Dear Freesurfer team, I have a more general question about how best to approach multiple comparison correction for a large dataset where permutations are not viable and where fsaverage resolution is too high. I've fitted a GLM with mri_fitglm in the fsaverage5 space, which results in smaller files and quicker compute times. Next, I've attempted to create MC simulations for fsaverage5 (following https://surfer.nmr.mgh.harvard.edu/fswiki/BuildYourOwnMonteCarlo), but am running into errors from mri_mcsim: Segmentation Fault (core dumped) mri_mcsim works fine on subject bert, however. I am aware that others also had this problem with fsaverage5: https://www.mail-archive.com/freesurfer@nmr.mgh.harvard.edu/msg70327.html Could you please advise on the best way to run MC correction with large-scale data (30k+ subjects)? Thank you for your help, Best wishes,

Peter PS Please find the full mri_mcsim output here: mri_mcsim --o ./mult-comp-cor/fsaverage5/lh/cortex --base mc-z --surface fsaverage5 lh --nreps 5000 --fwhm 10

7.1.1 cwd /<path>/fsaverage5/surf cmdline mri_mcsim --o ./mult-comp-cor/fsaverage5/lh/cortex --base mc-z --surface fsaverage5 lh --nreps 5000 --fwhm 10 sysname Linux hostname dev01.camhres.ca machine x86_64 user pzhukovsky OutTop ./mult-comp-cor/fsaverage5/lh/cortex CSDBase mc-z nreps 5000 fwhmmax 30 subject fsaverage5 hemi lh surfname white FixVertexAreaFlag 1 UseAvgVtxArea 0 SaveFile ./mult-comp-cor/fsaverage5/lh/cortex/mri_mcsim.save StopFile ./mult-comp-cor/fsaverage5/lh/cortex/mri_mcsim.stop UFSS (null) Creating ./mult-comp-cor/fsaverage5/lh/cortex Loading /<path>/data/fsaverage5/surf/lh.white group_avg_surface_area 84969.3 group_avg_vtxarea_loaded 1 Loading label file cortex Loading /<path>/data/fsaverage5/label/lh.cortex.label Segmentation fault (core dumped)