jorge luis wrote:
I computed the region areas by adding the areas of the
triangular faces inside these regions using the 
spherical coordinates of the vertexs and the Heron
formula for the triangle area. 
  
On fsaverage? If so, then you will need to take into account the effect that I described. Also, those ROIs are pretty small, so there could be some local distortions.
Another thing:

Should I use the sig.mgh file resulted from the
mri_glm estimation as the input to the
mri_surfcluster function in MonteCarlo simulations?
(plus the .csd file of course).
  
Yes, use the sig.mgh file

doug
In advance thank you a lot
Jorge


--- Doug Greve <greve@nmr.mgh.harvard.edu> escribió:

  
How did you get the 15 mm^2 regions? And how did you
know that they are 
15mm^2? There are some complications with using the
raw vertex areas on 
fsaverage. The total surface area of the average
will be wrong 
(inevitable with the way that fsaverage is
computed). However, there is 
a correction, and our tools take this into account.

doug

jorge luis wrote:

    
Hello all

I have made deep changes in 9 regions of a left
hemisfere of a subject surface after maped it  onto
the fsaverage subject sphere. The changes were made
      
to
    
have areas close to 15 mm^2. I computed the areas
      
by
    
add the areas of the  faces inside the regions
(computed using the vertexes spherical
      
coordinates).
    
The freesurfer sphere mapping is based in minimal
metric distortion, so, why I got the following
differences?: 

       
Region   Computed areas (mm^2)  Computed areas
      
(mm^2) 
    
        uing mri_surfcluster   as explained before
      
 
    
with the fsaverage sphere          
  1      27.56                   15.0522
  2      21.78                   15.0946
  3      21.41                   15.1087
  4      20.77                   15.1501
  5      19.28                   15.1797
  6      16.60                   15.1918 
  7      15.99                   15.2781 
  8      14.31                   15.3373
  9      13.89                   15.0541

In both cases the same surface vertexes  were found
      
to
    
be inside  the regions 


Another thing:

Should I use the sig.mgh file resulted from the
mri_glm estimation as the input to the
      
mri_surfcluster
    
function in MonteCarlo simulations? (plus the .csd
file of course).

In advance thank you a lot
Jorge


		
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-- 
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
Phone Number: 617-724-2358 
Fax: 617-726-7422

In order to help us help you, please follow the
steps in:
surfer.nmr.mgh.harvard.edu/fswiki/BugReporting



    



		
______________________________________________ 
LLama Gratis a cualquier PC del Mundo. 
Llamadas a fijos y móviles desde 1 céntimo por minuto. 
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-- 
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
Phone Number: 617-724-2358 
Fax: 617-726-7422

In order to help us help you, please follow the steps in:
surfer.nmr.mgh.harvard.edu/fswiki/BugReporting