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Visual Science > Motion Perception > Flashcards

Motion Perception Flashcards

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1
Q

what is the where? how? pathway called

A

dorsal

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2
Q

which area is involved with depth vision

A

V3A/V7

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3
Q

which area is involved with motion vision

A

V5/MT

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4
Q

which area is involved with hand actions

A

superior parietal lobule & inferior parietal sulcus

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5
Q

what does damage to area V3A/V7 result in

A

stereo loss

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6
Q

what does damage to V5/MT result in

A

akinetopsia

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7
Q

what does damage to the SPL & IPS result in

A

optic ataxia

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8
Q

what is the what? pathway called

A

ventral

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9
Q

which area is involved with colour vision

A

V4

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10
Q

which area is involved with object vision

A

lateral occipital cortex LOC

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11
Q

which area is involved with recognising faces

A

inferior temporal IT/fusiform gyrus

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12
Q

what does damage to V4 result in

A

achromatopsia

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13
Q

what does damage to the LOC result in

A

form agnosia

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14
Q

what does damage to the IT/fusiform gyrus result in

A

prosopagnosia

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15
Q

list the areas which are involved in the where? how? pathway

A
  • V3A/V7 - depth
  • V5/MT - motion
  • SPL & IPS - hand actions
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16
Q

list the areas which are involved in the what? pathway

A
  • V4 - colour
  • LOC - object
  • IT/fusiform gyrus - recognising faces
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17
Q

where does the where? how? dorsal pathway run through

A

through V5/MT, to medial superior temporal (MST) to the posterior parietal (PP) cortex

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18
Q

what does the where? and how? stand for in the dorsal pathway

A 
where = objects are 
how = to interact with them
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19
Q

where does the what? ventral pathway run through

A

from V1/V2, travels down to area V4 to inferior occipital temporal & into inferior temporal cortex

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20
Q

which RGC is the dorsal pathway mainly associated with

A

magno

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21
Q

which RGC is the ventral pathway mainly associated with

A

parvo

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22
Q

what does MT stand for in V5/MT

A

middle temporal (where it is located)

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23
Q

which is the general all purpose motion processor

A

area V5/MT

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24
Q

which are the more specialised motion processors

A
  • V5A/MST medial superior temporal area
  • STS superior temporal sulcus area
  • Occipital area V3 & superior parietal area V6A
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25
Q

where does area V5A/MST sit

A

next to area V5

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26
Q

where does area STS superior temporal sulcus sit

A

above V5A

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27
Q

which area sits at the more posterior areas

A

superior parietal area V6A

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28
Q

which areas are involved in more aspects of particular motion processing

A

occipital area V3 & superior parietal area V6A

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29
Q

what is there an increase of cells for in the extra striate cortex, compared to area v1

A

increase in the % of cells selective for a specific object property or attribute e.g. more cells interested in colour processing in area V4 than in V1

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30
Q

what type of organisation of a particular property is there in the extra striate cortex compared to v1

A

columnar organisation of a specific property

31
Q

what attributes do the cells RFs have in the extra striate cortex compared to area v1

A
  • increased RF sizes at all eccentricities
    &
  • increased RF complexity, responses increasingly resemble perception of object attributes
32
Q

what significance does an increased RF sizes at all eccentricities in the extra striate cortex have

A

analysing a bigger area of field than v1

33
Q

what is the increased RF complexity of in the extra striate cortex

A

of what we really see & whats out there in the world

34
Q

what type of VF representations does the extra striate cortex have

A

biased VF representations, with the highest areas lacking retinotopic or even hemi-field organisations
i.e. much larger representation of peripheral part of visual field than there is for central, visa versa for area v1

35
Q

how many v1 cells are direction selective

A

25%

36
Q

what are the 25% of v1 direction selective cells for only

A

only orientated stimuli

37
Q

which part are the oriented stimuli, direction selective cells in area v1 mainly in

A

layer 4B

38
Q

what do the direction selective cells in area v1 layer 4B respond best to

A

respond best to movement of the oriented stimulus in one direction = bar is same direction to the long axis of the contour/opposite (orthogonal) direction to the stimulus, but does not respond when bar is in the opposite direction to the long contour/opposite direction to same stimulus

39
Q

what do v1 cells tend to be broadly tuned for

A

movement speed

40
Q

what speeds does v1 prefer

A

slow speeds 1-20 deg/s

41
Q

what speeds do v1 cells rarely respond to

A

fast speeds >100 deg/s

42
Q

how many cells of V5/MT are direction selective

A

80-90% (compared to 25% in v1)

43
Q

how much larger are the RF sizes of V5/MT compared to v1

A

5x so they analyse motion over a wider range of visual field

44
Q

what are the direction preferences of area V5/MT independent of

A

the moving object’s other properties e.g. its colour, size, shape, orientation, contrast

45
Q

what do V5/MT cells only care about

A

direction

46
Q

what do V5/MT cells respond weakly to if at all

A

flashed, stationary stimuli so are pure motion detectors and velocity tuning (speed of stimulus)

47
Q

when do V5/MT cells only get excited

A

when an object is moving in the right direction and at which speed, doesn’t matter which stimulus is provided

48
Q

from a complete range of velocities from slow 2 to fast 256 deg/s, what do the majority of V5/MT cells prefer

A

moderate velocity of 20-50 deg/s

higher than v1

49
Q

what do cells of direction columns running through grey matter of V5/MT in adjoining/vertical columns interested in

A

the same direction of motion, but different to the column before

50
Q

how do the preferred direction of motion change between adjoining direction-selective cells recorded tangentially across the layers in direction columns of grey matter of V5/MT

A

changes systematically

= columnar orientation of direction preferences in that particular area

51
Q

what does the recording from left cortex V5/MT represent

A

right hemifield = whats recorded of right visual space

52
Q

which visual quadrant of V5/MT is over represented

A

lower visual quadrant (compared to upper visual quadrant)

