Vision 2 Flashcards

1
Q

Lesions to V1

A

Can occur due to accident or stroke
Patients report complete or total blindness (single/both hemispheres)
When asked to detect objects-appear blind
Monkeys are able to do visual discrimination
When humans are forced to guess, or use vision, they do well. Called blindsight

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2
Q

Patient TN

A

Lost V1 in both hemispheres due to stroke
Ordinary vision tests indicated complete blindness
Researchers asked him to walk down a corridor where they had placed obstacles without his cane
Avoided obstacles smoothly

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3
Q

Is the patient blind

A

Yes, if vision=conscious sight

No, if vision=visual processing (neural & behavioral)

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4
Q

What does blindsight teach us

A

Primary visual cortex is critical for the conscious aspects of vision

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5
Q

From V1 to V2

A

Neurons in V2 have similar response properties to neurons in V1
But V2 neurons respond to visual illusions (V1 doesn’t)
V2 neurons will respond to the edge of a rectangle
V2 responses are closer to our visual perception

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6
Q

From V1:

A
  1. The Ventral “what stream”

2. The Dorsal “where stream”

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7
Q

The Ventral Stream Pathway

A

Parvocellular LGN Neurons—–V1—-V2—-V4—–INferior Temporal Lobe (IT)

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8
Q

Ventral Stream Characteristics

A

Responses to increasingly complex stimuli
V4 responds to complex geometric shapes
V4: first area in ventral stream to show attention modulation
IT responds to visual objects in a position-invariant and size-invariant manner

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9
Q

Neurons in the fusiform face area in IT

A

Only respond to faces

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10
Q

What is the controversy surround the FFA

A

Kanwisher argues that FFA is selective to faces
“Expert Hypothesis”: FFA is selective to identifying objects of expertise (Not necessarily faces)
Support: Car experts and bird experts show increased activity in FFA when shown their object of expertise

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11
Q

Visual Agnosia

A

Severe and permanent impairment in learning and remembering to recognize visual stimuli

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12
Q

Prosopagnosia

A

If lesion in FFA can cause this difficulty in recognizing faces, or face blindness

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13
Q

Case study of 41 year old male patient with a right occipitotemporal tumor and a left anterior temporoinsular tumor

A

First resection surgery caused no neurologic deficit, but tumor continued to spread
Second resection surgery caused a strong and permanent prosopagnosia

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14
Q

The Dorsal Stream Pathway

A

Magnocellular LGN Neurons—-V1—V2—-V5(MT)——Parietal Cortex

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15
Q

Dorsal Stream Characteristics

A

Spatial attention-guiding our view to points of interest
Using vision for our guidance of actions
Detecting and analyzing movements

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16
Q

Change Blindness

A

Occurs because we cannot pay attention to the full field of view simultaneously

17
Q

Saccades

A

Fast eye movements that focus our fovea on a small area of interest at any time

18
Q

What is the dorsal stream critical for

A

For guiding visual attention

19
Q

Lateral Intraparietal (LIP)

A

Contains a map saliency of spatial locations, and attention to these locations

20
Q

Ventral Intraparietal (VIP)

A

Speed and direction of a visual moving stimuli; responses to visual stimuli with respect to vestibular and other input

21
Q

Medial Intraparietal (MIP)

A

Encode the location of a reach target in nose-centered coordinates

22
Q

Anterior Intraparietal (AIP)

A

Shape, size, and orientation of objects to be grasped, and hand reaching

23
Q

What can a unilateral lesion of the parietal lobe cause

A

Neglect Syndrome

24
Q

Neglect Syndrome

A

Lesion in right parietal cortex (key part of dorsal stream) following stroke
Cannot guide attention to the left field of view (represented in the right hemisphere)
Draws only right side of image

25
Q

Lesions in the Dorsal vs. Ventral streams have different effects

A
Ventral "What" stream lesions
-Patients can reach and grab normally
-For example, can easily grab a pencil, but can't say if it's a pencil or a ruler
Dorsal "Where" stream lesions
-Ignores pencil
-But if shown, can name it as a pencil