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PSYC 212 > Chapter 4: The Visual Cortex and Beyond > Flashcards

Chapter 4: The Visual Cortex and Beyond Flashcards

1
Q

how did the study of the visual cortex begin?

A

with cases of people who had brain damage

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2
Q

Optic chiasm

A

an x-shaped bundle of fibres on the underside of the brain

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3
Q

LGN

A

part of the thalamus that regulates neural information as it flows from the retina to the cortex and information flow

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4
Q

Visual receiving area/ V1/ Striate cortex

A

the place where signals from the retina and the LGN first reach the cortex

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5
Q

the retina to the cortex steps

A
  1. Visual signals from both eyes leave the back of the eye through the optic nerve and meet at the optic chiasm
  2. At the optic chiasm, some of the fibres cross to the opposite side of the brain from the eye they came from, resulting in each hemisphere corresponding to the contralateral visual field
  3. 90% of the signals from the retina proceed to the LGN, located in the thalamus of each hemisphere. The other 10% travels to the superior colliculus
  4. From the LGN, the visual signal travels to V1
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6
Q

how are neurons in the LGN organized

A

have centre-surround organization & receptive fields

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7
Q

where does the LGN receive most of its signals from

A

the cortex (feedback mechanism) but also receives signals from the retina

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8
Q

where is V1 located

A

in the occipital lobe

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9
Q

why is V1 called the striate cortex

A

it has a striped appearance when viewed in cross-section

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10
Q

how is a neuron’s receptive field determined

A

by presenting a stimulus to different places on the retina to determine which areas result in an exhibitory response, inhibitory response, or no response

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11
Q

Hubel & Wiesel’s receptive field method

A

projected stimuli on a screen and anesthetized an animal and focused its eyes with glasses. its eyes remained stationary and each point on the screen corresponded to a point on the cat’s retina, allowing them to determine receptive fields

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12
Q

where is the receptive field ALWAYS located

A

on the receptor surface

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13
Q

where is the receptive field for vision

A

the retina

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14
Q

who discovered simple, complex, and end-stopped cortical cells?

A

Hubel & Wiesel

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15
Q

simple cortical cells

A

Cells in the striate cortex that have inhibitory and excitatory areas arranged side by side. They respond best to bars of a particular orientation

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16
Q

oriented tuning curve

A

the relationship between orientation and firing, which is determined by measuring the responses of simple cortical cells to bars with different orientations

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17
Q

complex cortical cells

A

cells in the striate cortex that only respond when a correctly oriented bar of light moves across the entire receptive field

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18
Q

end-stopped cortical cells

A

cells in the striate cortex that respond to corners, angles, or bars of a particular length moving in a particular direction

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19
Q

feature detectors

A

neurons that respond selectively to a specific feature of the stimulus such as the orientation or direction of the motion

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20
Q

selective adaptation

A

A procedure in which a person or animal is selectively exposed to one stimulus and then the effect of this exposure is assessed by testing with a wide range of stimuli. Typically, sensitivity to the exposed stimulus is decreased

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21
Q

what are the 2 main effects of selective adaptation

A

Selective adaptation causes the neuron’s during rate to decrease and the neuron to fire less when that stimulus is immediately presented again

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22
Q

what neurons are affected by selective adaptation

A

those that respond to the stimulus

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23
Q

contrast threshold

A

the minimum intensity difference between the light and dark bars until the bars can just barely be seen

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24
Q

steps for measuring the effect of selective adaptation

A
  1. Measure a person’s contrast threshold to gratings with several different orientations
  2. Adapt the person to one orientation by having the person view a high-contrast adapting stimulus for a minute or two
  3. Remeasure the contrast threshold of all the test stimuli presented in step 1
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25
Q

psychophysical curve

A

a function of the increase in contrast threshold to the orientation of the stimulus

