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Pathology > Object perception - VS > Flashcards

Object perception - VS Flashcards

1
Q

which area in the brain of a monkey is all purpose simple form & all object processors found

A

V4/IOT (inferior occipital temporal cortex)

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2
Q

which area in the human brain is all purpose simple form & all object processors found

A

LOC (lateral occipital cortex) area

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3
Q

in both monkey and human brain, where are more specialised object processors found for recognising faces and buildings

A

IT (inferior temporal), fusiform gyrus, several areas

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4
Q

in both monkey and human brain, where are more specialised object processors found for spatial scenes/places and navigating through them

A

IT (inferior temporal)/ParaHippocampal gyrus

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5
Q

which serial processing is used to rebuild the object image

A

from: V1/V2 - V4 - IOT - IT (where real objects are encoded)

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6
Q

what are the form processing cells in area v1 & v2 and what do they respond to

A

orientation selective

respond to lines & edges

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7
Q

where are the form processing cells located in area v1 & v2

A

in interblob zones of layers 2-4A & 5-6 (in v1)

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8
Q

what are the form processing RF sizes in area v1/v2

A

relatively small 0.1 (fovea) - 2 (bit eccentric) degrees, depending on visual eccentricity

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9
Q

what are the form processing RFs organisation like in area v1/v2

A
  • simple ~15%: linear discrete ON & OFF sub-regions
  • complex ~75%: non-linear, overlapping ON/OFF regions
  • hypercomplex ~10%: end-stopped inhibition, so also size selective and well as orientation selective
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10
Q

what do RF organisations of form processing cells in area V1/V2 interested in

A

only like lines/edges of a particular orientation and hate ones that are at 90 degrees

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11
Q

how many % off cells in area v1 are orientation selective and what do they respond best to

A

75%
respond best to contours (lines, edges) over a narrow range of possible orientations but not to other orientations of the same stimulus

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12
Q

what are the orientation selectivity cells in area v1 responses independent of, and except which population

A

independent of the size of the oriented stimulus

except among a small population 5-10% of ‘end-stopped’ or hyper-complex cells

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13
Q

what two sub-divisions is monkey area V4 believed to contain

A
  1. one primarily concerned with colour vision

2. other mainly concerned with form vision

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14
Q

what are the RFs of the sub division of monkey area v4 concerned with form vision size, compared to area v1 at equivalent visual field locations

A

2-5x larger

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15
Q

what component is 2-5x compared to another component in a monkey brain

A

the RFs of the sub division of monkey area v4 concerned with form vision size, compared to area v1 at equivalent visual field locations

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16
Q

what does monkey area v4 sub-division concerned with form vision, contain none of, and only of which RF organisations

A

no simple cells (beyond v1 & v2)

all RF organisations are complex or many are hyper-complex (end-stopped)

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17
Q

in monkey area v4 sub-division concerned with form vision what are ~50% of cells

A

orientation selective

but they ALL prefer stimuli of a particular size (width verses length)

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18
Q

what do the ~50% of orientation selective cells in monkey area v4 sub-division concerned with form vision all prefer

A

stimuli of a particular size (width verses length)

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19
Q

how is RF sizes in functional specialisation for object & motion perception areas V4, IOT & IT compared to V1 cortex

A

increased RF sizes at all eccentricities (neurons analysing a larger region of space)

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20
Q

how is orientation selectivity in functional specialisation for object & motion perception areas V4, IOT & IT compared to V1 cortex

A

reduced orientation selectivity and absent in IT

replaced by size-shape or object category-selectivity

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21
Q

what are orientation selectivity in functional specialisation for object & motion perception areas in V4, IOT & IT replaced by

A

size-shape or object category-selectivity

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22
Q

how are the specific form attribute in functional specialisation for object & motion perception areas V4, IOT & IT compared to V1 cortex

A

columnar organisation for that specific form attribute that the area is responsible for and specialised to encode

