Collegeaantekeningen voor neuro b. Dit vak heb ik gevolgd aan de universiteit leiden voor de opleiding pedagogische wetenschappen. Let op: College 5 en 7 zijn in het Engels waardoor er vrijwel geen aantekeningen bij staan, wel de informatie van de slides.
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
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