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26
Q

orientation tuning curve

A

a function of the firing rate of a neuron to the orientation of the stimulus

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27
Q

psychophysical vs. orientation tuning curve for simple cortical cells

A

The psychophysical & orientation tuning curves are very similar for a simple cortical neuron. Demonstrates that feature detectors play a role in the perception

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28
Q

selective rearing

A

A process by which neurons adapt to the specific environment within which they live. This is achieved when neurons change their response properties so that they respond best to stimuli that have been repeatedly experienced in the environment

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29
Q

Blakemore & Cooper’s kitten orientation study

A

exposed kittens to only vertical or horizontal orientations. When they were removed from the tubes after 5 months, they seemed blind to orientations they hadn’t seen in the tube

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30
Q

selective rearing might help explain ____

A

the oblique effect

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31
Q

neural plasticity/experience-dependent plasticity

A

the capacity of the nervous system to change in response to experience

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32
Q

duration of selective rearing vs. adaptation

A

selective rearing: long-term
selective adaptation: short-term

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33
Q

locations in the cortex vs. retina

A

Locations on the cortex correspond to locations on the retina

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34
Q

retinotopic map

A

the electronic map of the retina on the cortex

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35
Q

spatial representation on the cortex

A

is distorted, with more space being allotted to locations near the fovea than to locations in the periphery

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36
Q

cortical magnification

A

the apportioning of a large area on the cortex to the small fovea

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37
Q

Cortical magnification factor

A

the size of the cortical magnification

38
Q

measuring the cortical magnification of your finger

A
  1. Hold your index finger up with your left hand at arm’s length
  2. While you look at it, hold your right hand at arm’s length about a foot to the right of your finger, positioned so the back of your hand is facing you
  3. Your left index finger activates an area of the cortex as large as the area activated by your whole right hand
39
Q

who discovered columns in the cortex

A

Hubel & Wiesel

40
Q

how is the striate cortex organized

A

in location & orientation columns

41
Q

location columns

A

columns that are perpendicular to the surface of the cortex so that all of the neurons within a location column have their receptive field at the same location on the retina and prefer stimuli with the same orientation

42
Q

orientation columns

A

columns that contain cells that respond best to a particular orientation

43
Q

where are orientations & location columns located relative to each other?

A

1 mm location columns contain within them orientation columns that cover all possible orientations

44
Q

hypercolumn

A

a location column with all of its orientation columns

45
Q

how is an image represented in the cortex?

A

by the firing of neurons sensitive to a specific orientation in many separate columns in the cortex

46
Q

tiling

A

the process by which columns work together to cover the entire visual field

47
Q

where does the visual signal go after v1?

A

proceeds to other areas in the occipital lobe & beyond, known as V2, V3, V4, V5

48
Q

extrastriate cortex

A

collective term for the visual areas in the occipital lobe and beyond known as V2, V3, V4, V5

49
Q

size of the receptive fields in the extrastriate cortex

A

gradually increases as we move to higher-level extrastriate areas because we are adding more aspects of the visual scene

50
Q

ablation

A

the destruction or removal of tissue in the nervous system

51
Q

object discrimination problem (Ungerleider & Mishkin experiment)

A

the animal was shown one object and presented with a two-choice task which included the target object and another stimulus. If the subject was able to discriminate between the two objects, it received a food reward

52
Q

landmark discrimination problem (Ungerleider & Mishkin experiment)

A

the animal’s task was to remove the cover of the food well that was closest to the landmark

53
Q

ventral pathway

A

what pathway; takes information from the cortex to the temporal lobe

54
Q

ventral part of the brain

A

the lower part where the temporal lobe is located

55
Q

dorsal pathway

A

where the pathway; takes information from the cortex to the parietal lobe

56
Q

dorsal part of the brain

A

the upper surface, where the parietal lobe is located

57
Q

feedback

A

the backward flow of information

58
Q

where do the ventral & dorsal pathways begin

A

the retina

59
Q

are the dorsal & ventral pathways connected?

