Dear HCP team, We are interested in using both task fMRI and diffusion MRI data to study white matter pathways between functional cortical regions. We are planning to use task fMRI activation to define several ROIs as seeds for dMRI tractography. We have several questions below and hope someone can help us.
As far as I understand, all tfMRI results (e.g. contrast maps) for each subject are in grayordinate space (let us only limit the discussion to the cortex), but the dMRI is volumetric data. That means I have to extract the MNI coordinates for each ROI from the contrast maps so that I can use them directly for dMRI tractography. How can I do this procedure from connectome workbench? 1. Usually when I do this in SPM (using traditional volumetric data), I need to first set up a threshold (e.g. p<0.05 uncorrected) to get the blobs and then write down their peak coordinates for further DTI analyses. However in the workbench, I cannot find a button to set a p value. All I can do in workbench is to manually slide the threshold bar from the Overlay Toolbox (i.e. Overlay and map settings—Palette--Threshold). What does the value mean in the threshold map (e.g. are these CIFTI SCALARS t-values or z-scores)? How can I transform it to the typical p value? Do you know any functions in the workbench that I can set a fixed threshold across subjects? 2. Let’s assume I now got a blob from certain threshold, how can I get its MNI coordinates from the workbench? I clicked the blob in the montage view and the information window gave me some XYZ coordinates. First, which surface should I use? midthickness, inflated or very_inflated? I found their vertex number for the same blob is identical but the xyz coordinates in each surface are quite different? Second, in SPM, the MNI coordinates are integers (e.g. -51, -45, 8), but why the xyz coordinates provided by the information window have decimal points (e.g. -51.2555, -45.8909, 8.1537)? Do I just round them up? 3. We are planning to extract each ROI’s MNI coordinates from each individual’s specific tfMRI contrast maps. That means we have to manually extract values from the information window for each of 1200 subjects. Are there any automated scripts (for workbench) that we can use to extract coordinate information from peak site of a blob (and batch for multiple subjects)? Sorry for so many questions and we appreciate any helps and advice. Best Yin _______________________________________________ HCP-Users mailing list HCP-Users@humanconnectome.org http://lists.humanconnectome.org/mailman/listinfo/hcp-users
