Hello,
You can do this in a single multi-group VBM ( taking care to make sure the template is balanced across groups ). However without controls, as you say, you can only test for structural differences _between_ these groups, with that caveat there are really no extra precautions that need to be taken.
Kind Regards
Matthew
> I have "inherited" a large movement disorders patient population (Structurals, DTI) with a large enough N for specific sub-categories. However, being a clinic, there are no normal
> controls that have been scanned. The question that I am trying to answer is what are the structural differences in the brains of each of these sub-categories.
> I was thinking of just comparing each specific subcategory with the other, for example, PD with essential tremor, and PD with Dystonia etc, using VBM. I wanted to know if this would be a valid approach to study differences between sub categories, in absence of any knowledge of how the entire category (Movement disorders), or each sub-category deviates from normals, and if I do an exhaustive VBM (i.e all possible pairings) to study this. What extra precautions would be needed for such analysis?
> Thanks,
> Sid.
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> --
> Siddharth Srivastava, PhD
> Functional Neurosurgery Bioengineer,
> Kaiser Permanente Medical Center - Dept. of Neurosurgery
> 1150 Veterans Blvd., Redwood City, CA. 94063
> (650) 299 2251
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