sdm-help-list > question about multimodal results
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Jul 21, 2020  04:07 PM | LI YAO
question about multimodal results
Hi everyone,

I'm working on a multimodal meta-analysis combining the VBM and functional data with SDM, there are a lot of regions in the results, but several of them were NOT showed in both separate VBM and functional meta-analyses.

For example, region A was found to have both hyperactivity and decreased volume in the multimodal meta-analysis, but in the VBM meta-analysis, region A was not shown in the result list (neither in the positive nor negative results), even when we set a lenient threshold as P<0.05.

From the paper and manual of SDM, I notice that the multimodal function of SDM is based on OVERLAPPING the maps of separate meta-analyses, making it is illogical and confusing to find a result in the multimodal analysis that is not revealed in the separate analyses.

So how to explain this phenomenon? Is that in relation to the SDM algorithm or the primary data?

Thanks in advance for your help and look forward to any responses.

li
Jul 24, 2020  01:07 PM | Lydia Fortea - Instituto de Investigaciones Biom├ędicas August Pi i Sunyer (IDIBAPS)
RE: question about multimodal results
Dear Li, 

The overlap between the results of the two separate maps depends wheter or not you specify the option "adjust the p-values to the best scenario"; which makes the p-values more liberal in the multimodal meta-analysis than the separate ones. 

Please refer to: https://www.sdmproject.com/old/manual_multimodal.php

Kind regards, 
Lydia
Jul 25, 2020  02:07 PM | LI YAO
RE: question about multimodal results
Thanks a lot for the explanation, it helps a lot!

Li