Dear Ken --
Although there are large overall GM reductions in Williams syndrome,
there may truly be regional increases as well. Have a look at this
study:
http://www.loni.ucla.edu/~thompson/WMS/wms.html
(It would however be interesting to check if patients who moved more in
the scanner look like they have more gray matter).
Best wishes,
Paul
Paul Thompson, Ph.D.
Associate Professor of Neurology
Laboratory of Neuro Imaging, UCLA
http://www.loni.ucla.edu/~thompson/thompson.html
On Jul 21, 2005, at 11:37 AM, Kenneth Rando wrote:
> We are using VBM in a study of gray and white matter differences in
> persons
> with Williams Syndrome. The results of the GM analysis agree in part
> with
> our hypotheses concerning reductions in patients relative to controls.
> However we also find a number of areas of unexpected gray matter
> increases
> in patients. We have observed in our statistical analyses of
> morphometric
> data from other image analysis software that eliminating patients with
> greater motion artifact produces results more consistent with our
> hypotheses, but of course reduces power.
>
> How sensitive is VBM to motion, and do ways exist to eliminate
> suspected
> artefactual results?
>
> Thanks.
>
> Ken Rando
>
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