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23
Q

how are the representation of central vision where perception mainly occurs in functional specialisation for object & motion perception areas V4, IOT & IT compared to V1 cortex

A

biased representation of central vision, where object perception mainly occurs, in object processing pathway areas only concerned with central vision, central 20 degrees where we identify & recognise objects and peripheral VF representations disappear the higher up the pathway you go

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24
Q

how is the retinotopic order in functional specialisation for object & motion perception areas V4, IOT & IT compared to V1 cortex

A

loss of retinotopic order

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25
Q

what does RF sizes increase with for V1, V2, V4 & IOT & IT cells

A

eccentricity, by a linear correlation

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26
Q

what does the increase in size of RF with eccentricity increase gradually from

A

V1 to V2 to V4 & becomes really large in IT & IOT cortex

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27
Q

what is the increase in RF size in V1 V2 V4 & IT & IOT mirrored by

A

increase in RF complexity

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28
Q

what are V1 and V2 RFs mainly concerned with

A

fragments of objects (lines and edges)

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29
Q

what are V4 and IT & IOT RFs mainly concerned with

A

simple geometric shapes & real objects and complex shapes (components of objects)

30
Q

what are most of the ~50% of v4 cells which are orientation selective

A

end stop tuned
to the size of the stimulus (like hyper column v1 cells)
where e.g. in a box RF, a line placed inside it must be confined to the RF size, if extended the RF will shut off

31
Q

what do the other of the ~50% of v4 orientation selective cells which are not end stop tuned respond to

A

respond selectively to simple geometric shapes (squares, rectangles) of a particular size e.g. can like a small rectangle placed in its RF, or a square placed in its RF or a rectangle placed in its RF..

32
Q

what do monkey IOT & IT cortex RF properties of single cells correlate with

A

object perception

33
Q

what are the monkey IOT & IT RFs like in relation to V4 RFs

A

much larger than V4 RFs & always involve the fovea & central (10-20 degrees) visual field

34
Q

what do the monkey IOT & IT RFs always involve

A

the fovea & central (10-20 degrees) visual field

35
Q

what do the monkey IOT & IT RFs cells respond to what type of stimulus

A

a specific form stimulus anywhere in their RF & regardless of its size

36
Q

what do IOT cells respond to

A

general shapes like squares or triangles, or to particular patterns

37
Q

what do IT cells respond to

A

only category-specific objects, like faces, hands or types of fruit

38
Q

what are the names of the dots/plots on a graph which shows a share cell in IOT response to particular shapes

A

rastor plots, the more there are, the more the IOT likes that shape i.e. stimulus fires lots of action potentials

39
Q

why are there rows of dots on the graphs which shows the amount of rastor plots of a shape cell in the IOT cortex e.g. a row of 8 dots

A

indicates that the stimulus was placed into the cell’s RF on 8 separate occasions to look at the cell’s response to make sure the activity produced by one stimulus presentation was reliable and consistent from one to the next

40
Q

what does an accumulative histogram show of a shape cell in IOT cortex

A

the number of action potentials that were fired shortly after the stimulus was presented, so a big mountain = a big response and no mountain = no response

41
Q

what does a histogram of different types of squares of a shape cell in IOT cortex results investigate

A

if its components of a square which fires action potentials and shows e.g. the cell may not like a square with a hole in the middle or patterned stripe squares, but may like the solid square

42
Q

what type or organisations are there for neurons in IOT cortex

A

columnar

43
Q

what do the vertical columns represent for neurons in IOT cortex

A

response of cells are the same to those types of stimulus can be, simple geometric and complex shapes, hands or patterns

44
Q

what do horizontally across the cortex cells represent in IOT cortex

A

types of cells you find are different preferences

45
Q

what does a recording from a monkey face cell in IT cortex show

A

that it can only respond to one face of interest where it gives a big response (out of 4 faces which was placed in its RF, the responses were completely different and depended on the face that was placed there) regardless of the viewing angle or facial expression

