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Sensation and perception > lecture 4 > Flashcards

lecture 4 Flashcards

1
Q

where do ganglion cell fibres leave the retina?

A

along the optic nerve

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2
Q

optic chiasm

A

cross over point of some of the optic nerves

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3
Q

what do optic nerves become beyond the optic chiasm?

A

the optic tract

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4
Q

what does the optic tract feed into?

A

the Lateral geniculate nucleus

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5
Q

how is information separated once it reaches the optic tract

A

by visual field rather than by eye

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6
Q

where is information from the right visual field represented?

A

the left hemisphere

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7
Q

where is information for the left visual field represented

A

the right hemisphere

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8
Q

what type of structure is the lateral geniculate nucleus?

A

bilateral structure

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9
Q

where does each LGN receive it input from

A

from the left and right eye, but keeps these inputs separate

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10
Q

what type of receptive fields does the LGN have? what is this ideal for? what does it not detect

A

centre surround antagonism receptive fields

ideal for detecting spots of light and edges

not able to detect orientation of bars/ edges

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11
Q

what is V1

A

primary visual cortex

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12
Q

where does V1 receive input from?

A

the LGN

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13
Q

feature of the LGN

A

striate cortex

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14
Q

activity of V1 cells when no stimulus present

A

baseline

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15
Q

what did Hubel and Weisel find caused a big response in V1 cells? what does this show?

A

when the edge of slide moved across the receptive field

V1 likes lines, not spots

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16
Q

what do V1 cells show a preference for?

A

lines of a certain orientation

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17
Q

how is V1 organised?

A

retinotopic mapping
cortical magnification
orientation columns

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18
Q

retinotopic mapping

A

objects close together in the visual field are measured by neighbouring parts of V1

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19
Q

cortical magnification

A

amount of cortex devoted to representing each area of the visual field is distorted
the fovea is represented by a large area of the cortex

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20
Q

orientation columns

A

orientational preferences of V1 arranged in an ordered way

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21
Q

how was the organisation of orientation columns recorded?

A

1) recording from an electrode penetrating the cortex perpendicular to the surface
2) recording from an electrode penetrating the cortex at an angle to the surface

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22
Q

relation of perpendicular surface cells?

A

an orientation column: all cells have the same orientation preference

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23
Q

relation of surface cells organisation at an angle

A

cell’s orientation preferences vary systematically

24
Q

monocular

A

respond to input from left or right eye, but not both

25
Q

is the LGN monocular or binocular?

A

binocular

26
Q

how many cells in V1 are binocular?

A

80%

27
Q

binocular

A

respond to inputs from both eyes

28
Q

ocular dominance:

A

most binocular cells respond better to one eye that the other

29
Q

how are cells with the same ocular dominance organised in V1?

A

in columns

30
Q

names of different cell types in V1

A

simple cells
complex cells
hypercomplex cells

31
Q

simple cell receptive fields

A

respond to oriented bars and edges
phase sensitive
elongated excitatory and inhibitory regions

32
Q

phase sensitive

A

response depends on position of bar within the receptive field

33
Q

orientation tuned neurons

A

neurons that respond best to their preferred orientation but also respond to other similar orientations

34
Q

complex cells

A

respond to oriented lines
no discrete on off regions
phase insensitive

35
Q

what do complex cells respond best to?

A

oriented bars and edges

a particular direction of movement

36
Q

another name for hypercomplex cells

A

end-stopped cells

37
Q

what do hypercomplex cells respond to?

A

bars of:

  • a particular orientation
  • moving in a particular direction
  • particular length
38
Q

how many visual areas beyond V1?

A

30+

39
Q

discoveries about visual areas beyond V1

A

areas seem to be specialised

areas are interconnected

40
Q

V3 function:

A

form

41
Q

V4 function

A

colour

42
Q

V5 function

A

motion

43
Q

importance of ‘what’ stream

A

recognising and discriminating objects

44
Q

where does the ‘WHAT’ stream travel?

A

ventrally to the inferotemporal cortex

45
Q

where does the ‘WHERE’ stream travel?

A

dorsally to the posterior parietal cortex

46
Q

what is the ‘WHERE’ stream important for?

A

determining where an object is and how to act upon it

47
Q

visual form agnosia

A

damage to the ventral pathway

cannot identify objects despite knowing their features

48
Q

monkey lesion study

A

Underleider and Mishkin, 1982

task 1: object discrimination
rectangle and prism in site
food is always under the prism

task 2: landmark discrimination
food always located close to the cylinder out of 2 possible locations

49
Q

result of the monkey lesion study

A

1) lesion to inferotemporal cortex causes problems for object discrimination but not landmark discrimination task
2) lesion to posterior parietal cortex causes problems for landmark discrimination but not object discrimination

50
Q

where is the damage in optic ataxia

A

dorsal pathway

51
Q

what symptoms seen in optic ataxia?

A

cannot grasp objects but can recognise and describe them

52
Q

are the what and where streams separate?

A

not totally, there are many connections between them

53
Q

which way does the signal flow in what and where streams?

A

upwards and backwards

54
Q

why can V1 cells be though of as feature detectors?

A

they respond to certain features of an image

55
Q

what happens as we move higher up the visual system

A

receptive fields get more complex, and the features they respond to more specific

56
Q

what is in area IT of visual system

A

cells that respond to faces

Sensation and perception (12 decks)

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