On 09/20/2017 01:54 PM, Elizabeth Bartlett wrote:
> Hello Freesurfer experts,
>
> I have performed a group level analysis of volume and cortical
> thickness using mri_glmfit and performed multiple comparisons
> correction with mri_glmfit-sim. I used the contrast matrix 0 1 0 to
> analyze 1 group with 2 covariates, along the 1st covariate (education)
> with the 2nd covariate being age.
>
> I get 2 significant clusters (after mult. comp. corr.) for CT and 2
> for volume. When I look at the values in ./cache.th30.abs.y.ocn.dat,
> the average CT values within my sample are 2.57 and 2.50 for the 2
> regions.
>
> _My first question is: _are the CT values outputted to ocn.dat
> adjusted for my 2nd covariate (age) or are they unadjusted CT values
> within the sig. cluster?
>
unadjusted
>
>
> The volume values contained within the ocn.dat files are also in the
> same range as the CT values, with averages of 2.50 and 1.87 for left
> superior frontal and right inferior parietal volume, respectively.
>
>
> _My second question is:_ What is the metric for volume reported in
> ocn.dat? These values seem too low to be total cluster volume for each
> subject expressed as mm^2. The volumes reported in
> ./cache.th30.abs.sig.cluster.summary are more like what we I expect
> for volume (283.24 mm^2). Could these values be the average volume
> surrounding each vertex in the inflated mesh (volume contained within
> the surrounding vertices)?
>
Yes, the average. You can multiply it by the number of vertices in the
cluster to get total volume
>
>
> Thank you,
>
>
> Elizabeth
>
>
>
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