Chapter 6 Part 1 Flashcards

1
Q

2 major object recognition pathways

A

o Dorsal stream “where”

o Ventral stream “what”

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2
Q

Dorsal Stream

A

o Dorsal stream “where”

 V1 to superior longitudinal fasciculus to posteroparietal cortex

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3
Q

Ventral stream

A

o Ventral stream “what”

 V1 to inferior longitudinal fasciculus to inferior temporal cortex

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4
Q
  • Dissociation of parietal and temporal lobe lesions in monkeys
A
o Object discrimination“what” task
o Landmark “where” task
o Parietal lobe lesioned
 Monkeys could do “what” task
 Could not do “where” task
o Temporal lobe lesioned
 Monkeys could not do “what” task
 Could do “where” task
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5
Q

Ventral stream cells demonstrate strong object selectivity

A

o Dorsal cells respond to stimuli in the fovea and the periphery
o Ventral cells respond to stimuli in the fovea
 People’s faces
o Card trick represents this
o Example; pictures of hands

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6
Q
  • PET Evidence
A
o Match based on the locations of the objects
 More dorsal stream areas activated
 (lateral)
o Match based on what the objects were
 More ventral structures activated
 (bilateral)
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7
Q

Visual Agnosia (patient D.F.)

A

 Failure of object recognition
 Damage from carbon monoxide
 Probably ventral stream damage
o Explicit matching task
 Does not do well in matching the orientation of the slot
o Action task
 Does well in inserting the card into the slot

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8
Q

Optic Ataxia

A

 Can hold cards in the right orientation to the slot
 Can’t correctly insert card into the slot
 Inability to use visual information to guide movement
 Patients can identify objects
 Patients have difficulty picking up objects i.e. too high, too low, wrong hand position
 Probably damage to the dorsal stream

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9
Q

Perception for identification vs perception for action

A

o Ventral is perception for identification

o Dorsal is perception for action

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10
Q

Object Constancy

A

o The same object looked at from different viewing angles can look vastly different on the retina
o However, we know the shape is constant despite what the retina perceives

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11
Q

Object Constancy: View dependent frame of reference

A

Recognition involves comparing the retinal image to multiple mental representations from different viewpoints

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12
Q

Object Constancy: View invariant frame of reference

A

An object’s properties are analyzed and compared to single representations

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13
Q

Evidence the brain uses both theories of object constancy

A

o Ventral stream neurons show object constancy

 Angle of hand does not affect the firing of the cell

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14
Q

Hierarchical coding hypothesis

A

o Builds up a perception based on the features of an object and cell response
o Example: table (legs, surface, rectangle)
o Gnostic units (grandmother cells)
 These cells allow us to know what an object is because they fire
o Gnosis means knowledge

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15
Q

Hierarchical coding hypothesis: Grandmother cells Controversy

A

 The concept of grandmother cells is more problematic than it first seems
 What objects you have never seen before? Do the neurons not fire until you see that object? What about before that object existed?
 The loss of one neuron would mean you could not recognize that object anymore
 No reason the perception of a table is in a certain neuron

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16
Q

Hierarchical coding hypothesis: Ensemble Coding

A

 These neurons are a part of a group of neurons that fire in specific pattern
 The overall pattern of firing creates the perception of a table
 If one of the neurons die, as long as the overall pattern is maintained you can still identify the object