fMRI research- localizing cognitive functions

Question 1

Localizing cognitive functions:

Answer 1

• One important approach to use fMRI is to localize cognitive functions in the brain with the goal of understanding better how the process works, this helps us studying the vision of humans
  
  • The same approach can be applied to understanding higher level visual concepts.
  • The brain encodes information, some parts of the brain is overrepresented. Other parts further out in the periphery, where this is localized is important to understanding how it related to other cognitive functions.
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Question 2

understanding face processing- Kanwisher

Answer 2

• they attempted to investigate how faces are represented in the brain
• they presented their participants with images and measures the bold sig. they then contrasted face processing to the processing of objects.

Question 3

understanding face processing

Answer 3

• K found a region located in the fusiform gyrus, responding more strongly to faces than objects
• they could show this result reliably in most of their participants, and they could replicate it with different partip.

Question 4

controlling the study

Answer 4

• To rule out that this result was simply due to using objects as a control category they replicated the study with the contrast faces> scrambled faces
• Another condition of taking the face and scrambling them, so there is the same low level activation happening.
• They also used another category of objects for the contrast faces>houses, by scrambling the faces in the previous condition you destroy all the structure in the image, another condition with structure they can look at is houses as an alternative to scrambled faces.
• they saw the gyrus activated again so that’s 3 for 3 activations in this area

Question 5

contrasted faces with different body parts

Answer 5

• Really trying to run through possible explanations of things which can impact their results. Again the analysis confirmed that the initial findings of stronger activation for faces in the fysofrom gyrus.
  
  • This finding has been replicated many times and it is one of the strongest fMRI research.
    They even named the region ‘fusiform face area (FFA)’.

Question 6

other places discovered since K

Answer 6

• Fusiform face area (FFA)
• Parahippocampal place area (PPA)
• Extrastriate Body Part Area (EBA)

Question 7

arguments against K

Answer 7

• one argument is that it would be simply impossible if the brain had ‘modules’ for all possible objects- the existing modules already take up a lot of space
• we would run out os space and couldn’t represent everything we know

Question 8

is the FFa really doing face processing?

Answer 8

• Gauthier asked partip to distinguish between ‘Greebles’ and faces. during the experiment they became ‘experts’ of the Greebles,
• when the participants do not know much of the greebles, the FFA responded strongly to faces, but not G
• however after becoming ‘Greebles expert’. the FFA also responded strongly to Greebles

Question 9

Gauthier et al., results

Answer 9

• the activation of FFA may be reflective pf expertise, everyone is just an expert of faces.

Question 10

another interpretation of the FFA role

Answer 10

• another interpretation is that the FFA represents what is typically found in the center of our vision.
• in this view, FFA is specialized for objects that require high resolution, meaning they are processed foveally.,

Question 11

Malach assumptions

Answer 11

• argue that the organizational principle in the ventral visual cortex might follow cortical topography (eccentricity mapping)
• the visual system might not be organizedby specific object categories, but by where our visual field objects are usually encountered
• places/houses are represented in the PPA not because this is the module for places, but this is where the visual system processes objects that are usually encountered in the periphery of our visual field

Question 12

coding schems

Answer 12

• research found evidence for all three coding schemes- and suggested that all of them may be true
• the fMRI signal might therefore reflect a mixture of different coding schemes
• this is an example of how hard it is to interpret fMRI results/

Question 13

Haxby and collegues

Answer 13

• found that the brain uses distributed code to represent many different object categories
• they argued that in order to represent all possible objects, objects must be represented in a distributed fashion
• this means that all objects are represented in the entire ‘object region’ in the brain, not only in specialized modules

Question 14

how are the objects encoded in the brain

Answer 14

• based on the idea that the brain uses a distributed code to represent all possible objects, researchers build classifiers to learn the codes of the fMRI results
• it is now possible to predict which object a person is seeing from patterns of fMRI activity with high accuracy.