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Sensation and Perception > Retina to Cortex > Flashcards

Retina to Cortex Flashcards

Chapter 3

1
Q

The pathway from the retina to the primary visual cortex goes through the __ before going to the primary visual cortex in the occipital love

A

lateral geniculate nucleus

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2
Q

The optic nerves from each eye meet at the __, from which the fibres from the left visual field of each eye make their way to the right LGN (and vice versa)

A

optic chiasm

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3
Q

The lateral geniculate nucleus is a part of the:

A

thalamus

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4
Q

The lateral geniculate nucleus is:

A

Arranged in layers

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5
Q

Layers 1 and 2 of the lateral geniculate nucleus are:

A

Magnocellular layers from M (parasol) ganglion cells

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6
Q

Layers 3-6 are:

A

Parvocellular layers from P (midget) ganglion cells

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7
Q

Layers 1,4,6 (of the LGN) receive input from :

A

The contralateral eye

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8
Q

Layers 2, 3 and 5 (of the LGN) receive input from the:

A

ipsilateral eye

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9
Q

Konicellular layers may be involved in:

A

Color vision

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10
Q

Konicellular layers may be involved in color vision and get input from:

A

K type (bistratisfied) ganglion cells

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11
Q

The two main visual pathways in the cortex:

A

Dorsal (“where” or “how”) -> spatial + motion

Ventral (“what”) pathway –> object recognition, object perception and color perception

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12
Q

The visual system maintains:

A

Seperate pathways from the retina through cortex for processing different information

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13
Q

optic nerve fibres representing half of the visual field of each eye:

A

cross over to the contralateral side at the optic chiasm on their way to the LGN

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14
Q

Layers 1 & 2 of the LGN are :

A

Magnocellular layers from M ganglion cells

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15
Q

Layers 3 - 6 of the LGN are:

A

Parvocellular layers from P ganglion cells

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16
Q

Layers 1 , 4 and 6 process signals from:

A

The contralateral eye

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17
Q

Layers 2,3 and 5 process signals from the:

A

The ipsilateral eye

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18
Q

The primary visual cortex is also known as the

A

striate cortex

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19
Q

The primary visual cortex contains about

A

200 miillion cells

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20
Q

The circular receptive fields of the RGC’s and LGN are replaced by :

A

Elongated “stripe” receptive fields (different shape in retina vs V1)

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21
Q

Retinotopic mapping:

A

The relative position of objects within the two halves of our visual field is maintained in V1

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22
Q

Cortical Magnification:

A

The relative position of objects within the two halves of our visual field is maintained in V1 BUT relative size of the retinal image is NOT

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23
Q

Cortical Magnification:

A

The relative amount of V1 dedicated to processing visual information from the fovea is much greater than the amount dedicated to processing information from the periphery

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24
Q

Visual Crowding:

A

Objects in our peripheral vision have much lower resolution than those in central vision

This can lead to visual crowding, where peripheral objects are hard to detect because of “clutter”

Even though the object may be discernable alone, other objects around it cause it to be missed

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25
Q

Relative position of the retinal image is __ in the location of neurons that process that image in V1

A

maintained

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26
Q

The number of neurons that process a visual stimulus in V1 is much greater for stimuli in the __ of vision than in the ___

A

central part, periphery

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27
Q

neurons in V1 respond best to:

A

bars of light

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28
Q

Simple cells:

A

Respond best to bars of light (or dark, but not both) with a particular orientation and location on the retina

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29
Q

Complex cells:

A

Respond equally well to bars of light and dark, with a particular orientation BUT anywhere within their receptive field

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30
Q

Who discovered the shape of V1 receptive fields

A

David Hubel and Torsten Wiesel were awarded the 1981 Nobel Prize for Physiology and Medicine
their discovery was accidental

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31
Q

Simple cells respond most strongly to

A

bars of a specific orientation

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32
Q

simple cells respond less strongly to:

A

bars of light of similar orientation

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32
Q

Contrast __ the orientation tuning of simple cells

A

contrast does not affect the orientation tuning of simple cells BUT it DOES affect the MAGNITUDE of their response

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33
Q

complex cells:

A

have an orientation-tuned response too, but the location of the stimulus within their receptive field is not important

34
Q

Complex cells are also :

A

Highly responsive to moving bars of light within their receptive field

35
Q

The receptive fields of complex cells are generally __ than those of simple cells

A

The receptive fields of complex cells are generally larger than those of simple cells

36
Q

End-stopped cells in V1 are

A

Selective for the length of the bar of light they are stimulated with

37
Q

What is the structure of V1:

A

Organisation of the different visual information streams is maintained in the layered structure of V1

38
Q

The layers in V1 maintain:

A

The different visual processing streams

39
Q

How is information processed in V1?

