Dear Freesurfer experts,

I got the area of a cluster by two methods, and found the results were inconstant.

Method 1: During group level analysis, the individual surface was normalized to fsaverage. I exported the cluster area and label file by command mri_surfcluster.

The command ws as followed:

mri_surfcluster --in ./sig.nii.gz --subject fsaverage --hemi lh --centroid --annot aparc --thmin ${thp} --sign ${sigsignTemp} --no-adjust --minarea ${tharea} --sum area${tharea}.${sigsignTemp}${thp_infilename}.cluster.summary --o area${tharea}.${sigsignTemp}${thp_infilename}.cluster.nii.gz --ocn area${tharea}.${sigsignTemp}${thp_infilename}.ocn.nii.gz --olab $Dir_Subj_fMRI/$out_dir_group/$analysis/$contrast/label_area${tharea}.${sigsignTemp}${thp_infilename}/label

Method 2: I calculated the cluster area using the label file outputed by mri_surfcluster via the matlab funciton read_curv. I did this to test the method for calculating the area of a label manually drawn by me.

1, I first got the area of each vertex by the command

area = read_curv('../fsaverage/surf/lh.area');

2, I red the IDs of vertices in the label file and added 1

3, I got area values of vertices in the label file and summed them.

I found the areas calculated by the Method2 were much smaller(except one ROI) than the ones exported by mri_surfcluster as shown below.

Area from Method 1：

# ClusterNo Size(mm^2) NVtxs Annot

1 833.94 1999 postcentral

2 578.52 1300 precuneus

3 243.78 463 middletemporal

4 184.72 344 inferiorparietal

5 111.76 292 insula

Area from Method 2：

ClusterNumber Area(mm^2) NVtxs AnotomicalRegion

1 637.39 1999 postcentral

2 480.44 1300 precuneus

3 140.37 463 middletemporal

4 166.33 344 inferiorparietal

5 112.76 292 insula

What's the reason? Where did I do wrong in the method 2?

Thanks.

Best,

zhiwei

-----------------------------------------------

Zhiwei Wang（王志伟), Associate Investigator

International Center for Primate Brain Research

Center for Excellence in Brain and Intelligence Technology

Institute of Neuroscience,Chinese Academy of Sciences

Room 215, Building #5, 500 Qiangye Road, Shanghai, 201602,China