L17 - Face Perception in the Brain

Question 1

Why study faces?

Answer 1

• Can tell us age, gender, emotion, and who they are
• Where someone looks, and if they are trustworthy, interested in us
• Most frequent cue we see

Question 2

What was the case study of PS?

Answer 2

• Woman came to London and got hit by a bus on the head
• Sustained damage to occiptal and temporal lobes of brain
• Profound inability to recognise faces = prosopagnosia
• Impairment effecting recognition of identity from faces
• But knows who people are from other cues
• Called acquired prosopagnosia, and others are natural/through the lifespan

Question 3

What did Bruce and Young do?

Answer 3

• Cognitive model of face processing
• Two distinct pathways for processing for visual identity and facial expression processing
• Structural encoding initially where you extract details from faces and when trying to extract facial identity, you have the proportions for each person
• Identity and expression are diff aspects of processing
• One pathway is fixed, and the other is not

Question 4

What is Prosopagnosia?

Answer 4

• Acquired through occipitotemporal cortex damage
• Unable to recognise familiar faces, inc family/self
• No impairments in identity of familiar
• Ability to recognise and name other objects is spared
• Within Bruce & Young model, prosopagnosia deficit located at face recognition unit stage

Question 5

What is the neural basis of face perception?

Answer 5

• Dorsal visual stream: concerned with locating objects in space to the ‘where’ pathway: occipital to parietal lobes
• Ventral visual stream: concerned with identifying objects: ‘what’ pathway: occipital to temporal lobes = where face perception occurs

Question 6

What is the Fusiform Face Area (FFA)? (With study)

Answer 6

• Area of brain specialised for processing faces
• Put people in scanners and presented them with faces vs other categories of objects to compare brain activity
• Specific brain region called Fusiform Face Area in the Fusiform Gyrus - responds more strongly to faces than other objects
• Even when changing the faces stimuli (mismatched), area responds more preferentially to faces

Question 7

What are the face-sensitive areas in the brain?

Answer 7

• Occipital Face Area: specialised for faces and shows physical aspects of stimuli
• FFA: specialised for faces and invariant aspects of faces e.g identity
• Superior temporal Sulcus: responds to face and body and has a dynamic stimuli and changable aspects of aspects e.g expression

Question 8

Describe the Occipital Face Area in more detail

Answer 8

• Located in inferior occipital gyrus
• Early stage of face perception
• Sends input to fusiform and superior temporal regions
• Defined by greater response to faces than non-face categories = not anatomically defined but functionally defined, like the other areas
• Responds to upright and inverted faces
• Sensitive to physical changes in stimulus

Question 9

Describe the Fusiform Face Area in more detail

Answer 9

• Located in the fusiform gyrus
• Defined by greater response to face vs other non-face categories
• Responds more to upright faces
• Sensitive to changes in identity, relatively insensitive to physical changes
• Acquired prosopagnosia usually due to lesions in or around FFA

Question 10

Study looking at OFA vs FFA

Answer 10

• Presented morphs between Mag Thatcher and Marilyn Monroe: people will either see one/other
• Adaptation was then repeated so neurons became fatigued
• Had 3 conditions: identical - where both pics are same, within - changing physical features but keeping identity, between - physical features and identity different
• Greater signal change in OFA when physical properties were changed
• Greater signal change in FFA when perceived identity change

Question 11

Describe the Superior Temporal Sulcus in more detail

Answer 11

• Located in superior temporal sulcus
• Responds to faces, but also to other stimuli like bodies, eye gaze
• Changeable aspects of faces (viewpoint, gaze direction, expression), but not identity
• Responds to moving bodies and to changes in gaze direction

Question 12

What was the updated model of face perception?

Answer 12

• Distributed neural system for face perception
• Core system: includes Inferior occipital gyrus, lateral fusiform gyrus, superior temporal sulcus
• Core system interacts with extended system: includes amygdala etc.
• Proposed that there are two pathways: facial expression, and identity

Question 13

Is the FFA expertise or specificity? (specific to faces or region that responds preferentially to a category that we are expert at) (what are the arguments)

Answer 13

• Domain-general (expertise) vs domain-specific (face specificity)
• Expertise argues that face-specific mechanisms are highly specialised for distinguishing between exemplars of a category
• Face-specificity: argues that face perception is a process occurring in dedicated, specialised cognitive and neural mechanisms: faces are specific discrimination

Question 14

What is evidence for the face specificity hypothesis?

Answer 14

• FFA responds more to faces than non-face categories
• Activation to faces is more consistent and much more robust than face-selective activity in OFA and STS
• But this neither conclusively provide evidence that FFA activation to faces supports this because faces are so special and theres nothing similar we are so familiarised to

Question 15

What is the evidence for the expertise account?

Answer 15

• Faces require discrimination within a category
• We become experts at face discrimination through prolonged experience
• FFA sensitive to expert within category visual discrimination

Question 16

What was an exp on greebles? and on the real world?

Answer 16

• Can train people to recognise these figures and distinguish between them
• Increased response in FFA to upright faces vs inverted greebles
• Real word expertise: Found an increased FFA response for cars vs birds in car experts and vice versa for bird experts

Question 17

What was the case study of RM?

Answer 17

• Prosopagnosic: could not identify himself/wife BUT collected miniature cars and was unimpaired in recognising them
• Cannot be purely down to expertise
• No known cases where recognition of faces and objects have both been impaired while recognition of non-expert objects is spared

Question 18

What else is the FFA important for?

Answer 18

• Object processing = but not as much as face processing
• Ventral stream important for object processing
• Maybe there is relevant info processing in objects for other things in FFA
• It is not amplitude of response but pattern of response that might contain info for discriminating between objects
• But Prosopagnosia and visual agnosia speak against this idea as they can do one but not the other

Question 19

What was the third model?

Answer 19

• Same processing stream at one point before it splits into facial expression and identity
• In order to show expression and identity are separate pathways = need to show double dissociation = where people have impaired recog of identity but not in identity and vice versa
• Prosopagnosics are impaired with facial identity, they also are slightly impaired in expression recognition and vice versa in other conditions so double dissociation can not be proven

Question 20

Do familiar faces have an emotional signal?

Answer 20

• Emotional response to neutral familiar faces can be measured by skin conductance response - automatic and unconscious = seen in prosopagnosia patients too
• Familar faces elicit greater SCR than unfamiliar
• Two face recognition pathways: conscious and unconscious

Question 21

What is Capgras delusion?

Answer 21

• Believe familiar people have been replaced by impostor
• Able to recognise familiar faces, but no emotional response (increase in SCR)
• Further evidence for dissociation between emotional response to faces and face recognition
  But patients with ventromedial frontal lobe damage have no SCR to familiar faces, and no Capgras delusion