sdm-help-list > How to create a mask; Practically
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Aug 5, 2020  02:08 AM | danielkwasi
How to create a mask; Practically
Dear All,

Greetings and trust you are doing well.

I am currently working on fMRI meta-analysis using SDM-PSI version 6.21. I must say, I am new to fMRI and so I have been reading and following SDM's tutorial, video, and publication on meta-analysis religiously. For this, I sincerely appreciate the availability of this software. I would be most grateful if you can help me navigate the other stages as the literature is not specific enough. We have read the references on the SDM's website including the 3 on "mask" but they seem not to adequately tackle our problem.

I have proceeded through the steps successfully up to the "Assessment of heterogeneity and potential publication bias" stage specifically, the "extract" stage. That is, I understand I have to create a mask and also I know the general use of a mask. But the question is "how do I create a mask when I am interested in the whole brain (whole-brain analysis)?

For example, we are comparing how people with depression process information compared with healthy controls, in general. So,
1. How do I get the MNI (XYZ) coordinates to input into the software as we are looking at the whole brain difference rather than ROI? I have been reading the SDM's user forum but none addressed my need although some were very useful. 

2. The SDM software gave some options (about 4), but we don't know which one to choose as it is not clear why we should choose option A rather than option B.

3. If I am creating a mask then how many masks to I have to create in order to fully examine the whole brain differences between the two groups?

How can we solve these challenges especially, the first point.

Thanks you very much for your help. 

Best wishes,