W5L1 - fMRI Research 1
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Recap of W4: What and why do we see with fMRI scans. How is it analysed
Local activity in scans because signal quality is better due to oxygenated blood Statistical Parametric Mapping: General Linear Model is usually fitted to brain activity at each voxel
Recap of W4: BOLD Signal. What does it tell us
• BOLD measured while participants engage in a cognitive task • Repeated measurement of brain activity is required for the whole brain because signal noisy • Differences in BOLD signal tell us something about whether a brain regions ‘is engaged’ in the task
Localising cognitive functions: Kanwisher et al. (1997) and the Fusiform Face Area (FFA). What was it contrasted with. How are the findings
Faces > Objects Faces > Scrambled Faces Faces > Houses Faces > Hands Activation in FFA Great example for a well controlled experiment. Reliable in most participants and replicable.
Other modules found other than FFA
Parahippocampal Place Area (PPA): Houses & Places Extrastriate Body Part Area (EBA): Body
1st Argument against Modulaity. Gauthier & Tarr (1997)
After greeble expertise, FFA responded to greebles. FFA reflecting expertise.
2nd Argument against Modulaity. Malach et al. (2002)
Visual system not by specific object categories; but by where in objects are usually encountered (Cortical topography/eccentricity) Coding driven by resolution needs: (1) High Resolution = Centre = Faces = FFA (2) Peripheral Resolution = House/Place = PPA (that’s where places/houses usually are encountered in our visual field )
Modularity, Expertise and Eccentricity
Evidence for all 3 - true to some extent. fMRI signal might therefore reflect a mixture of all three coding schemes