W2L2 - Neural mechanisms of face perception in humans and non-humans

Question 1

Evidence for face neurons from human adaptation

Answer 1

• Faces show adaptation
  
  • Like Neurons
• Bistable perception in semi-upright
  
  • See one face then the other
  • Suggest neurons adapted to see one face than the otehr

Question 2

What are the 3 studies of neural mechanism of face-processing in non-human primates

Answer 2

• Single Cell
• fMRI
• Microstimulation

Question 3

Non-Human Primate Study (1): Single Cell Study in face-processing in non-human primates

Answer 3

• Non-human primate has face neurons
  
  • Face cells in IT (fusiform gyrus) responded to an intact face
  • Not selective for individual features presented in isolation

Question 4

Non-Human Primate Study (2) :fMRI study in face-processing in non-human primates (READING)

Answer 4

• Identified “Face Area” using fMRI
  
  • In temporal lobe
• Recorded 400 cells in “Face Area”
  
  • 97% of visual cells responded exclusively to faces.
• Apple and clock showed some response (roundness? property of faces?)

Question 5

Non-Human Primate Study (3): Micro-stimulation in face-processing in non-human primates. Methods and Results

Answer 5

Is IT (Fusiform Gyrus) a face perception area?

• Stimulated neurons in IT and influence face/flower perception

Results

1.) Stiimulation

• Especially 50-100ms
• Higher likelihood to see faces at all levels of noise

No stimulation

• Equal probability to see face/flower
  2. ) Stimulation effect greatest for face-sensitive cells within IT

Question 6

What are the human physiological evidences for specialised facial pathways

Answer 6

1. ) MEG
2. ) fMRI
3. ) ECoG
4. ) Stimulation

Question 7

Human Study (1): MEG Study for face-perception in humans neural.

Answer 7

MEG (Cross of EEG and fMRI)

• Temporal responses for faces consistently higher M170 compared to cars and shoes
• No difference between novices and experts
  
  • Suggesting signal for faces

Question 8

Human Study (2): fMRI Study for face-perception in humans neural.

Answer 8

Manipulaed parts and configuration of faces and houses.

FFA

• Faces have bigger respones than houses, hands, two-tone-faces
• Does not depend on changing spaces or parts
  
  • Sensitivity to faces

LOC (Lateral Occipital)

• Bigger reponse to changes in Parts
• No difference for faces or house
  
  • Insensitive to identity
  • Senstivity to whether 2 images are the same

Question 9

Human Study (2.5) fMRI Study for face-perception in humans neural. What happens to bistable stimuli and FFA

Answer 9

For bistable stimuli, the FFA responds more strongly when subjects perceive a face than when they do not

• Suggests FFA is activated specifically by whole faces, not by low-level stimulus features that comprise faces

Question 10

What are neural evidence (not greebles) to suggest FFA is related to level of expertise

Answer 10

• Car expert no centre of right FFA (subset of FFA) for bird object
• Bird expert no centre of right FFA (subset of FFA) for car object

Question 11

Why are cars, birds, dogs criticized for using as expert for face-perception? (What are face-like properties)

Answer 11

They do not have face-like properties

• Similar features arranged in similar configurations
• Recognition at subordinate level
• Stimuli for which participants are experts

Question 12

What happens when greebles become experts in FFA vs novices

Answer 12

• FFA fMRI response change
• Part whole effect (for upright)
  
  • Greeble expert recognition behaviour and physiology consistent with that found for faces
• Configural effects not present in novice data

Question 13

Comparative fMRI: Human v Macaque

Answer 13

Activate the same areas

Question 14

Face Perception: 8 Epilepsy Faces Single Units

Answer 14

• Single units responded not only to faces, but familiar faces such as Halle Barry
• Not only face information, but person-identity units

Question 15

Human Study (3) Face Perception: fMRI + ECoG

Answer 15

• Category-selective response in ventral temporal cortex (VTC)
• High Frequency Broadband (30-160HZ) [only high]
  
  • Strong positive correlation between fMRI and ECoG signal in HFB
  • Spatial coupling was tighter for face-selectivity than house selectivity

Note: HFB

Question 16

Human Study (4) What happens with FFA is electrically stimulated. ECoG + HFB

Answer 16

• Left and right FG contained face-selective high-selective HFB
  
  • EBS of right FG: Distort face-selective distortions
  • EBS of left FG: Distort non-specific vsual changes (e.g. color)
• Stimulation of sites that caused face-related changes (right FG) were more face-selective