> Thank you for the previous response. I will try setting up the matrix
> this way.
>
> This is the design I came up with for the unmodulated data, and would
> like to perform the same on the Jacobian modulated data, with the goal
> of looking for regional gray matter volume differences in the same
> individuals between two scans:
>
> 1.) Paired t-tests
> 2.) "Grand Mean Scaling" value of 100
> 3.) Select "proportional threshold masking",
> 4.) Select "analysis threshold" of "0.8" (80%)
> 5.) At "implicit mask" ignore 0's,
> 6.) No "explicit mask",
> 7.) At "global scaling calculation" select "user-defined", and enter
> results of get_integrals (to globally normalize for total gray matter
> volume).
>
> I am wondering if I can skip steps 3-7, since I am more interested in
> regional differences in gray matter volume rather than regional
> differences in gray matter volume relative to changes in total gray
> matter volume?
I would suggest a threshold rather lower than 0.8, as this is likely
to exclude quite a lot of the grey matter from the analysis. If you want
absolute differences in GM, then disable the proportional scaling.
Best regards,
-John
--
Dr John Ashburner.
Functional Imaging Lab., 12 Queen Square, London WC1N 3BG, UK.
tel: +44 (0)20 78337491 or +44 (0)20 78373611 x4381
fax: +44 (0)20 78131420 http://www.fil.ion.ucl.ac.uk/~john
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