Neuroscience of object and face perception Flashcards

1
Q

How is object recognition rooted in fundamental aspects of cognition?

A

o Memory
o Decision-making
o Actions and so forth

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2
Q

Where is the visual centre of the brain?

A
  • The visual centre: the back part of the brain
    o Occipital lobe
    o If you hit the back of your head, you are more likely to ‘see stars’ – visual centre
    o However, there is a very large portion of your brain that is linked with vision
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3
Q

What does LOC stand for?

A

Lateral occipital complex

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4
Q

How is the LOC linked to object recognition?

A
  • Broken into 2 streams
    o Lateral and ventral aspects of the occipital lobe
  • Responds to complex object shapes (e.g., shapes, faces and 3D forms)
    o Tend to find, with fMRIs, that this area of the brain responds most to complex objects
    o Responds to whole objects, but not scrambled objects
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5
Q

What has been found in patients with LOC damage/lesions?

A

E.g. patient DF with LOC damage

  • Not only was LOC severely damaged, but the remaining areas in the ventral stream showed no more activity
  • E.g. if you showed DF a picture of a bed, they would not be able to recognise it
  • DF: poor object recognition
  • Matching task, DF scored poorly when compared with controls
    o Say which things are the same or different
  • Grasping task: comparable with controls
    o Location of the object – more about picking something up – accurately picking something up and recognising where it is in space
    o DF was perfectly in line with controls – preserved spatial recognition
  • DF can still say where things are in space, this could be as the dorsal pathway of his visual pathway is not damaged
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6
Q

What do V1 and V2 do? Similarities and differences?

A
  • V1 and V2 do relatively basic visual processing
    o Share when looking at where things are and what they are
    o But diverge, you have more activation going into the parietal cortex (spatial abilities) and another stream going down into the temporal cortex
    o STS is also involved – ventral stream
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7
Q

What are the dorsal and ventral pathways?

A
  • Shared processing in earlier visual areas and then these diverge
    o Dorsal pathway is where
    o Ventral pathway is what
  • Linked to the parietal and temporal cortex
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8
Q

What is the dorsal pathway?

A
  • The occipito-parietal pathway
  • The ‘where’ pathway
    o helps determine where an object is
    o analysing spatial configurations between objects
  • Specialised for spatial perception
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9
Q

What will a lesion in the bilateral parieto-occipital region do?

A

o “To the patient a chair is flat, though he knows from experience that his visual impressions are cheating him …. A stair is a flat inclined plane with no protruding steps, and yet he knows from the light and shade that he ought to see the steps ……”

  • The patient was able to identify objects, but he was impaired at judging the distance/depth of objects relative to health control.
    o Problem: processing of depth
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10
Q

What is the ventral pathway?

A
  • The occipito-temporal pathway
  • The ‘what’ pathway
    o helps determine what we’re looking at
  • Specialised for object perception and recognition
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11
Q

What will damage to temporal-occipital regions do?

A
  • Deficits in recognition following damage/lesion

- Leads to several types of agnosia

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12
Q

What will LOC lesions lead to?

A
  • Not only was LOC severely damaged, but the remaining areas in the ventral stream showed no more activity
    o Mainly damage to the ventral stream and has more damage with object recognition
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13
Q

Through what two visual streams does visual processing occur?

A

o Ventral ‘what’ stream – object recognition

o Dorsal ‘where’ stream - vision for action to objects

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14
Q

What is agnosia?

A
  • Breakdown of the ventral and dorsal pathways
  • From the Greek word for ‘lack of knowledge’
  • The inability to recognise objects when using a given sense, even though that sense if basically intact
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15
Q

What are lesions?

A
  • Non-human animals
  • Damage brain area or impair its function and then observe the effect on task performance
    o we can determine whether an area ‘is involved’ in task
  • Neuropsychology (humans)
  • Look at behavioural, cognitive or emotional effects of damage occurring ‘naturally’ to the brain
    o e.g. strokes, tumours, head trauma, neurodegenerative disease & neurological disorders – but PLASTICITY…
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16
Q

What is apperceptive agnosia? (simple terms)

A

o Failures in object recognition linked to problems in early perceptual processing
o Damage to both V1 and V2 areas – issues with ventral and dorsal pathways

17
Q

What is integrative agnosia? (simple terms)

A

o Can see individual parts but unable to use this information to recognise things – issues with “wholes”.

18
Q

What is associative agnosia? (simple terms)

A

o Can integrate parts to see wholes but issues with final recognition
o Fail at the last stage of perception
 Can’t say what something is

19
Q

What is prosopagnosia? (simple terms)

A

o Normal vision and recognition except for faces

20
Q

What do individuals with apperceptive agnosia have (lesions)?

A

Right-sided parietal lesions

21
Q

What do individuals with apperceptive agnosia broadly have trouble with?