53
Q

which field representation in V5/MT show general bias and what for

A

in the more peripheral field representation

for fast speeds and for direction of motion away from the centre of gaze

54
Q

what does lower visual field and direction biases suggest about area V5/MT

A

area V5/MT may also be involved in the initial stages of processing the specific directions of ‘retinal image motion’ associated with computing ‘optic flow’ patterns that typically occur during forward self-motion/navigation through the environment
e.g. when we drive down an open road and when we look into the distance, there is no movement of the image as you’re fixing on a stationary point in the FOV. but objects which are close & at ground level or trees near by in the periphery appear to whiz by us quickly, which is called optic flow. most things we navigate through are at lower part of visual field, as they’re at ground level & fast motion is out at the periphery & biased of V5/MT is at lower quadrant which indicates single cells at V5/MT represent optic flow.

55
Q

which complex type of visual motion and role does the dorsal sub-division of MST (dMST) have

A
  • wide field
  • expansion/contraction
  • rotary & apparent (phi) motion + 3D motion in depth + optic flow
56
Q

which complex type of visual motion and role does the ventral sub-division of MST (vMST) & STS have

A

‘structure-from-motion’ & ‘biological’ motion

57
Q

which complex type of visual motion and role does the occipital area V3 & superior parietal area V6A have

A

also optic flow & or motion in depth

like dorsal sub division of dMST

58
Q

what is the pattern between RF sizes and eccentricity in V5/MT & V1

A

linear relationship of RF from 0-50 degrees eccentricity

RF sizes increase with eccentricity at all locations & 5x wider than V1

59
Q

what is the pattern between RF sizes and eccentricity in MST

A

increase of RF sizes with eccentricity, some single cells with 100% RF sizes (cells seeing motion in almost the entire VF), but the mean RF size in MST is 40 degrees

60
Q

give examples of more complex wide-field (RF sizes = 100x100 degrees, so the semi-field where single cells are able to report motion in the opposite semi-field anywhere as their RF’s are huge) moving stimuli to which different, highly specialised direction-selective dMST, but not V5/MT cells respond

A
  • cells which prefer objects which move in one direction and another cell which prefers object moving in the opposite direction (vertically and horizontally)
  • another cell likes rotary of clockwise spinning but hates spinning of objects in opposite direction, where as another cell prefers the opposite
61
Q

give an example of a dMST cell’s opposite responses to looming & receding optic flow

A

this cell is excited by the textured random-dot display moving towards it (at walking pace of 0.2m/s) & is inhibited by the same display moving away

62
Q

where in the human brain is area V5/MT located

A

middle temporal MT cortex is located, at the junction of the inferior occipital sulcus (ios) & the superior temporal sulcus (sts) at left and right hemispheres, and is at back end of middle temporal gyrus

63
Q

what are the ventral part of MST & superior temporal sulcus interested in

A

structure from motion & biological motion = something we do all the time

64
Q

what is structure from motion

A

showing somebody dots which are moving in a direction & what they will see is a cylinder rotating on the screen, there is not actually a cylinder but a series of dots which indicate an object is moving in 3D space. so get to see structure of object through component of motion

65
Q

what is intact in a classic case of akinetopsia

A
  • visual fields
  • VA stereo acuity
  • colours
  • objects = stationary
    = unconscious aspects of motion processing spared
66
Q

what does a px complain of with akietopsia

A

visual motion made them feel tired & unwell with
- pouring tea ‘frozen glacier’
- crossing the street ‘vehicle approaching from their sound’
- crowded room ‘people suddenly appearing’
= conscious aspect of motion messed up

67
Q

what damage to brain can result in akinetopsia

A

a venous infarct/stroke which took out hV5/MT+, V5/MT on both sides of the brain & MST entered on brodmann areas 19 & 37

68
Q

what other motion perception and other deficits are experienced in a case of akinetopsia

A
  • no simple or complex objects moving faster than 10-15 deg/s (did have perception of objects moving slowly as v1&v2 are intact in her brain, but disappear above 10-15 deg/s)
  • reduced temporal frequency selectivity
  • no or reduced 3D, apparent or structure-from-motion vision
  • no smooth pursuit/tracking eye movements to targets >10 deg/s
69
Q

what are a patient with akinetopsia contrast sensitivity functions like

A
  • acuity/CS functions for stationary gratings is similar to that of control subjects ~30cpd = 6/6
    however
  • it is significantly reduced for drifting (moving) gratings at all spatial & temporal frequencies
70
Q

what are a patient with akinetopsia temporal frequency like

A

non existent as she can’t see flicker more than 10x per sec
same for peak spatial frequency at 5cpd & for lower 1cpd, & control can see flicker at 40-50x per sec which is behind magno processing for motion selectivity

71
Q

what is a patient with akientopsia spatial frequency like

A
  • high spatial frequency same as control

- reduction at low spatial frequency

72
Q

what underlies the sparing of navigation (i.e. based on optic flow) & some catching abilities (if moving slowly) in a px with akinetopsia (bilateral area hV5/MT+ lesions, veneer stroke centred on brodmann areas 19 & 37)

A

another prallel magno & motion/spatial vision pathway via v1 & v2 to areas v3 & v6A

two parallel pathways that come out of v1 & v2 that are involved in motion processing, one goes from/through V5/MT, other goes through V3 into area V6A

73
Q

is area V5/MT selectively activated between optic flow vs random directions

A

no, as both stimuli equally activate area V5/MT

74
Q

which area is selectively activated between optic flow vs random directions

A

V3 & V6A is activated by optic flow stimuli and NOT by random directions

so lets us navigate through environments

Visual Science (14 decks)

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