Dear all,
In a VBM study we find a strong association between a clinical measure and pulvinar volume. We are able to replicate this in a second completely independent sample.
A reviewer is concerned about the location of this association. He states:
The area with the greatest change in volume is adjacent to the atrium of the lateral ventricle, precisely where it begins to curve downward. In other words, the surface of the pulvinar is surrounded by cerebrospinal fluid on three sides (dorsally, laterally, and caudal). Structures along the ventricular surface are particularly liable to artifactual "loss of volume" when there are minute changes in ventricular volume, and this is in proportion to the degree to which they share surface with the ventricle. Even a tiny change in overall brain volume is likely to result in the hot spot for loss of substance at the points where the brain tissue is surrounded by CSF.
We are correcting for total native GM in our analyses, not total brain volume. Could anyone comment on the validity of the reasoning of the reviewer? Would the way to go be to show results hold when controlling for total ICV or not controlling for brain volume at all?
Best,
Diederick
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