A couple of things:

(1) Perhaps the groups are not different.

(2) You might have outliers in your data - if you plot the values for each subject, do you see that a few subjects are not consistent with the rest of the subjects.

(3) Did you inspect the grey matter segments before creating the model? If not, I would look at the segments and make sure that the segmentation worked. Check for normalization, image artifacts, homogeneity of the tissue.

(4) Motion will be visible of the T1 as the image will not look clear, but blurry and with ringing lines in the brain.

Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Postdoctoral Research Fellow, GRECC, Bedford VA
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
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On Tue, Aug 5, 2014 at 2:40 PM, Raphael F.C. <[log in to unmask]> wrote:

Dear experts,

I am new to VBM analysis and I performed an analysis between control and patient groups using vbm8 toolbox, evaluating white and grey matter. I got results, but almost every blob would only appear if I do not use the FWE correction.

I followed the instruction from the manual http://dbm.neuro.uni-jena.de/vbm8/VBM8-Manual.pdf.

My questions are:

1) Could any of these results (or at least some of the blobs) be related to movement? I checked images before the analysis with "Check images homogeneity using covariance" and there were no outliers.

2) Which are the areas most susceptible to movement artifacts? Would it be those near to edges and CSF? Is it detectable just by looking?

3) Is there any other advice you would give to a VBM newbie?

Thank you very much for the attention, and I apologize if this issue has already been pointed out before. But I could not find it in the forum archives.

All the best,
Raphael

Ps.: I pasted below one result for white matter with FWE correction. I am not sure if the blobs are real results or some kind of artifact.