from mri_glmfit-sim --help

csdbase.sig.voxel.mgh - the sig volume corrected for multiple comparisons on a voxel-wise basis. The threshhold and sign are irrelevant. The value at each voxel is the corrected -log10(p-value) for that voxel.

It is computed from a simulation in which gaussian noise is smoothed, then converted to p-values (log10(p)), then the maximum log10(p) is found. This is repeated 10,000 times to give 10k maximums. A corrected p-value for each voxel is then computed based upon the rank of the raw pvalue in this list of 10k.

On 6/10/2022 4:14 PM, Mark Ebden wrote:

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Hi,

I was wondering if anyone knows how the numbers in cache.th40.pos.sig.voxel.mgh are computed, or where I'd look to learn this. There is a one-liner in the documentation but I'd like the mathematical details of the correction etc. so I can determine what the final numbers (from 0 to 1) represent. I've noticed from browsing the plot in FreeView that significant areas have values close to 1, which is puzzling.

Thanks if you could point me in the right direction.

Kind regards,

Mark

Mar



Mark Ebden, D.Phil

(Pronouns: He/Him)

Research Analyst



The Hospital for Sick Children

555 University Ave, Toronto ON M5G 1X8

P 416.888.0841

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