A

Information is processed in V1 columns that have preferred occular dominance

40
Q

Each ocular dominance column contains:

A

Smaller columns with shared orientation selectivity

41
Q

Combining two ocular dominance columns results in:

A

Hypercolumns

42
Q

Hypercolumns contain:

A

information from both eyes, each ocular dominant columns contains all possible orientation receptive fields

43
Q

The different visual processing streams are maintained in

A

the layered structure of V1

44
Q

Describe the visual stream of m RGC’s (parasol) that result in dorsal pathway:

A

parasol RCG’s -> magnocellular layer of LGN -> 4ca -> thick bands in V2 -> area mt (motion) -> parietal cortex -> DORSAL pathway (“where”/”how”)

45
Q

Describe the visual stream of P RGC’s (midget):

A

Midget RCG,s -> parvocellular layer of LGN -> 4cb -> interblob (layers 2/3) -> pale /thin bands of v2 -> v4 -> inferotemporal cortex (object recognition) -> VENTRAL pathway (form, color)

46
Q

Describe the visual stream of bistratisfied RCG’s:

A

bistratified RCGS -> koniocellular layer -> blobs -> thin bands -> v4 -> inferotemporal cortex –> ventral pathway

47
Q

Layers of V1 maintain:

A

The separation of visual processing streams

48
Q

Neurons with the same or similar orientation tuning are arranged in __ in V1

A

columns

49
Q

Ocular dominance columns contain:

A

All possible orientation-selective columns from each eye

50
Q

selective adaptation is a technique that has also been called:

A

called psychologist’s electrode because of the way we can use it to probe how different parts of the visual system work

51
Q

Adaptation:

A

A reduction in response to prior or sustained stimulation

52
Q

Selective adaptation:

A

A technique where we can selectively deactivate groups of neurons through adaptation by presenting a stimulus for an extended period of time

53
Q

We can compare visual areas based on the following characteristics:

A

-The types and distributions of neurons
-The other areas of the brain they connect to
-The properties to which the neurons are tuned (motion, color, orientation, form)
-the retinotopic map of the visual field is maintained in each visual area

54
Q

Segregation occurs

A

Early and is maintained throughout the visual pathways

55
Q

The Dorsal Stream

A

-the “where” or “how” pathway

-represents properties that relate to objects’ motion or location

-guided action

56
Q

Describe the dorsal stream path:

A

V1 -> V2 -> MT –> the parietal lobe

57
Q

The Ventral Stream:

A

The “what” pathway

Represents properties that represent objects’ identities (shape, color)

58
Q

The Ventral Stream:

A

The “what” pathway

59
Q

Desctribe the ventral stream path:

A

V1->v2->v4 towards the inferotemporal cortex

60
Q

Different lesions in the cortex can cause:

A

Specific deficits in visual tasks

61
Q

The landmark task:

A

impaired with parietal lesion (dorsal stream)

62
Q

The object task is impaired with:

A

an inferotemporal cortex lesion (ventral stream)

63
Q

Visual form agnosia (LO lesion)

A

An inability to recognise objects by their shape despite being able to see them

64
Q

Manual estimation:

A

Use the distance between index finger and thumb to estimate the size of an object

65
Q

Grasp calibration:

A

Adjust the distance between thumb and forefinger the match the size of the object as you reach to grasp it

66
Q

Segregation in processing visual information:

A

occurs early and is maintained throughout the visual brain

67
Q

Lesions in the dorsal stream:

A

are associated with impaired performance in visually guided tasks

68
Q

Lesions in the ventral stream

A

are associated with impaired performance in object recognition task

69
Q

Beyond V1, visual areas become:

A

More specific in the type of information that they process

70
Q

V4 processes

A

colour, edges, curvatures

71
Q

Lateral occipital cortex (LOC) and inferotemporal ( IT ) process:

A

objects, faces and places

72
Q

MT processes

A

motion

73
Q

In V4, multiple simple cells

A

with slightly different orientation selectivity synapse onto a neuron in V4 to form a contour-selective receptive field

74
Q

Three areas of the inferotemporal (IT) cortex have been proposed as:

A

modules coding for specific stimuli:

75
Q

the fusiform face area (FFA) of the IT responds best to

A

faces, or contexts that imply faces

76
Q

The parahippocampal place area (PPA) (of the IT) responds best to :

A

places, and layouts (eg rooms)

77
Q

The extrastriate body area (EBA) (of the IT) responds best to:

A

full bodies and body parts

78
Q

do we have individual neurons that code for specific people?

A

probably not – most neurons will respond to many stimuli and we don’t have enough neurons to individually code for every person and object this way

79
Q

distributed coding

A

, where multiple neurons firing at specific rates will code for a person or object

80
Q

specific parts of the inferotemporal cortex code for

A

faces, places, and bodies

81
Q

We likely use multiple neurons firing at different rates to

A

code for different people and things

82
Q

Selective adaptation for spatial frequency:

A

Evidence that human
visual system contains neurons selective for spatial frequency

Sensation and Perception (19 decks)

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