A

yes

60
Q

what direction does information go in the dorsal & ventral pathways

A

bidirectional

61
Q

Milner & Goodale claimed that ____

A

the dorsal stream provides information for how to direct action to a stimulus & should thus be called the how or action pathways

62
Q

Milner & Goodale’s double dissociation experiment

A

Demonstrated double dissociation experiments with DF, a woman who suffered damage to her ventral pathway. She performed poorly in the static orientation-matching task but did well as soon as action was involved

63
Q

double dissociation

A

in brain damage when function A is present and function B is absent in one person, and function A is absent and function B is present in another. The presence of a double dissociation means that the two functions involve different mechanisms and operate independently of each other

64
Q

length estimation task

A

people were better at estimating lines if they grasped them (dorsal pathway) as opposed to perceiving them (ventral pathway)

65
Q

infereotemporal (IT) cortex

A

an area of the brain outside V1 involved in object perception and facial recognition

66
Q

where do neurons have the largest receptive fields

A

Infereotemporal cortex (IT)

67
Q

Gross et al’s IT cortex experiment in monkeys

A

recorded single neurons in anesthetized monkeys’ IT cortexes while presenting them with a variety of stimuli. They found a neuron that refused to respond to any of the standard stimuli and would only respond to a handlike shape with fingers pointing up, demonstrating that neurons in the IT cortex respond to complex stimuli.

68
Q

hippocampus

A

an area associated with forming and storing memories located in the medial temporal lobe (MTL)

69
Q

patient HM

A

Patient HM had his hippocampus removed in an attempt to eliminate epileptic seizures. The procedure eliminated his ability to store experiences in his memory

70
Q

Gelbard-Savig et al’s MTL neurons & videos experiment

A

Participants viewed video clips and some neurons responded better to particular clips. When they thought about the clip, the neurons also responded, demonstrating that MTL neurons that respond to perceiving specific stimuli might also be involved in remembering those stimuli

71
Q

do receptive fields change?

A

yes, they are flexible in response to our environment

72
Q

Kapadia et al’s neural flexibility experiment

A

recorded neurons from a monkey’s visual cortex and found that when the “outside the receptive field” bars are presented along with the “inside the field” bar, there is a large increase in firing, demonstrating neurons’ flexibility

73
Q

contextual modulation

A

the effect of stimulating outside the receptive field

74
Q

perceptual organization

A

the process by which small elements become perceptually grouped into larger objects

75
Q

how do feature detectors demonstrate the stimulus-physiology relationship

A

they show how the stimulus leads to the activation of cells

76
Q

how do feature detectors demonstrate the physiology-behaviour relationship

A

they show how the activation of cells makes you perceive something

77
Q

the neural map in V1 is determined by ___

A

stimulating various places on the retina and noticing where neurons fire in the cortex

78
Q

nasal retina

A

the part of the retina closest to the nose

79
Q

temporal retina

A

the part of the retina closest to the temples

80
Q

connections from the temporal retina are ___

A

ipsilateral

81
Q

connections from the nasal retina are ____

A

contralateral

82
Q

how are receptive fields in the retina organized?

A

in circular receptive fields

83
Q

what is each location and orientation column responsible for?

A

detecting its own orientation

84
Q

where are neurons’ receptive fields located in the retina vs. the cortex

A

every neurons has its receptive field at about the same location on the retina

85
Q

cortical representation of a stimulus

A

has to contain information that represents the stimulus

86
Q

damage to the ventral pathways results in ___

A

difficulties with object discrimination

87
Q

damage to the dorsal pathway results in ___

A

spatial deficit

88
Q

Mortimer Mishkin

A

discovered the what and where pathways by doing experiments on monkeys

89
Q

experiments with patient DF demonstrate

A

that the dorsal stream is associated with action

90
Q

size of receptive fields throughout the visual system

A

The increase in receptive field size continues through the what stream so that neurons at the apex of this stream in the IT cortex have the largest receptive fields

PSYC 212 (11 decks)

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