Dear Doug,

As you suggested yesterday, I launched the GLM to check for interactions group-age with the contrast:

0 0 +1 -1

And I obtained this image:

Then I re-launched my model including age as a covariate and I obtained very similar results:

Finally, I re-launched the model excluding age and I obtained a very different thing, which is actually more consistent with my data:

How shall I interpret this? Shall I exclude age from my analysis? (I do not really expect it to have an influence on my variable y)

Thank you,

Vale

---

From: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of Greve, Douglas N.,Ph.D. <DGREVE@mgh.harvard.edu>
Sent: Wednesday, August 28, 2019 6:03 PM
To: freesurfer@nmr.mgh.harvard.edu <freesurfer@nmr.mgh.harvard.edu>
Subject: Re: [Freesurfer] Fw: question on GLM

 

It is showing
b = g2 - g1
so negative means that g1 > g2


On 8/28/19 1:59 PM, Barletta, Valeria wrote:
>
> Forgot to report my contrast matrix:
>
> -1 1 0 0
>
>
> Thanks,
> Valeria
> ------------------------------------------------------------------------
> *From:* Barletta, Valeria
> *Sent:* Wednesday, August 28, 2019 1:02 PM
> *To:* Freesurfer support list <freesurfer@nmr.mgh.harvard.edu>
> *Subject:* question on GLM
> Good afternoon!
> I have a question on the Freesurfer GLM.
> The command:
>
> mri_glmfit-sim --glmdir
> ${glm_dir}/${hemi}_contrast-${contrast}_${surfname_cme} --cache 1.3 neg
>
> is giving me blue clusters (see attached picture). Do blue clusters
> mean that my variable y is LOWER in the FIRST or the SECOND group
> listed in the FSGD file?
>
> Thanks,
> Valeria
>
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> Freesurfer mailing list
> Freesurfer@nmr.mgh.harvard.edu
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