Neuroscience of object and face perception

Question 1

How is object recognition rooted in fundamental aspects of cognition?

Answer 1

o Memory
o Decision-making
o Actions and so forth

Question 2

Where is the visual centre of the brain?

Answer 2

• 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

Question 3

What does LOC stand for?

Answer 3

Lateral occipital complex

Question 4

How is the LOC linked to object recognition?

Answer 4

• 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

Question 5

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

Answer 5

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

Question 6

What do V1 and V2 do? Similarities and differences?

Answer 6

• 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

Question 7

What are the dorsal and ventral pathways?

Answer 7

• 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

Question 8

What is the dorsal pathway?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

What is the ventral pathway?

Answer 10

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

Question 11

What will damage to temporal-occipital regions do?

Answer 11

• Deficits in recognition following damage/lesion

- Leads to several types of agnosia

Question 12

What will LOC lesions lead to?

Answer 12

• 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

Question 13

Through what two visual streams does visual processing occur?

Answer 13

o Ventral ‘what’ stream – object recognition

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

Question 14

What is agnosia?

Answer 14

• 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

Question 15

What are lesions?

Answer 15

• 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…

Question 16

What is apperceptive agnosia? (simple terms)

Answer 16

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

Question 17

What is integrative agnosia? (simple terms)

Answer 17

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

Question 18

What is associative agnosia? (simple terms)

Answer 18

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

Question 19

What is prosopagnosia? (simple terms)

Answer 19

o Normal vision and recognition except for faces

Question 20

What do individuals with apperceptive agnosia have (lesions)?

Answer 20

Right-sided parietal lesions

Question 21

What do individuals with apperceptive agnosia broadly have trouble with?

Answer 21

• 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.

Question 22

What is the perceptual problem in individuals with apperceptive agnosia?

Answer 22

The integration of spatial information

Question 23

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

Answer 23

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

Question 24

What do individuals with integrative agnosia have (lesions)?

Answer 24

E.g. Patient HJA – impaired intermediate vision

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

Question 25

What do individuals with integrative agnosia have trouble with (broadly)?

Answer 25

• 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

Question 26

What is preserved in individuals with integrative agnosia?

Answer 26

• 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

Question 27

How is integrative agnosia different from apperceptive agnosia?

Answer 27

• 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

Question 28

What do individuals with associative agnosia have (lesions)?

Answer 28

E.g. Patient FRA

o Bilateral lesion of the anterior inferior temporal lobe

Question 29

What are individuals with associative agnosia able and unable to do (broadly)?

Answer 29

• 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

Question 30

How is associative agnosia different from integrative agnosia?

Answer 30

• 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)

Question 31

What are individuals with prosopagnosia unable to do?

Answer 31

• 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”

Question 32

What do individuals with prosopagnosia have (lesions)?

Answer 32

E.g. Patient FB

- The fusiform gyrus lesions

Question 33

How do individuals with prosopagnosia overcome this problem?

Answer 33

• 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

Question 34

Are there face detection cells?

Answer 34

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

Question 35

What have fMRI studies found out about prosopagnosia?

Answer 35

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

Question 36

What did Tarr & Gauthier (2000) find in regards to prosopagnosia?

Answer 36

• 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

Question 37

What are Greebles?

Answer 37

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

Question 38

What are some critical thoughts on greebles?

Answer 38

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?

Question 39

What is the perceptual issue in individuals with prosopagnosia?

Answer 39

• 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