46
Q

in the ventral, what? processing stream, where is area v4 located

A

on the lingual gyrus

47
Q

what does area v4 in the ventral what? processing stream represent

A

form & colour

48
Q

in the ventral what? processing stream, where is the IOT/LOC located

A

inferior temporal sulcus and gyrus

49
Q

what does the IOT/LOC in the ventral, what? processing stream represent

A

all objects, general object processor

50
Q

in the ventral, what? processing stream, what does the IT/fusiform gyrus represent

A

specific objects (faces)

51
Q

when images of a banana vs scrambled version of banana (stimulus) was presented to a person and the activity of the brain was monitored, what was the difference in cortical action with the LOC, compared to area V1

A

LOC only activated with the real object - banana
V1 was not activated when viewing banana vs scrambled version as cells in V1 like oriented lines in the scrambled version and the blocks and edges too

52
Q

what type of objects is the LOC activated by

A

all types of objects

53
Q

what area is only activated by faces

A

face area on fusiform gyrus (not interested in objects)

54
Q

what usually happens in a general form agnosia (damage to LOC)

A
  • conscious visual sensation of the components of objects is preserved (because area v1 & v2 is intact)
  • but px cannot recognise whole objects that they see or understand their meaning (what they are and what they’re there for)
  • although memory of what they look like & their purpose are preserved
55
Q

what usually happens in category-specific agnosia (damage to fusiform gyrus)

A
  • is restricted to particular classes of object
  • most commonly faces = prosopagnosia, but can be just animals or buildings etc which can be damage to areas right near the fusiform gyrus
56
Q

what can be seen in form agnosia, damage to LOC

A

lines and contours and other elements due to v1 being intact

57
Q

what cannot be understood in form agnosia, damage to LOC

A

the over all picture, what it is

58
Q

what can carbon monoxide poisoning effect

A

inferior occipital & temporal parts of the brain and can cause a bilateral LOC lesion

59
Q

what remains intact from a LOC lesion

A
  • visual fields
  • VAs, stereo
  • spatial acuity
  • colours
  • motion
60
Q

what cannot be matched with a person with LOC lesion

A

simple shapes or simple objects

nor can they copy-draw familiar objects but can reproduce-draw them from memory

61
Q

what can people with prosopagnosia: damage to fusiform gyrus not recognise

A

faces, including their own

62
Q

what can people with prosopagnosia: damage to fusiform gyrus identify

A

familiar people from other visual cues e.g. hair colour, spectacles & from their voice
can also interpret emotions in facial expressions, even though unable to identify to whom the face belongs to, as this involves another part of the brain called the amygdala

63
Q

what are the physical properties of real objects e.g. your own face

A

invariant, they are immune to changes n ambient illumination, viewing angle, size, location

doesn’t change from moment to moment, regardless of other things that do change

64
Q

what is the fundamental challenge of the perceptual ventral stream

A

is to create object-based representations of the physical constancies, while ignoring these other random factors e.g. when light levels drop

65
Q

extra striate cortex contains neurons that represent…

A

object constancies e.g. faces, regardless of their viewing angle, location, size or expression

66
Q

but what do the perceptual constancies for object forms, colours & motion seem to be represented in

A

different, widely separated (located in different parts) extra striate cortical areas

67
Q

what are objects with similar features (faces or volkswagons) represented by

A

many single cells as a ‘population code’ e.g. face cells in IT cortex respond to several faces with similar features, not just to one (such as cells in a monkey brain tend to encode particular categories of people, e.g. some cells like people with narrow thin noses with eyes close together but hate, people with round flat noses with eyes wider apart and vise versa) so has category specific rather than groups of faces in the IT cortex

68
Q

in the extra striate cortex, only damage to the fusiform gyrus can cause…

A

prosopagnosia

69
Q

in the extra striate cortex, none of which cells are orientation selective

A

LOC cells

70
Q

in the extra striae cortex, damage to area V5/MT in the left cortex would result in…

A

right hemi-akinetopsia

Pathology (20 decks)

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