college aantekeningen deel2 neurobiologie

College 5 Neurobiologie

We kunnen gevoelens niet zien maar gezichtsuitdrukkingen wel

Neural basis: visual processing
Visual stimuli are first analyzed in the primary visual cortex (V1)
 Retina (rods and cones; staafjes en kegeltjes) --> optic nerve --> thalamus
 Basic properties
V2-V5: more complex aspects

Neural basis: the “what” and the “where”
Two streams
 Ventral stream: what you see (occipital  temporal)
- Identifying: chair is a chair
- Couples with memory representation
 Dorsal stream: where is it in the space (occipital  parietal)
- Location in the space and movement




Regions specialized in face processing
 Occipitial face area (OFA)
- Located in the inferior occipital gyrus
- Configuration of the face
 Fusiform face area (FFA)
- Part of the fusiform gyrus (boven)
- Identity (gezicht koppelen aan mens)
 Superior temporal sulcus (onder) (STS)
- Changeable aspects of the face




Face processing: “core” and “extended” systems

,Occipital Face Area vs Fusiform Face Area




Zelfde stimulus herhalen --> het signaal en dus respons wordt minder --> adaptation, als er iets veranderd in het
gezicht dan wordt er weer hetzelfde op gereageerd, maar als hetzelfde gezicht zonder aanpassing komt dan wordt
er gesproken van adaptatie; van een verschillende hoek/verschillend lichtval dan kan het nog steeds gezien
worden als hetzelfde gezicht

Morphing of faces from Marilyn Monroe to Margaret Thatcher
 OFA related to degree of physical difference between images (structureel)
 FFA related to who the participant perceives it to be (identity)

Rival claim for fusiform face area
 Expert in visual discrimination for within category, not for faces per se
- Prolonged experience with face exemplars
- Training on other objects can lead to FFA activation
- Can distinguish males/females
- Learn to categorize
 BUT: the impairment of a prosopagnosia (niet meer mogelijk om gezichten te herkennen) patient was
specific to faces
 Role in non-face perception is debated
Face recognition unit: entiteit van gezichtsverwerkingsmodellen die gezichten herkent
Person identity node: entiteit van gezichtsverwerkingsmodellen die semantische (feitenkennis) en perceptuele
informatie over een bepaald individu aan elkaar koppelt

Superior Temporal Sulcus (STS)
- Responds to changeable (fleeting) aspects of face (gaze, poses; they come and go)
- 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 other’s action in one’s own motor system
- Role in emotional expression recognition is less clear

Eye gaze perception
- Eye-contact (communication, dominance)
Smaller dark region surrounded by white sclera
- Intention knowing without asking
Direction of gaze provides clues to mental states such as intention
- Involved in joint attention (social development, cooperation) Waar kijkt mama naar, dat is dus
interessant; aandacht is gericht op een object door de reactie van iemand anders op dat object
 Judging gaze direction activates STS not FFA, but judging face identity activates FFA not STS
 Gaze cueing task (je ziet een gezicht of een dubbele pijn, eerst recht gezicht, daarna kijken de ogen een
andere kant op)
- STS responds more to eye cues than arrow cues

, - Effect greater when cued to empty space rather than object; als er iets onverwachts gebeurt dan
wordt er langer naar gekeken
- Autism: problem with joint attention and lack of eye contact
No modulation effect of empty space & social significance of gaze rather than gaze perception pers
In monkeys, STS cells are sensitive to gaze direction
STS takes head position information too
- For example, this neuron could be said to code the locus o attention (down, in this case) rather than
eye gaze per se.
Gaze = Staren

POINTING
 Proto-imperative “give me that”
- Reward based learning
- Kijken of mama naar je vinger kijkt
 Proto declaritive “look at that”
- Join attention related, involves understanding what the other sees
- Lack of proto-declarative pointing can be a marker for autism
- In infancy there are two types of pointing; 1 is ze willen iets krijgen. 2 is ze willen dat er naar iets
gekeken wordt
 Moving the eye where the other is pointing/looking activates STS in fMRI studies
 Pointing is not readily used/understood by other animals (dogs being notable exception)
 In monkeys, cells in STS already respond
 to both looking and reaching direction and more when they correspond
- Basis for coding intentional vs. accidental actions

PERCEIVING BODIES
 EBA (extra-striate body area)
- Abstract description of body plan
- Graded response
- Responds more to body parts and bodies than other objects and faces
 FBA (fusiform body area)
- More to whole bodies instead of body parts
 STS (superior temporal sulcus)
- Dynamic bodies

Perceiving bodies: STS and Biological Motion
- Led lights on joints (record in dark)
- Verschil detecteren tussen de aanwezigheid van een mens vs. beweging cues op zichzelf
- STS: processing van lichaamsbeweging; detecteren van biologische beweging
- V5/MT: detecteren van visuele beweging

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

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

 Simulation
 Seeing an expression activates sensory-motor mechanisms that produce expressions
 Watching expressions produces tiny changes in facial muscles (electromyographic)
 Bite task selectively disrupts the recognition of happy expression