In case anyone wish to perform a multiple comparison on the cortex, I have written a MATLAB function that gives the threshold for t statistic: http://www.stat.wisc.edu/~mchung/softwares/pvalue/pvalue.html
You need to compute the area of all triangles by yourself to be put into the MATLAB function and requires some sort of surface-based smoothing that controls the amount of FWHM. The detail can be found in http://www.stat.wisc.edu/~mchung/papers/ni_heatkernel.pdf
Moo.