On 11/26/2016 09:31 PM, Elijah Mak wrote:

Hi there,

What is the correct way to plot, at each vertex, the Cohen's /D/ after a /mri_glmfit/ comparison? I've seen a few variations posted on the mailing list.

Is gamma.mgh / rstd.mgh is the correct formula?

Yes

Does rstd.mgh represent pooled SD across both groups (patients and controls)?

pooled

Secondly, after plotting the effect size across the whole brain, is it feasible to test whether there are regional differences in effect size by using /mri_segstats/ and /aparc/ to extract the ROI-averaged effect size in /fsaverage/ space, and then perform a paired t-test between say, frontal vs occipital ROIs?

Do you mean use ROI averages as the samples and then test across ROIs? This would be unusual as the interpretation is problematic. I would probably compute a single number per subject that is a weighted sum/difference of the ROI values, then test whether this one number of different across subjects. This would allow you to generalize to subjects that you have not seen rather than to ROIs you have not seen (which probably does not make sense).

Thank you.

Best Wishes, Elijah

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