Hello FreeSurfer Developers,

 

I'm attempting to build my own Z Monte Carlo on fsaverage5, as described on the BuildYourOwnMonteCarlo tutorial (https://surfer.nmr.mgh.harvard.edu/fswiki/BuildYourOwnMonteCarlo), but I get a segmentation fault.

 

As a reproducible example, the following command tries to compute 10 replications at FWHM=15 and save it in a subdirectory fsaverage5 of my current directory.

 

$ mri_mcsim --o ./fsaverage5 --base mc-z --surface fsaverage5 lh --nreps 10 --fwhm 15

 

Issuing this command leads to a segmentation fault. The full output is in the attachment (mri_mcsim_error.txt), and here are the last lines before the error happens:

 

Loading /Applications/freesurfer/7.1.1/subjects/fsaverage5/surf/lh.white

group_avg_surface_area 84969.3

group_avg_vtxarea_loaded 1

Loading label file cortex

Loading /Applications/freesurfer/7.1.1/subjects/fsaverage5/label/lh.cortex.label

Segmentation fault: 11

 

Adding the «--debug» option gives no additional information. If I add the “—no-label” option, it works. However, I need those labels for later use in mri_glmfit-sim so that does not solve the issue.

 

Using fsaverage6 instead works fine:  “$ mri_mcsim --o ./fsaverage6 --base mc-z --surface fsaverage6 lh --nreps 10 --fwhm 15” gives no error messages.

 

I've searched the list and no similar errors have been reported. Does anyone have any thoughts on how to trouble-shoot this one?

 

1) FreeSurfer version: freesurfer-darwin-macOS-7.1.1

2) Platform: macOS Big Sur 11.4

 

PS! I’m also aware that permutation testing is in general recommended rather than Z Monte Carlo simulations, but in this particular application the dataset is so large that permutation testing is likely not a viable option, due to computing constraints.

 

Best regards,