I've been looking at the Small Volume Correction Statistics and previous posts on the topic. One post mentioned that there should be little difference between an explicit mask and masking with during SVC (with the exception of smoothing and hyperparameters). To control for these two things, I did small volume correction on the data with the mask.img file. Thus, the number of voxels analyzed and the statistical signifcance should be the same.
However, what I found was the FWEp values are the same, the cluster sizes are the same, the FWEp for the voxels are the same, the uncorrected statistics for clusters and voxels are the same. The difference is in the FDR corrected statistics. They have changed.
(1) Why would the FDR statistics change if the search volume is the same?
(2) The FWEc and FDRc values are identical (and do not match the table). For example, a cluster of 273 voxels has a FWEp for the cluster of .009 -- so it seems that the FWEc value should be 273 as it was with the whole brain statistics. FDRc value of 305 doesn't exist in the table. The largest cluster is 273 voxels and is not significant with FDR correction. Am I miss understanding what SVC is doing or is something else going on with the data?
Any thoughts would be appreciated.
Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Office: (773) 406-2464
=====================
This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED
HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is
intended only for the use of the individual or entity named above. If the
reader of the e-mail is not the intended recipient or the employee or agent
responsible for delivering it to the intended recipient, you are hereby
notified that you are in possession of confidential and privileged
information. Any unauthorized use, disclosure, copying or the taking of any
action in reliance on the contents of this information is strictly
prohibited and may be unlawful. If you have received this e-mail
unintentionally, please immediately notify the sender via telephone at (773)
406-2464 or email.
