Class_03_Perception, and Visuospatial Processing and Action

Question 1

How Pathway

Answer 1

Where pathway
Dorsal pathway
V1 -> Parietal lobe

Question 2

What Pathway

Answer 2

Ventral pathway
V1 -> Lateral Occipital complex (LO) -> Temporal lobe

Question 3

Blood Supply for Both Pathways

Answer 3

Posterior cerebral artery (PCA)

Question 4

Damage to Ventral Pathway

Answer 4

Problems with recognition

Question 5

Damage to Dorsal Pathway

Answer 5

Problems with using vision for action

Question 6

Agnosia

Answer 6

Without knowledge
- Inability to recognize things from sight

Question 7

2 Forms of Agnosia

Answer 7

1. Apperceptive agnosia
2. Associative agnosia

Question 8

Apperceptive Agnosia

Answer 8

Failure in recognition
- due to deficits in the early stages of perceptual processing
- with intact sensation of light
- is not blind
- cannot form the perceptions that they used to before brain damage
- color, motion and form
- cannot copy drawings

Question 9

Associative Agnosia

Answer 9

Failure in recognition
- unimpaired perceptual processes
- a problem with linking perception to existing knowledge

Question 10

Stages of Visual Perception by Lissauer (1890)

Answer 10

1. Conscious awareness of a sensory impression
   - processing of things like color, motion and form
2. Visual percepts are connected to knowledge that we have
   - to memories

Question 11

Types of Apperceptive Agnosia

Answer 11

1. Cerebral achromatopsia
2. Akinetopsia
3. Visual form agnosia
4. Visual texture agnosia
5. Integrative agnosia
6. Hemiagnosia

Question 12

Visual Form Agnosia

Answer 12

could not recognize objects by sight
- could not copy simple line drawings
- rare

Question 13

Cause of Visual Form Agnosia

Answer 13

1. Carbon monoxide poisoning
   -> damages temporal lobes
2. a heart attack
   -> damages occipital lobes

Question 14

Test of Perceptual Problem in Representing Form

Answer 14

1. Efron shapes task
   - whether pairs of shapes are the same or different
2. Birmingham Object Recognition Battery – BORB
   - Silhouettes of animals

Question 15

One problem with interpreting tests of basic visual perception

Answer 15

Cannot really be sure why patients are failing
- recognizing common objects, or judging line lengths
- “blinked his eyes everything would come clear”
- scotomata across visual fields

Question 16

Scotomata across Visual Fields

Answer 16

• ‘blind spots’ may have prevented him from identifying contours of objects.
• couldn’t see his scotomata
• very common in visual form agnosia
• occipital lobe damage
• bilateral visual form agnosia
• simply have low quality vision, not necessarily impaired form perception

Question 17

Case D.F.

Answer 17

Lateral Occipital Complex Damage
- Lack of oxygen associated with carbon monoxide exposure
- basic form perception

Question 18

Texture Agnosia

Answer 18

Visual agnosia for textures
- Ventral pathway damage
- a different part of the ventral pathway than object form

Question 19

Integrative agnosia

Answer 19

Problems with integrating parts of objects into whole percepts
- unable to classify drawings of real and unreal objects
- Wide spread ventral visual pathway damages

Question 20

Case HJA

Answer 20

• Widespread damage to his ventral visual pathways caused by a stroke
• identify objects by touch
• not by vision
• could make good quality copies of pictures
• could not name what he had drawn
• could not gesture the use of objects that he could not name
• “failing to integrate the two things he saw into a single object within his perception”

Question 21

Ipsilesional

Answer 21

something on the SAME side of the body as the brain lesion

Question 22

Contralesional

Answer 22

something on the OPPOSITE side of the body as the brain lesion

Question 23

Objects in the right visual field are processed in…

Answer 23

contralateral hemisphere, i.e. the left hemisphere

Question 24

Objects in the left visual field are processed in…

Answer 24

contralateral hemisphere, i.e. the right hemisphere

Question 25

Lateral Occipital Complex

Answer 25

Visual object recognition - can’t recognize shapes by form - can recognize texture

Question 26

Hemiagnosia

Answer 26

lesions in ventral pathways - impaired at recognition of shapes and objects presented CONTRALESIONALLY

Question 27

Associative agnosia

Answer 27

- can perceive normally - cannot recognize what they see - cannot associate the perceptions with knowledge of what they are seeing - copy images well - not able to name what they had drawn - can draw objects from memory - indicating that they had access to the meaning and visual structure of objects

Question 28

If a patient can see but cannot copy this may indicate...

Answer 28

Apperceptive agnosia - visual form agnosia

Question 29

If a patient can copy, this may indicate...

Answer 29

Associative agnosia - because we assume that they must be able to perceive to be able to copy - Integrative agnosia, can still copy shapes

Question 30

Cognitive Model of Object Recognition

Answer 30

1. Perceptual Processes -> Apperceptive agnosia 2. Association Processes -> Associative agnosia

Question 31

2 Causes of Associative Agnosia

Answer 31

1. Impaired access to stored knowledge of the shapes of objects 2. Disconnection of that knowledge from semantics

Question 32

Associative Agnosia: Loss of Stored Structural Knowledge of Shape

Answer 32

Right occipito-temporal damage - stroke in the posterior cerebral artery - good basic visual sense - inability to recognize objects from vision - can copy drawings but can't name them - poor drawings from memory - can't distinguishing real from unreal objects - knowledge of visual shape is impaired

Question 33

Associative Agnosia: Loss of Access to Semantics

Answer 33

- cannot name objects from vision - good basic perception - good stores of structure of object shapes - good knowledge of structural representations of objects (real/unreal) - can determine objects' size - can perform semantic tasks, such as orally describe objects - disconnection between stored structural knowledge of the shapes of objects and semantic information