Thanks doug I first merge the data using command of mris_preproc and then do the GLM analysis using command of mri_glmfit. After that, using the following command to look the result:

mri_surfcluster --in leg.volume.lh.10/g2v2/sig.mgh --csd /usr/local/freesurfer/average/mult-comp-cor/fsaverage/lh/cortex/fwhm15/pos/th13/mc-z.csd --mask leg.volume.lh.10/mask.mgh --cwsig leg.volume.lh.10/g2v2/cache.th13.pos.sig.cluster.mgh --vwsig leg.volume.lh.10/g2v2/cache.th13.pos.sig.voxel.mgh --sum leg.volume.lh.10/g2v2/cache.th13.pos.sig.cluster.summary --ocn leg.volume.lh.10/g2v2/cache.th13.pos.sig.ocn.mgh --oannot leg.volume.lh.10/g2v2/cache.th13.pos.sig.ocn.annot --annot aparc --csdpdf leg.volume.lh.10/g2v2/cache.th13.pos.pdf.dat --cwpvalthresh 1 --o leg.volume.lh.10/g2v2/cache.th13.pos.sig.masked.mgh --no-fixmni --bonferroni 2 --surf white

Did you mean that I multiple the value by the number of vertices (NVtxs, which in the file of cache.th13.pos.sig.cluster.summary ) to get the total volume for the cluster?

# ClusterNo Max VtxMax Size(mm^2) MNIX MNIY MNIZ CWP CWPLow CWPHi NVtxs Annot 1 4.623 7401 1647.03 -8.8 -49.3 5.4 0.00719 0.00559 0.00878 4199 isthmuscingulate 2 3.984 46872 1185.43 -7.7 -71.9 50.4 0.06375 0.05929 0.06820 2487 precuneus 3 3.960 57039 3597.23 -10.6 64.4 -5.0 0.00020 0.00000 0.00040 5545 frontalpole

Wang Kangcheng Faculty of Psychology, Southwest University, China Email: kangchengwang0808@gmail.com / wangkangcheng.001@163.com Address: No.2 Tiansheng Road, BeiBei District, Chongqing, 400715,P.R.China