Collegeaantekeningen neuro b

College 5 / Neuro B
Why are faces important?
 We cannot observe people’s thoughts and feelings but we can observe their faces
and bodies
 Strong incentive to extract socially relevant information from faces and bodies
- Inferring identity  is het dezelfde person of niet
- Inferring emotion from expressions
- Inferring intentions from gaze/body language

Neural basis: visual processing
 Visual stimuli are first analyzed in the primary visual cortex (V1)
 worden geanalyseerd in de occipatale cortex in de achterkant
van het brein.
- Retina (rods and cones or ‘staafjes en kegeltjes’)  optic nerve  thalamus
- Basis properties
 V2 – V5: more complex aspects  zijn wat meer complexe aspecten van de stimuli.
Ze kunnen vormen verwerken of kleur of iets aan het bewegen is of iets stabiel is

Neural basis: the what and the where
 Two streams
- Ventral stream: what you see  meest belangrijke voor als je wat ziet
o Identifying: chair is a chair
o Coupled with memory representation
- Dorsal: where is it in the space
o Location in the space and movement

Regions specialized in face processing
 Occipital face area (OFA)
- Located in the inferior occipital gyrus
- Configuration of the face
 Fusiform face area (FFA)
- Part of the fusiform gyrus
- Identity  identiteit van een gezicht of het een bekend gezicgt is
 Superior temporal sulcus (STS)
- Changeable aspects of the face

Face processing: ‘Core’ and ‘extended’ systems

,Occipital face area vs Fusiform Face area
 OFA
- Early stage of analysis
- Upright and inverted faces
- Sensitive to any physical change in the face stimulus
 fMRI paradigm: with repetition of the ‘same’ stimulus the signal reduces – called
adaptation
- physically same vs categorically the same
 FFA
- Later stage of analysis
- Upright face
- Sensitive to categorical perception – to invariant aspects
o Same face even if different images of the face are used
o Identity, recognizing known faces
 Prosopagnosia
- Impairment in face processing
- Inability to recognize previously familiar faces while earlier processes are spared
- Related to damage to FFA


Occipital Face Area vs. Fusiform Face Area
 Morphing of faces from Marilyn Monroe to Margaret Thatcher
 OFA related to degree of physical difference between images
 FFA related to who the participant perceives it to be

Rival claim for Fusiform Face Area
 Expert in visual discrimination for within category, not for faces per se
- Prolonged experience with face exemplars
- Training other objects can lead to FFA activation
 BUT: the impairment of a prosopagnosia patient was specific to faces
 Role in non-face perception is debated

Superior Temporal Sulcus (STS)
 Responds to changeable (fleeting) aspects of face (gaze, poses)
 Responds to bodies as well as faces (biological motion)
 Receives multi-sensory inputs (e.g. sights and sound of speech)
 Links ventral to dorsal system allowing mirroring others’ action in one’s own motot
system
 Role in emotional expression recognition is less clear

Eye gaze perception
 Eye contact (communication, dominance)
- Smaller dark region surrounded by white sclera  bij mensen en er is meer
contrast waardoor het makkelijker te zien is.
 Direction of gaze provides clues to mental states such as intentions
 Involved in joint attention (social development, cooperation)

,Eye gaze perception
 Judging gaze direction activates STS not FFA, but judging face identity activates FFA
not STS
 Gaze cueing task
- STS respons more to eye cues than arrow cues
- Effect greater when cued to empty space rather than object
- Autism: problem with joint attention and lack of eye contact
o No modulation effect of empty space
o Social significance of gaze rather than gaze perception per se  ze
snappen niet de social relevance van oogcontact

Eye gaze perception
 In monkeys, STS cells are sensitive to gaze direction
 STS talks head position information too
- For example this neuron could be said to code the locus of attention (down, in
this case) rather than eye gaze per se

Pointing
 Proto-imperative ‘give me that’
- Reward based learning
 Proto declarative ‘look at that’
- Joint attention related, involves understanding what the other sees
- Lack of proto-declarative pointing can be a marker for autism
 Moving the eye where the other is pointing/looking activate STS in fMRI studies

Pointing and reaching
 Pointing is not readily used/understood by other animals (dogs being a notable
exception)
 In monkeys, cells in STS already respond to both looking and reaching direction and
more when they respond
- Basis for coding intentional vs. accidental actions?

Perceiving bodies
 EBA (extra-striate body area)
- Abstract descripition of body plan
- Graded response
 FBA (fusiform body area)
- More to whole bodies?
 STS (superior temporal sulcus)
- Dynamic bodies

Perceiving bodies
 Eba responds more to body parts and bodies than other objects

Perceiving bodies: STS and biological Motion
 Led light on joints – recorded in dark
 Discriminating biological from random or non biological

,  Different from visual movement perception of V5

Integrated different sensory inputs and STS
 Single-cell recordings in monkeys
 Activation in STS increased when the same vocalization is both seen and heard

Recognizing expressions
 Using dynamic information, STS
- But: impairments in recognizing facial expressions not linked to the STS but found
following lesions to extended system
 Mapping faces onto regions specialized for emotional stimuli
- Separate pathways for different emotions
o Selective lesions to amygdala (fear) and insula (disgust)
 Simulating the expression motorically
- Lesions to sensorimotor areas

Recognizing expressions: simulation
 Seeing an expression activates sensory-motor mechanisms that produce expressions
 Watching expressions produces tiny changes in facial muscles (electro-myographic)
 Bite task selectively disrupts the recognition of happy expression

Inferring traits from faces
 People tend to infer traits from faces but why?
- A grain of truth?
- Self-fulfilling prophecies?
- Using expression cues to make trait inferences?
- Culturally generated stereotypes, with little or no objective basis?
 All of these may be true to some extent
 Note: does not mean we can reliably predict traits of an individual, only that we can
do so above chance given a large sample of individuals

Agression and facial width-height
 Testosterone at puberty linked-both to facial growth (longer, less-round faces) and
aggressive behaviour
 Facial width-to-height ratio predicts objective measures of aggression in hockey
players

Competence – going beyond what is given
 Pairs of faces from US congressional election (winner and runner-up)
 Only unfamiliar faces used
 Participants are asked to rate how competent a person looks
 Traits inferences influence voting behaviour

Truthworthiness
 Neutral exression with a smile like facial configuration
 Halo effect: beautiful = good
 Faces morphed with your own face are rated as more trustworthy