A
  • Patients may be able to identify conventional objects
  • Recognition poor with unusual views, parts-separated objects
    o But able to identify conventional objects even with poor discrimination of parts
  • Recognition poor in perceptual matching tasks
  • People with damage to the parietal lobe cannot match objects which are inverted
  • Can see some differences with images that have ‘a base’ – trucks have a base, but the keys don’t. So, when they know it should look a certain way, they can recognise what it should look like because they know it needs to be transposed
  • Similarly, there was poor recognition performance with parts-separated objects.
  • But the patients were able to identify whole objects with conventional views.
22
Q

What is the perceptual problem in individuals with apperceptive agnosia?

A

The integration of spatial information

23
Q

What are individuals with apperceptive agnosia able to identify and not identify?

A

o Able to identify conventional objects but sometimes have real issues with copying objects
o But recognition poor with unusual views, parts-separated objects,
o Able to identify conventional objects even with poor discrimination of parts
o Unable to draw copies of objects by extracting the relevant parts of it

24
Q

What do individuals with integrative agnosia have (lesions)?

A

E.g. Patient HJA – impaired intermediate vision

o Bilateral lesions affecting lingual and fusiform gyri extending into inferior, posterior temporal lobe

25
What do individuals with integrative agnosia have trouble with (broadly)?
- Some images are imposed and it’s not actually clear what is behind or in front - People with integrative agnosia are not very good with these aspects of processing o Occlusions in particular o Having difficulty with spatial relationships - Patient HJA: Unable to integrate features into parts or parts of an object into a coherent whole o They cannot tell where one object ends and where another begins o Can’t put the bits together – take all the information together - Copying without normal object recognition, along with (initially) spared stored visual memory o E.g. can draw a plane from memory but can’t necessarily say what it is - Apparently good long-term memory for the visual properties of objects, just cannot name what they are
26
What is preserved in individuals with integrative agnosia?
- Matching is preserved o Some issues, particularly with occlusion o Memory is intact o But cannot say what it is right at the end as a whole object
27
How is integrative agnosia different from apperceptive agnosia?
- Different from apperceptive agnosia, patients with integrative agnosia are able to match images of objects seen from unusual views - But unable to integrate features into parts or parts of an object into a coherent whole
28
What do individuals with associative agnosia have (lesions)?
E.g. Patient FRA o Bilateral lesion of the anterior inferior temporal lobe
29
What are individuals with associative agnosia able and unable to do (broadly)?
- Able to copy drawings and colour in the components of complex drawings o Can distinguish different parts of objects and spatial relations between objects o BUT cannot identify objects – failure at the last point of object recognition
30
How is associative agnosia different from integrative agnosia?
- Different from integrative agnosia, patients with associative agnosia are able to accurately perceive and distinguish an object (e.g. colouring the parts of objects) - But unable to recognise objects or assign meaning to an object (e.g., its functions)
31
What are individuals with prosopagnosia unable to do?
- Failure to recognise faces o ‘face blindness’ - Pallis’s (1955) patient put it: “I can see the nose, and mouth quite clearly but they just don’t add up. They all seem chalked in, like on a blackboard. I have to tell by the clothes or voice whether it is a man or a woman”
32
What do individuals with prosopagnosia have (lesions)?
E.g. Patient FB | - The fusiform gyrus lesions
33
How do individuals with prosopagnosia overcome this problem?
- Tend to use other cues like hair style and clothing | o Can recognise the sex of the face, whether it is happy or sad and even if it is attractive, but can’t recognise it
34
Are there face detection cells?
o First face detection cells were discovered by Gross et al (1972) o Single cell recording in monkey temporal cortex o Cells did not respond to simple stimuli nor to other complex objects
35
What have fMRI studies found out about prosopagnosia?
o Seem to have an area of the brain dedicated to faces but also to other body parts – recognition - With fMRI studies they have studied types of observations o face and objects have different brain areas activated o FFA – fusiform face area o Parietal place area – part of brain which is activated when recognising famous places o We have neurons which are preferentially associated with certain individuals  E.g. can see responses of different, individual neurons • Fire when looking at one celebrity and then don’t with another
36
What did Tarr & Gauthier (2000) find in regards to prosopagnosia?
- Expertise - FFA = Flexible Fusiform Area? - FFA as a system specialized for fine discriminations / subordinate categorization - Processes all complex objects (not just faces) o When you have to make fine discriminations o Recognition through complex discriminations - Activation of FFA increases with expertise in novel stimuli - greebles
37
What are Greebles?
Tarr & Gauthier (2000) - Invent something that had the properties of faces: o Hard to discriminate o Largely similar o Varied in particular way o Training took weeks to learn about them and how to distinguish them - had a 'gender' and belonged to one of 5 families - After discrimination training, brain activity shifts from object area to face area
38
What are some critical thoughts on greebles?
o They are not completely non-face like and so undermines argument o Can a specialized system be co-opted for similar objects? o If FFA mainly specialises for faces does it matter if it is somewhat domain general?
39
What is the perceptual issue in individuals with prosopagnosia?
- Cognitive model of the way we process faces - Seems to be all the face processing stuff o People with prosopagnosia can do all of this, but there is a problem in the final stages o People are forming a neurological model for prosopagnosia - This cognitive model holds up when looking at brain regions of facial processing