thalamus

93

What are color opponent cells?

bipolar cells that are directly connected to one kind of cone in the field center and indirectly to a different color preference in the field surround

94

The retina contains what 5 types of neurons?

  1. rods
  2. cones
  3. bipolar cells
  4. horizontal cells
  5. ganglion cells

95

At the chiasm, the axons from the _____ half of each retina cross over to the opposite side.

nasal

96

This is a ganglion cell excited by light shining in the periphery and inhibited by light shining in their center.

an off-center ganglion cell

97

The retinal ganglion cells group together at the optic disk forming _____.

the optic nerve

98

What controls the size of the pupil?

the ciliary muscles

99

What does reduced cGMP concentration cause?

closure of nonselective cation channels in the surface membrane --> hyperpolarization of the cell

100

What is an on-center ganglion cell?

ganglion cell excited by light in their center and inhibited by light in the periphery

101

Ganglion cells only care about ____.

contrast

102

Layers 1, 4, and 6 of the ______ receive input from the contralateral eye.

lateral geniculate nucleus (LGN) of the thalamus

103

What does PDE activation do?

hydrolyses cGMP to reduce its concentration

104

Name the ganglion cell type: spatial vision- motion and depth low acuity (crude) large receptive fields responsive to motion no color vision (input from rods) layers 1 and 2 of the LGN

magnocellular ganglion cells

105

Layers _____ of the lateral geniculate nucleus (LGN) of the thalamus receive input from the contralateral eye.

1, 4, and 6

106

Lesions in the middle temporal (MT) area result in ____.

impaired motion and depth perception

107

Category 1 and 7 ocular dominant cells are ____ driven.

monocularly

108

The back of the inner eye contains the ____, which is the receptive organ of the eye.

retina

109

Photoreceptors talk to ____ and ____ cells.

bipolar; horizontal

110

Synchronous activity from both eyes is necessary for ______ during development of the visual cortex.

establishment of proper synaptic connections

111

The output neurons of the retina, the ______, group together at the optic disk.

retinal ganglion cells

112

Ganglion cells have _____-shaped receptive fields and come in on-center and off-center types.

donut

113

These cells are sensitive to depth perception.

binocular cells

114

What absorbs the photon of light?

vitamin A