09-10. extrastriate processing Flashcards

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1
Q

2 main extrastriate pathways?

A
  1. dorsal (dorsal fin –> dory –> top)
  2. ventral
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2
Q

What does the dorsal pathway connect?
(LGN layer, pathway, cortex)

A
  1. MAGNO cellular layer
  2. MT (middle-temporal visual area)
  3. Parietal cortex
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3
Q

What is the dorsal pathway most important for?

A

“where” / “how” pathway
(dOrsal = hOw)

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4
Q

What is MT important for?

A

Motion perception!

Specifically direction, more than just flickering

MT = MoTion

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5
Q

What does the ventral pathway connect?
(LGN layer, pathway, cortex)

A
  1. PARVO cellular layer
  2. V4
  3. Inferotemporal cortex
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6
Q

What is the ventral pathway most important for?

A

“what” pathway

venTral = whaT

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7
Q

What is V4 important for?

A
  • form
  • color

V4 –> “FOURm” & color

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8
Q

How is V4 sensitive to form and curved edges?

A
  • V1 cells have preferred orientations that indicate short, straight edges
    –> V1 tells us BARS
  • V4 cells combine info from V1 cells to add bars and make a CURVED edge
  • curved edges important for perceiving CONTOUR / form
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9
Q

How does the IT cortex perceive form?

A
  • V1 = straight
  • V4 = curves, contours
  • IT cortex = SHAPES
  • cells in IT cortex respond to combinations of contours, with relatively large receptive fields
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10
Q

What experiment is the PARIETAL cortex crucial for?

A
  • landmark / “where” task
  • monkey learns that food is in the bin with the object near it
  • with damage to PARIETAL cortex…
    –> they have trouble identifying WHERE food is
    –> struggle with SPATIAL LOCATION
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11
Q

What experiment is the IT cortex crucial for?

A
  • object / “what” task
  • has to differentiate between a square/triangle or between red/green to get food
  • with damage to IT cortex…
    –> struggle with FORM and COLOR
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12
Q

What happened with the patient with ventral stream damage? What could/couldn’t she do? What does this tell us?

A
  • couldn’t identify objects, but could draw pictures from memory
  • couldn’t report orientation of slot, but could insert a card into it
  • affected VERBAL report, NOT her ACTION
  • ventral / IT is essential for identifying objects
  • there might be information that a person doesn’t have conscious access to
    –> may be in the dorsal / MT pathway
    –> she was able to complete motion/action, but not perception
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13
Q

Dissociating perception and action meaning…?

A

Idea that perception and action happen in different visual pathways

Ventral –> Perception (end of alph.)
Dorsal –> Action (beg. of alph)

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14
Q

How to study dissociation in non neurologically compromised people?

A

Compare the effects of an illusion on…
1. judgement on appearance of stimulus (perception)
2. motor actions towards it
–> like picking it up

ex.
- small stick that looks bigger (like railroad track illusion lines)
- dots surrounded by other dots

  • motor action is the same for the same physical stimulus, regardless of perception
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15
Q

What is modularity?

A

Very specialized processing locations for different visual / brain functions

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16
Q

Fusiform Face Area?

A
  • special area to identify and perceive faces
  • doesn’t work when faces are scrambled
  • brain activity in FFA ONLY when participants CONSCIOUSLY perceived a face
17
Q

Extrastriate Body Area

A
  • area to identify and perceive body parts
18
Q

Parahippocampal Place Area

A
  • responds selectively to large-scale spatial layouts such as landscapes and buildings
19
Q

Distributed coding meaning?

A
  • Objects represented by activity in many regions of the brain
  • despite modularity, there’s a lot of areas involved in perceiving all sorts of things
  • distributed coding is really important for effectively communicating stimuli
    –> single neurons are ambiguous